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Rallyspitman
03-13-2012, 08:49 AM
Okay, So I'm de-winterising my 1991 PS190 and the block drain plug thread is screwed. Years of corrosion in the thread have damaged the plug. I've figured out (I think) that the fitting is 1/4 NPT tapered. But question is, is the thread in the block a taper thread or a parallel thread. I need to re-tap the thread with the correct tap so need to figure this out.

Any ideas?

Of course I should also probably do the manifold drains as well as they are getting pretty screwed up. Any idea when thread these are? Parallel or taper?

mikeg205
03-13-2012, 11:43 AM
Okay, So I'm de-winterising my 1991 PS190 and the block drain plug thread is screwed. Years of corrosion in the thread have damaged the plug. I've figured out (I think) that the fitting is 1/4 NPT tapered. But question is, is the thread in the block a taper thread or a parallel thread. I need to re-tap the thread with the correct tap so need to figure this out.

Any ideas?

Of course I should also probably do the manifold drains as well as they are getting pretty screwed up. Any idea when thread these are? Parallel or taper?

my 95 was npt...just had to chase threads...now keep anti-seize over winter..no more problems

TNPIG
03-13-2012, 12:28 PM
I just ordered these for my 84 S&S.
http://www.skidim.com/prodinfo.asp?number=MCM001

learjet2230
03-13-2012, 01:19 PM
I just ordered these for my 84 S&S.
http://www.skidim.com/prodinfo.asp?number=MCM001

I highly reccommend those. Awesome!