I am not aware of it causing damage to a motor, but having no back pressure can cause you to lose low end power unless the motor is built for it.
Are we talking full pipes the length of your car, or zoomie headers? There's a big difference when your asking about engine damage...
It might not hurt your engine but it definately won't help it. If you do any long rides with it, you'll be exhausted by the time you get to your destination from listening to all that racket and it doesn't help with your gas mileage either. Straight/open pipes just scream "I Need Everyone To Notice Me!". A nicely tuned full exhaust just sounds so much better and it will help your engine run much more smoothly.
We've always heard stories that it'll bend your exhaust valves because when you shut off the hot engine cold air will crawl up there and shock the valves thermally.Never happened to me,,I never ran one that long as I can't stand the noise. There are ratrodders who drive their cars that way and I havent heard any damage stories. I do know one thing though, that happened to me, is that if the engine sits outside over an extended period of time or in a wet/humid environment,,,moisture will get into those cylinder(s) and cause rusting. That's the cylinders with the exhaust valves open (to the elements and no manifold or a short pipe for an exhaust). Like I said it happened to me and I lost an aluminum V8 that way (iron liners).
With zoomies cold air will certainly warp valves but everything has to be just right (or wrong) for it to happen. Back pressure...I love when that comes up. I'd like to challenge this post to someone explaining in professional terms how constricting an exhaust system builds power, high RPM or low RPM, and some of the associated dynamics. Now I'm pretty familiar with small engine requirements on that score since some mixture is pulled back in to help run the motor. I'm stopping there because we're not talkin about mini-bikes or lawn mowers here. Any takers?
I'd venture a guess that most of the responses here that say it's harmful are repeateing stories that we have heard over the years. I certainly heard it when we were trying to test start an engine with NO manifolds way back when. It never happened. If you can list a specific instance with all the details that caused the valves to warp on a perfectly good engine because you had short pipes, I'd love to hear about your actual experience. Until there are an overwhelming number of detailed cases proving this old wives tale, I will treat it as an old wives tale.
No, but drivin' habits associated having them on there can tax a motor to it's limits. If it's a hotrod, it needs straight pipes!. And ignore all of the negative (guessing) that reducing back pressure will result in a loss of power or 'warp' the valves on a 4-stroke automobile motor. I've never seen a warped exhaust valve. Seems like somebody that ran short headers and ruined their valves would have a picture of one?. Actually, allowing a motor to breathe by clearing obstructions in the exhaust pipe, almost without exception, will result in better performance.
The old wives tail about warped exhaust valves is just that, an old tail. It most likely came about from guys a long time ago doing short little straight headers and leaning out the motor to the point of burning the inferior material valves that existed back then and not realizing what really casued the problem. It was NEVER the cause of straight pipes per se. As for back pressure, that is also complete and utter Bull Shit. Highlander has it right here. The only time back pressure can help is in a system that is way too big of a diameter for the engine and back pressure can be a band aid, but a properly designed exhaust system will ultimately have as little pressure in the system and is possible. The idea behind a proper exhasut system is to extract the exhasut frm the cyclinders and dispose of it while not allowing burnt gases to reenter the combustion chamber during overlap. There is a lot of science involved with figuring out optimum diameters, lengths, timing of the two pulses (gas particles and Pressure waves) refracory waves etc. But "Back pressure" is Never part of the equasion when it's done right. PERIOD, End of Story.
I have them on my flathead... Noise isn't bad at all. My Flowmasters I have on some of my other cars are louder than the flatty straight pipes
Straight pipes.........Saves Lives.....No damage at all to any engine . only to your EARS. I would like to hear more on the street if the cops would use ear plugs..............Ol Deuce.......
I have run straights on everything I've owned and never had a problem one. I have never heard a car with properly installed straight pipes that sounded like shit or that was "too loud". It's definately not a rat rod thing. The baddest ass hot rods I've ever seen had straight exhaust on them, and Flowmasters and the like, are for gay muscle cars and jacked up ree-haw shit.
Hmmmmmmm??? well if straight pipes supposedly do damage, I guess we better get in touch with Harley-Davidson then, theres a lot of them with straight pipes in my neck of the woods. The Cop's never seem to bother them for noise. Michael
I have been running them for 5 hard years now with now problems!!! It only gets loud when you really get on it but idle and cruzing down the road not bad at all no louder than a flowmaster......
I've never had any problems. I have a straight pipe on my 52 Pontiac with a Flathead 8 and it's not even loud. My 64 also has dual straight pipes and I haven't had any trouble with it either. It's not loud at idle, just if i rev it up... cruising isn't bad either. With the windows up the sound in the car is just like having a mild muffler.
i have straight pipes on my 69 caprice! 350 small block. no mufflers! and an h pipe! not loud when it idles or when im driving! just when i get on it! been like that for 7 years! and no problems! i dont care what people think or say! its what i like!!!!!
Been running open, lakester headers on my roadster for 3 years. Knock on wood, no engine damage yet and I've driven her down the interstate at well below freezing and in 100+ degree weather (Are you tough enough?). Pretty loud at idle, really loud when you get into it, but as has been said, when cruising the hwy, it's really nice. I would suggest earplugs or turn off the hearing aids. In a roadster, on a long road trip the wind noise and buffeting are more annoying than the headers. After 3+ hours you are ready for a stretch and a cool one or a hot one or both. If it ain't loud, it ain't a hot rod and besides loud pipes save lives.
NO NO NO! Before asking a question, ask it out loud (to yourself) first and then think about it before posting such a question...
If the straight pipes are run out to the back bumper it is not loud inside at all. Even my edsel which runs open lake pipes that dump at the back wheels is not loud inside unless you are right next to a concrete divider or in a tunnel. When it's idling it is no louder than cherry bombs or smitthys and really only gets stupid loud around 3500rpm and up
Looks like this has been beat to death by now but I will chime in anyway. If the pipe diameter is too large and/or the pipes are too short, a given engine will see poorer performance, particularly at lower rpms. Have you ever tried to run an engine with no headers at all? They run like crap. You need a certain amount of flow to help scavenge. Similarly, the frequency of the reversion pulses changes as pipes get shorter or larger. Almost like a boat running through a canal. Some of the wake of the boat hits the walls of the canal and comes bouncing back. For a given boat speed, these wave reflections can interact with your original wave (wake) to cancel each other out, or to end up twice as much, and everything in between. This is what 'tuning' an exhaust is all about. Harley guys are the worst when it comes to going to open (no baffles) and larger diameter and shorter pipes. They look great and sound great but in most cases take away some performance. If this was the route to maximum power every race car would have super short, super large diameter exhausts - and these are modified motors looking for max power at elevated rpms. They don't, and that tells us something. That said, I swapped out the headers on the car in my avatar for a set of lake pipes. These are basically open although there is a rudimentary baffle at the outlet. I did lose low rpm torque but they look better and sound better plus you can see them pop at night when you back off the gas. Plus they leave nice soot marks down the side of the car, like a WWII bomber. So, in the end do what you want - just be aware of whatever baggage is associated with whatever you decide upon.
I've heard the same thing from people about the warped valves. I just wouldn't have them any other way. That's one of the things I really enjoy about hot rods, the rebel attitude!
The Jalopy Journal
