On my truck it has a bunch of exhaust leaks on teh manifolds and cat air tube. I's wonderin what does this do to the engine am i loosing power? or torque? or burning exhaust valves? I know it sounds like crap and i bought a pair of headers and i'm gettin duals w/ glasspacks and echo tips for Christmas. What kind of gains can i expect with this. Its gonna have a x pipe at the cat.

 

I am no expert (read a few books and made a few purposful leaks in my muffler so it would sound like a truck), but I fail to see how a leak can do anything but help reduce back pressure. Some say too low of backpressure will burn a valve, but I have yet to be convinced. Too high of backpressure I would think would cause heat buildup and burn a valve. The only time a leak would be a problem is if it upsets the tuning of the exhaust system so as to reduce the cylinder scavenging effect. I kind of doubt that would happen with only a leak. Typically when someone drops all but the manifold and it runs poorly it is because there was a certain amount of tuning in the pipe and they destroyed it, not that they don't have enough back pressure. Now, if your engine had radical valve overlap you would need backpressure at low rpm to keep the fuel air mix from passing right through to the exhaust, but typically that is on a racing car and meant to be driven at high rpm which cures the blow thru problem by running everything much faster. Unless you feel a power loss I wouldn't worry about it, especially since you will have a whole new exhaust setup soon. (Seeing your name I must note this applies to gasoline engines. I don't know squat about diesel exhaust flow).

 

I have heard, on another site posting, that too much back pressure will increase torque but decrease horsepower, and too little back pressure will increase horsepower and decrease torque. Or it was the other way around. In any case, you sacrafice one for the other. There will be a medium in between to get the most torque and hp at the same time, I just don't know how they figure that out. Probably through extensive dyno testing and ising different size pipe, diff mufflers, cats, headers, tips, etc.

Ryan

 

For the most part, exhaust leaks make a lot of noise, however they do tend to unbalance the exhaust pulses and make each cylinder react just a little differently with regards to mixture (especially true with a "V" engine-unless you have equal leaks on both sides). A properly sized dual exhaust with x or h pipe and headers will add to both bottom end and top end. Yes it is true that an open system will help higher rpm power and sacrifice a little on the bottom, however the opposite is only true to a certain point, then you lose both if to restrictive-more hp than torque granted, but both will fall non-the-less. Your engine will determine thru cam, intake, comp. ratio, ect. what type of exhaust will gain you the most hp and torque were you want it in the rpm range. Having said all that, you can't go wrong with a free-flowing system even in a bone stock truck.

 

I's talkin to my machining teacher at school and he said that if you dont got at least 1 foot between the exhaust valves and end of the pipe, warped valves happen cuz wen ya shut the truck off cold air goes up the pipes and hits the hot valve, then warps it. I'm runnin open headers on my truck for the time bein' (waitin for duals next week) so i reckon it'll be ok. What can happen if ya stay with open headers for a long time on a 302?

 

> What can happen if ya stay with open
>headers for a long time on a 302?
Well, ya might get a ticket...

 

Because exhaust pulses,it pushes exhaust out and then draws air in through a leak.Its usually a small amount but if you have an O2 sensor down pipe of the leak(as you usually do)it will sense a lean condition and add more fuel to the mixture.This will reduce your fuel economy but the amount will probably be imperceptable.I fix leaks because I hate the sound.
Dave

 

generally speakin, if you loose back pressure you will loose some torque, but not enough that you will ever notice. i've burned/warped exhaust valves on a tractor due to no backpressure, but that was after probably hundreds of hours of use, and they graddually got worse not all at one time thing, so i think you will be safe.