Does anyone know where to get an internal-hex allen-type, steel NPT plug. I've searched at my local hardware and automotive stores but they only carry brass or galvanized plugs with a square head.

Try http://www.jegs.com/

They have a huge assortment of different AN and metric fasteners in their catalog.

If you are looking for plugs for the intake manifold look in the yellow pages for a store specializing in hydraulic equipment. I bought SST plugs for my 240Z but had to order them. The threads are not "NPT" ...... they are "BSPT" which has slightly different thread counts. BS is not Bull $^!# it is British Standard. Plugs are made by Parker fittings. They do have different types and materials in the catalogue. Do not use brass due to galvanic action with aluminum.

Thanks for the info, I'm trying to find a plug that will fit the thermostat housing on an early 240. It's close to a 1/4" plug but not quite. What I have found so far is all standard thread pattern.

Have you looked in the hardware section of Lowe's or possibly Home Depot? Never know what you can find there, they (Lowe's) usually have a lot of things you wouldn't expect. Can't vouch for HD, as I have a hard time finding anything in those stores, they are some of the most dis-organized places I've ever seen.......

I have been looking for BSPT plugs for the exhaust manifold in order to eliminate the "Air Galley" part of the Emissions System. My local full service hardware store carries a selection of BSPT fittings, but I cannot find one that will fit. Does anyone really know (for sure) what size plug is needed so I could have them order the right ones? Please!

I agree with Keith on Home Depot. I have a heck of a time finding things in those stores. "Just ask a clerk"? Ha! Try finding one that will give you an answer.

I've tried Home Depot and Ace hardware. They only have NPT and it has the square head. We don't have a Lowe's up here. I did find the allen head type at a performance automotive but they are also NPT. The thread count is very close but it will strip if I force it in there.

Hey Ed, I drilled the hole and tapped it for 1/4" NPT. I had the same problem as you. Couldnt find metric plugs here. Got a NPT tap from the local tool supplier. Worked well.

My .02

Chris