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LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Header gasket port matching

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Old Jan 27, 2009 | 10:39 AM
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Default Header gasket port matching
Is it worth it to match your header gaskets to the headers or is it a waste of time?
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Old Jan 27, 2009 | 11:09 AM
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Originally Posted by moderate Z28
Is it worth it to match your header gaskets to the headers or is it a waste of time?
It's always worth it to make sure that your heads, intake, and headers are port matched. The unobstructed air flow is worth a couple of ponies. I have never done it though.
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Old Jan 27, 2009 | 11:47 AM
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I got the Percys gaskets and there very close. Only certain spots could be a little bigger. I wonder if my Dremel will do it?
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Old Jan 27, 2009 | 12:39 PM
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i wouldnt bother with it. too many things to screw up with porting heads. not so much exhaust but still
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Old Jan 27, 2009 | 01:50 PM
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As long as the gasket and header flange are marginally larger than the exhaust port (no lip obstruction) it's fine. Matching them won't net much performance.
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Old Jan 27, 2009 | 01:55 PM
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I would try to make sure the gasket and or header is not obstructing the exhaust port on the head. If the gasket is hanging into the exhaust port I would trim it back.
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Old Jan 27, 2009 | 03:29 PM
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The gasket should not hang into the passage, but having the header and gasket
larger than the head export interface is actually good for preventing reversion.
Artifically enlarging the exhaust port on a head isn't going to help you any.
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Old Jan 27, 2009 | 04:02 PM
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And just for those who don't know what "reversion" is, it's when the exhaust pulse travels back up the exhaust/header and back into the head, killing scavenging. If the header flange is larger than the port, it's like the pulse hits a "wall" when it gets back to the port.
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Old Jan 27, 2009 | 05:20 PM
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Originally Posted by James Montigny
The gasket should not hang into the passage, but having the header and gasket
larger than the head export interface is actually good for preventing reversion.
Artifically enlarging the exhaust port on a head isn't going to help you any.
Originally Posted by SprayedLT1
And just for those who don't know what "reversion" is, it's when the exhaust pulse travels back up the exhaust/header and back into the head, killing scavenging. If the header flange is larger than the port, it's like the pulse hits a "wall" when it gets back to the port.
I knew what reversion was already, but I didn't know that having a header and gasket larger than the head exhaust port helped prevent it. You never stop learning.
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