74Runneer

Do i keep the the crossover passage or plug it up?? I have a 74 318 with headers and dual exhaust, 600 cfm 4 bbl carb, mild cam, 302 casting heads ported and polished, and an edelbrock performer intake. When i took my heads in to get a valve job they suggested that i plug the crossover passage because I only drive it in when the weather is nice out and he said i could gain hp by plugging it. BUT, I have heard from many of you guys that i should leave it because it will keep the fuel in suspension, and maybe it will help with my bogging issue. But that issue might just be from my carb (needs to be rebuilt). Let me know what you think! Thanks

440roadrunner

Not all that familiar with your weather up there, but I would tend to lean towards plug it.

This is a CHANGE from my former thinking. Today's fuel, all of which contains some alcohol, has changed this thinking.

74Runneer

The coldest weather it sees is probably 60s or high 50s. But usually in the 70s.

TVLynn

It heats the intake for quicker warmup's Won't fix any driveabiilty problems

74Runneer

Okay thanks! Will I see performance gains if I plug it? Colder denser air = more power?

440roadrunner

You need all the help you can get with "today's gas". I'm now running Holley TBI injection, but before I pulled off the carb, the biggest help to hot starting was:

Installed rear mount electric pump and eliminated the mechanical pump

Installed a fuel vapor return system. Use Wix 33040/41 fuel filter.

Installed a thick isolator gasket, available cheap through Summit, etc, but I found one right down at O'Really

Ed carbs are probably worse for fuel boil, because the float bowls are down low in contact with the engine. Holley bowls are "up" with some air circulation

Many think that aluminum manifolds "dissipate heat" but this is not the case. The SOURCE of heat is the heads and engine, and they simply transfer heat from the hot heads, into the intake, and being aluminum, it heats up pretty fast.

There is no advantage between iron and aluminum manifolds for fuel boil.

74Runneer

440 Roadrunner, so are you suggesting that i plug the passage? I currently dont have any troubles with hot starts at the moment. Are your suggestions for engines that have trouble with hot starts?