I would appreciate some well founded opinions concerning the performance of the new intake manifolds vs. the older ones.

I am running a dual plane aluminum hi rise now. It is an Offenhauser dual port 360 degree hi rise. Back in the 70's this was way out in front of other intakes, and was a highly prized intake for sbc's. I am also running a splash pan in my valley to keep hot oil from hitting the bottom of the intake.

I have been told that I should be running a RPM Airgap because it is of the newer technology and is a better dual plane manifold. Of course it too keeps hot oil from affecting the intake as well. But no one seems to be able to give me any real solid reasons as to why this manifold is really any better than the Offy I am currently running. I hate spending upwards of $200 just to see which is better.

At the same time I am really wondering whether my 350 might not be better served running a good single plane intake instead of a dual plane. I realize the dual is supposed to promote low end power and the single promotes high end power, but all I am concerned with is 1/4 mile times, not dyno results.

You can see what I am running on my signature down below. The rear gears are 3.73's currently, and rear tires are 28".

Any help out there?
Thanks

I won't speak to or offer an opinion on which is better. I am sure the argument for the newer intake is technology and research. The runners are designed to have more velocity etc...

From what I see in your signature, it looks like the prime candidate for a single plain, you have large heads for a 350, a big cam, manual shift, forged bottom end. I don't know about the dual plane that you are running but, to me a new RPM would be a mismatch for what you have now.

How high do you spin that engine now? Is that a solid or hyd cam? Looks like you built it for high end HP more than torque so that's why I don't understand the dual plane intake. Seems like a mismatch (IMO).

I am running solids, and shift her at 6500 with peak torque at 6300

That's about what I thought, seems to me a single plane would be a better match. I am sure others will have input on this.

I seem to remember that the Offy Dual Port was just that!! It was made such that it had two ports in each intake runner and was, (I think), made like a dual plane..

A smaller top port for the front barrels and a larger bottom port for the rear barrels..

Is your manifold made like that or is it made more like a regular single plane intake??

I also think OFFY made a 360 degree open plenum dual plane they called the Port-O-Sonic 360. It looked kinda like a dual plane except the runner walls were held back so that it in essence was a single plane.

I have a feeling that if you like the way you run now that you probably have the 360 intake.

I have an old Offy cat. but as usual can't find it!! I will say that I think Offy has made some really good manifolds AND they are still good if used like they were meant to be ran, imho... Even to this day sorta thing...

Please come back with more info..

pdq67

all I am concerned with is 1/4 mile times, not dyno results.

I would change a few more things than just the intake manifold, like the rear gears and the tranny. 3.73 gears with 28" tires are costing you a lot of time. At 120 mph you are only running 5500 rpm, surrendering all that power above.
I made a 505 hp 350 and put it in my 3600# simulator car and it ran 11.88 with 3.73's/M22, 11.21 with 4.56's/M22, and 10.96 with 4.56's/M20.

Yes mine is the dual port 360 degree that has the runners divided top and bottom. Rather a unique design. My son has a RPM Airgap on his 350 and its quite different.

I run through the traps at about 5780 rpm @ 124 mph.

Single plane intake and more gear as onovakind said.

Boy, I sure wouldn't have thought Offy's old Dual Port 360 intake would run as good as you say!!! BUT it was designed to keep port velocities really high which at those rpm's it should really be doing which promotes max. torque production!!

I always thought that the D/P-360 should really be more like the old E-brock SP-2P which is a torque producing economy intake but apparently from what you say Offy has/had the dual runner concept figured out VERY WELL, imho!!

Yes, you will be better off with a modern dual plane AND I would consider besides the RPM, a Holley 300-36 or a Weiand Stealth if you can get a price break on either.

AND both of them are GOOD ones too!! (I personally lean towards the 300-36 intake)....

Or even the cheap RPM knock-off if you are low on bucks!

Now before we get started here on the merits of d/p vs s/p intakes, I'm saying this b/c I honestly feel you will gain more midrange torque then you will gain top end power if you switch to say a Victor Jr. single plane intake..

BUT after you telling us how good the D/P 360 is running, you may not gain as much mid range as you would if you were running say a Performer???

So maybe a Victor Jr. will do you well???? Sorry, I just donno???

Please come back and tell us how it turns out..

pdq67

I agree with more gear but, that was not the question. I am sure a lot of people would suggest less cam, smaller heads etc...

Sounds like he is running pretty stong with the gear he has.

Are you squeezing it? If so, I would stick with the gears you have.

nope, no bottle, just motor. How about the Weiand team 'G' single plane? Anyone had any luck with those?

I had a good conversation with an engine guy on the team G 7525 single plane manifolds yesterday. Supposed to have the normal idle characteristics of a dual plane in 383-406 applications. His first hand experience was good power both low end and at high RPM. He said that with his 383 he had power over 7300 RPM using that manifold. He also said his power brakes still worked good which was my concern. Bad part is that that P/N is discontinued but can be special ordered. He had two of the 7525's in his shop but they were the last two available at Summit.

Team G is a good choice.IMO

What are your ETs and 60's like with the Offy? Your MPH is awesome . . . I'm tempted to say leave well enough alone!

In theory it looks like a good application for a Vic Jr or Team G. I generally have heard more good about the Vic Jr than the Team G. The tEam G has slightly smaller runners than the Vic Jr which would in theory help your midrange over the larger runner single planes. A Vic Jr or Team G could be a good thing for your combo, but I know nothing about the Offy you have now.

I probably just muddied the waters a little - sorry. smile.gif

I have an Offy Port-O-Sonic on my .030" over 330 64 Olds F-85......well it came with the car, but it's ancient tech. Sounds like a modern dual plane manifold, with your 6300-6500 rpm range, would be a good match. If going to the 8000 rpm range, go single plane......IMHO.

As others have suggested, I'd agree with them, Vic Jr. You'll lose alittle at lower rpm, but to fix this, have your muffler shop make you a set of 18 inch collector extensions.

Bolt them on one day at the track, paint a white stripe front-to-back, run all day, look for the paint discolored, cut there with hacksaw. Now you've gained back some low rpm torque.

Do the same to your axle shafts next time they are out of the housing. Paint a white stripe the full length, lightly scribe a line, install axle. The next time your doing rear axle maintainence, the scribed line will be a telltale sign of axle twist. I say this because of 500 hp, 28 inch tires, probably min 9 inches wide, 3.73 gear, and last, but not least, 4-spd. You gotta be doing some hi-rpm clutch dumps.

As Eric68 suggested, if it ain't broke don't fix it! 124 mph is awesome! But still, a gear change would be on my list, to maybe a 4.30:1. Theorywise, one should cross the finish line at the same rpm as peak hp.

Theorywise, one should cross the finish line at the same rpm as peak hp.

You want to exceed the peak power point by several hundred rpm at the finish line. This will assure you of having produced the highest average power.

OK, I stand corrected.

Thanks! Hey Everett, sweet 68 there

I found a Weiand team 'G' Air Gap single plane, anyone here have an experience with one of those?

If you are talking about the 7530 team g, that is what i have on my 388. Seems to work pretty well, although I haven't compared it to anything else on this engine. The casting quality wasn't very good though...every port had some very rough areas in them, but they was easy enough to clean up with a die grinder.

yes I believe its a 7530. Thanks graemlins/thumbsup.gif

Picked up a good used 7530 Team G Weiand for less than 1/2 the price of new, so am going to try that. Now I have to wait for summer to see the results................UGH I hate winter
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