My stock manifolds are leaking bad, and need new gaskets, perfect time to just swap headers (same labor). I will then be getting a custom exhaust installed within the week as well, but until then, i am sure the new headers will not fit my current system (unless I purchase an extended Y pipe connector). I am looking to cut costs a bit and just get the headers without the Y-pipe connectors (unless the exhaust shop cannot or will not build these for me).

Will it hurt my car in any way, other than illegal noise levels if i ran the headers open, not connected to my exhaust system? Can open headers shoot flames that may melt wiring or other tubes? It would only be for 2 days at most and I drive maybe 20 miles during that time. I'd be driving as low an rpm as possible, using overdrive the entire way.

I've been reading this will cause my engine to run much leaner, so IN the event this would be ok for a short time but the engine will run almost too lean, can i not disconnect the MAF which causes the ecu to run rich automatically? I was also considering a fuel pressure regulator and umping the pressure to 46PSI.

 

if you're talking about getting shorty headers, you run the risk of burning a lot of stuff up. just wait and do it right; open headers are way to loud for street driving

 

your engine requires a certain amount of back pressure .... like 1ADAN said the risk just isnt worth it... just wait the wk and do it right....

 

Just drive it normal. Open headers will not harm anything.

 

oldest old wife tale in the book...backpressure, it's not a 2 stroke!!!!!!!!! there's a difference between sacavenging, exhaust pulses/speed & backpressure. If you think backpressure is good, ram something up your tailpipes and take it for a spin to see how much faster it is

only risk w/ short open headers is warping the exhaust valves if they are chilled down suddenly by cold air.

 

so exhaust valve burning is complete myth also?

 

i never said it would be faster or increase torque thinking about the longevity of his engine life

 

no but it's not the result of something as ridiculous as too little backpressure. Apart from AF mixture issues burnt valves are usually the result of a thing valve (too many or too aggressive re-cuts) or another issue that reduces valve to seat time. This is when the heat gets expelled so if it's either sticking open or there is another reason for reduced seat time, that will cause a burnt valve.

 

honestly, and this isn't a personal attack but I have a couple questions

how old are you ?

where did you hear this ?

seriously, please answer those questions


Your engine is an air/fuel pump.

Try this experiment.

inhale as deeply as you can for a 3 count counting one-one thousand, two one-thousand ...

then, hold your breath for 2 seconds and blow out as much air as you can through your mouth in 3 seconds.

Then do the same inhalation process.

Next, take your hand, place it over your mouth and apply firm pressure, enough so you can still exhale a bit and the air escapes out of the sides of your hand. Now do the 3 second inhale and then try the exhale. What happenes when you go to take your second breath? Did you notice that since you could not expell all of the old air that you could not inhale as much volume because your lungs were still partially full of old air.

That is what back pressure does to your engine. If you can't scavenge out all of the exhaust gas then some remains, you can't fill the chamber with as much new, denser cooler air and thus make less power.

common sense clearly is in play here and thus why I'm serioius when i ask where has this back-pressure myth been started and from where was it heard. My own son said the same thing to me. That's when i asked him if I should pull the long tubes off of his LT1 and put back the stock manifolds.

he said that he read that misinformation on an automotive forum and when i asked him why did he think we got such large gains from long tubes vs the restricitve manifolds and Y pipe is when light shone upon him and he got it.

 

^^^ Agreed 100%

I was browsing the Avalanche boards the other day and someone talking about how true duals were bad because the truck needs a certain amount of back pressure to run. Years ago i'd have posted up that he was an idiot and needs to stop posting but this old myth is so wide spread that even the Mythbusters wouldn't be able to convince the general public that it's wrong.


To the OP, it'll be loud as hell but you'll be fine. I guarantee that the loud exhaust ticket won't be cheap though.

 

I worked at a shop and we had a tool to measure backpressure and we hooked it up on a car to see if the cat or muffler was restricted to the point of to much backpressure but it was a newer car and the recommended pressure was 2 lbs or less IIRC . The only reason I would not run true duals on a stock or mildly built 3rd gen is because the o2 sensor wouldn't read right .

 

just so my post was clear - my concern was with having high temperature exhaust gases (and possibly flames) exiting under the hood near wiring and other parts due to the shorty header length; i'm not touching on anything pressure related

 

running true duals won't matter for the O2 sensor since it only reads off the dr. side bank anyway. Duals won't change that. If there is a problem w an injector for example on the pass side, it won't pick it up. I had that issue, I welded a bung on the pass side and wired it so that i can swap between sensors. The malfunctioning injector showed up immediately.

