To those that think manifolds perform even in the same ballpark with a decent set of full length headers: You're wrong. No other way to say it. The dyno sheet above says about 20 hp & 25 lb-ft.; and thats on a motor that looks like its only making 320 hp. Immagine what the falloff is on a motor flowing enouth to make 500. I'm guessing its in the range of 40 horses.

Any race car you see that runs manifolds does so either because: A) class rules. or B) They like the look and are willing to deal with the lost performance. On most any typical carbureted V8, exhaust manifolds are the single biggest performance bottleneck in the equation.

If you don't like headers because you're experience is that they all leak and create problems; you likely aren't much of a Hot Rodder. A good set of headers properly installed (yes, it may take more than just bolting them on...) should not leak a bit. If you're having issues with burning plug wires: address the issues! its called Hot-Rodding, and it may take some ingenuity (thats the FUN part!).


Now, if you want to run exhaust manifolds and get the max performance out of a stock package (Pure Stock & F.A.S.T. guys are great at this), then thats another conversation all together. But to say that manifolds perform on par with a good set of headers is just plain Mis-informed. (and yes, I'll include the vaunted HP manifolds in that statement)