Ford 460 Backfire Through Carb? All Answers

Q

My ’82 Chevy Chevette has 97,000 miles and runs fine, but when I slow down it backfires. I’ve been to many mechanics but they can’t seem to fix the problem. One told me to clean the carburetor but that didn’t help. Another suggested a tuneup and timing set; that didn’t help either.

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I put additives in the gas and checked the exhaust and all connections, all to no avail. Now I’m afraid to drive. I take care of my car and don’t want to give it away. – R.C., Shirley, N.Y.

A

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First of all, it is important to know where the explosion is coming from. True misfire originates in the engine compartment and is caused by unburned fuel igniting in the intake manifold. This type of explosion or backfire usually bursts the carburetor and can even cause flames to shoot out of the carburetor throat.

There’s another type of explosion that, while not technically a backfire, still makes a lot of noise. This is an explosion of the exhaust system or muffler. It is caused by the ignition of excessively rich exhaust gases in the exhaust system.

In his book Car Care Q&A; For example, former Popular Mechanics columnist Morton J. Shultz lists a number of causes of misfires and muffler explosions. These include leaking engine vacuum, worn distributors, incorrect ignition timing, dirty or worn carburetors or worn parts in the intake or exhaust valve train.

If your condition is a true misfire — that is, if the noise is coming from the engine — the mechanic should check for gasoline leaking through the carburetor into the engine, which is caused by a worn needle valve or a high float level.

A faulty positive crankcase ventilation (PCV) valve or a faulty exhaust gas recirculation (EGR) valve can also cause a misfire.

Q

My husband fills the gas tank as full as he can and clicks every bit in. He then bounces the car up and down, still trying to squeeze in more gas. Is this dangerous? The pump handle says not to overfill. – M.S., Glen Cove, N.Y.

A

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I bet your husband has spilled gas down the side of the car many times while filling up this way. There’s no good reason to do it. In addition, on a warm day, a tank that is too full will force expanded gasoline out of the overflow. This could cause a problem with the charcoal canister – a smoke storage device – as it could become flooded with gas.

Ford, for example, says that the “fuel tank is usually full after three automatic nozzle shut-offs.”

In other words, after the pump has started, you can try filling it a little more until it shuts off two more times. After that, don’t try to squeeze in anymore.

Personally, I like to set the pump handle for slow, automatic dispensing, and when the nozzle shuts off, I round the amount down to the nearest quarter and leave it at that.

Conclusion: The bit more gas is not worth the possible consequences.

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Bob Sikorsky, has written several automotive books. Write to him c/o Lifestyle, Sun-Sentinel, 200 E. Las Olas Blvd., Fort Lauderdale, Florida 33301-2293.

Dear Tom and Ray,

My daughter drove to soccer practice in our 2001 Mercury Sable Wagon. As she turned the key, there was an explosion that appeared to blast the intake manifold off the engine. Needless to say, it rode a bit rough after that. The mechanic could not speculate as to why this happened. But I really need to be able to reasonably intelligently discuss this with my father-in-law, who is a car expert. Otherwise he thinks I’m unmanly. Please help. – Brian

TOM: Well, maybe you should stop wearing those floral sundresses on New Year’s Eve, Brian. That will go a long way in winning him over.

RAY: I’m wondering if it could be the manifold gasket that’s blown and not the manifold itself? I’ve never seen a manifold actually blow off an engine (although I’d love to!), but I can give you a semi-intelligent explanation for a blown manifold gasket, which is a rubberized “gasket” that sits between the manifold runs and the engine.

TOM: If the manifold gasket had already cracked or ruptured in some way, that would have resulted in extra air being drawn into one or more of the cylinders, resulting in what is known as a “lean condition” — that is, too much air, not enough gas .

RAY: My brother usually has too much gas, but that’s a discussion for another day.

TOM: A lean condition can also be caused by a bad fuel injector or a misfiring coil. But whatever the cause, a lean condition can lead to a misfire, which is an explosion in a cylinder that happens when it’s not supposed to – when the valves are open instead of closed.

RAY: And a misfire can go in either of two directions: it can either go through an open exhaust valve and exit out the tailpipe, or it can go through an open intake valve and exit out the air intake, which is what happened in your car, Brian.

TOM: The most common way to identify the misfire is by the loud “ka-boom” it makes, and occasionally by the parts of your former header or exhaust system rattling down the road behind you.

RAY: I suspect a kickback blew away what was left of your already damaged manifold gasket. This caused the car to run rough.

TOM: If the manifold itself really did fly off, it would have to have been a damn misfire – like the ones they use in the William Tell Overture. Or the manifold must have been cracked or loose before the misfire occurred.

RAY: In either case, now that you’ve replaced the gasket and reattached the distributor, you’ve probably solved the misfire problem as well. So I guess you’re good to go, Brian.

TOM: But if the car fails again, you can impress your father-in-law by asking him what else besides a cracked intake manifold or manifold gasket could cause a lean condition in an ’01 Sable Wagon. Then just nod your head as he goes through the list and say, “Yeah, I thought so too.”

* * *

Dear Tom and Ray,

We had a dead battery and called for a jump start. The serviceman could not start the battery with his cables. Then he turned over another battery and put it on top of my battery. Is this a common practice and is this a safe practice? Could this have caused damage to the electrical system? He left all the accessories on and my headlights went out and the alternator had to be replaced. – Suzanne

TOM: Can it cause harm? Apparently yes!

RAY: It shouldn’t if done right (ignoring the issue of spilled battery acid for a moment). When you jump start a car, you are essentially touching the terminals of two batteries together. They only do it via cable. So if you remove the wires it should work the same electrically.

TOM: Unless you touch the wrong terminals together.

Ray: Bingo.

TOM: And that guy did that. He connected the batteries backwards. They were connected in series – like when you string several batteries together in the tube of a flashlight. So instead of 12 volts, it sent 24 volts through your electrical system.

RAY: But some things just can’t handle 24 volts. Your headlights, for example, probably burned out right away. And if you had other lights on, like the taillights, they probably would have burned out too. Or at least suffered damage that would have shortened their lives.

