Offenhauser to Holley 2 barrel adapter

[bubbasimms]

I've been searching and hunting for an adapter to mate the 2 barrel holley to the Offenhauser intake. I have the Spectre Racing adapter that fits the intake and the carb but how are you supposed to bolt them together when the adapter has counter sunk hex head holes for the bolt heads and holes on the intake are to close to the body for nuts? Anyone have a good adapter in mind?

['68OrangeSunshine]

Is this an L6 project?

[bubbasimms]

Yes it is, sorry, didn't include that

[geezer#99]

Take a pic of what you’ve got.

[bubbasimms]

The issue is where the adapter bolts to the intake. The holes are machined to hold the bolt head. This wouldn't be a problem if there was room for a nut or bolt head on the bottom side. There isn't, so you cannot tighten the bolt once it enters the machined hole, nor can you run a bolt from the bottom. The machines hole fits a 3/8 bolt/nut and the threads in the intake are 5/16. Simple solution, after I slept on it, was to just drop a 3/8 nut in the machined hole to fill the void. The 5/16 bolt slips right through the 3/8 nut and the nut levels the surface so you can tighten the 5/16 bolt. Easy peazy.

[geezer#99]

I’m a bit confused!
Are you bolting the adaptor straight to the manifold or to the plate that is held down by the countersunk screws.

[bubbasimms]

It's all one piece, 4 bolts down into the manifold and 4 bolts up into the carb.

[geezer#99]

Not saying it won’t work but I thought you needed the plate that bolts to the intake with the countersunk holes.
Then you bolt a 2bbl to 4bbl adaptor to it.
Looks like yours is a 2bbl to 2 bbl adaptor, but I could be wrong on that too.

[54blackhornet]

Post a photo of carb sitting on adapter might help ?

[bubbasimms]

It's all a one piece adapter. It goes from a square bore 4 barrel offenhauser intake and adapts it to a 2 barrel Holley. It is one piece that allows a 2 barrel carb to sit on a 4 barrel intake. Picture a standard V-8 intake with blind threaded holes for 4 studs to mount a four barrel carb, but the holes in the carb are machined to a hex head shape. You can't tighten a nut onto the stud when the surface it tightens against is a countersunk hex head. Long and drawn out and a simple fix when I stepped away from it. My point is this adapter has a major design flaw and I was looking for a different adapter. All good now.

[3757chevy]

Use an allen head bolt, then you won't need the 3/8" nut as a filler. The allen head bolt will go down into the recess on the plate.

[geezer#99]

Originally Posted by bubbasimms

It's all a one piece adapter. It goes from a square bore 4 barrel offenhauser intake and adapts it to a 2 barrel Holley. It is one piece that allows a 2 barrel carb to sit on a 4 barrel intake. Picture a standard V-8 intake with blind threaded holes for 4 studs to mount a four barrel carb, but the holes in the carb are machined to a hex head shape. You can't tighten a nut onto the stud when the surface it tightens against is a countersunk hex head. Long and drawn out and a simple fix when I stepped away from it. My point is this adapter has a major design flaw and I was looking for a different adapter. All good now.

Post another pic of the completed adaptor install.

[bubbasimms]

I looked at an Allen head bolt but it's threaded for 5/16 and the machined hex head is a 3/8. A 5/16 Allen head will almost slip through a 3/8 bolt hole. It leaves very little surface area for the Allen head to sit on.

[3757chevy]

Originally Posted by bubbasimms

I looked at an Allen head bolt but it's threaded for 5/16 and the machined hex head is a 3/8. A 5/16 Allen head will almost slip through a 3/8 bolt hole. It leaves very little surface area for the Allen head to sit on.

Oh well, It was a thought.

['68OrangeSunshine]

I was going to mount a 2 bbl, progressively-linked Holley-Weber carb on my 292, only 42 years ago, but increasing difficulties let me be talked [by a slick hotrod shop operator] into buying a Holley 4 bbl 8007 [390 CFM] instead.
My only regret is that he didn't talk me into a Carter AFB when they were still available.
It took me 27 years to admit
I Hate Holleys.
Now I run a 500 CFM Edelbrock 1404 on the Offenhauser intake with Clifford headers.