I have firm belief that the cause of burned valves with short pipes is due completely to human error, lack of understanding and poor judgement. I believe this myth has been perpetuated by actual 'evidence' of having burned valves but the attribution of the cause is incorrect. He has a hot rod he builds. He uses the engine out of an old Camaro that had glass packs on it.
When it's all done he drives it around and it's loud. One day he tears his heads off cuz it's running crappy and discovers burned valves. He looks over at his friend and says, "Damn short pipes. The builder had heard the story, was warned by his friends that his pipes should be longer, ordered them anyway and learned his lesson. Now he is preaching the gospel and telling all his car friends and everyone on the message board about how he put short pipes on his 'ride' and they burned up the valves.
They looked like burned brussel sprouts on the end of black sticks. His testimony is revered by his crowd because his rod is the baddest one and they go on and wash, rinse, repeat the story.
Perpetual motion myth. It even generates it's own energy. The guy with the burned valves jetted his carburetor incorrectly and set his float level too low. He didn't set his timing correctly either and had a late spark right at TDC, not before. The lean condition combined with a late spark left some of the lean over oxygenated intake charge still burning when his exhaust valves began to crack open.
The still slightly burning superheated exhaust gasses from too much oxygen in the AFR from incorrect carburetor settings slowly overheated his valves and they deteriorated over time until they began to even crack a bit. At that point the performance drop off was noticeable enough where dude began to look into it.
After months of troubleshooting he finally tore the heads off and discovered burned valves and gave attribution to the short pipes rather than his lean mixture and retarded timing.
I agree with DucatiKiller that straight pipes by themselves are not to be blamed; if the valves are prone to getting burnt there is clearly another issue going on. I don't have practical experience to support this, but fluid dynamics theory would suggest this is the case.
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Active 4 years, 3 months ago. Viewed 6k times. Jonathan Musso Jonathan Musso 4, 9 9 gold badges 23 23 silver badges 51 51 bronze badges. I've heard this from people to. Interested in what people say. I really don't know for sure, so will leave a comment I've seen too many engines, and I'm talking engines with grunt, where people are running straight pipes out of them I mean, look at all the rat rods with the stubby pipes on them Maybe without any pipes on them Active Oldest Votes.
I gotta say it's not likely to be a burnt valve. These engines seem to be mechanically pretty bulletproof. If the valves don't provide a complete seal, for whatever reason, the hot gases are forced past the valve which eat away or burn away the edge of the valve due to concentration of heat and pressure.
Mostly cause I can't think of any more. Incorrect Valve Seal - for whatever reason wear, weak spring, valve lash etc - reduces the quality of valve-seat contact and hence impedes heat dissipation through conduction to the head. Also, as the seats wear choice of materials and the valves recede into the head, valvelash is lostwhich leads to the same, improper contact.
A burnt valve can happen for one of many reasons, but the underlying issue is, the valve is not sealing correctly and allows hot engine gases during the combustion phase to leak past the seal which is formed by the valve and seat. When the seal is lost, the hot exhaust gases escape past the valve can happen to either the intake or the exhaust valve, but is much more common on the exhaust and wreak havoc.
The burnt valve is usually not the cause of the issue, but more so the outcome of a different issue. Valves in and of themselves could not stand up to the extreme environment of the combustion process. When a valve closes and is sealed against the seat which is embedded into the headone of the salvation factors for the valve is heat transference.
The head absorbs some of the heat which is collected by the valves. This heat is then transferred out to the coolant system, which takes it away from the area and allows things to run as we consider normal. This causes several different problems within the engine:. A valve can get into non-sealing state for several reasons. These might include, but aren't limited to:.
Any one of these can cause a valve to stay open during the combustion event, which allows very hot gases to escape past the valve. Since it is not allowed to fully seat, there is nowhere for the excess heat to go. It stays at the valve head and damage soon occurs.We love loud cars that make strange noises even though they are harmful to our ears. There is just something about them that excites our senses as motorheads.
The flutter of a turbo, the whine of a supercharger or the grumbling of a straight pie exhaust can always turn heads. Since these sounds are so desirable, car enthusiasts spend loads of money on acquiring turbos and superchargers. However, the majority of us do not have that kind of money so we look for a quick fix.
In comes the straight pipe exhaust system, which is the easiest way to make your car sound louder. In essence, a straight pipe exhaust is an exhaust system that involves joining a pipe directly from the exhaust headers and taking it straight to the end tip without the involvement of a catalytic converter or a muffler at any point. Straight pipe exhausts are loud. Really loud. Which is why they are usually found in racing engines and performance vehicles.
These exhaust systems let exhaust gases flow freely from the engine allowing them to go in the atmosphere directly through the exhaust tip. These systems reduce back pressure from the engine which allows exhaust gases to flow freely and help the engine perform without hindrances. You get better fuel economy and slightly better horsepower. However, the size of the pipe is important. You need to get a proper analysis by a certified mechanic to get the best output for your car.
