Port/header interference
05-19-2005, 10:49 PM
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Join Date: Feb 2005
Location: near Sears Point Raceway CA
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Port/header interference My "Fast Burn" crate motor requires LT1/LT4-type exhaust header flanges because of its "D" shaped 78cc exhaust ports. 1-3/4" OD header tubes are the minimum to clear the D ports.
Only Edelbrock makes air-tube equipped headers this car needs to pass emissions tests. The Edelbrock tech said they use 16 gauge steel. The header pipes alternate between 1-5/8" & 1-3/4" to maximize scavenging effects. He said the 1-3/4" pipes will clear the D ports but the 1-5/8" pipes will slightly obstruct the ports. Two cylinders per side will clear, two cylinders per side will not clear.
But because the performance is generated upstream in the head, the four non-cleared ports won't decrease power. The only issue is the sealing, solved with Fel Pro gasket #1407, which will require some minor trimming.
I can't help but think the non-cleared ports will impede performance. What do you folks think?
Only Edelbrock makes air-tube equipped headers this car needs to pass emissions tests. The Edelbrock tech said they use 16 gauge steel. The header pipes alternate between 1-5/8" & 1-3/4" to maximize scavenging effects. He said the 1-3/4" pipes will clear the D ports but the 1-5/8" pipes will slightly obstruct the ports. Two cylinders per side will clear, two cylinders per side will not clear.
But because the performance is generated upstream in the head, the four non-cleared ports won't decrease power. The only issue is the sealing, solved with Fel Pro gasket #1407, which will require some minor trimming.
I can't help but think the non-cleared ports will impede performance. What do you folks think?