TOM: And the alternator can’t take 24 volts because the diode bridge burns out.

RAY: But there will be no hidden damage. Anything that was damaged will catch your eye because it’s not working now or it’s on fire.

TOM: But you might notice that everyone on your car radio is now talking twice as fast.

* * *

RAY: Some accessories can handle it. For example, if your windshield wipers had been on, the motor would have simply made them wipe so fast that the raindrops would not have known what hit them.

TOM: All powered off accessories would be protected, as would any components protected by fuses or fusible links.

If you own a motorcycle, you may have had the misfortune of having your motorcycle suddenly shoot gas out of the carburetor. You should be concerned about that, and rightly so.

You might be wondering, could this damage something? Is it safe to drive like this? If your motorcycle carburetor is spewing gas, it could be due to a faulty float needle valve. It could either just get stuck, or it could be so worn out that it can no longer function properly. Repairing or replacing the float needle valve can usually solve your problem.

This could be a stressful issue but we will try to get you back on the road as soon as possible. Your bike may be new or old, but there is always a way to fix it. In this article we will tell you why it is spitting gas and how to fix it.

Why the carburetor spits out gas

Why is your motorcycle spewing gas out of the carburetor? As mentioned earlier, there is one root cause that usually leads to this. The cause is a defective float needle valve. The float needle valve has a very important but simple job as it regulates the flow of fuel. When this float starts to wear out, it prevents the valve from actually closing. This means you have a constant flow of gas. This will start flooding the engine, shooting gas out of the carburetor and can even soak your air filter.

You may find that these problems appear after your bike has been parked for a very long time. During this time, the fuel in the carburetor goes bad. Be careful not to use gas with more than 10% ethanol. The ethanol will quickly wear out on your float needle valve and cause it to go bad. Ethanol-free gas is best when you want your gummies to last as long as possible.

Finally, this could be due to modifications you made to the bike itself. If you make major exhaust changes, it can affect the engine quite a bit. However, this can have a big impact on things like back pressure, flow, and sound. In general, the engine is not retuned and the timing is not adjusted to match. As a result, you may be riding too fat and over-inflating the bike. Some tuning on the bike should fix this problem.

Is it dangerous?

You may be wondering, is it really bad for your bike if this happens? The answer is yes. Engine overflow can cause engine damage. As the fuel overflows, it begins to flow back into the intake. To do this, it has to run down the actual cylinder walls. This is bad for many reasons. The first is that it contaminates your oil and prevents it from lubricating everything properly. Second, it will cause additional wear on your piston rings. Obviously these are both very big deals as they can result in you having to replace or overhaul your engine.

Second, there are safety concerns when gas spurts out of the carburetor. This gas is still very flammable. High temperatures can cause the fuel to ignite and result in a fire. You don’t want to ride your bike while it’s spraying fuel everywhere. This could cost you your bike or even your life if it suddenly catches fire.

If you notice that your carburetor is spewing fuel, you should fix it as soon as possible. This contributes to your safety and ensures that you do not cause any additional damage to your bike. Taking the time to get your bike working properly before riding it will pay off enormously later. It can ultimately save you thousands of dollars as a result of a major engine failure.

How to fix a spitting carburetor

Your carburetor performs a very important job on your bike. It is responsible for supplying the correct gas-air mixture to your engine. It does this by first regulating the flow of air through them. As air flows through the main bore, it draws fuel into the airflow. This mixture then flows into the engine through the intake valve.

If your carburetor is spewing fuel, you need to get it repaired as soon as possible. Even if you think you know what’s causing the fuel to spit, you should always diagnose the problem first. This can save you a lot of time and money. Taking the time to find out exactly what broke on your bike should always be your first action before replacing things.

If you determine that the float needle valve is in fact the problem, you will need to replace or repair it. Depending on your specific make and model, repair kits are available that can bring your stuck or worn valve back to life and save you a lot of money. You can also replace the entire unit at any time. Depending on your specific make and model, aftermarket “upgrades” are also available that claim longer life and better performance.

If you find that your problem is due to tuning, you’ll need to do a little tweaking to get things back to where they should be. You can adjust the carburetor to make the bike run leaner or richer. If you need to adjust other software controlled timings, you may need to take your bike to a professional.

If you encounter this problem, it is a fairly common problem that many people don’t know how to solve. There are countless posts on motorcycle forums for almost every make and model. Look there for your specific bike and you may be able to gain some insight into the cause and how to fix it yourself.

How to prevent a motorcycle from spitting in the future

So how can you prevent your motorcycle from spewing gas out of the carburetor in the future? As previously mentioned, the most common cause of this problem is a bad float needle valve. The best way to prevent this phenomenon is to make the float needle valve durable and functional for as long as possible.

The best thing to do about your float needle valve is to watch what fuel you put in your bike. Ethanol is your float needle valve’s worst enemy. Therefore, you should pay attention to the ethanol content in your fuel. The higher the ethanol content, the faster the gummies will be eaten up. This will destroy the valve. If you can get ethanol free gas that would be best for the longevity of the plastics. If you use E85 fuel in your bike, your float needle valve will pay the price almost immediately.

The second important thing you can do to avoid your carburetor spitting out gas is not to let your bike sit idle for very long. Otherwise the gasoline will get old and thus dangerous for the carburetor. If you do this frequently or even occasionally, you may start to notice such symptoms. Although you won’t be riding your bike much anytime soon, it’s still a good idea to get out and start it up every once in a while to pump fuel through the engine. This will help keep your bike running as it should for as long as possible.

The problem I’m having here is that I’m getting a misfire through the barrel of my carburetor on the driver’s side front. It doesn’t happen when I’m idling, it only happens when I give it a little gas, then farts and the engine dies. I ran a 600 cfm Edelbrock, then tried a 750 and it had the same problem and it was an oversized carb anyway. Today I installed the 600s again. So maybe a valve timing could be off and that’s what’s causing the misfire? It’s a rebuilt engine so I know it’s not a worn rag or a broken valve. Everything is new with less than 30 miles. Thanks in advance!

