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When taking off the intake I noticed blocking plates on the rear water channel ports on both the intake and the heads. Whats up with that? I thought it was a feature of the factory gasket but it isn't. There is a plate per port (4 total), easily removable. What would be the advantage of having those rear ports not have coolant flowing through them?
The factory gasket has a metal plate in it maybe 2. It's been a while. Iirc the front crossover runs through the length of the intake so it doesn't matter too much that it is blocked as coolant still makes its way back there.
Cool. I figured it didn't matter to much, I could tell water was getting through, just thought it was odd that GM would block it off....then again there are a lot of things on the '84 that have me scratching my head.
the front crossover runs through the length of the intake so it doesn't matter too much that it is blocked as coolant still makes its way back there.
If the rear ports are open, coolant will flow through the floor of the intake to the front/ t-stat housing. Warms the floor for less fuel puddling. If rear is closed....heat transfers through water pretty good, and like 84 4+3 said, it is open to the front crossover, so that water under the intake is going to heat up about as fast either way.
FYI, in my CFI car, I chopped that "under intake" coolant passageway apart and closed it off -trying to get a lower intake temp. It made no discernible difference. So ports closed or open, I don't think you'll notice a diff.
The rear ports should be blocked by the intake gasket.
In cold weather you probably activate the heater core.
The heater return hose goes to a port at the rear of the intake near the EGR valve and flow in the channel under the intake.
In warm weather when the intake does not need any extra heat there will not be any flow in the heater core.
'84 crossfire question
If the rear ports are open, coolant will flow through the floor of the intake to the front/ t-stat housing. Warms the floor for less fuel puddling. If rear is closed....heat transfers through water pretty good, and like 84 4+3 said, it is open to the front crossover, so that water under the intake is going to heat up about as fast either way. 
