[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?

[Formulajones]

Yeah pretty much.

Ive run just about everything here without a heat cross over, even when I lived in ohio as daily drivers and never had any drivability issues. No icing if the carb or anything like that.

The bird is the first and only car that I've run a separated heat cross over, because it's factory designed that way if you run the OEM aluminum intake setup. With the cross over and it's heat shields it still does a pretty good job of isolating heat from the intake. A noticable difference just by touch compared to the iron setup that has heat blowing right through it. I've also noticed an improvement in the summer here in Arizona with hot starts and today's crappy pump gas. It's much better than the iron piece with a functional heat cross over. Plus aluminum does a better job dissipating heat anyway.

[Donovan]

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?

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.

[68 Firebird]

Yeah part of me wants to try it with the separated crossover.
Sure it would reduce heat to carb and intake overall.

Gerry

[Formulajones]

The only reason I run the separated cross over on my Firebird is because I wanted to keep the divorce choke functional. Even though we're in Arizona and it gets over 100 degrees, we also see sub freezing temps when the sun goes down and since I drive this thing year round, it's nice to have the choke. I always thought it was kind of neat that Pontiac has a factory setup like this so I take advantage of it.

Otherwise I'd just block the cross over all together like I do on most of the other cars here.

[68 Firebird]

Thanks for taking the time to provide your feedback.
Much appreciated. Thinking I will just take the plunge and see how it goes.
I do like the look of the aluminum intake!!
Be safe

Gerry.

[68 Firebird]

anyone install a 9796614 intake in a 68 Bird with Ram Air Pans??

Gerry

[Formulajones]

Can't imagine it would be an issue given the fact that it's no taller than a factory iron intake.

I installed it on my 70 RAIII Formula and that RA air cleaner fit exactly as it did with the iron intake.