Is your car misfiring? It can often sound like a gunshot, if not a “cough” or “spit.” While engine misfire (or “post-ignition” if it occurs when the engine is already off) will not harm your vehicle, it can be uncomfortable and disrupt a smooth drive.

Why did your car misfire from the exhaust? And how do you prevent the problem from occurring again? Today our ASE certified technicians explain why your car is failing and what it means.

What causes an engine to backfire?

A car will usually backfire because the engine slows down too quickly. However, there are several possible causes.

A few reasons why the exhaust could backfire:

Your engine was braked too quickly

Your gasoline contains a lot of alcohol

High engine temperatures

Another possible cause of your misfire is a spark plug that refuses to “spark” when the exhaust valve opens. When the air/fuel mixture has become too rich, unburned fuel remains in the exhaust system. The misfiring spark plug ignites the rich air/fuel mixture and causes a loud “pop” in the tailpipe.

When your car is brought to our Grand Prairie auto repair shop for an exhaust system inspection, we will tell you the exact cause of your engine misfire.

How do I protect my engine from misfiring?

A misfire is obnoxious and obnoxious. Luckily, there are a few ways to cure an overactive tailpipe.

Some ways to stop a misfire are:

Gradually lower the engine speed

Change the brand of fuel to one with a lower alcohol content

Adjusting the carburetor for lower engine temperatures

If the cause of the misfire is a rich air-fuel mixture, talk to our specialists about increasing your air volume. The experienced technicians at our Dallas-area dealership were able to resolve some of the airway restrictions, increase engine cooling air volume, and minimize the risk of a backfire.

Schedule an exhaust service with our Grand Prairie dealership

While a backfire from the tailpipe won’t harm your car, it can be scary and intrusive. Make sure your vehicle is working properly by scheduling an exhaust system inspection today at Christian Brothers Automotive Green Oaks in Grand Pairie, Texas.

The iconic big-block V8 started life as a gas-guzzling beast to power big cars, but it gained a loyal following in the performance world. You will hardly find anyone mentioning the “Lima” family of engines when discussing the history of Ford Motor Company. The term Lima comes from the fact that these engines were built at the Ford plant in Lima, Ohio. Within the Lima family is the legendary Ford 460 cubic inch big block V8. In modern terms, it’s worth noting that this equates to a whopping 7.5-litre displacement. The term “big block” almost feels like an understatement. Although the Lima engine days ended over 20 years ago, you can still find Ford 460 enthusiasts using the old school big blocks for everything from driving old trucks and vans every day to high compression, nitrogen breathing, Fire-breathing and light-speed dragster builds. While the small block format of V8s has largely conquered the automotive world, there’s still a lot of love for the old-school big blank. In fact, there are still companies that make race-ready engines based on the Ford 460.

Big Block Origin History Another name you may come across when referring to the Lima engines is the Ford 385 series engine. However, the name does not come from the displacement of any of these engines. Instead, it comes from the 460 engine’s 3.85-inch crankshaft stroke. You can easily see why many choose to call them Lima engines; It makes things a little less confusing when all the possible numbers are thrown around. The 460 is not the only Lima engine. In fact, it’s not even the most famous Lima engine. That honor goes to the 429 cubic inch V8. If this sounds familiar to you, it should. The 429 is one of the most iconic Ford Mustang engines. It was found under the hood of Boss 429 Mustangs in 1969 and 1970. It was also used in the 1971 Mercury Cougar. There was also a smaller displacement engine in the Lima family. The 370 cubic inch big block was found under the hood of medium duty trucks like the F600 and F700. In addition, a performance version with a displacement of 514 cubic inches was available through Ford SVO. While all of these engines are excellent on their own, here we’re focusing on the 460.

Ford 460 V8s through the years The 460 first appeared under the hood of the 1968 Lincoln Continental Mark III. While initially exclusive to the Continental Mark III, it found its way into 1972 Mercury vehicles and the Ford Thunderbird. The engine remained a staple of the Thunderbird through 1976. It also saw its final year in the Mercury Cougar in 1976, although other Mercury vehicles continued to use the 460 through 1978. However, this marks the end of the 460’s use in standard passenger cars. The Arab oil embargo of the 1970s led manufacturers to look to more fuel-efficient options as gasoline prices skyrocketed. That’s not all she wrote for the 460, however. While it was no longer used in everyday passenger cars by 1978, the 460 continued to be used in light trucks such as the standard F-150 and F-250. In addition, the 460 could be found in Econoline vans and super-duty trucks. The 460 could even be found in many production campers and campers in the 70’s and 80’s. However, all good things must come to an end. Production of the 460 and the entire Lima engine platform ended in 1998. It wasn’t a bad run, however. With tightening emissions restrictions and more powerful but smaller engine rivals like the Ford Modular V8, it’s all the more impressive that the old-school, pushrod-equipped big block has had a healthy thirty years on it.

Ford 460: Specifications When they say big block, they mean it. The 460 engine is a massive piece of metal that you almost need a shoehorn to get in and out of a car. The engine measures 34 inches long, 32 inches wide and 30 inches high. That means you need almost 27 cu. ft. of real estate under your hood. While you’re reaching for the shoehorn, get yourself a decent engine jack as well. These monsters weigh 720 pounds without oil. As we mentioned earlier, Big Block almost seems like an understatement. By today’s standards, the horsepower output of these big-block V8s isn’t all that impressive. Especially considering the post-embargo changes that were made. It’s worth noting, however, that these figures were nothing short of remarkable when they were first published. From 1968 through 1972, the pre-embargo 460 big blocks produced 365 hp and an impressive 388 lb.-ft. of torque. Peak power was achieved at 4,400 rpm, while maximum torque was at 2,800 rpm. Because of this, the big block carries a stigma for low-end grunt. All of that torque hits you almost instantly the moment you put your foot down. It is a good feeling! As mentioned, the 460 stroke is 3.85 inches. In addition, the bore of the cylinders is 4.36 inches. Most performance claims for the 1968 thru 1972 460s come from their 10.5 to 1 compression ratio. In their original form, these engines were not to be scoffed at. Unfortunately, 1973 brought significant drops in all fun numbers on the 460. Bore and stroke stayed the same. However, the compression ratio was lowered to 8.5 to 1, resulting in a massive drop in power to meet emissions standards. The compression ratio remained that low for the remainder of its production. Over the years we have found many different variants of emission control devices, carburetor settings and fuel injection systems. In general, post-embargo 460s produced between 205 and 275 hp, with torque leveling off between 345 and 375 lb.-ft. There was also a variant of the 460 made specifically for use in police cruisers. In terms of performance, however, it did not differ from the standard road versions.

