I have a 350 with vortec heads and LT4 Hot Cam. Need to know what intake manifold to use. Should I a dual or single plane? If so, do you recommend a specific brand or have a part #. Thanks

 

Don't use a single plane intake, thats just old crap technology. Get a Edelbrock RPM Airgap Vortec intake. It will make the best average power of any intake out there. Or if you live in a cold climate just the RPM version with out the airgap.

 

An Edelbrock RPM Air Hap dual plane will be fine. Part number 7516 I believe. I have one that is port matched to my heads and it's a nice piece. Under 6500rpm, it kills any intake out there. More average TQ and HP throughout the rpm range.

As far as "old crap technology goes"...I'm leaning that way because it will add about 30hp on the top end compared to the port matched Air Gap. Super Victor Vortec

 

This is an interesting article about the rpm air-gap manifold. There also have been a couple of other articles written recently in other magazines and it looks like the air-gap is the best dual plane out there right now if your engine needs to go to 6000-6500 rpm's. The Victor Jr is good between 3000 & 8000 rpm's if you're looking for top end, but if most of your driving is on the street, why would you want a top end manifold.
http://www.popularhotrodding.com/eng...406phr_airgap/

 

Thanks for all the info and link.

 

What kind of car is this going into? If its a thirdgen, check out our local SoCal thirdgen club at http://www.sc3g.org/ We look forward to having more carbed cars involved.

 

Installed my RPM Air-Gap manifold (#7516) this past Saturday. I can feel a significant difference between the regular Performer I had on and the Air-Gap. My engine pulls cleanly to 6500 rpm, something I wasn't able to do with the regular Performer. I will try to get it to the track next weekend and see if there are any differences at the end of the 1/4 mile. Just for your info, I am also using a Hot Cam Kit with Fast Burn heads but this engine is in a 87 Monte Carl SS which currently runs consistent 12.90's at about 106 mph. If I can gain 2-3 mph on top end i'll be satisfied, I think this manifold will do the trick from what I can feel in the seat of my pants difference.........John

 

Very nice to hear! Did you do any port matching on the intake to match the heads? Looks to me like the intake ports were designed for a stock Vortec Iron head port size. If you ever do that, post results please I matched mine(and it required a lot of meat to be taken out) but never had any before/after results. Goodluck out there!

 

No I didn't do any matching. I didn't take any measurements, but when you lay the intake gasket on the manifold, there was room to remove some material. My theory is that the runners were formed to perform at the size they were made, what little gain would be made by opeining it up a bit would be minimal so I left well enough alone. Sometimes when you open things up too much you see no gain or I've read that you can actually loose a little also. I like the way it feels now so i am satisfied at this point. Maybe in the future if I do a cam upgrade I'll open it up a bit....John.......

 

Port matching is overrated, it does not significatly change power at all. The only place it matter is on a full out race car where they are trying to squeeze every last drop of magic hp oil out out the cast iron.

 

I have the normal non air-gap Performer RPM on my car under a 2" tbi and it'll pull to 6000 pretty good which is where my cam/heads no longer make any power. The July 2004 Hot Rod does a comparison of a bunch of Edelbrock manifolds and they liked the air-gap RPM the best.

 

Chey chuck all for those with vortec heads, what springs are you using? I had my heads machined to handle the the LT4-hot cam lift but have not replaced the springs. What would you recommend? Would rather have the ones that came with the heads replaced now then to have it fail once the engine is assembled and running.