[JCs70]

i am building a mild 454 .30 over for my 70 chevelle, 10.25 compression cast crank, oval port heads, not the peanut ports.(they are off a 427 vette) roller rockers, 552, 555 lift cam. It also has a 6speed and 3.73 rear MSD ignition. My question is what is the best intake to run for this engine n setup. I was thinking about the Performer RPM Air Gap, but im not sure if i should use a dual plan, i know it will give me better top end, but my engine will not be very high revving, any help would be great. I also planned on using a holley street avenger electric choke, vaccume secondaries. Somthing around 700cfm. If any one has any advice i would greatly appreciate it. This is my first engine i am building. Not bad for a 19yr old kid. Also...i dont know much about my cam, here are the specs, if someone can help me out it thank you...

Lift .552int - .555exh
Dur @.050 int230, exh236
Adv. Dur. int.274, exh.286,
Lob Sep 110

Thanks again. Josh

 

[greg_moreira]

As far as the intake goes, the rpm is the way to go. Whether it be the regular rpm, or the rpm airgap doesnt make a lot of difference to me. Both are high rise dual plane intake manifold and either fall in line well with your total buildup. The performer rpm and the performer rpm airgap is basically the same intake, however the airgap has....well.....an air gap to better isolate the carb from heat. Sometimes its worth it, sometimes its not, but I dont imagine a huge difference by any means. If you have the hood clearance and a couple extra bucks, the airgap will do. If not, just the perfomer rpm(non airgap) is plenty fine.

The cam specs are nice for a mild street 454 and you could pull it off with a good half point less compression, but it should still run on pump fuel on a good tuneup with the current compression.

More about intake manifolds.....both of those are dual plane intakes as I was saying. Dual plane is typically the way to go for a street motor as they provide better low and midrange with some added throttle respons. A single plane intake manfold(like the edelbrock victor intakes) are intended for higher rpm useage/better high end power. One of those would not be necessary on your motor cause you would never see the benefit of a good single plane on top of that motor cause the rest of the engine will run out of steam before the intake can really show its stuff well. So, all youd really be doing is giving up some low/mid range torque without gaining much(if anything) in the horsepoer dept.

The regular performer intake(not the rpm) is also a dual plane intake....but it is a low rise style. Id say that manfold doesnt quite have the guts to do your motor justice. Its better on real mild, mostly stock type applications so either one of the performer rpm intakes will do best for you.

I probably didnt need to say all that.....but eh well...I figured Id lay it all out anyways just in case any of it was useful to you.

 

[Whittaker]

I had tried the 770 Street Avenger on my car when it was a .30 over 454 and I fell short on the top end. I use a 870 SA now jetted down a bit. You can get bassically the same carb as an 850 as a take off from the ZZ502 crate engines. I had one with only $200 or so in it. But I liked the Street Avengers looks.

 

[Motorhead62]

I would use the Performer RPM air-gap. I also use an 870 avenger on my Chevelle and I like it.

 

[SS4speed]

Josh,

I think that Greg hit all the facts just where they should be, that's solid advice. With a Manual, you can always go more carb, but as you stated, you want it streetable and you don't plan on revs. So, I would stick around a 750 CFM for that size engine. No need for a 780 or above, as it sounds like you don't plan on breaking the 6K mark. On intakes, (as others here) I have become a fan of the RPM airgap, not to mention it fits under most hoods without any problem. For the RPM and being on the street, with those gears, you will like the Dual plane intake imo. Especially if you drive in any traffic or have a lot of stop lights around.

Fred.

 

[Motorhead62]

Your engine combo is very close to mine. The XE274 has a very nice lope at idle! The 870 Avenger is the way to go. I get 14 MPG on the highway with no overdrive. I love the driveability of the carb. It is the best vacuum secondary carb I have ever used. In my opinion the 700 -750 is too small.

 

[ak69]

The dual plane RPM is the right way to go, and the 770 avenger is the match for it. I put mine back on the car to slow it down at the track, still ran 11.58 ET with this carb.

 

[JCs70]

thanx chris, just curious, u said our setups were very close, u have any performance numbers for your motor. Just kinda tryin to get an idea...thanx Josh

 

[SMS]

I vote for the Weiand Stealth. Tony at AFR said this intake made more power than the air-gap on AFR heads.
Steve