tbi adapter advice

So I'm finally ready to do the tbi conversion on my '87 Suburban. I had a thread about it on here long ago...

I'm looking for an adapter to go between my spreadbore manifold and the TBI... many to choose from. I was wondering if there is any one that is best? Or any I should avoid? It looks lie mostly the affordable ones are made by Trans Dapt but there are several styles...

Any input is appreciated. Thanks guys!



EDIT: Looking at this one maybe? It's a good price... Pros/Cons?

http://www.righttoolusa.com/p/Trans-...r-7822840.html

Looks like that one is only 1/4" thick or so, I wouldn't go less 3/8", preferably 1/2" in aluminum. Steel you might get away with 1/4", as long as you have clearance for the threaded end of the bolt. I made my own so I can't comment on other's quality.

Haven't had much luck with Transdapt 1/4 inch metal plate adapters. Much better luck with 1/2 inch aluminum Holley adapters for a few dollars more.

The biggest issue with 1/4 plate adapters is not enough metal for TBI bolt threads. Look at the TransDapt adapter and draw a line from mounting bolts to intake. See the TBI bolts in the path? If they go though adapter by 1 thread it hits intake and pushes adapter up causing a vacuum leak.

Mount the TBI on adapter with gasket and tighen before putting the adapter on intake to check and see/trim bolts so they don't go through!

Attachment 3013

There's also a center mount.

Attachment 3014

Thanks guys. Will look at the Holley adapters.

Go to JY and pull a 454 TBI adaptor, It's a GM factory part. Spreadbore to TBI.

How about this one? look ok?

http://www.summitracing.com/parts/HLY-17-41/

Quote:

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Originally Posted by jim_in_dorris

Go to JY and pull a 454 TBI adaptor, It's a GM factory part. Spreadbore to TBI.

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I've got one of those big ugly things here on the bench I don't know what to do with...

Quote:

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Originally Posted by Xenon

How about this one? look ok?

http://www.summitracing.com/parts/HLY-17-41/

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That's the one.

Thanks guys! Ordering one now.

Well, it's on it's way. Hopefully have this thing fuel injected within a few weeks... don't wanna fight with a carburetor all winter.

hope you have a 454 TB to go on that. the bores are too big for the 4.3/5.7, the smaller tbi won't cover it.

You sure? IIRC the SB will go on big bores just not other way around... I know I've used that adapter and SB but not sure what SB gasket I used? I think the open center gasket...

I had to go back to the transdapt plate because the bores were sticking out from under the TB every time I sprayed carb cleaner at the gasket in the two spots it stuck out it would raise the idle.

I've run the Holley 17-45 adapter, which is for a square bore flange, with my stock small block tbi unit for over 10k miles now with no vacuum leaks or other issues.

Actually yes, I have a 454 TB sitting on it. It's not installed on anything at the moment, but it is loosely bolted to an Edelbrock performer 289 manifold just for grins. And it has a squarebore to spreadbore adaptor between the manifold and the TBI adaptor. It sure sits up high.