Unleashing the 460’s Full Potential The drop in performance didn’t deter hot rodders and racers, however. Despite being smothered by the factory to meet emissions and fuel economy standards, the 460 still had a tremendous amount of untapped potential that could be unearthed with some hand tools and a little know-how. To this day, if you venture out to a drag strip, you’re likely to see a Foxbody or older Mustang driving a carbureted 460 big block and doling out monstrous power figures. According to Hot Rod Magazine, a 460 block of bone stock can produce over 900 horsepower. It is common for 460 blocks to undergo a minor machining operation that increases the cylinder bore and lengthens the crankshaft stroke. Combined with high compression pistons, this is a winning formula for monumental horsepower. Even if you’re a die-hard fan of small electronically fuel-injected, turbocharged V8s like most power builds no longer have; It’s easy to appreciate a good old fashioned big block build. There’s still so much love for the old-school big-block Ford that you can still buy crate 460 engines from performance vendors like Summit Racing. Many of the crate engines available are authentically remanufactured for 460s. There’s even a 460-based Ford Performance engine available, displacing a massive 572 cubic inches. For them, too, there is a virtually unlimited supply of aftermarket performance upgrades. These include forged high-compression steel pistons, performance connecting rods, aftermarket cast iron and aluminum cylinder heads, performance intake manifolds, and the list goes on and on. In addition, searching for stock parts is not a problem. Many parts are still available at your average parts store, and it’s not at all uncommon to find a 460 in a junkyard.

The boss block is back. The Ford 460 crate engine is a small block Windsor engine that produces 575 horses. Also known as the Z460, this legendary engine features high-flow Z-heads. If you are looking to replace the engine in your vehicle with one that has more horsepower, or make engine modifications to increase horsepower, the Ford 460 crate engine is a great engine. Read about the history and specs of Ford’s latest ‘old’ Ford 460 crate engine.

History of the Ford 460 Crate Engine In the past, the 460 was only found in Lincolns. However, when Ford discontinued the 429 they used in Thunderbirds, it dropped the 460 in the Thunderbird. Eventually, Ford used the 460 in other Ford and Mercury models, including the F-Series pickups. The 460 was phased out in cars in 1979 as Ford downsized cars, but you could still find it in E-Series vans and F-Series trucks in the 1990s. The 460 engines built before 1972 had 365 hp at 4,600 rpm and 485 lb.-ft. Torque at 2,800 rpm. In 1972 Ford increased power to 212 hp at 4,400 rpm and 342 lb.-ft. Torque at 2,600 rpm. When fuel injection came into play in the 1980s, power dropped to 245 hp and torque increased to 400 lb.-ft. of torque. The compression ratio changed from 10.5:1 for the pre-1972 engines to 8.5:1 for the 1972-up engines.

What are the specifications of the Ford 460 Crate Engine? The Ford 460 crate engine — the Z460 — makes 575 hp and 575 lb.-ft. of torque. It runs on pump gas so you can ride it on the street or on the track. The bottom end features a forged steel SCAT® crank, Mahle® pistons, Clevite® bearings and SCAT® forged H-beam bars, all in a 351-based small-block Ford. This crate engine has a displacement of 460 cubic inches with a bore of 4,150 inches and a stroke of 4,250 inches. The block features a 9.5 inch deck. The top end features a .594 inch / .618 inch lift hydraulic roller camshaft. The cam has a duration of 242 degrees on the intake and 248 degrees on the exhaust at .050 inches. The aluminum Z cylinder heads feature 2.02″ intake valves and 1.60″ exhaust valves. The rocker arm ratio is 1.65:1 and the compression ratio is 10.0:1. Ignition timing is set at 32 degrees at 4,000 rpm and maximum revs are 5,600 rpm. Ford recommends the use of an Edelbrock Super Victor intake manifold (PN 2924), long headers and a Holley® 850 CFM carburetor. The firing order is the same as the 5.0L HO and 351W firing order: 1-3-7-2-6-5-4-8.

Which models have the Ford 460 crate engine? The 460 was used in Lincolns, Thunderbirds, some Mercury models, and F-Series trucks and E-Series vans. You’ll typically find a 460 in LTDs, Torinos, Rancheros, and Country Squire cars.

In the five decades since Ford’s 460-cubic-inch “Lima”-series V8 first debuted under the hood of the 1969 Lincoln Continental MKIII, the mighty slant-valve big-block has built a solid reputation for durability and ease of modification. Although factory high-performance development peaked in 1971 with the 370-hp 429 CJ-R, you don’t need a rare muscle car core engine to get plenty of power.

Thanks to the fact that Ford started stuffing 460s into pickups and Lincoln luxury barges in the smog ’70s, there are millions of core engines available just waiting to be plugged and stroked into top-notch street and strip performers. And thanks to Edelbrock’s Power Package top-end kit, the usual guesswork involved in choosing the right combination of heads, cam and induction is eliminated. Let’s see how Donnie Wood and Steve Chmura of R.A.D. Auto Machine turns a 460 into a stubby 501ci stroker with over 500 lb-ft of torque from 2,300 to 5,300 rpm.

