Quote:
Originally Posted by Tim Corcoran
I'm curious about the difference between filling the heat cross over in the heads with aluminum and eliminating the cross-over on the intake manifold. Wouldn't that have the same effect?
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since there are crossover passages in both center exhaust bowls, when you block it at the flange you still have the opportunity for crosstalk on the same bank.
fill the crossover ports in the head and it's fully isolated. You can hear a difference between all 3, the stock intact tract, the isolated banks and the full fill. It's not a huge performance difference in terms of power but would be relevant if you've ultra-tuned your engine in many other areas.
Obviously, both types of block-out will let the carburetor run cooler in any case.
For me in the south, I had done a lot to improve drivability in the heat. I had to chase this as it would vapor lock easily. Starting with a thick carb gasket, and moving through putting a large can fuel pump, insulating all the fuel lines in the engine compartment and finally swapping on the HO intake with no cross-over and block off plates, packing foil down into the cross-over ports. This really helped with top end full throttle back to back and just ease of starting after having parked for a bit.
I suspect the fuel formulations are just really volatile compared to the leaded gas of the old days.