3.4L w/ 2gen 3.1 Aluminum heads needs good intake manifold

[donk_316]

Ok, Im swapping on some 2nd gen aluminum heads onto my 3.4 in my fiero. The combustion chambers are opened up to 32cc's and i have doubled up on the head gaskets and im running 11.5 compression. I need a good intake. Not worried about the plenum as i am building a dual throttle body and seperate plenums. The intake manifold i got with the heads sucks. Which manifold has the best potential for performance?

[v6h.o.]

you "doubled" the head gaskets?
like stacked two together? i hope not...

what size thickness of headgasket did you use?

the best intake manifold would likely be the 3400 lower manifolds from the 96-current engines.
BUT since thats a GEN3 intake you cant use this manifold.

your unfortunatly stuck with the Only GEN2 manifold, any 3.1L/2.8L manifold, which for performance sakes... are shit. what i would do if you are stuck using this manifold is what a member on here did. Franz reworked the lower manifold and made a completely custom lower that... well i shouldnt talk about it. its not my manifold. and he has yet to post pics publicly..

you should actually swap on some GEN3 heads. 3400 heads have 1.76 inch valves (compared to 1.72) and have the best flowing port designs of any 660 yet. that and the combo of the 3400 lower manifold would make great high flowing rpm power. or just the whole gen3 complete top end...

[donk_316]

Hey thanks for the reply. Yes i Doubled up 2 .059 head gaskets. Done a it a million times on SBC and BBC's. Im kinda stuck with these heads cause of my headers and so on.

I agree with you as far as the 3.1 manifold being shit. Unequel length runners and the factory plenum is rediculusly small. If i could i would use the fiero lower as it kicks the crap out of most of the ones ive seen.

Did the Camaro 3.4 ever come with 2gen heads? It had a "decent" manifold.

[bszopi]

The Camaro (well, any RWD for that matter) has never come with aluminum heads.

[donk_316]

So basically all gen2 intakes sucked ass then?

[Corpse]

Yes. I believe there was really only one intake/plenum setup made for Gen II. I dunno, maybe they helped the flow with the 3.1 plenum but, I have never noticed any difference looking inside the two.

So, if you use Gen II heads and you don't want to do something nutty to improve the intake setup, don't plan on high-output. It really is a horrible intake setup. Go Gen III. Gen II is a bad Generation to work with.

-Dave

[XLR8ING]

Genn III intake bolts on Gen II heads, but the ports don't line up right, and the Gen III uses thicker gaskets.
I've tried this, and it should be able to be done, but will require some customizing in a few areas.
Most importantly, Gen II intake ports are narrow and tall, and Gen III ports are shorter and fatter. Porting on both intake and heads can fix this for the most part.
The biggest problem I see is sealing everything properly. If you can get someone to TIG weld some metal on the intake it might work that way. Just a thought.
I gave up on my intake swap when I realized the intake gasket didn't work.

[donk_316]

Thanks guys, with the help of a forum member im currently swapping to a gen3 top end. Thanks again.

[XLR8ING]

Genn III intake bolts on Gen II heads, but the ports don't line up right, and the Gen III uses thicker gaskets.
I've tried this, and it should be able to be done, but will require some customizing in a few areas.
Most importantly, Gen II intake ports are narrow and tall, and Gen III ports are shorter and fatter. Porting on both intake and heads can fix this for the most part.
The biggest problem I see is sealing everything properly. If you can get someone to TIG weld some metal on the intake it might work that way. Just a thought.
I gave up on my intake swap when I realized the intake gasket didn't work.