I replaced my original intake manifold with a new Edlebrock over the weekend. There are the exhaust passages that heat the bottom of the manifold / choke etc?.... What have some you used to block the passages?
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I have blocked the heat passages in past engines, and I DO NOT recommend it! It only resulted in rough idling and poorer performance. This modification is performed on engines that are ran at the drags or road races on 90+ degree days, out in the desert. On a 'street' engine, this mod will not only slow the warming-up of the choke and the engine on cold mornings, but will cause 'hard starting', less efficient fuel atomization which keeps the fuel 'droplets' out of suspension and lowers fuel economy and washes the lubricating oil off of the piston rings and will cause rapid ring, piston and cylinder wall, wear. Since 'Heat is Energy'(Horsepower)your engine will be making less of it. If you still insist on blocking the passages, don't bother 'driving' aluminum blocks into them! They will only disintagrate over a short period of time. The best, long lasting way, is to just slide a very thin (aprox. .020")sheet of Stainless Steel UNDER the intake manifold gasket and only covering that Port on each side. One of the best improvements you can make for increasing Horsepower (and Torque), is to create a 'Cold Air Induction' this will account for a true 10% increase!! That's 33 Horsepower on a '71 Engine! P.S. You can also add a 1 inch thick phenelic (plastic) spacer under the carburater, for heat insulation.
Thank you Marlin for your advice. Just to be accurate, the ports I'm speaking of are on the intake side of the head. The intake manifold covers just a tad of the bottom port. Since I posted yesterday, I've spoke to several people on this issue. They have said that those are register ports and are created at time of manufacturing and they do nothing. Hmmm.
...Yes! There are 2 Small ports, CENTERED, on each Intake side of the head, one above the other!(I'am assuming we are talking about Cleveland Heads). The Upper port Is 'Nothing'. The LOWER port is your crossover for exhaust gases. Goos-Luck with it!
Marlin your right, those are the ports I was talking about. I went over to my friends shop and he had a wide-body over there with the same set-up as mine. His ports were open also. Thanks for your help!