Exhaust Manifold Drain port plugs

[bjanakos]

After chasing down my exhaust noise issue, I found it was caused by a missing exhaust drain port plug. Whew, nice easy quick and cheap fix (or so I thought)....

I pulled one out from another port to get an idea of the size and it would not go back in (now I need two!) After further inspection, it looks like the threads were mashed, or broken off inside the manifold. They appeared to be 1/8" NTP plugs, so I tried to run a trace through the threads, but it was not going in easy.... I stopped there and tried to look online for some specs, but I a coming up short...

My questions for the collective is.... What is the proper thread for the small exhaust plugs? And where can I source them? I am thinking that the yellow brass plugs have have now are not a good idea with salt water running through there....

[prowlersfish]

Are these in the Exhaust port or water jacket ? Most likely they rusted out so the holes maybe over size from what they were

[bjanakos]

It's this part



Each one of those ports has a bras plug on the bottom.

[mikeandanne]

You have a couple of options near as I can tell, If those are NPT you will have to have a specific NPT tap to chase the threads, you could drill out for a helicoil and go that route,or drill to the next size pipe thread if possible to get in there and plug that way. Remember all pipe threads are tapered that is how they seal, not sure what you used to clean the threads.

[larryeddington]

"Are these in the Exhaust port or water jacket ? Most likely they rusted out so the holes maybe over size from what they were"

Paul pretty certain the larger ones at either end are exhaust, I guess to be used for some other installation. The 1/4 plugs let the water drain from these log manifolds and another at the base of the riser.

[bjanakos]

not sure what you used to clean the threads.

A 1/8" NTP Thread chaser.