Single vs: dual plane intake

Who was the one that e-mailed me about the Holley intake? I am still interested if you want to get rid of it. I am still searching if anyone else knows where I can get one. Thanks, Matt

 

terminology

Offenhauser uses the description "Offenhauser Dual Port intake manifolds feature completely separate runner systems for the primaries and secondaries"

Does this mean the same thing as dual plane??

I'm using one under an Edelbrock 500 cfm carb, seems to work well.

Van

 

Van: No, and yes they are a dual plane. I don't know if it was you, but a while ago someone said they were going to use this manifold and I would like to know what the outcome is. The Offy dual port has 2 separate runners on the "same" runner. The primary side is much smaller to maintain the charge speed of the primary charge. When the secondaries are opened up, the secondary charge follows the same path but thru a much larger runner. They meet at the head port and supposedly create quite a swirl there for good mixing of both charges. It sounds like a good idea. Glad it's working fine for you.

 

Jim,

I did ask some questions back a bit about Holley 390 cfm vs Edelbrock 500 on this manifold, so might have been me. Early times yet on the results, I've had several other issues to deal with in between, but so far I'm quite pleased with the Edelbrock on the Offy. MUCH easier to set up, better low end response and also a little more on the top end. May just be that I could not find anyone who could get the Holley set up right, dunno. But out of the box with no tuning the Edelbrock ran better than I ever got the Holley.

I've not tried a 4 bbl. before, but since several people talk about poor low end perf., I've got to guess the Offy IM has something to do with my satisfaction.

I'll know more in a few weeks, after some tough trails planned in July.

HTH,
Van

 

I ordered mine from Advance.

 

Van: Yea, I think you'll be happy with the Eddy Carb. They are basically just modern, updated Q-jets. Although 500cfm is a bit much for the 225/231 it doesn't really matter on the AVS carb. The secondary "air valve" will only open as much as the engine can such in air. Basically, the secondary is an infinitilly adjustable venturi secondary. Eddy's are also adjustable "6 ways from Sunday", so they can be tuned for anything.

Good luck with it.

 

Just for the record, I have an 84 EF 231 in my jeep. It has the holley 390 carb, hei dist powered with a msd box, outside the frame headers, stock cam, balanced and blueprinted lower end, and I am running the heavy odd fire flywheel rebalanced for the EF motor.

For a manifold I am running a Smokey Yunick single plane manifold, I think it is a weiand(SP?), don't really remember, got it free, just remember the Smokey Yunick name on it.

Anyway, I really want to try a edelbrock on it just to see the difference, because it really runs and performs well, can't really imagine it running any better. It has a very slight hesitation at part throttle when it is cold, smooths out as it warms up, very slight and just don't know if it is the manifold, or a timing or carb tune issue. As I said, would like to try an edelbrock, when I get one for around 30 bucks I just might!!

I have plenty of low end. I am running 4.88's but even with the Warn overdrive engaged (about 3.66 ratio after overdrive), it still has plenty of low end, talking high range here. Of course I am running 30" tires which helps. I imagine most others will be running larger tires. This is my daily driver.

My biggest driveability issue was the holley carb on hills. I installed the bowl baffle (whistle) in the front bowl, homemade a vent tube connecting the 2 vents (ala the truck avenger carb), slightly lowered the bowl float levels, and generally fiddled with the mixture, idle, and timing. I didn't get high speed and change any jets from what was in it. Someday I plan to, but with hopes of improving fuel economy more than more power. Anyway, those modes made it a real climber, not quite as good as a quadrajet (with which I have much more experience) but a huge difference from stock.

Bottom line, I wouldn't be scared of a single plane, especially if you are running lower gears. If you are slightly undergeared to begin with, then it might be more noticeable.

 

I give up, if I can't find one locally by tomorrow night I'm just going to order the single plane from Summit. At least I'll know it'll be bran new and not cracked. Then I'll get back to you'all with what happens with the pro-jection adaptation.