I was wondering if any amount of backpressure is needed for the 4.3l when getting a new exhaust? I've always had a 4cl car and i know they need a sufficiant amount of back pressure in the exhaust or you will lose power. So i was wondering what a good size of tubing would be for an exhaust like 2.5, 3, 3.5?

 

Backpressure being required for an engine to operate properly is a myth. There can never be too little back pressure. There is such a thing as an exhaust that is too large however. Basically, you want the exhaust sized appropriately such that the scavenging effects are maximized. Scavenging is when one exhaust pulse pulls along the next as they travel through the exhaust pipes. Too large of an exhaust and the pulses slow down too much when they expand in the large tube and do not have enough momentum to aid the next pulse. This is what happens when people throw on a large exhaust and loose low end torque.

Unless you have done things to shift the power or torque higher in the RPM, you don't need anything larger than a 2.5 through out. The reason why the factory pipe necks down after the muffler is because of how much the exhaust gasses have shrunk due to cooling. Going 2.5" all the way will improve the top end without changing the low end.

A set of headers and a larger y-pipe coupled with a larger cam will really wake these engines up!

 

Good advice kyle sounds like what im looking for, good thing I looked before starting a thread!!!

 

alright thanks i was thinking about going to a 2.5 pipe anyways and later on down the road my dad has a spair 350 sitting in the garage from his nova and i was thinkin about buying that and his old B&M roots blower off him and putting that in there....

 

sounds like a sweet idea to me

 

yeah i know but that wont be for a while down the road i still have to pay it off first