See All 20 Photos See All 20 Photos The Ford 429 and 460 blocks have the same bore diameter of 4.36 inches, but juggle stroke to add 429 (3.59 inch stroke) or 460 (3.85 inch stroke) cubic inches receive. Any sound 429 or 460 block can be converted to our 501 with a .0305″ overbore and 4.3905″ bore diameter. However, note that Ford 429/460 blocks come in three different deck heights: 10.3000 (1968-1970), 10.3100 (1970-1971) and 10.322 (1972 onwards). Each subsequent increase in deck height lowered the compression by about one point as Ford entered the smoggy seventies. Make sure you know what deck you have before ordering parts to avoid piston to head contact and unwanted compression ratio errors. Our 1971 block has a deck height of 10.3100 inches machined to .010 inches.

And thanks to the replacement of the heavy cast-iron heads and header with lightweight aluminum, the end result weighs about the same as an all-iron 351, so it doesn’t impede rearward weight transfer to the slicks or the front axle sinks into the mud, like may be the case!

See All 20 Photos See All 20 Photos The Eagle Stroker Kit (PN 15015) includes crank, rods, pistons, rings and bearings. The forged steel 4340 crank (82.2 pounds) accepts flexplates from automatic transmissions and flywheels and shafts from manual transmissions. The 4.140″ stroke is .290″ longer than a standard 460 and .550″ longer than a standard 429.

See all 20 photos See all 20 photos The pin points to the rounded transition between the rod journal and the counterweight cheek. This premium feature eliminates stress risers that form at the abrupt 90 degree joints found on stock crankshafts. The bob weight is 2.185 grams, similar to a Chevy big block.

See All 20 Photos See All 20 Photos Although some 429 and 460 blocks have four-bolt main caps, this common two-bolt block is adequate for naturally aspirated applications with crank speeds of 6,000 rpm. Higher crankshaft speeds, forced induction and nitrous applications should use aftermarket Ford Racing blocks or – if you can find one – early 70’s Cobra Jet blocks to ensure long life. For this mild fun-in-the-sun build, the stock cast-iron main caps are machined to precision and then secured with standard .5-inch screws to 100 ft-lbs of torque.

See all 20 photos See all 20 photos The Eagle kit comes with forged rods and Mahle pistons with friction reducing skirt coatings. The 4340 bars (PN FSI6700) measure 6,700 inches center-to-center and are big-block Chevy sized at 2,200 big-end diameters. The tool steel pins measure .990 x 2.520 with a wall thickness of .180. Rings are Mahle (PN 4395 MS-16) 1.5mm/1.5mm/3.0mm with hand filed end spacings of .018 and .020 inches.

See all 20 photos See all 20 photos With the 28cc Mahle piston bowls and .010″ top cut, the compression ratio is 10.0:1 to the point. The gray coating on the piston crown reflects the heat of combustion to control detonation.

See All 20 Photos See All 20 Photos As a testament to the versatility of the Ford big-block – and the widespread popularity of cubic inches – this 501 is fitted to a 1979 Ford F250 4×4, hence the use of a truck-style oil pan with a rear sump. Not shown is the Melling M84D oil pump and extension tube required with the truck pan. The Eagle bars use ARP 7/16-inch fasteners torqued to 65 ft-lbs.

See All 20 Photos See All 20 Photos Using the many dyno hours Edelbrock has invested in perfecting their Power Package top end kit, R.A.D. chose kit number 2045 for 1968 1987 Ford big blocks. Included in the kit is a flat tappet hydraulic cam with 290/300 degrees advertised duration, 234/244 degrees duration at .050″ lift, .556/.581″ lift and a cam standoff angle of 108 degrees. With the host vehicle’s C6 automatic transmission, a stall speed of 2,500 rpm and a final drive ratio of 4.11:1, the camshaft complements the 501’s strong mid-range torque.

See All 20 Photos See All 20 Photos Also included in the Edelbrock Power Package top-end kit, the timing set features one-piece pulleys to eliminate the risk of pulley failure when using seam chain pulleys. The hand shows the stock 429/460 fuel pump cam which must be retained if a mechanical fuel pump is used. Builder Chmura says, “Some Fords have a one-piece fuel pump eccentric drive, others have this two-piece unit. The two-piece has less friction.”

See All 20 Photos See All 20 Photos Thanks to their aluminum construction, the Edelbrock Performer RPM 460 heads included in the Top End Power Package Kit shave over 50 pounds compared to stock iron heads. The 292cc intake ports are modeled after Ford’s finest CJ-R castings, but with Edelbrock’s added touch for even more flow. The 100cc flat bottom exhaust ports are a radical departure from the full oval shape seen on stock Ford castings. Edelbrock testing found that the smaller orifices deliver faster exhaust velocity for better scavenging of spent gases.

See all 20 photos See all 20 photos Edelbrock offers the Performer RPM 460 with 75cc (PN 60679) and 95cc (PN 60669) combustion chamber volume. We went with the larger 95cc chambers to get 10.0:1 compression with our piston and bore combination. All Edelbrock 429/460 heads feature large 2.19/1.76 (I/E) valves with hardened seat inserts for safe use with unleaded gas.

See all 20 photos See all 20 photos At 35.6 pounds, the aluminum heads are each 30.4 pounds lighter than a fully dressed 460 iron head (66 pounds). Fel Pro composite head gaskets were used (PN 1018). Thickness is .055/.041 inch (neutral/crushed).

See all 20 photos See all 20 photos The 429 / 460 V8 family of engines has two different lengths of head bolts: 5,060 and 5,750 inches. The Edelbrock Power Package Top End Kit (PN 2045) contains high-quality spare parts from ARP. Despite the difference in length, they all torque to 150 ft-lbs with a coating of molybdenum grease to prevent seizure and inaccurate torque readings.

See All 20 Photos See All 20 Photos To reduce friction between the rocker arm and valve stem tips, Scorpion 1.73:1 roller rocker arms (PN 1023) replace the stock Ford steel parts. These 8.680″ long, 3/8″ diameter pushrods are constructed of .080″ wall chrome-moly tubing. It’s the turn of the lifter preload. The Edelbrock-supplied valve springs exert 120 pounds closed and 310 pounds at .595 inches of travel.

See all 20 photos See all 20 photos The Shorty dyno headers have 1″ primary tube diameters and 2″ collector outlets. They are similar to those that get installed on the engine once it’s in the Ford F250 4×4 pickup truck it’s being built for.

