Plug thread (intake manifold)

[Xplitive]

Looking to plug the port in the intake manifold. It’s 596069 in the parts book or possibly 587502 for detoxed vehicles (believe that’s what mine was originally).
What is the thread on this adapter and, if a plug is available locally, what material (cast, brass, etc) would be best? Trying some NPT, AN, other stuff laying around, while NPT seems close, it doesn’t go but a turn or 2.

[Yorker]

Looking to plug the port in the intake manifold.
what material (cast, brass, etc) would be best?

JB Weld

[ren ching]

My WAG would be BSPP. 1/4" maybe? Do you have a caliper? You can measure thread pitch and diameter if you do. McMaster Carr sells some BSPT (British Standard Pipe, Taper) and BSPP (Bloody Sodding Pain, [in the] Posterior) fittings that might work.
Other options include welding or brazing up the fitting. I don't like "ruining" parts that re hard to find or where I don't have a spare. Another option would be to turn the pipe and its flare nut into a cap. I have done that by cutting off the pipe flush with the top of the nut, and then welding or brazing it shut. But I probably wouldn't do any of that if I only had one. Someone will want that part.

You can always drill and tap the manifold to the next largest american pipe thread and put any old plug in there. Done that more times than I can remember, Including manifolds that are still on the car. Use some grease in the tap to catch the pieces.

[Griffinwerks]

I would guess the manifold is BSPP. It is a straight thread evidenced by the sealing washer so it is NOT BSPT or NPT. The easy way would be to install a flare cap replacing the tube attached to the fitting, should be available at your local hardware store or (//www.mcmaster.com/flared-fittings/type~cap/) .

[series guy]

You can always cut the threaded top portion off of your fitting and weld up the hole.

[loose gravel]

To paraphrase Dr. McCoy, "God sakes man, get some thread gauges!" Where I live there is a hose and fittings shop, one in your area? If so take in the offending parts and see what they have. Then report back to us. ;^)

[siiirhd88]

I've read that this thread is 3/8 BSF and supposedly the same size and thread as the oil sump plug. I've also read that it is UNF, which would be the same as a fine thread bolt. I'd first check by fitting a UNF bolt in the hole, unless you have a spare sump plug.

Bob

[Xplitive]

To paraphrase Dr. McCoy, "God sakes man, get some thread gauges!" Where I live there is a hose and fittings shop, one in your area? If so take in the offending parts and see what they have. Then report back to us. ;^)

The fact that only the most experienced Series people have chimed in, and none agree, should mean a rookie like me should not be trusted with any measuring instrument. But point taken, ordering the plug itself and May throw in an extra sump plug and will have to find some gauges.. later I’ll tell everyone about dropping off some parts today to be tig welded at a local shop and the welder says “must be whitworth or something British, else there would already be adapters made”

[series guy]

The oil sump plug is the same thread as the heater outlets on the cylinder head but i'm thinking these are larger than the intake vacuum port…… and they are