83 Crossfire TA

iTrader: (2)

Any suggestions what intake to run with vortec heads and a TBI.

I don’t think that I could justify the $3xx cost of the GMPP one so I’m probably going to go with an adaptor plate on something but what? I’m thinking open plenum would be better, but I haven’t found anything appropriate… I wish I could find a small runner, single plane like the wieand x-celerator or even a torquer II… not that this thing is going to turn any real rpm, it’s going in a truck, I just don’t see a reason for the “signal enhancing” characteristics of a divided plenum (though at this rate I probably will end up going with one).

So what have you guys done/used? How did it work?

83 Crossfire TA

iTrader: (2)

58 views and no one has any thoughts/experience?

Dewey316

Mark,

Definatly the right track. I honestly haven't looked into specific vortec intakes. I would look for any low-rise single plane, and then look at the port size. Does Wieand make a team-g manifold for vortecs?

I do very much agree, that the open plenum is optimal for TBI.

83 Crossfire TA

iTrader: (2)

and that's the problem, I can't find an open plenum manifold that has relatively small runners appropriate for my 350 truck engine. I could really care less if this thing pulls at all north of 4000 or so rpm, but will kill for all the torque (and consequently efficiency) that I can get from idle to 2500rpm. Honestly, in normal driving between the 33” tires and 3.42 gears I only exceed 2500rpm when I’m doing something stupid.

I’m half tempted to get my hands on a factory vortec manifold, ditch the top of it and build myself something like the crossfire setup, but from what I’m seeing I have 2 problems with that: the vortec manifolds are going for insane prices on ebay for a used manifold and it looks like the runner openings are very close to the flanged surface between the top and bottom halves which is going to make it difficult to package things so the air/fuel turn around into the runners well, where on the crossfire setup the port openings basically started on the plenum floor giving you some clearance to work with…

kdrolt

Why don't you just stick with the CFI intake? It's very good for the rpm limit and application you've imposed.

Fast355

iTrader: (2)

I very much disagree, after running many different intakes the single plane that I ran was about the worse choice for TBI. In fact, I would run the stock intake over the single plane that I had. My engine, even after lots of tuning was a slug until about 2,200 rpm compared to a decent dual plane.

I recomeend a dual plane intake with an adapter and maybe a slight amount of trim work to the center divider of the intake.

TBI doesn't rely on a vacuum signal as much as a carb, but a single plane eliminates the resonance of a dual plane intake and much of your low-midrange torque and fuel mileage.

Dewey316

What combo did you run it on? I did not notice any real torque loss on my motor, when I switch, and it was much smoother in the mid-range RPMs.

Fast355

iTrader: (2)

I tried it on three different engines, along with the stock intake, and a performer RPM. The RPM spreadbore and single plane both had extreme a/f mixture variations between cylinders when used with the projection TBI-carb adapter that places the TBI on the front of the intake. The stock intake, Holley projection intake, and edelbrock TBI intake greatly reduced this. I found that a spreadbore performer rpm intake with the factory 454 TBI adapter and 454 TBI worked well too.

I ran the single plane on 2 different engines and noticed a substantial torque loss that could not be tuned out. Then again my 5,300 lbs brick pulling a trailer with 3.08 gears makes the difference very pronounced. I noticed a loss of torque, in exchange for a slight HP improvement over 4,500.

Engine A.) 355 w/ Mellings MTC-1cam, ported 601 heads, 1 7/8" primary headers, and a 454 TBI.

Engine B.)355 w/ LT1 cam, ported 601 heads, 1 7/8" primary headers, and a 454 TBI

Engine C.)312 w/ L82 cam, ported 081s, 1 7/8" primary headers, and a stock 350 TBI.

83 Crossfire TA

iTrader: (2)

Fast… what single plane were you using? I’m wondering if it is more a question of runner size then a question of the divided rather then the single plenum, since the only reason that a divorced plenum should help anything is the signal to a carb which should be a non issue with TBI setups.

When you ran the spacer/adaptor did you use a 2 hole or open one? As an alternative I was thinking of running an open adaptor on something like a performer or the professional products knockoff and possibly cutting a slot in the plenum divider.
----------
because it won't bolt to the vortec heads that I'm probably putting on the engine...

Fast355

iTrader: (2)

The Weiand 7546 X-Celerator with an advertised power band of 1,500-6,000.



The spacer was the holley projection adapter with 2" holes seen in the above pictures.

83 Crossfire TA

iTrader: (2)

Huh... what does the factory 454 adaptor look like?

Ronny

iTrader: (1)

Holley-Weiand makes a vortec dual plane manifold for carb applications. i supect the configueration/flow is similar to my holley projection dual plane for tbi. rate up to 6000 rpms.

Chuck!

I have the performer rpm vortec on my car and I miss some of the low end power. Do they make just a normal performer manifold for it? Might be the way to go.

83 Crossfire TA

iTrader: (2)

Edelbrock makes a Performer, Professional Products makes a knockoff of that and Weiand has an action plus, all rated from idle to 5500rpm.

My instinct probably ranks them in reverse order, I’m not sure for any real reason… Weiand first (probably because it’s a square bore, I don’t see how an adaptor plate like we’re talking about will get even fuel distribution spraying into a spread bore), Professional products second (not sure why, I just get more of a warm fuzzy looking at the pictures of it then the E-brock) and finally the e-brock.

83 Crossfire TA

iTrader: (2)

Huh I wonder if it wasn’t the spacer rather then the manifold/open plenum. At this point I’d say that the argument is academic since there does not appear to be a small runner, open plenum manifold for the vortec heads for me to try it on anyway…

Z28 Boy

you can take a look at my site in my signature below. i have done some pretty extensive (i mean expensive) TBI mods to a vortec headed engine.

-brian