273 guys..Heads up!!!!

omahamoparguy said

I would not worry about blocking the heat riser. You gain very little form it really, AND, it makes it hard for the engine to warm up. I mean the intake is goin to warm up eventually anyway. The heat riser is there to make some vapors out of the fuel when the engine is cold. After the heat riser thermostat in the exhaust (if you have one) open up the heat riser has little effect on the intake manifold. You waste a lot of fuel by blocking the heat riser and cause some oil wash in the cylinder walls. I know everyone does it and I have done this in the past but now I have changed my mind on this after careful thought.

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I upgraded my car to a factory 4bbl manifold and 500 cfm AFB carb. Since then I've had the heat soak problem. I have to hold the throttle wide open and crank for a while to get it started when hot.

I have heard of two solutions. One is to partially block the heat rise passage with just a 1/4" hole to allow some gas to get through for warm up. The other solution is to install an insulating gasket (phenolic?) between the carb and intake.

I prefer the second solution for all the reasons you described. But I'm just wondering if it's enough to fix the problem. I would prefer not to have to pull the intake manifold back off if the carb insulator doesn't fix the problem.

Also, I have read that if you don't block this passage, the heat will burn the paint off the intake manifold. Don't want that!