EVOM?
Billy Boat?
Agency Power?
Fab Speed?
X51 headers?

I find NO evidence that headers by themselves add any HP!!

If you guys have some independent DYNO tests that would be helpful.

Test
- Stock exhaust - ____ HP
- Stock exhaust with aftermarket headers. -_____ HP

 

Well on some cars the stock manifolds are very restrictive so headers makes power gains in all RPMS....but on 996's Porsche is getting like 95% of the power of the engine, so in order to see MAYBE 15-20 hp...you need to do intake, headers, cats, mufflers, ECU. Headers by themselves may LOSE you power in the low RPM range in order to gain you a few HP in the high range.....now if you want sound, then headers, sport cats and mufflers will get you a really nice sound.....

 

Forget about what a dyno may say or maximum power gains. Will putting a less restrictive exhaust on your car make it quicker from a stop to speeds above 100? Most likely not and it will probably be slower on a NA engine. You may get a little more power at the high rpm's, but if it takes you longer to get to that point, why bother? Without other mods, it is nothing but "bling".

 

Actually you're partly right, the volumetric efficiency (ve) of the m96 is about 83% per unit fuel used. A chevrolet v8 stock is around 60% ve, so adding headers to the SBC will add huge power gains, while the m96 already has headers stock and merely switching to a slightly better designed unit may add 3-5 hp on a good day. When the SBC engine is tuned to the same 83% ve, you're pushing 575 hp. In short, the H6 m96 porsche engine is already operating close to 90%, those last 10% ve numbers are the hardest to maximize. It's all about ve in racing engines, esp NA varients. Forced induction, via boost, can actually push beyond 100%ve.
Check out "The Chevrolet Racing Engine" by Bill 'Grump' Jenkins, it explains all the principals of building NA racing engines pushing 100% ve, a bit dated, but an excellent read.

 

Thanks for that !

 

I second TTsurgeons comments. Having driven Vettes for almost 20 years before my 2002 c2 I bought in June, I got Huge gains from headers on carburated smallblocks. Simply viewing the stock cast irons on a smallblock versus any good header system will demonstrate this. When I first had my c2 on the lift I realized I already had headers, the stock ones!! I do think 100 cell cats on a stock header setup would increase horsepower, but only about 10 HP more would be my quess.

 

How about going for headers that are lighter than stock and having them ceramic coated?

 

Have any of you besides deputydog95 that did a before and after dyno for headers? I have been hearing a lot of it doesn't do you any good but I have yet to see it proven.