Holley TBI adapter

[PJG1173]

what are you guys thoughts on this adapter? I haven't been too impressed with the way the transdapt 1/4" plate style adapter fit. matter of fact I had to use a spread bore to square bore adapter to make my adapter work where the intake wasn't blocking the throttle blades. is this a better alternative? I can get one of these through amazon for $50.
http://www.holley.com/17-45.asp

1852

[EagleMark]

I've liked all the Holley adapters I have used over the 1/4 plate adapters! More money but at least they are machined straight not just a flat piece of metal. The flat 1/4 inch metal adapters I use a gasket and sealer both sides to avoid vacuum leaks.

Also make sure to mount your TBI with the bolts your going to use and snug them down and make sure none of the bolt protrudes through the adapter, hitting the intake causing it to separate and cause a vacuum leak. Get shorter bolts or use washers.

[PJG1173]

thats what I'm afraid of... I check for vac leaks all the time since it started to warp just from tightening the adapter bolts before I even put the TB on it. yes I also not happy that I had to shave the TB bolts to keep them from hitting the intake. I am not a fan of using rtv on things that come in contact with gas, so i just used the gaskets that came with the adapter.

[EagleMark]

Sensor safe gasket sealer both sides of bottom gasket, light coat, wipe clean inside after tightening up, let it dry overnight and it will be fine. Top to TBI I don't like to use sealer but them dam 1/4 plate adapters it's just about mandatory... you'll have way better luck with the Holley.

[JeepsAndGuns]

Thats the adapter I am using. I have not had any problems with it, and it fit like a glove. Its roughly 1/2 inch think if I remember correctly.

[Nasty-Z]

Yes , the Holley is about 1/2" thick and it is of good quality .

I bought one a while back , it worked out good .

For some of the latest ones I have done though , I have just made my own.

TOM

[PJG1173]

awsome just what I needed to hear. one is on the way.

Tom,
how did you make your own? I have thought about attemting to make one myself. Do you have access to a machine shop, or did you just get creative with some random tools?

[Nasty-Z]

Tom,
how did you make your own? I have thought about attemting to make one myself. Do you have access to a machine shop, or did you just get creative with some random tools?

I used a piece of 1/2" Aluminum and patterned it after the Holley piece , My TBI is 2.2" Bore so I would have had to modify the Holley piece anyway , so I just thought it simpler to make my own.

I made it in a Machine shop I have access to , but I suppose a sawzall / cutoff wheel and a hole saw would produce the same results , a little touch up with a sanding roll and it would be as good as the Holley unit.

TOM

[EagleMark]

There are also a couple differant TBI units. one with 2 holes seperated and one that has center open.

Divided.
http://www.gearhead-efi.com/Fuel-Injection/attachment.php?attachmentid=1873&stc=1&d=1331309000

Open
http://www.gearhead-efi.com/Fuel-Injection/attachment.php?attachmentid=1874&stc=1&d=1331309000

I beleive the open ones came on Camaro and Caprice. With that in mind and proven results of CFM Tech spacer that has a split opening for divided TBI
http://marine-performance-parts.com/cfmtechpowerplatefor435057gmtbiwsingleaircleanerst ud.aspx

We used the divided TBI and made the adapter open while also machining the intake for straight shot passages when we made the TBI adapter at the machine shop for my sons 345 IH motor.

http://www.gearhead-efi.com/Fuel-Injection/attachment.php?attachmentid=1574&stc=1&d=1328417373

[PJG1173]

what would the advantage be to the open one?

[EagleMark]

Airflow can be used from both sides, balenced. There is a difference in intake manifolds as well between the 2. The IH maifold was also machined/seperated like the adapter to match the intake of open TBI.

But if you don't have your intake off like we did during a rebuild then just use the CFM adapter with open TBI gasket.

[PJG1173]

Hmm I'll have to look at that. i don't think the divider in my plentum comes all the way up to the top of the flange. the adapter under my tbi adapter is open, so I guess I am already good there. I can't find a good enough pic of the holley adapter to see if it is divided all the way down or not.

[EagleMark]

I used a piece of 1/2" Aluminum and patterned it after the Holley piece , My TBI is 2.2" Bore so I would have had to modify the Holley piece anyway , so I just thought it simpler to make my own.

