Headers on 327

[Jim H.]

Hi Group,
Any suggestions on headers for my '65 327/350 Corvette? Installed 2.5" MagnaFlow exhaust system.Would like headers that require the least amount of modification to the exhaust system; good performance; <$400/pr.
Thanks,
Jim Hilton
43119
Colorado

[Steven B.]

Re: Headers on 327

Jim, I have used Hedman's twice on C3 street applications because they fit very well. make certain the ones you choose will accomodate all of your accessories like AC and generator/alternator. 'Used Hooker side mounts for the race car. If you intend to keep the headers/hedders on for sometime I suggest coating inside and out. You may want to do some research on the flow/back pressure for your entire system.

Steve

[Duke W.]

Re: Headers on 327

A "327 LT-1" configuration was recently test on a lab dyno with both headers and OE manifolds. Headers produced 8 percent more peak torque but only about 1-2 percent more peak power. That was, of course with open exhaust.

Now you put even the very efficient (for a 327) C2 2.5" exhaust system on the engine and you're adding about 3 psi exhaust back pressure at high revs. This is going to negate a good part of the wave dynamics scavenging that headers can produce with no exhaust back pressure on an engine with moderate to high valve overlap, and, in fact, since that effect is mostly in the mid range rather than the top end, headers and mufflers may actually reduce top end power relative to the OE manifolds because the exhaust from each cylinder has to be pumped through about 34" of relatively small diameter pipe rather than being almost immediately dumped into a 2.5" pipe, and there is little harnessing of wave dynamics at the top end. You need a very high overlap racing cam for that - a cam that would be utterly ridiculous for a good road engine.

Bottom line - don't screw up your car with headers. They won't do much for engine performance with a reasonable road exhaust system, but they will fry plug wires, increase heat transmitted to the cockpit, leak, come loose, drag on the ground...

If you want "more power" research "massaged heads".

Duke