robertfrank

iTrader: (27)

So I peeped this on a hot rod site last night and it gave me an idea. I don't plan on going ballistic with my newest L03, just minor bolt on' s till I get the LT1/TBI hybrid build done. I plan on either this opened up to 50mm and port matched to a 1204 gasket or a performer EGR intake with an adapter plate . What do you guys think?

arrg

I just measured a stock tbi intake gasket pn 10159409. 1.23" x 2.02" Just a tiny bit bigger than a 1204. I've read through the post you referenced and got the pictures from. Didn't he say this work involved welding in the plenum? I think he hit water when he cut it like that. The local u-pull it has 5 of these that people have already pulled just sitting under the hood. Maybe I should go pick one up and start grinding just to see.

robertfrank

iTrader: (27)

I didn't read that far into it but I've ported a stock TBI intake before and got all the way up to 54mm and still hadn't hit water. So I wouldn't think there'd be any problem to doing this. If the weather is good I might pick one up at one of the local boneyards. There's literally 50 TBI vehicles I can choose from

Schurkey

What are you trying to gain?

As I see it, you've got marginally more plenum area, and you've allowed both planes of the manifold to pull from both throttles. The effect is that you'll likely get more airflow through the engine. I would expect better high-rpm horsepower IF (and ONLY IF) you haven't screwed up the fuel distribution.

Wild guess: this is like every other carve-the-divider-between-the-planes-down-to-nothing deal. The lower plane now runs rich, the upper plane now runs lean, because liquid fuel in the upper plane falls over the edge into the lower plane, but none of the liquid fuel in the lower plane can travel "uphill" to the upper.

Good luck. I fear for the pistons fed by the upper plane, (2, 8, 3, 5) and the rings and cylinder walls on the pistons of the lower plane (1, 7, 4, 6.)

robertfrank

iTrader: (27)

I see what you mean now that you mention it. Ok so how do you think only trimming down the divider say a half inch? Leaving a good lip on the divider floor so fuel doesn't shoot down into the lower floor? It still might get some residual fuel from the upper plenum but I think it would be minor

arrg

Couldn't you gain the same thing with an open hole spacer?

robertfrank

iTrader: (27)

True, just bouncing ideas for something different. I've done spacers before and it's kind of a pain to get set up before

Schurkey

Gain plenum...lose hood clearance

robertfrank

iTrader: (27)

True.

Fast355

iTrader: (2)

Look for an old Weiand 7525 or an old Edelbrock Torquer II. Both are low rise single planes. The Weiand is Q-Jet pattern with EGR and the Edelbrock a Holley pattern without EGR.

robertfrank

iTrader: (27)

How well would they work with TBI? I'm only familiar presently with using dual plane intakes

Fast355

iTrader: (2)

TBI engines run better with single plane manifolds than they do with dual planes.

Dewey316s 305 ran really well with a single plane. And several of us 350 truck guys have run single planes.

Schurkey

Carbs are "wet-flow" in the intake manifold.

TBI is "wet-flow" in the intake manifold.

I don't know how the engine would know the difference between carb and TBI. Any intake manifold that makes power with a carb will make power with a TBI.

Any intake that gives-up power with a carb will give-up power with a TBI

(Assumes similar RPM ranges, cam, compression, heads, etc; and further assumes that the fuel curve of both the carb and the TBI, and ignition timing are suitably tuned to the engine.)

Fast355

iTrader: (2)

The difference between Carb and TBI is with the TBI you are not relying on vacuum signal to the boosters to pull fuel in as well as the fact the injectors do a better job atomizing the fuel than a carb. With the TBI you will not lose the driveability and low-end torque you will with a carb. Even when I ran a Victor Jr under a TBI, I did not lose any noticeable low-end torque. The torque converter would lockup and drop the engine down to 1,200 rpm and at light throttle it would still accelerate with a locked converter in 4th gear. Try that with a Holley and a Victor Jr, lol. I had dyno runs with both the dual plane and single plane down to 2,200 rpm. From 2,200-3,000 the torque curve was dead even, above 3,500 the single plane took off and by 6,500 rpm was more than 40 hp ahead. The TBI running better on an open plenum also has to do with the fact that the intake system is no longer divided. In a normal dual plane TBI system without an open center spacer the small TBI bores have a hard time supplying enough airflow for the engine. The same throttle body that is often too small for a dual plane intake manifold works much better on a single plane.

robertfrank

iTrader: (27)

So I thought I'd show my lesson in futility . I picked up another stock intake for $20 From one of the local yards. It's actually the same part number as the one that's on the car. I ported out the bores to 50mm and did a port match the the runners. After some paint it's ready to bolt on. Crazy thing I noticed was that there already is a port that feeds both sides of the engine in the Intake from the factory. I did have a small mishap with the shallow side a friend of mine had to weld up lol.

DynoDave43

iTrader: (11)

Why futility Robert? Seems like you ought to be able to make some modest increases in performance...5 or 10 horse, if that's the bottleneck?

robertfrank

iTrader: (27)

Eh, I wouldn't see it totally as the bottleneck. Truthfully if I could find another set of swirl ports I'd port them in conjunction with this intake . I plan on doing the ultimate TBI mods and rebuilding the stock unit tomorrow. I picked up two 454 TBI units today for $50 from a local yard so im going to use one of the stock injector pod spacers from one as well. I have a stock Bcar/Vortec cam (L31 or B-body LT1 camshaft 10243779 191/196 - .418/.430 111 LSA) im tempted on using. At this point I don't want to go far past the stock tune as of yet so I'm just trying to streamline as much of the airflow as possible.