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Old 05-30-2009, 10:57 AM   #81
Spectria, L1 MT
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Re: 4.3 CPI Injector replacement pictures

Quote:
Originally Posted by BlazerLT View Post
I believe those ports are for your EGR valve gas circulation and not your exhaust and that would explain the carbon buildup from a rich running engine. I wouldn't cause too much of a problem but it will be limiting the EGR gas going into the cylinders. No biggie but make sure you clean it out good. Been noticing any pinging lately?
I know this is late but I just noticed your note about the exhaust ports leading from the head to the intake manifold.

Those are to allow exhaust gas to heat the intake manifold to allow for better atomization of fuel in the intake, otherwize the intake would freeze up and fuel would condense in the manifold and not reach each cylinder.

This method has been used forever on v-engines. Later on they also tapped these ports for the EGR.

It is important that the passage be clean, and the new intake gaskets should have one small and one larger opening for these ports. this allows flow, otherwize the exhaust just comes up and sits in the manifold, condensing and hardening into what you see in the pics.
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