I have searched the threads on this subject but still have two questions. The exhaust manifold is from a 240Z.

Are the six holes in the exhaust manifold for the smog rail able to be plugged by a 1/4 inch BSPT (British Standard Pipe Tapered) plugs?

Should the plug material be steel or brass and is there an advantage to using a regular hex head over an internal hex head (allen wrench to remove it)?

McMaster-Carr has many choices and these things are not cheap!

Thanks so much,

Gary

I'm pretty sure that's what I used on a '73 exhaust manifold many moons ago. Stack two plugs in each hole, only torquing down the 2nd to make them easier to remove. Here's a picture of a couple of the plugs I happened to save.

Thanks for the confirmation. I ended up going with a 1/4 inch BSPT steel pipe plug with a hex head for the exhaust manifold and brass plugs with an internal hex for the intake manifold where the coolant inlet and outlet were. Now to get the old fittings to let loose their grip!