Thread size for vacuum port on Offy BA 4 barrel-intake under carb mount base?

[AnthonyG]

I have an Offy 4 barrel intake for a BA. The internal thread to provide vacuum via a threaded vacuum adapter port has a thread issue I’d like to clean up via a tap. Anyone know what the size its supposed to be’s?

[Mart]

Can you just measure it and see what thread it matches most closely? It's probably NPT but hard to say from here. NPT thread specs are easily found by googling.

[19Fordy]

Anthony; Is the port you are asking about the one in the lower left (1st photo) of this 390 Holley (4160) List 8007 with the rubber cap over it? If so it appears to be pressed in, not threaded. The same is true of the other port for vacuum.

[Bored&Stroked]

Originally Posted by AnthonyG

I have an Offy 4 barrel intake for a BA. The internal thread to provide vacuum via a threaded vacuum adapter port has a thread issue I’d like to clean up via a tap. Anyone know what the size its supposed to be’s?

My guess is that it would be 1/8" NPT - that is what I've seen on most manifolds. I do NOT have your manifold - so consider this a wild ass guess!

[Bob C]

I think this is the manifold.

[19Fordy]

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Oh my gosh Bob, thanks for posting that photo. Somehow, I misinterpreted the original post. I was way off base.
I have that Holley 4 barrel intake on my 8BA and that fitting is 1/8-27 threads like Bob said.
I use that port (second photo) to operate my vacuum wipers. The short straight fitting that screws into the intake and the 90 degree brass elbow takes a 9/16 wrench. Teflon tape on threads.

[AnthonyG]

sorry for late replies. computer crashed and took a while to fix. the female threaded vac porrt is on rhew manifold just below the carb mounting surface

[AnthonyG]

https://www.fordbarn.com/forum/attac...8&d=1726944705

[AnthonyG]

Thx 19Fordy

[AnthonyG]

Thx 19fordy! Sorry reply is so late. Old Man back issues make everything I do take 5 times as long. I got a couple of 1/8-27 NPT TAPS & there was enough land towards the bottom of the thread so was able to get threads straitened out. I dipped the threaded vacuum fitting 1/8 27 NPT threads in RTV ( PROBABLY overkill) but no more vacuum leak! &?was able to adjust the idle on the two Holley 94 setup!