The intake on my car is the one by Cutler EFI, Holley bought out Culter and the intake is now know as the Holley EFI direct port. Culter stats were 1800~6800 rpm.
I saw increase in airflow as measured by the MAF sensor @ wot.... 82 grams larger than the stk LT1 manifold and stk throttle body.
Since I was set firm on maintaining a mass air meter with my swap It allowed me a means of quantifying the benefits of the single plane swap with comparison in Grams of air flow at wot with both intake configuration with the motor and meter remaining the same.

I also saw a reduction in the amount of throttle it took to maintain the car at 75mph:
stk manifold... 19 % throttle
single plane.... 12.5 throttle

The low speed air flow has had to increase with the swap and has picked up the efficiency. The throttle bore size on the
Holley 4 barrel compared to the 48 millimeter size of the stock LT1 throttle body bores is smaller and you have to remember that the EFI four barrel throttle bodies have progressive linkage so your driving around on small throttle bores until you reach 36 % throttle angle and the rear barrels begin to open.
At wot the 4 barrel throttle body is 300 cfm larger than the stock 780cfm piece.
The last thing that showed improvement over the factory intake configuration was the MAP percentage at WOT. This went up to 99 percent where previous to the swap 96% was the best percentage I would see.... This would have to be due to a less restrictive breathing intake configuration.
The injector placement is better with the aftermarket intakes as they point the injector at a better angle than the factory intake did. They aim more to the center of the cylinder bore.
I posted this info back in 1998 when I did the swap but I could not find the old thread so I dug out the notes.
Hope this helps out...


Jeff Taylor

 

very interesting findings........im looking at yoru pics, but i dont see how the MAF is retained......where is it?

 

Sux that my Laptop crashed and all my pics are gone
I made a mold for a plastic air duct that allowed me to retain
the MAF meter to a stock ramair box. There is a featureon my car in the November 2003 Hemmings Muscle machine magazine.
One of my co workers took pics of the car this summer at the CZ28.com nats and I just talked with him and he will get me the pics and I'll update my site ...SOON.
Wait I'll scan the picture from the magazine on my desk..

 

Thats awesome Jeff! Now if I could only get one of those molded elbows from you Your brother made it, correct?

Jason

 

Jeff

All of your post makes sense except that part.

The stock intake manifold has about the best injector placement you can get on a SBC side by side intake port. (except maybe for down nozzels)

The reason I say this is because I've mocked up intakes on cylinder heads and setup the flow path of the injectors and they are about as close to the back of the valve as you can get in that configuration. The LT1 is good for the way it's setup but is not even close compared to a LS1 setup, which is about as close to perfect as possible.

I then tried to translate the injector positioning from the LT1/4 intake over to a Single Plane intake and the injectors end up in the middle of the intake port, which is obviously not good.

Interesting that you went to the 4bbl type TB. What hood are you running on your car now?

Over the winter I'm going to work on a single plane bolt on setup for LT1's Basically a plug n play except for a few bolt holes that need to be put into the cylinder heads.

Bret

 

Jeff, you wouldn't happen to know the part number for that Intake would you? Seriously thinking bout goin that route, do you have any before and after dyno numbers? Thanks for the info.

 

Nice post and setup Jeff. One question, what stock piece are you refering to?

 

KMOOK: the factory LT1 throttle body {48mm} vrs the holley 4 bbl throttle body I'm running.

 

According to Steve Quinn back when I was kicking around doing this swap, he felt the injector placement was better in the cutler unit than the factory LT1 manifold. So I'm just repeting what he told me. I Also know Steves custom intake he did on his ride has the injectors stood up like the aftermarket sbc manifolds...
...but thats a bad ***** on Quinns car thats like no other!

 

Where is the MAP sensor located on the Cutler EFI intake?

 

I have the plug to make these and my Cousin is the vaccum forming source I use. The Picture I'm working on uploading to my web page right now is of the piece we made to fit under a factory firehawk hood back in '98.

The pictures taken by my co-worker {that I'm waiting to recieve} are of my newer piece we made this summer, it has incressed internal volume and is much larger due to the new found room provided by running a VFN 4" ramair hood

 

hose barb on the intake plunum down about 1.5 inches from the TB flange, and the map sensor hangs off a mounting stud. on the TB.

 

http://home.comcast.net/~hotrodhawk/...3/site1002.jpg

I didn't realize how much you had to cut out of the cowel with that 4bbl setup.


Any dyno or back to back track numbers?

My guess with the right camshaft is about a 30-40hp gain and TQ gain from 3000 on up with ALOT more at TQ peak.

Bret

 

http://www.hotrodhawk.com/third_stag...d_pictures.htm
Updated link 3-27-04

Stroker the car picked up 2.7 mph from the swap but the cam was not right back then, now how ever were getting there
The throttle responce is cRaZY. Updated link 3-27-04

 

That about what I thought the duct would look like.

Yeah, the camshaft requirements for a single plane vs a LT1 intake are vastly different.

I've done some single plane carb conversions but we are just starting on a EFI one soon. I want to be able to incorperate the N2O system in our setup so you don't into the cowel like yours.

3mph is a pretty good gain for a intake at the power level you are talking about.

Bret