 

I ran my car with open headers from the house to the exhaust shop 20 miles away. Only b/c I hadn't changed the front springs yet during my swap and it wasn't gonna be able to make it onto the trailer. It didn't seem to hurt anything but I did wake up the neighbors 2 blocks away. lol

 

torque im not sayin that you need to be as restrictive as possible and if anyone doesnt think that open exhaust can cause a burnt exhaust valve should read up on it a little more

now that said im 28 and probably have logged more hours under the hood of more vehicles then most 28 yr olds... im not sayin it will go to crap if you jus fire it up and take a ride... im sayin that if its gonna be a week before he puts an exhaust on it that could potentially harm the engine... your exhaust is like anything else... say fuel flow... more fuel is better right.... but only to a certain extent... the same goes with more free flowing exhausts vs. no exhaust

 

I am in no way saying you should be driving it around town but I don't think it would cause major problems for you to run it to the shop to get the exhaust put on. Just be careful and check your engine bay to make sure everything is out of the way.

 

That is a tool to measure if the cat converter is going bad, 2 PSI is very low and i'm sure in other stock applications the actual static pressure inside the pipe can go higher than that. The term "Back pressure" sounds correct in that application however it is not. You are simply measuring the static pressure in the pipe to check for a restriction. Some newer cars actually run a small restrictor in the downpipe to increase the static pressure in the exhaust manifolds, apparently it's some sort of emissions deal. I've seen a 2.5" downpipe restricted down to 1.75" on a GM 3400 V6 from a mini-van.


A properly designed exhaust system has a pipe size that takes into account for the actual power output of the engine, too large and you lose velocity, too small and you create a restriction. The idea is to maintain good velocity throughout the system while taking into account for other factors like space, weight, ground clearance, available mufflers and of course add-ons like balance pipes and X pipes. That is where scavenging comes in, with good velocity each previous exhaust pulse will actually help draw all the exhaust out of the cylinder making room for fresh air and fuel. That's where i believe torque_is_good was going before.


I agree with 1ADan, fire is also a risk.


mightymaro94, there are a lot of causes for exhaust valve failure like wear and tear, detonation, high combustion temps etc.. open exhaust is typically not one of them. With completely open ports (no header or manifold) it would be possible to warp the stem however with shorty headers of the common Fbody length it's extremely unlikely.

 

your all wrong hahaha

 

they really should instate an IQ threshold to be able to sign up here...dayum!

 

[quote=Purple82TA;4739053]That is a tool to measure if the cat converter is going bad, 2 PSI is very low and i'm sure in other stock applications the actual static pressure inside the pipe can go higher than that. The term "Back pressure" sounds correct in that application however it is not. You are simply measuring the static pressure in the pipe to check for a restriction. Some newer cars actually run a small restrictor in the downpipe to increase the static pressure in the exhaust manifolds, apparently it's some sort of emissions deal. I've seen a 2.5" downpipe restricted down to 1.75" on a GM 3400 V6 from a mini-van.
I believe IIRC it said 2psi was good with a max of 5psi allowable .

A properly designed exhaust system has a pipe size that takes into account for the actual power output of the engine, too large and you lose velocity, too small and you create a restriction. The idea is to maintain good velocity throughout the system while taking into account for other factors like space, weight, ground clearance, available mufflers and of course add-ons like balance pipes and X pipes. That is where scavenging comes in, with good velocity each previous exhaust pulse will actually help draw all the exhaust out of the cylinder making room for fresh air and fuel. That's where i believe torque_is_good was going before.
I totaly agree .

 

and these so called tuned headers & rest of exhaust only work in a certain power-band depending on design, nice for a roundy round car that runs WOT in the same range most of the time, useless on the street and practically impossible. The best you can do for your street motor is allow it to breathe and choose the headers that give the best compromise between fit and efficiency. not saying that tri-t's, necked down merge collectors, stepped primaries and such don't work but for a street car it's usually a waste of time.

 

well my exhaust system, once installed will be the same as the typical length on stock. Reading the backpressure thread basically explains what this will do so I am aware that the longer exhaust will be more tuned for low RPM usage. I spend 90% of my time between 1000-3000 rpm. It's a Daily Driver.

What i havent read up on yet is what wider exhaust will do to the pressure waves. My guess is the waves will be longer but just crest higher, which means back pressure will be reduced but not to an extent it could cause fresh air to flow all the way up the pipe against the pressure waves to disrupt my valves. is this close to being correct? Basically even if outside air had the ability to travel ALL the way back up my entire exhaust system and to my valves, by the time they hit the valves, the air temperature would be equal to or slightly less than the exhaust coming out. the A.I.R. system in a car already injects outside cold air directly outside the engine block already...

 

I didn't want to get into it but yes, you can design an exhaust that will reduce low end torque but help with top end HP or vice versa.

But, a fallacy that continues to poke it's head is the "you need backpressure" statement.