oil presure threads

[Don]

I have just put together an engine with a dual relief case. The fitting for the oil pressure guage (1/8 npt) leaks at the case threads. The threads in the case do not look damaged, and I don't see any cracks. Before i chase the threads does anyone know if they are 1/8-27 npt (North America) or 1/8-28 npt (European). I have sealed it temporaily with a custom made fitting and o ring)

thanks, don

[tiagosantos]

Hey Don, I thought they were M10x1mm threads in the case.. Might be close enough to the NPT threads, but I know cip1 (and of course, the Vee specialist places) have m10x1 oil pressure senders or various adapters for the different threads..

[SR Racing]

They are M10, but most everyone has used NPT 1/8-27 on the cases. Normally if you use Teflon tape or paste they will seal fine. If the sender is bottoming out on the case, you will have to do something different (like helicoil, etc.)

[smsazzy]

I found that if you don't use teflon tape it will leak pretty bad. Try that and see how it works.

[sharplikestump]

edited for clarification

One other possible solution is to machine that surface sufficiently (remove surface material, allowing the sender to travel further into the tapered hole), effectively tightening the fit, provided the threads have not been stripped.
Mike P.

[SR Racing]

Or perchance is there a such a thing as a tapered Helicoil?

Nope. Don't think they have a pipe thread helicoil. You use a straight M10 coil. (They make the senders with M10 fittings.) (Or use your method.)

[brian]

Be very careful driving a pipe fitting into a case. The tapered threads of a pipe fitting will split the case and you will have a much bigger problem. I use teflon paste, liberally coat the threads and install firmly not tight. Let the engine sit a while for the paste to set and you shouldn't have a leaker.