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Oil check petcocks thread size
Posted: Tue Jun 23, 2020 9:09 pm
by MudsT
Been dealing with drips from my oil check petcocks on my 26 Canadian built coupe. Thought that I'd just change them out with new ones, original style, from Lang's. Removed old petcocks but new ones seem to be larger diameter and will not screw in. Anyone have an idea why this might be such a problem? Difference between USA and Canadian built. Lang's part issue?
Re: Oil check petcocks thread size
Posted: Tue Jun 23, 2020 11:02 pm
by Scott_Conger
1/8 NPT is a tapered thread. There is some chance that the die was not threaded on far enough, I suppose.
Re: Oil check petcocks thread size
Posted: Wed Jun 24, 2020 6:08 pm
by MudsT
Scott,
I picked up a die for that thread. After some iffy starts I did manage to run the die down further than threads supplied. Reversed the die and chased threads further. Now catching several more threads and new petcocks will work. Thanks again great info. Doug
Re: Oil check petcocks thread size
Posted: Wed Jun 24, 2020 6:36 pm
by Scott_Conger
I'm glad it worked, but it is a tapered thread and the die is not reversable and still get the designed thread. If it doesn't drip, then no harm no foul and am glad you're moving forward with your project.