Hi,
I'm new to the forum & to Chevy V8's. Been playing with old British sports cars mostly. Now, I'm putting a 1988 TBI smallblock truck motor in an '85 Jaguar.
I've Been lurking here a while & learning what I can.
I'm currently taking all my accessories & TBI stuff of the old motor & putting it all on a goodwrench crate motor (pre '86) using a NAPA rebuild gasket set.

The question:
The rearmost coolant ports on my heads & on my intake manifold are full size & look like all the other coolant ports. The gaskets have these ports blocked by a metal plate that has about a 1/16 inch hole drilled in it. The plate is clearly stamped "rear port". I foolishly tossed the old gaskets without noticing how they looked. It looks like the plate could be easily removed, but I can't help wonder why it's there.
Can anyone shed some light on this?
THANKS!
Jim

 

The water flow to the heater core comes from back there; that restrictor plate limits that flow somewhat, to keep it from diverting too much flow from the radiator.

 

Thanks! I feel better now.
Jim

 

The rear coolant passages on the TBI intake are connected to the front passages by way of a water jacket around the TBI base. My conjecture is that GM wanted to cool the TBI.( The 454 TBI used a quadrajet intake with an adaptor which included a water jacket.) So, I further conjectured that in order to maintain a flow of water from the front of the intake to the rear heater supply, the rear passages were restricted. Just my guess.