See all 20 photos See all 20 photos Inexpensive and easy, a Spectra Ford Duraspark electronic distributor (PN FD03) fires the spark plugs. Ignition timing is set at 37 degrees BTDC.

See All 20 Photos See All 20 Photos Also part of the Edelbrock Power Package Top End Kit, the RPM Air Gap Dual Plane Intake Manifold (PN 7566) increases low-end and mid-range torque by giving both banks of cylinders equal access to the fuel mixture available in the joint plenum.

See all 20 photos See all 20 photos EFI may be crisper and quicker to start, but for price per dollar spent, carburetors are hard to beat. We chose this 750 cfm Brawler Four Barrel from Holley. Straight out of the box it delivered optimal air/fuel ratios without fiddling with the jets, let alone fiddling with a laptop.

See All 20 Photos See All 20 Photos The proof of the pudding: 518 horsepower at 5,200 rpm under light loads and a whopping 590.6 lb-ft of torque low down at 3,400 rpm. Even better is the availability of 500 lb-ft from 2,300 to 5,300 rpm. This makes the vehicle in question feel like it’s being thrown down the road (or strip or track) by a giant’s hand. Rounding it all out is the modest price tag of just under $8,000 in parts. Get a used Ford 460 and then turn it into a torque beast by following these instructions. You will not regret it!

4. Incorrect spark firing order

Today’s electronically controlled engines with coil-on-plug ignition systems essentially eliminate this problem – but on older models with ignition distributors and plug wires, it’s possible that your spark plugs are connected to the distributor in the wrong order. If the spark ignites in the wrong cylinder at the wrong time, this leads to misfires, among other things! This problem can also occur when the spark plug leads are crossed, for example after you’ve replaced your spark plugs – but again, modern cars have largely eliminated this problem. Hooray for progress!

3. Bent or damaged valve

As you can see, timing is critical to the safe and smooth operation of your engine. In interference engines, a type of engine where the valves open into the space soon to be occupied by the rising piston, these valves must close before the piston arrives. If the engine timing system fails, the pistons could hit the open valves, bending or breaking them. This prevents them from forming a good seal when closed and could cause the engine to backfire. While this type of damage is uncommon, it is very serious and will require a major engine service to get your engine working again.

You are getting in your car to start your morning commute when you suddenly hear what sounds like a gun being fired! But hunting season is over and you’re sure it wasn’t coming from a neighboring yard – so what was that loud POP!? It’s not a gun and it’s not a firecracker. It’s your car that’s backfiring!

This explosive sound is scary in itself, but it’s even more alarming when it’s followed by a loss of vehicle performance. If you’re wondering “why is the popping backfire on my car,” read on to learn what’s causing the noise and how to deal with it.

How your engine works

Your car’s internal combustion system uses flammable liquids, air, and controlled explosions to power your vehicle. Misfires occur when this system isn’t working as it should, which is why understanding how the engine works is important to figuring out why your car is misfiring.

Here are the basic steps your internal combustion engine follows to convert fuel and air into horsepower:

Step 1: Ingestion

The intake valve on your fuel cylinders opens, drawing a mixture of fuel and air into the engine.

Step 2: Compression

The intake valve closes and a piston compresses the air-fuel mixture mentioned above.

Step 3: Combustion

When the mixture is fully compressed, a spark plug “fires” electricity into the air/fuel mixture, igniting it in a small, controlled explosion.

Step 4: Power Stroke

The gases from the air-fuel combustion push the piston back in what is known as a “power stroke”. This reaction pushes the crankshaft, which activates the gears and ultimately turns your car’s wheels.

Step 5: Exhaust and Drivetrain

The exhaust valve opens and closes, allowing smoke and combustion residues to escape through the tailpipe. The entire process repeats itself while your engine is running, with multiple pistons and cylinders working together to spin your bus (or car) wheels all the way around.

So why is my car failing?

Typically, a misfire occurs when one of the above explosions occurs outside of your fuel cylinders. Some misfire travels back to the intake valve, while others exit through the exhaust system – causing a type of misfire known as “post-ignition”. Post-ignition can sometimes result in visible flames shooting out of the tailpipe. Oops!

Backfire and post-ignition should be considered as they can cause engine damage, loss of power and reduced fuel efficiency. There are a variety of factors that can cause your car to misfire, but the most common are a bad air/fuel ratio, a misfiring spark plug, or plain old-fashioned bad timing.

Poor air/fuel ratio

Proper fuel to air ratio is critical to proper engine combustion. If there is too much of either, you can have an engine that is ‘running rich’ or ‘running lean’ – neither is a good thing.

When an engine is running rich, it has too much fuel and too little air, which slows the combustion process. If combustion is not timely, the exhaust valve will open while the air/fuel mixture is still igniting, causing this explosion to “slosh” out of the cylinder and create a loud popping sound.

On the other hand, an engine that is running lean has too much air, which also retards combustion and causes misfires. If you think your vehicle is running too rich or too lean, have your engine checked by a trusted Firestone Complete Auto Care expert. We are looking for the following troublemakers:

Faulty oxygen sensors

On newer vehicles, computer controlled sensors help ensure the air/fuel ratio is correct. However, if a sensor fails, it can change the air/fuel ratio and cause sluggish or delayed combustion. If this is the case, your Check Engine Light might be screaming at you.

Leaking exhaust systems

Exhaust system leaks, sometimes referred to as vacuum leaks, can sound more like a squeak than a pop as excess air is drawn in. All that extra air mixes with the fuel and creates the wrong ratio for proper combustion.

Dirty air filters

Even something as simple as a dirty air filter can potentially trigger a kickback. Because air filters allow clean air to enter your engine, a dirty filter can restrict airflow into the intake and create a poor air-fuel ratio.

Faulty injectors

Injectors that deliver too little or too much fuel to the cylinder can also create a poor air-fuel ratio.

misfiring

Spark plugs that fire out of sequence or do not fire at all can also cause misfires. Short circuits in the wiring, incorrect wiring, or damaged distributor caps that deliver the charge to the wrong outlet at the wrong time are much more common in older vehicles. But even in newer cars and trucks, connectors can fail or wear out over time due to carbon buildup.