Straight pipes also make your car stand out in the crowd. You can apply a chrome finish to the exhaust tip to make it look appealing.
Various types of welding methods are used to give beautiful colors to the tip. You can find green, blue and red colored patterns on the tip that make it look highly appealing. Furthermore, you can go for a twin pipe setup for an even better aesthetic. In the racing world the more exhaust pipes you have the sportier your car is. That is why many modern sports cars come with quad exhausts instead of twin exhausts.
The straight pipe exhaust system lets out the true sound of an engine. Since there are no restrictions in the way like a muffler, the car sounds raw and pure.
However, you might have to rethink starting your car early in the morning as that would definitely wake your neighbors. Just like everything else in the world, a straight pipe exhaust system has its advantages and disadvantages. It is up to us to decide what to sacrifice and what to gain.
The H. Engine damage from running without exhaust system? Is that true or just some BS? All I really need it to run for is to warm up enough to open up the thermostat and get the engine refilled with coolant, finish setting the points, and testing out the carb.
BS in my books. About the only thing that might hurt an engine is to run with no exhaust manifolds at all and then when the engine cooled it could warp the valves. My two cents. MacMar 23, I was told back when, that the open exhaust ports no manifold or headers let cold air hit the valves when shut down, and could warp them as Mr Mac said.
Whereas the heated pipes would keep the atmosphere warmer til the valves had a chance to cool down. If its got headers or manifolds but no exhaust system, I wouldn't worry about it. BudJ63Mar 23, I've heard many times about the possibility of warping the valves HemiRamblerMar 23, Oh i hate that tale I'd bet the guy that started that owned an auto exhaust shop back in the 40s.
I tried on Harleys and my old big block Chevy My only concern would be running it too lean. After "sea trials" then you can break it back to just headers. Headers are just a good idea from a scavenging designe standpoint When will this old wives tale die???? It likely won't make any more power or cause your car to run any better or faster than if it had a properly designed, 'muffler equipped 'exhaust system either, but that's another matter.
The worst it will do is likely piss your neighbors off, gain you a few tickets for excessive noise and damage your hearing, but that's all! Last edited: Mar 23, Nope, it's crap. You have a big ol' hunk of iron that's real hot I don't buy it either. Have been hearing this for years but nobody can tell who it happened to.
This won't hurt normal use thereafter. Won't hurt the engine at all,,but it may sterilized the operator BeepMar 23, On certain '60s Ferraris it said in the Workshop Manual to take off the headers and run it without.Let's take a closer look at how they work! Valves are quite diverse and may be classified into a number types. When log lighter is burning, close the fireplace screens. This causes excess emissions begin to seep out of the exhaust pipe.
Running an engine low on oil will often burn one or more valves before the main bearings start to pound. Log lighter measures approximately Additional straight-pipe recommendations include: 20 pipe diameters for degree elbow, tee, filter, strainer, or thermowell;Re: Straight pipe water heater or use flex hose Dielectric unions or nipples are a must by code Wether or not to hard pipe it is up to you, but there's a fairly high failure rate on the flex connectors.
Automatic wet standpipe systems are the most popular choice. Restrain pipe and ensure there is no stress, shearing, or pulling on the valve. When the metal reaches the proper temperature, plumbing solder wicks into the joint between the pipe and the valve by capillary action and makes a watertight seal when it cools.
In this article, I have covered classifications of valves and functions of valves. If the engine is running very hot a lot of the time, then the oil could evaporate over time and travel through the PCV system, into the air intake, and eventually out the exhaust.
If you need to cut your pipe, cut as cleanly and squarely as possible. Now, it is true that such valve burning has occurred as a result of the exhaust mods, but it isn't due merely to a lack of backpressure.
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It's important to remember this is a measurement device and should be plumbed accordingly. Well, almost done. This valve has 1. My brother drove an F with a similar exhaust for over k miles, and again no burned valves.
Plug valve used as on-off stop valves and capable of providing bubble tight shutoff. A baffled exhaust, straight thru the middle still creates the reverse wave by virtue of the baffle.
According to the Burn Foundationoverscald burns occur annually in the United States. This is an easy solution to address the problem. I still can't wipe the smile off my face when I hear the sound this muffler makes. In vertical pipe runs, flow should always run up and not down. The head loss of a pipe, tube or duct system, is the same as that produced in a straight pipe or duct whose length is equal to the pipes of the original systems plus the sum of the equivalent lengths of all the components in the system.
Get a close-up, cutaway view of a stop valve, gate valve and ball valve, along with detailed explanations of how they work and advantages and disadvantages of each type.
