Tbi to carb manifold

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Jbaer

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What's up guys andchicks.? Doing a tbi to carb swap on an 89 2500 5.7. I have a holley strip dominator intake manifold and can't figure out why I can't get the 4 center bolts to line up right.... if someone has any idea please help. Thanks
 

evilunclegrimace

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What's up guys andchicks.? Doing a tbi to carb swap on an 89 2500 5.7. I have a holley strip dominator intake manifold and can't figure out why I can't get the 4 center bolts to line up right.... if someone has any idea please help. Thanks
The holley strip dominator intake is for pre TBI cylinder heads.
 

Gramps

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You have to drill out the center holes in the intake to correct the angle so they will line up with the holes on the tbi heads.
 

Nad_Yvalhosert

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Swirl port '87-'95 heads have their center 4 bolts canted at 72°
You have two options:
1: yank the heads and install '86 or older.
2: return/exchange the manifold for use on '87-'95 heads
Don't drill the manifold, you'll never get it to seal or torque correctly.
 

Schurkey

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I've got an Offenhauser manifold that a previous owner drilled to fit the goofy bolt angles on TBI heads. Best done in conjunction with angled "wedge" washers so the bolt head isn't stressed.

I looked at going the other way--re-drilling a TBI manifold to fit older cylinder heads. I didn't see any way to make that work. The manifold has hollowed-out sections around the bolt holes that would be weak. I've heard--but not seen--that other folks made it work. I don't understand how.

Perhaps a moderator will move this thread to the LSX + Carb Swaps sub-forum.
 

DerekTheGreat

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Going to bet that if you're using the stock heads the rest of the engine is stock too. Can't imagine it is going to play well with that single plane manifold, certainly won't be dominating at the strip... My advice would be to sell that manifold and use the proceeds to buy something like this instead: If you must go back to the 50's.
 
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Erik the Awful

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Yup, that's not an ideal combination. It'll be a dog, but if you're making do with what you have, you'll need to hog out those holes and install these $14 angled adapters.

I put an Edelbrock C3BX on a set of TBI heads with these adapters. You have to be very careful about hogging out the holes while keeping them lined up. The adapters are brittle, so if you're close, you really don't want to hammer them in place. Check fitment, trim, check fitment, trim. Light tapping is okay to get them in place.
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tayto

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slotting the centre holes and using angled washers works fine for adapting an older sbc intake to the TBI/TPI style heads. "you'll never get it to seal or torque correctly." is completely false, have done 4 conversions now without issues.
 

tayto

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Yup, that's not an ideal combination. It'll be a dog, but if you're making do with what you have, you'll need to hog out those holes and install these $14 angled adapters.
i used these on the last one i did, but i took the adapters to a belt sander so i was only left with the angle. worked good.
 
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