Intake manifold advice for VORTEC style....

[steve cowan]

I have to believe......the more cfm a head flows......the bigger the demand for the single plane, no? Could the Airgap manifold in his testing done well because its so much easier to support 260 cfm, than if the heads moved say.....300cfm?

I agree,
I didn't test on my bench prior, but I suspect 30 cfm loss with airgap at a guess.
I was lucky as both intakes port match close. Air gap as cast,
Victor was cleaned up and carb flange to taper spacer matched.
Victor was quicker and faster in the eighth but air gap quicker in t60 ft.
I have a 300-25 as well, they look like a good casting.

[steve cowan]

I done a lot of testing this year at the track 50 plus passes and differences in air gap and single plane VIC JNR was 2 tenths and 2 mph up on the single plane.
The air gap was quicker in the 60ft by a few hundredths, this is after also testing a 830 annular, 950 hp and 850 race demon.
Best results were with 950 hp, would pull 1" vacuum through finish line at WOT.
Tried alot of different spacers, with the tapered you will have to blend carb base/ plenum area but then it will mess you up for standard 1"/2" etc spacers for alignment, something to consider.
On a linear acceleration scale my car ran well
383sbc
235-242 SFT
Dart 165cc heads out to 178cc. 1.94"-1.5"valves.
261cfm@550" in
177cfm@550" ex
3650 pound streeter
1.57
7.42 @ 91.50mph
11.71 @ 114.48 mph
In my opinion yours will run very well either way, air gap is not an issue to 6000rpm

Thanks for the testing Steve. I'd thought about trying a dual plane on my 421 but after reading your testing thoughts I think it would be a waste of time.

Hi Jim,
I think testing and reporting back helps everyone, application and expectations trump opinion, I think a modified airgap in a pure street application works pretty well, but I am partial to a single plane

[zums]

A stock super victor 2913 or gm vortec eliminator{same thing} will drop a 280-290 cfm head to 230 on some ports, the air gap would be even worse, as far as intake csa goes some quick dirty reference for the popular ones are vic jr smallest- 2913 larger, holley strip dom 300-25 larger then 2913, if you need actual csas post up and i will dig thru my notes tomorrow
Tom

[77cruiser]

I done a lot of testing this year at the track 50 plus passes and differences in air gap and single plane VIC JNR was 2 tenths and 2 mph up on the single plane.
The air gap was quicker in the 60ft by a few hundredths, this is after also testing a 830 annular, 950 hp and 850 race demon.
Best results were with 950 hp, would pull 1" vacuum through finish line at WOT.
Tried alot of different spacers, with the tapered you will have to blend carb base/ plenum area but then it will mess you up for standard 1"/2" etc spacers for alignment, something to consider.
On a linear acceleration scale my car ran well
383sbc
235-242 SFT
Dart 165cc heads out to 178cc. 1.94"-1.5"valves.
261cfm@550" in
177cfm@550" ex
3650 pound streeter
1.57
7.42 @ 91.50mph
11.71 @ 114.48 mph
In my opinion yours will run very well either way, air gap is not an issue to 6000rpm

Thanks for the testing Steve. I'd thought about trying a dual plane on my 421 but after reading your testing thoughts I think it would be a waste of time.

Hi Jim,
I think testing and reporting back helps everyone, application and expectations trump opinion, I think a modified airgap in a pure street application works pretty well, but I am partial to a single plane

Is your Vic. ported? Mine is so Thinking it might lose more yet with a DP.

[steve cowan]

Thanks for the testing Steve. I'd thought about trying a dual plane on my 421 but after reading your testing thoughts I think it would be a waste of time.

Hi Jim,
I think testing and reporting back helps everyone, application and expectations trump opinion, I think a modified airgap in a pure street application works pretty well, but I am partial to a single plane

Is your Vic. ported? Mine is so Thinking it might lose more yet with a DP.

Just deburred and open plenum to suit R and M tapered spacer,
Tom has good information there, I agree DP will hurt cfm for sure.

[econo racer]

At 3900 lbs. I would use a rpm dual plane.

[Roadknee]

Thanks for the testing Steve. I'd thought about trying a dual plane on my 421 but after reading your testing thoughts I think it would be a waste of time.

Hi Jim,
I think testing and reporting back helps everyone, application and expectations trump opinion, I think a modified airgap in a pure street application works pretty well, but I am partial to a single plane

Is your Vic. ported? Mine is so Thinking it might lose more yet with a DP.

