Intake manifold question

[Palimino]

Fairly new to this site but not wrenching on vehicles. My question concerns the coolant loop under the intake manifold, I am putting a 66 351 together, plan on adapting a TBI to replace the 2bbl carb, is the coolant loop that appears to run under the runners for fuel/air delivery necessary/required? Thinking of deleting this. Ideas/thoughts? Thanks

[Quigley]

I don't believe there is a coolant loop under the intake.

[Palimino]

The reason I asked is there is a smaller opening near the single port on each head that mates to the intake manifold that doesn't connect to the interior flow path where fuel/air runners are, and that's why it appears to be for coolant flow.

[tbucketnut]

I havent had my 305 apart yet but are you talking about the exhaust gas crossover? I was under the impression these manifolds were dry, no coolant.

[Palimino]

Those are the ones, just didn't know their function and if they were necessary, also thought they might be a vent from the crankcase?

[tbucketnut]

No the purpose is to route exhaust gases to the bottom of the carb for a better cold start operation. Many people block them off if they want to eliminate heat at the manifold for performance operation but your cold start warm up will suffer in the winter time. To work properly you need a heat riser valve on one exhaust manifold like this one ;;
https://www.summitracing.com/parts/oer-3887023?seid=srese1&gclid=EAIaIQobChMIioa83aKs5wIVg8DACh2mBQesEAQYASAB EgIE2fD_BwE

BTW, you dont happen to have a spare dent/rust free GMC oil pan do you?

[Palimino]

Thanks for the info Steve, not sure I will need this with the TBI I will be using in the future and the only oil pan I have comes with an engine attached. Joe

[tbucketnut]

Palimino, I sent you a message.
Steve