Bad timing

In the four steps of engine combustion, timing is everything. If the timing isn’t right, valves may open or close at the wrong time, and the spark may come early or late. Any time the fuel-air explosion isn’t properly compressed, ignited, and contained, a misfire can occur. “Bad” timing is more of an issue in older vehicles with timing belts and catalytic converters. Newer engines with computer controlled timing are more reliable and less likely to misfire.

Why do cars fail to shift gears?

Not all misfires occur when you start the engine. Sometimes it can happen when you shift gears. However, the loud pop you hear when shifting gears is actually afterfire. Most of these occur on manual vehicles that use a clutch to shift gears. Depressing the clutch and shifting from one gear to the next can still allow fuel into the cylinders, especially when shifting at higher RPMs.

All that unburned fuel collects in the exhaust and ignites when you let go of the clutch. While this may sound alarming when it happens, post-ignition when shifting will not necessarily damage your vehicle.

Fire up your engine on all cylinders

Does the sound your car makes when you start it remind you of fireworks on the 4th of July? Then it’s time to take care of those combustion problems! Visit your local Firestone Complete Auto Care or book an appointment online for help troubleshooting engine misfires.

The Drive and its affiliates may earn a commission if you purchase a product through one of our links. Continue reading.

According to EFI Systems marketing, carburetors are prone to cold starting problems, poor fuel economy and complicated maintenance. And while they’re not as efficient as modern fuel management systems, they’re certainly not as bad as many make them out to be. A well-tuned carburettor can be just as roadworthy and smooth to drive as a fuel-injected car.

That doesn’t mean you don’t need to know a carburetor, though. As a classic car owner, you need to spend some time under the hood making adjustments to ensure the system is running properly.

Don’t worry. You don’t have to be a rocket scientist to set a good baseline. You also don’t need to know the intricacies of carburetor theory to keep your historic ride going. Plus, you’ll enter the ring wearing weighted gloves while The Drive’s crack team stands ready to arm you with the knowledge you need to make that thing purr like a kitten.

Carburetor Basics

Estimated time required: 30 minutes to an hour

Difficulty level: beginner/intermediate

Vehicle system: fuel delivery

What is the adjustment of a carburetor?

So what exactly are we customizing and why are we customizing it? To be honest, this article is all about making adjustments to your idle mixture and RPM. The reason for this is that this is the one thing that most carburetors have in common. Although they look different and handle full load conditions in different ways, most rely on the same basic principles for setting idle conditions – even the methods of making adjustments are very similar.

The main goal of these adjustments is to achieve the appropriate engine idle speed while ensuring that it runs as smoothly as possible. In this way you establish the correct fuel-air mixture at idle and establish an excellent basis for further tuning.

Keep in mind that a carburetor supplies air and fuel to the engine differently at idle than it does at full throttle. In short, as soon as you step on the gas pedal, separate systems and components come into play. They too must dial in. But before you get into that, you want to make sure you have all of your idle settings so all of the systems come together to determine how the vehicle behaves in park or neutral and what it has to work with while you’re leaning in.

You can make these adjustments with the external idle speed screw and idle mixture screws. Remember that the location of these screws is different for each carburetor model, so you will need to refer to your specific carburetor’s manual to find their exact location. For example, Holley carburetors typically have the idle mixture screws on the side of the metering block, while Rochester and Edelbrock carburetors have the idle mixture screws on the front of the carburetor.

The reason you need to make adjustments is because the carburetor cannot. As the temperature, altitude and even the weather change, the atmospheric pressure also changes, meaning there is more or less air available to the engine. Because the adjustments you make are analog, the amount of fuel going into the engine doesn’t change with the atmosphere. So you need to adjust the carburetor to correct the running state of the engine at idle. Make sense?

Let’s get into that!

Observe manifold vacuum while making adjustments., Hank O’Hop

Carburetor adjustment safety

Unless you set the baseline, the adjustments you make to the carb will be made on the fly. While the pros don’t seem to mind, it’s still important to be aware of the risks before getting started. Be sure to follow these safety tips throughout the procedure.

Look for fuel leaks. Carburetors are found in older vehicles and there is always a chance of fuel leakage. If you spot one, make sure you deal with it appropriately before proceeding. Even a tiny misfire is enough to start a gas fire at the distributor – ask me how I know that.

. Carburetors are found in older vehicles and there is always a chance of fuel leakage. If you spot one, make sure you deal with it appropriately before proceeding. Even a tiny misfire is enough to start a gas fire at the distributor – ask me how I know that. Keep your fingers away from the motor fan. Most of the time you work away from the fan. However, there is always a risk of coming into contact with it and injuring yourself.

. Most of the time you work away from the fan. However, there is always a risk of coming into contact with it and injuring yourself. Keep away from hot surfaces. Some parts of the engine can get hot enough to cause a second or third degree burn. The carburetor itself shouldn’t get anywhere near these temperatures, but you should still be mindful of hand placement while you work to avoid burning yourself.

. Some parts of the engine can get hot enough to cause a second or third degree burn. The carburetor itself shouldn’t get anywhere near these temperatures, but you should still be mindful of hand placement while you work to avoid burning yourself. Never put your fingers near or in the opening of the carburetor. When the engine is running, it can backfire and send a fireball through the carburetor. The resulting flame and pressure can cause serious injury.

. When the engine is running, it can backfire and send a fireball through the carburetor. The resulting flame and pressure can cause serious injury. You work with moving parts and strong chemicals. It is advisable to wear safety goggles and protective gloves to keep skin and eyes intact while working.

Everything you need to adjust a carburetor

We can’t tell you what you have on hand, but we can tell you won’t need much to make adjustments to your carburetor. In fact, the only tools you really need are a screwdriver and your ears. However, if you are looking for a simpler method that will positively determine the operating condition of your engine when tuning, you should expand your collection.