Your car runs just under 12 flat and in a datalog you posted a while back 4 seconds were above 5500 rpm (top of 1st and 2nd gear) with 8 seconds below 5500 rpm. Your final pull in third gear is nearly 5 seconds long from 4600-5400 rpm. I think a dual plane with a good double pumper would make a big improvement on your car.

[randy331]

Or since the heads flow decent air, and it has a decent converter in it.....a single plane

I don't really think you should pick the intake by flow. Pick an intake that will support the rpm range the rest of the combo will make power at.

I'd hate to cripple a Decent cylinder head with a dual plane, if the dual planes only advantage was below 4500 rpm. Plan on shifting about 6300-6500 max.

From the dyno/track tests I've done and seen by others I trust, the cross-over where a single plane starts out powering a dual plane is 4500-4800 ish rpm. Below that rpm a dual plane has always been better,.. above that rpm a single plane has always been better. It doesn't seem to be related to anything but rpm so far. cfm - cubes - cam etc don't seem to matter, just rpm.

Hoping to make 475-490hp if that sounds realistic.

That's more than realistic I think. Pseudo made over 500 at the same cubes, close on cam, more comp, but... un ported small port vortec bowties heads.

If I was going to pick an intake for your combo, I'd put a Motown on it. It has had a better power curve than the other single planes we've tested it against. It has made more power below peak HP and the same peak HP. It has scored the best in EMC testing and that is the rpm range your working in.
The gm intake mentioned and 2913 eddy will run good too, but as mentioned it needs some porting.

With your combo and stall speed,... single plane all the way if I was doing it.

Randy

[77cruiser]

Hi Jim,
I think testing and reporting back helps everyone, application and expectations trump opinion, I think a modified airgap in a pure street application works pretty well, but I am partial to a single plane

Is your Vic. ported? Mine is so Thinking it might lose more yet with a DP.

Your car runs just under 12 flat and in a datalog you posted a while back 4 seconds were above 5500 rpm (top of 1st and 2nd gear) with 8 seconds below 5500 rpm. Your final pull in third gear is nearly 5 seconds long from 4600-5400 rpm. I think a dual plane with a good double pumper would make a big improvement on your car.

You remember that or did you find it? I don't even remember posting it here.

[Roadknee]

Is your Vic. ported? Mine is so Thinking it might lose more yet with a DP.

Your car runs just under 12 flat and in a datalog you posted a while back 4 seconds were above 5500 rpm (top of 1st and 2nd gear) with 8 seconds below 5500 rpm. Your final pull in third gear is nearly 5 seconds long from 4600-5400 rpm. I think a dual plane with a good double pumper would make a big improvement on your car.

You remember that or did you find it? I don't even remember posting it here.

Little of both. You posted on the Chevelle site.

[77cruiser]

Your car runs just under 12 flat and in a datalog you posted a while back 4 seconds were above 5500 rpm (top of 1st and 2nd gear) with 8 seconds below 5500 rpm. Your final pull in third gear is nearly 5 seconds long from 4600-5400 rpm. I think a dual plane with a good double pumper would make a big improvement on your car.

You remember that or did you find it? I don't even remember posting it here.

Little of both. You posted on the Chevelle site.

Thanks.Thought I was cracking from trying to quit smoking.

[CGT]

If I was going to pick an intake for your combo, I'd put a Motown on it.

Discontinued isn't it?

[steve cowan]

If I was going to pick an intake for your combo, I'd put a Motown on it.

Discontinued isn't it?

They say still available
But I think I will buy one just in case

[1980RS]

I have a 406 that I will be using to test 3 sets of Vortec heads on this year. 1st. will be bone stock Vortec heads with and dual plane, 2nd will be a mild ported set that flowed real well with the dual plane, then a ported Super Victor. 3rd, a set of the earlier 206 large port Vortec heads with some porting work with both intakes. I know that with my other 406 I tested 4 or 5 intakes and the Super Victor ported won out ET wise over all of the others. The 300-25 Strip Dominator made the most MPH and HP. The Air Gap came in 3rd, but this was well built 406.

[CGT]

If I was going to pick an intake for your combo, I'd put a Motown on it.

Discontinued isn't it?

They say still available
But I think I will buy one just in case

I think the vortec one is discontinued, maybe the standard 23 isn't