Choosing an exhaust system
We start from the rear. From the end of the headers to the rear tail pipe, bigger is better. The bigger diameter pipe, the more straight, the less restrictive muffler, the better. If noise is an issue, you have to balance free flowing exhaust and power with noise of course. We’d recommend 2½-3” pipes, with a single “turbo”-style muffler on each pipe. Remember that the system must exit behind the car so exhaust gasses don’t enter the car at idle, it could kill you.
While choosing the rear part of the exhaust is simple in the sense that bigger is better, this does not apply to headers. Tube length and diameter must be carefully selected, because it affects power and at what rpm that power comes. When looking at the Hooker Headers site, a small block Chevy header would have either 1 5/8”, 1 ¾” or 1 7/8” outside diameter. A smaller V8 should choose 1 5/8”, a medium size V8 (like a 350”) 1 ¾” and big blocks from 1 7/8” up to 2”. Often when that choice is done, the length is given. Just like with carb size, header diameter should be conservative in 1500-6500 rpm car, but can be more in a 4000-7500 rpm screamer. And here the advice is clear, if in doubt it’s better to have too narrow and long pipes than too thick and short pipes.
Further tips on choosing exhaust, if we go out of the ordinary, is to buy headers that reflect the firing order of the engine. As an example the firing order of a Chevy V8 is 1-8-4-3-6-5-7-2. Cylinders 1-3-5-7 are on the left side of the engine seen from the driver’s seat. This means that the exhaust order in the Left and Right header becomes L-R-R-L-R-L-L-R, which is of course not optimal, L-R-L-R-L-R-L-R would be better. This can be obtained with headers where some pipes cross under the engine to the opposite site. We’ve not used them ourselves so how big the gain is we don’t know. And be warned if you buy them, the car doesn’t sound like a V8 anymore… The second tip is to insert a cross, let the pipes meet in an “X” before the mufflers, it evens out the pressure. Such “X” pipes can be bought, you don’t need to fabricate yourself.