55.2-59 Oil Pressure line hole

[db56]

My 235 had the oil line coming from the bottom of the engine to the oil pressure gauge. I need to find a plug for that hole in the engine when the oil line is removed.
Does anyone know what type and size is correct and where I can find one?

I've checked with 2 auto parts and hardware stores. No luck.

thanks

[mr48chev]

There are rubber plugs around and some searching can probably find one with the correct diameter to plug the hole in the firewall. On the other hand I have plugged small holes like that with a machine screw with a nut and washer on the inside before.

[nvrdone]

are we talking about where the line fastens to the block or where the ling goes thru the fire wall to the gauge? If its on the block I think its a standard 1/8" pipe plug.

[dsraven]

threaded holes in the engine block will simply be a national pipe thread like nvrdone says. you could just pick up a few different sizes and try them or you could take the old line fitting with you and match up a fitting. should be 1/8 npt I think. I gave my old gauge set away to a fella who needed one or I would check the line fitting for you.

[_Ogre]

you need to remove the fitting, not just the oil line
the oil line is a 1/8" compression fitting, the only place i've seen 1/8" copper line used

[mr48chev]

Once again, good complete with exacting information on what you are asking about info in the question gets better answers the first time around rather than turning it into a guessing game as to what you are asking about as it is quite obvious that those of us who answered have different ideas of what the question actually was.

[dsraven]

hey db56, did you get it figured out?

[db56]

Originally Posted by dsraven

hey db56, did you get it figured out?

Yes, turns out a 5/16" 24 fine thread should work.
Thanks

[db56]

Originally Posted by mr48chev

Once again, good complete with exacting information on what you are asking about info in the question gets better answers the first time around rather than turning it into a guessing game as to what you are asking about as it is quite obvious that those of us who answered have different ideas of what the question actually was.

Fixed. I needed to temporarily plug the hole in the engine where the oil pressure line goes so I could drive to the shop without oil leaking. Thanks

[db56]

Originally Posted by _Ogre

you need to remove the fitting, not just the oil line
the oil line is a 1/8" compression fitting, the only place i've seen 1/8" copper line used

Done. Thanks

[db56]

Originally Posted by mr48chev

There are rubber plugs around and some searching can probably find one with the correct diameter to plug the hole in the firewall. On the other hand I have plugged small holes like that with a machine screw with a nut and washer on the inside before.

Thanks, I found something that will work.

[db56]

Originally Posted by nvrdone

are we talking about where the line fastens to the block or where the ling goes thru the fire wall to the gauge? If its on the block I think its a standard 1/8" pipe plug.

Yes. The copper tubing is 1/8". The plug is 5/16"
Thanks

[dsraven]

if it is a short trip thats probably fine but maybe you wanna put a nut on the bolt first, screw the bolt in till it gets tight and then tighten the nut down to keep it in place. an o ring, then a washer, then the nut next to the block would be an idea as well. just so you don't screw up the threads in the block by tightening the bolt down to keep it in place.
I doubt if GM installed a regular thread into the block in an oil gallery because regular threads are not made to seal like a pipe thread or an o-ring backed thread would. since I have never seen a oring style fitting in a GM oil gallery before, on an old engine, I would say either that hole was "repaired" previously or it is a pipe thread. pipe threads are a tapered thread so the more the fitting is turned the tighter the fitting is in the hole. maybe just get'er done with the bolt for now but plan on looking into a little further when you get the truck back. I assume you are taking it to a shop for some repair so, if thats the case, make sure to tell them to keep an eye on that fitting plug so it doesn't come undone and they don't realize it. that could spell disaster in a short time.
here is a little blurb on fine thread fittings vs pipe thread fittings.
https://hydraxio.com/unf-vs-npt/

[db56]

Originally Posted by dsraven

if it is a short trip thats probably fine but maybe you wanna put a nut on the bolt first, screw the bolt in till it gets tight and then tighten the nut down to keep it in place. an o ring, then a washer, then the nut next to the block would be an idea as well. just so you don't screw up the threads in the block by tightening the bolt down to keep it in place.
I doubt if GM installed a regular thread into the block in an oil gallery because regular threads are not made to seal like a pipe thread or an o-ring backed thread would. since I have never seen a oring style fitting in a GM oil gallery before, on an old engine, I would say either that hole was "repaired" previously or it is a pipe thread. pipe threads are a tapered thread so the more the fitting is turned the tighter the fitting is in the hole. maybe just get'er done with the bolt for now but plan on looking into a little further when you get the truck back. I assume you are taking it to a shop for some repair so, if thats the case, make sure to tell them to keep an eye on that fitting plug so it doesn't come undone and they don't realize it. that could spell disaster in a short time.
here is a little blurb on fine thread fittings vs pipe thread fittings.
https://hydraxio.com/unf-vs-npt/

Good idea. Thanks for the advice.

[daveshilling]

Just do an LS Swap. That should take care of the hole.

Just Kidding (=

[mr48chev]

Originally Posted by db56

Yes. The copper tubing is 1/8". The plug is 5/16"
Thanks

That hole has PIPE threads not straight 5/16 threads. If you ran a 5/16 bolt in and tightened it tight you probably ruined the threads. Finger tight ok though. Straight threads would have required a gasket behind he fitting when it was screwed into the block.