Thread size question - Intake manifold for triple Weber's

[D Calkins]

Anyone know what size these threads are? I assumed they were pipe threads, but they are not 1/4 or 3/8th NPT. This is the vacuum source for the brake booster, right?

 

[shigeta]

The tools to identify a thread are cheap, simple, and readily available. With a caliper and thread gauge, you can accurately measure the size and pitch in seconds.

Here are some mid-tier examples from McMaster, though cheaper versions can be had from other sources.

Metric thread gauge:
https://www.mcmaster.com/product/2071A18

Caliper:
https://www.mcmaster.com/product/4996A72

 

[boonies]

I had the same question a few weeks ago. @StephenZ shared his measurement for the smaller holes and I found it to be a match.

smaller are 3/8-24, I can't remember the larger size, I think 5/8-18...

 

[ScottAndrews]

I would assume that these need to have some sort of barb fitting attached to them to connect the vacuum hose. What would be the proper slant to use? Teflon tape?

 

[ScottAndrews]

I would assume that these need to have some sort of barb fitting attached to them to connect the vacuum hose. What would be the proper sealant to use? Teflon tape?

 

[D Calkins]

That is an odd size & thread type for a vacuum source that needs to seal.