Now push the angle stop valve onto the pipe as far as you can. Let's start with Valve definition. This area is for the optimum mixing of the gas and air. Look I like straight pipes like the rest of ya. Existing internal oil feed pipes that are not accessible outside of the building and do not have a fire valve, can have one added at the first point where the pipe appears internally.
Ill help you out man, more then likely the valves have been heated to many times and are now brittle. The keys and escutcheons are available in an array of beautiful, decorative finishes and include either a straight or angled valve.
Calculate and summarize the pressure loss in each section. Assume a 6" angle valve for Schedule 40 pipe size. When you screw the handle counterclockwise to close a stop valve, the valve stem presses against the water inlet toward the bottom of the valve.
Causes Of Burnt Valves Or Engine Valve Failure Explained
If your valve is soldered on: Cut the pipe just below the existing valve. This process is known as unsweating pipe. This is a basic plumbing process frequently used in improvement projects. If all you need is repeatability and are not concerned with accuracy the measurement is not for accounting purposesthe length of the straight runs can be less than in Isolation valve or service valve with screw.Log In. David Simpson, PE MuleShoe Engineering In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual.
Galileo Galilei, Italian Physicist. Teach me and I remember. Involve me and I learn. It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. Sherlock Holmes - A Scandal in Bohemia. Thank you for helping keep Eng-Tips Forums free from inappropriate posts. The Eng-Tips staff will check this out and take appropriate action. Click Here to join Eng-Tips and talk with other members!
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is it a myth that running straight pipes will burn up valves?
Join Eng-Tips Forums! Join Us! By joining you are opting in to receive e-mail. Promoting, selling, recruiting, coursework and thesis posting is forbidden. Students Click Here. Related Projects. Hello all. This is my first question posted and it's probably something that varies with each situation, but is there a standard requirement for pipe diameters up and downstream of control valves? I have a 3" line that drops approximately 15' down from a pipe rack and am leaving 3 diameters of pipe on the upstream side and 3 pipe diameters downstream of a 3" control valve at grade.
I have read that leaving 3 diameters upstream and 3 diameters downstream of a control valve is a good practice, but have never seen it mentioned anywhere else. Is this a standard practice or does it vary with different scenarios? Thanks in advance for any advisement in this matter.
In nearly every case the underlying intent is to prevent a swirling flow from "screwing" itself through a narrow opening and overriding the control function e. Pipe of the '30's and '40's was far rougher than today's pipe, and had a chance to dampen swirl. A persistent swirl in modern steel pipe will last for a few thousand pipe diameters. In plastic pipe it is a few tens of thousands of pipe diameters. Having said that, a LOT of people don't believe me story of my lifeand will fuss at you if you don't provide SOME straight pipe around a control valve.
I find that life is awfully short to fight this battle on every control valve and if the client wants some straight pipe I rarely try to educate them, I just call out "X diameters of straight pipe before and after control valve" on the drawings.It's not straight pipes that would "burn valves" or damage your motor, it is the lean condition that can result from changing exhaust systems.
Most of the current aftermarket 'straight pipes' do have some restriction in them. Usually enough to create the backpressure needed to keep the exhaust pulses moving the right direction. If it's something that you've modified yourself, and they are very short stop before the footpeg mount, etcthen it could be an issue.
If you have a fuel injected model, and it has a pyrometer or something similar in the exhaust side of the head, this can actually mess up the reading - so all EFI models aren't bullet-proof when it comes to tuning a straight-through exhaust.
Bottom line - are straight pipes 'good' for an engine? In most cases without other radical modificationsnot really.
Will they hurt an engine? In most cases, not much, or not at all. Are they the best way to make power? Not usually. Straight pipes or "drag pipes" won't burn your valves unless you grossly misinterpret the re-jetting of the carb and then burning a hole in a piston is more of a possibility than burning a valve, but you get almost NO benefit from drag pipes unless you are drag racing.
You've actually lost HP installing them. Without going into too much detail Install a quality exhaust system, you'll gain back the HP you've lost and then some I'm not sure about the V-star, is it fuel injected or carbeurated?How Car Exhaust System Works
If it has carbs then they need to be rejetted a bit richer to compensate for the faster flowing exhaust. You need to do that to get the best of the mod anyhow. I'm not sure about burnt valves, but I do know you can melt a hole in a piston from running too lean, been there and done that. BTW, fuel injection should be able to compensate, but I'd have a dealer check to be sure. The sole purpose of an exhaust system is to dissipate the heat away from the valves.
So in theory, the answer is no. The same volume of exhaust moves past the exhaust valves at the same temperature whether you have sound deadening or straight pipes. Back-pressure created by sound deadening devices does not contribute to a cooler anything. You're looking for that sound right? There are systems that do that and you don't need to jet or calibrate a thing.
Most of the aftermarket pipes I've ever installed came with jetting suggestions or the suggested jets themselves. Answer Save. Favorite Answer. Be sure you properly re-jet your carb or re-map your processor and you'll be fine.