[68 Firebird]

Years ago I picked up a factory 140 intake for a few bucks at the E-town swap meet.
I then had a winter project where I removed exhaust crossover and seperated water crossover
.
Did light gasket match and removed casting flash. Heck it looked awesome.

Made aluminum block off plates for head and installed. Well it worked too good!
After test runnning in garage on the area below Q-jet was cold!!!
After test run for 45 minutes it was barely warm. And she had slight hesitation
Going heavy throttle on take off. Even with 180 stat I was running.
Also Exhaust note changed and well I reinstalled the 9794234 and all
Returned to normal.

Have followed the repop aluminum thread and just know I would be sent one
with wacky ports. So my question is why not just buy the iron exhaust crossover
And try my modified intake again. Exhaust crossover would keep Q-jet choke
satisfied and some heat while transfer to bottom of intake. Just spitballing and
Have the 140 and crossover sitting on shelf as garage art!!!

Also I do like the look of the 2 piece intake as well.

Gerry

[b-man]

Pretty sure you’d find that the iron HO/RAIV crossover will hit the bottom of your intake.

The lower plane on the aluminum intake is shallower than on the iron intakes to make room for the crossover.

[68 Firebird]

Yup kinda was afraid of that.
Thanks

Gerry

[68 Firebird]

I thought the aluminum intakes were exact copies of iron.
Only exhaust was separate casting!!!
Bottom pics appears similar to my modified iron intake.
I may be wrong but just thought it might be doable.
Intake would get some heat, but not full force of heat.

Gerry

[Formulajones]

Ive had the thought that I could make that setup work and was in the process a few years ago but never finished the project. At the time the heat cross over parts were on back order and I didn't revisit it. Other projects took priority.

I tend to think that what might not clear could be clearances. There is a lot of meat there

[Goatracer1]

Years ago when I first started racing my GTO I removed all heat sources. The carb ran so cold that in the Fall I had to leave the engine running in the staging lane or the carb would frost up.

[Donovan]

Yes you can do that and would result in the functional iron equivalent of the HO/RA intake.

I did something similar with a 234 manifold. I also have a 71 455HO setup. Once you remove the extra stuff it's the same dimensions.

I don't own a 72 two piece setup anymore. But this had the one year only choke stove and it was also riveted to the bottom of the intake. If you tried to use that crossover, I think it might hit.

If you use the commonly reproduced 69-71 exhaust crossover you'll be able to do the combo on your modified intake fine.

[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.