TOMThat adapter above we machined above on the IH is also 1/2 inch aluminum. Even with that stock TBI bolts are to long and hit intake manifold! So you can imagine how bad they are with 1/4 inch. If a guy is unaware and tightens them down he'll bend the adapter causing a severe vacuum leak. If done on an aluminum intake the steel TBI bolt will damage/gouge the intake as well causing a vacuum leak.

If we had a 10 commandments of EFI one would have to be "Thou shalt not have vacuum leaks" ! If we had a 10 commandments of EFI conversion one would have to be "Thou shalt measure your TBI bolts in adapter" !

[1project2many]

I made it in a Machine shop I have access to , but I suppose a sawzall / cutoff wheel and a hole saw would produce the same results , a little touch up with a sanding roll and it would be as good as the Holley unit.

That's how I made the adapter for my monoblade TB on the 302 intake and the IAC valve housing on the Toyota engine.

I also used studs threaded into the adapter plate then ground slightly below flush to prevent any contact with other parts. Makes it nice when setting the TB back on.

[EagleMark]

I also used studs threaded into the adapter plate then ground slightly below flush to prevent any contact with other parts. Makes it nice when setting the TB back on.Never thought of that? Great idea!

[Nasty-Z]

I actually did the same thing when I made mine , I use 1/4" bolts to attach so I countersank the bottom of the adapter plate , threaded the hole 1/4-28 and threaded in flat head machine screws till they were tight and sealed them with red loctite . Now 3 1/4-28 nuts and the TBI is off .

TOM

[lightning-jr]

Seems I did a good bit of "configuration" on that Holley adapter before I was happy with it.

A decent part for the job in the end.

[PJG1173]

Ok, I got my tbi adapter in the mail yesterday. I guess I missed the fine print or something because it is a 2" bore. will my 1 11/16 work with this? when I put the gasket over it there is a big difference and when I bolt one of my junk TB's to it there are some of the passages exposed on the bottom of the tb when I use the 2" gasket that would normally be covered.

[Nasty-Z]

It will be fine

TOM

[EagleMark]

Seems I did a good bit of "configuration" on that Holley adapter before I was happy with it.

A decent part for the job in the end.What exactly did you need to do? It's a fine piece when compared to 1/4 plate steel adapters...

[PJG1173]

do I use the 2" gasket or the 1 11/16?

[EagleMark]

do I use the 2" gasket or the 1 11/16?Hmmm? Sure you can't return it for correct one?

The Big Block TBI gasket is very thin in arease and does tend to cause vacuum leaks, on the other hand if you use the SB gasket you'll have exposed gasket in the bores. I don't like extra gasket in the bores as it came start to break down and fly through motor. Not that I think little pieces of gasket material would hurt it... just don't like the idea.

Mount up your TBI with both gaskets and look from underneath, sounds like the BB gasket would have none exposed in bores, but may be better with SB trimmed in bores?

[Nasty-Z]

Yup , Mark hit it , use the SBC gasket trimmed up to match the larger bores .

I used the "Holley" (Made by me) adapter on my dad's S10 on top of a single plane intake for years without an issue , 2" bores with a SBC TBI on top using a modified SBC gasket .

TOM

[PJG1173]

I may look into seeing if I can order another one with the correct bores or have the local machine shop use this one as a template. I'll use this one on my next project since I already have a BB TB for it.

[EagleMark]

Or use this?

[PJG1173]

Or use this?

that will work! :thumbsup:

another question I've had...
is the placement of the tb on the opening have an affect on anything? i.e. on a square bore intake would it make a difference if it was more oriented towards the front, middle, rear, of the opening? keeping in mind this is a v6 so the intake ports are not symetrical from side to side like a v8

[EagleMark]

I'd shoot for center. Although the SpreadBore adapter, or at least one is set to rear?

[lightning-jr]

What exactly did you need to do? It's a fine piece when compared to 1/4 plate steel adapters...

The bores had to be enlarged to match my TB. I blended it to the intake, after having to open the manifold some. There were width and offset problems. I cut the rear 1/2 of the bore outlets back about 45*, maybe 1.5".