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anybody ever run round port headers on d port heads? leaks? what gaskets?
Sure, it is done all the time. The headers are not supposed to match the exhaust port, but should ideally be larger on all sides. This helps combat reversion. No way they should ever match. I feel bad when I hear about guys trying to match up their exhaust ports to their headers. How do you tell a guy he just spent a lot of time slowing his car down? The top NHRA Pro Stock engine builders don't even run a perfect match on the intake sides. That looks better on the flow bench (when you flow one direction, anyway), but we don't race flow benches. The number I hear most is about .060" larger on all 4 sides. That is the cylinder head runner larger than the intake manifold. That is for the same reason, reversion control. Since they (Pro Stock) run carbs, I was not so sure that applied to EFI, since booster signal strength is so important to them. In my limited testing it appears to work qually as well with an EFI car. Did on mine, at least.
Just use the gaskets that came with the headers, as long as nothing obstructs flow going into the headers. I use high temp, sensor safe silicone gasket sealer on mine. Exhaust leaks not only screw up your fuel trims, they kill power. There are also extreme duty header gasket out there that last much longer than what comes with most headers. Don't worry about the gaskets matching the heads, as long as they don't cover part of the port & the header will seal to them.
Good luck, Ed
Last edited by Ed Wright; Feb 5, 2005 at 08:37 AM.
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