I am having a disagreement with a buddy with an LT1.On the same long block(say a stock LT1) which indution system would
make more power a stock LT1 intake with a 52mm t.b. or an
Edelbrock Performer RPM Airgap with a properly jetted holley
750dp.Power only mileage and tunability not included.

 

I would *guess* the LT1 intake because it's less restrictive and has more open runners/shorter runners.

 

power only? like peak numbers? I would say the Airgap would give you much better peak numbers, but the LT-1 would give you abetter curve alltogether (better streetability i suppose)

though the airgap IS a dual plane... its a big dual plane...
Yeah imma have to say bigger peak #'s for the airgap.

 

The short runners of a LT1 intake do not really completment the cam timing. The motor is peaking at 5500rpm.. that has Dual plane written all overit. If the cam was more oriented for high rpm, it would be much closer. Look at the GM LT4 crate motor that comes with a carb. Its rated at the same HP as the LT4 FI motor.

 

something to keep in mind...

single plane manifolds usually have better peak HP numbers than dual plane manifolds (usually).

the lt1 intake is nothing more than a very big, very short runner, single plane manifold.

would be interesting to see a cfm flow comparison of the two, but i can't imagine the performer rpm air gap having better cfm flow (considering the turns and changes in direction the air has to go through, and the longish runners) vs. the very short, very direct lt1 runners. plus the lt1 is a dry flow design, optimized only for airflow since it doesn't have to keep fuel in suspension. the performer rpm air gap is designed to keep fuel in the air, which can compromise the overall cfm airflow ability of the manifold.

 

<b>89rs w/a 400, some aluminum things and a 4.10 gear


and it sounds like this

idle.MPG</b>

okay, dude, I know a boat motor when i hear one.
make a video I can see then Ill beleive that!

 

So if an LT1 intake is a little better than an RPM Airgap,and an air gap is almost as good as a Victor jr..Then does that mean an LT1
is as good as a Victor jr.?

 

Carcraft
Test of a 350 using TFS heads and a XE268.
Baselined with a performer rpm. 397hp at 5700 (way above stock LT1 cam range) and 413ft/lbs at 4500.
Same intake with a tapered spacer, 407.7hp and 415ft/lbs at 4400.

Average torque (the best indicator of overall powerband) was 394ft/lbs from 3200-6000 with no spacer and 397.8 with.

Vic jr intake
Baselined at 407hp at 5700 and 404ft/lbs at 4900.
Average torque 388.9
Vic Jr with spacer. 408.9hp and 407.8 at 5000!!..
Average torque 390.1

Superchevy test was similar.
Tested on a solid cam 350 (with 250degrees at 050), the non-airgap rpm, a HVH dual plane, Vic JR and the HV1000 brodix intake.
The performer rpm made 419hp (at 6200) with a tapered spacer and the HVH intake make 429 (torque was over 400 from 4100 through 5200 and hp was over 425 from 5900-6400).

The vic jr made a best of 425 (with 422 from 6000-6400). And the HVH intake made 427. The vic jr only made over 400ft/lbs from 4500-5100 and the HVH intake at 2 points (4800 and 5000)

I doubt a HOT LT4 cam would favor the single plane better the this solid.

There was also the test of a 96 LT1 motor with a Qjet dual plane intake (jan97 hotrod). It made 366hp at 5250 (about the same peak that the FI LT1 has) and with the HOT LT4 cam made 422hp at 5750 (again, amost identical to the FI-LT1 with the HOT cam).

And the crate LT4 that GM offered in 96 that was rated at 421hp with a dual plane and the HOT lt4 cam.

I dare say that most 350s would need more cam timing that this, to see much of a benefit from a Single plane-LT1 type intake.

GM did not make the LT1 intake design for performance. It was for hood clearance.


boat huh..

not a lot of water in this file
rev

 

The XE268 is relatively close to the cam specs of gm's hot cam. in a similiar test to the first test you mention, a 350 with the fastburn heads and a hotcam makes around 420-430hp, so same ballpark as that TFS-headed 350. the info you posted showed that the motor did indeed make the most power with the most open intake, the spacered victor jr. now granted, the numbers are very small, but the question is which would make the most power.

now if you want to talk average torque, drivability, what makes sense, etc., then most definately the dual plane performer RPM makes good sense! you only give up 5-10 hp but gain torque and drivability and efficiency on the bottom end.

the only way a dual plane would make more power than an lt1, is if the runner size/length of the dual plane was such that it had some resonant tuning going on (like a TPI system), and it was at/near the HP peak in order to boost that peak.. Otherwise, that dual plane is just a bigger restriction than the single plane or lt1 design manifold. Same reason even stock L98's with majorly tame cams show nice gains when going to a less restrictive intake.

Back in the real world though, the question is kind of moot. a stock lt1 block doesn't need enough airflow to make either intake a signifigant restriction (were' talking differences of 5-15hp at the most), so for all intents and purposes they are kind of equal. there's been great street buildups on both intakes.

 

That why I said I was specifically referring to torque in my first reponse. Torque is what makes mild combinations fast. And a stock LT1 head/cam is a mild combination.

There was also the test of the 400 that chevy hiperf built. The performer rpm and 1 5/8" headers combination gave 20ft/lbs of torque in the 4000 rpm range at a cost of 6hp at the peak.

Im not questioning the conclusion of more max Hp. But if its a 5hp peak increase at the cost of a loss of 15ft/lbs of torque in a number of places,, it is pretty much a nobrainer.

The motor is going to be spending much more time in the torque range than the HP peak range especially when using stock gearing.

 

Regardless of cam profile, you can't SERIOUSLY be comparing TFS heads to stock LT1 of even LT4 heads. The stock LT1 heads are only 170cc runners. The LT4s are a little better, but not like an aftermarket designed to support high RPM power.

 

oh - ok

i think we were both agreeing but saying it in different ways.

Just because a given combo makes more power doesn't mean it's better...

 

what the heck? i said it first!