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- #21
Oops posted twice.
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Yeah.. I'd be ABSOLUTELY certain that is BSPT before you go running a tap into the block. Meaning, if you don't know how to accurately measure thread diameter and pitch of the new OEM plug you need to have someone else do it.
If PO used a 1/4 tap the old plug should now compare pretty well to a 1/4PT fitting if you can find one to compare.
I looked at the threads today with an inspection camera, and there doesnt seem to be any sign of cross threading. I assume the only reason the npt fitting will even start is because its close, and tapered. That rambling was just frustration and exhaustion coming out.
Its amazing how much info the Internet has, I've learned way more than I've ever wanted to know about pipe threads. Thank you Bloc for sparking my interest. I measured the new plug, outside diameter at threads is 13.818, and minor diameter is 12.5984, or a little less because the threads are sharper than my caliper.
1/4BSPP is 13.157 major, 11.445 minor diameter.
So maybe it isn't british pipe thread after all? I can't quite squeeze my calipers up to the block to measure that, but I might have a t gauge small enough at work.
Back to the plug. The specs are actually closer to 14x1.25mm
Also I don't have the little drain cock type fitting with the hose off the side on the side of my block, were those only on earlier 1fz's? Mine is a 97 since it wasn't previously stated. So many questions ugh