Putting a mechanical oil pressure gauge on the NPT port of a 42 Draft block in the engine compartment. I want to see how it correlates to a dash gauge I have.

Can I use a jam nut to fix the orientation to where I need the gauge to sit?

NPT threads are tapered, so a jam nut won't work.

You can try tightening it just enough to seal and depending on how much farther you need, you might be able to tighten it in to a place you can see the gauge.
But don't over tighten it!

Jim

Got it. Thanks, Jim.

I have used a short length(6") of stainless steel hose with 1/8" male pipe threads on each end to add a mechanical gauge. One end threads into the case, the other into a brass T fitting. The stock sender on one branch and a 1/8" copper tube on the other branch leading to a gauge in the cabin. A 6' length is barely long enough, but I have not been able to find anyone selling 1/8" copper in 8' lengths.

Thanks @930cabman - I have the really slick 42 draft block that has the hose into the case and then provisions for a single pole gauge sender, the stock idiot light and then an NPT port that i'm not using. I have a new pressure gauge in the cabin (from the single pole sender) and was just wanting to install a gauge on the bock just to double-check the one in the cabin...but the orientation of the face when tightened down on the block couldn't be at a worse orientation.

Since it's just for confidence and won't be in there forever, i may just install it and let it fall where it falls - not a big deal to do a little yoga to see the face a few times for the rest of the summer....

I have never heard of a 42 Draft block, excuse my ignorance. A double check is always a good thing.

https://www.42draftdesigns.com/content/Inst...locationKit.pdf

unfortunately, they don't make them anymore as they're a good kit.