Tool

screwdriver

vacuum gauge (optional)

AFR indicator (optional)

Organizing your tools and equipment so that everything is within easy reach will save you precious minutes waiting for your handy dandy kid or four-legged helper to bring you the sandpaper or blowtorch. (You don’t need a blowtorch for this job. Please don’t let your child give you a blowtorch – NB).

You also need a level workspace, such as a a garage floor, driveway, or street parking lot that is also well ventilated. Check your local laws to ensure you are not violating any codes when using the road as we will not disrupt your ride.

How to adjust a carburetor

Let us do this.

Remove the engine air filter. The air cleaner and filter assembly must be removed to access the carburetor. Locate the adjustment screws. Before you begin, familiarize yourself with the location of the idle mixture and idle speed screws. (Optional): Connect vacuum gauge. If you are using a vacuum gauge for this procedure, you should find it and connect it to a manifold vacuum fitting before starting the engine. (Optional): Set baseline. If the carburetor is new or has been rebuilt, you should set it to the “factory” setting. You can do this by adjusting the idle mixture screws 1.5 to 2 turns out and the idle speed screw 1 to 1.5 turns in. Let the engine warm up. Engine operating temperature is directly correlated to proper air and fuel mixtures. So be sure to run the engine and allow it to reach normal operating temperatures before proceeding. (Optional): Adjust the idle speed screw. If you set a baseline in step 4, chances are a bit high when idle. Be sure to set it so that you start at normal engine speed. You may need to do this during warm-up if the idle RPM is too high after a “factory spec” reset. Adjust the air-fuel mixture. Begin by adjusting the idle mixture screws in or out in 1/8 turn increments. If you have more than one idle screw (most two- and four-barrel carburetors do), be sure to adjust each in direct proportion to each other as you proceed.

Holley idle mixture screw location. , Hank O’Hop

Rochester idle mixture screw location., Hank O’Hop

Observe the condition of the engine and proceed with the adjustment. After each adjustment, allow the motor a few seconds to adjust. If it gets rough or the vacuum drops, go in the opposite direction with the idle mixture screws. When engine speed settles down or vacuum increases, continue turning the screws in the direction you were until maximum engine speed or vacuum is reached.

Adjust the idle mixture until you get the highest steady vacuum reading., Hank O’Hop

Test the engine at idle and revving. Once the peak operating condition is met, rev up the engine and monitor the condition as the RPM drops back to idle. After revving up, the idle state may change and you may need to repeat steps 6 and 7. Adjust the engine idle speed. Idle speed will increase when proper adjustments are made. Once you have reached optimum operating condition, adjust the idle speed screw as needed.

Holley idle speed screw location, Hank O’Hop

Rochester idle speed screw., Hank O’Hop

Sometimes you need a certified mechanic

As much as The Drive loves to put the “you” in do-it-yourself, we know that not everyone has the right tools, job security, free time, or the confidence to tackle major auto repairs. Sometimes all you need is quality repair work done by professionals you can trust, like our partners, Goodyear Tire & Service Certified Mechanics.

Pro tips for adjusting a carburetor

Here are The Drive’s pro tips for adjusting your carbs.

Proper ignition timing is important to keep your engine in peak operating condition. Keep in mind that modern idle devices usually require more advanced timing, and you can expect to increase the initial timing by a few degrees to get the best results.

Don’t make the mistake of assuming the float bowl levels are fine. Any time you make adjustments, it’s a good idea to check and adjust the fuel level to ensure the engine is idling and otherwise operating properly.

A factory reset isn’t always necessary, but it can be useful. Especially if you don’t know the current running condition or the carburetor is brand new or newly reconditioned.

Even when a carburetor is brand new, it still needs adjustment. Your engine, its condition, location and weather all play a role and the carburetor needs to be properly adjusted.

Adjusting a carburetor is something you do frequently. It may sound silly, but sudden changes in weather and elevation affect the way your car drives. As the seasons change or you travel, you should adapt accordingly.

Tuning carburetors is more than adjusting idle mixture and RPM. If you want to partially improve performance and go full throttle, then you need to delve further into tuning the carburetor. This is where things vary by carburetor, taking you a step up from the beginner level of tuning.

Remember that idle speed screw. If you find that you have to do more than two turns to keep the car going, chances are adjusting the idle mixture screws won’t make a difference. If this is the case, the carburetor may need a thorough cleaning, or more advanced tuning steps may be required.

Carburetor FAQs

You have questions, The Drive has answers!

Q: How do you tell if a carburetor is rich or lean?

A: One way to tell for sure is to “read” the spark plugs. If the spark plug tip is white, the mixture is lean. If it’s brown or black, it’s rich. However, this method is usually associated with injection and off-idle carburetor adjustments, since these colorings come from partially and wide open throttle. At idle, a lean condition lowers engine speed. If it’s too rich you can generally tell by a strong smell and/or smoke coming out of the tailpipe. An AFR meter is a great tool for accurately measuring these conditions.

Q: How do I know if my carburetor needs adjustment?

A: Simply put, bad running conditions are a sure sign. A rough idle, poor throttle response and excessive fuel consumption are all signs to look out for. If the carburetor has been sitting for some time or has not been serviced for a long time, you may need to clean it first.

Q: How do you adjust the mixture on a carburetor?

A: Adjusting the mixture on a carburetor is done in a number of ways and the steps ultimately depend on the model of carburetor you are working with. At idle, however, most carburetors simply need to be adjusted with the idle mixture screws.

Q: How do you reduce the fuel consumption of a carburetor?

A: Making sure the carburetor is properly adjusted is a big step in improving fuel economy, but it’s not the only thing you can do. It is also important to tune the carburetor over the RPM range. In addition, since the system is mechanical, you need to practice driving habits that use less fuel.

Q: How do you check the air to fuel ratio on a carburetor?

A: The best way to check the air/fuel ratio is to use an AFR gauge. Tuning by ear or with a vacuum port are effective ways to determine running condition, but don’t actually read the air-fuel ratio. AFR gauges use an O2 sensor, just like modern cars, to provide an accurate and real-time reading. If they’re within your budget, these carb tuning tools are worth investing in.

Learn more about carbohydrate adjustments in this video

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