Technical SBC stripped threads in block - opinions? (Repair Update 5/8)

I have been chasing this oil leak for quite some time and finally decided to tear off the intake manifold and driver side head. I found the problem -- mostly stripped threads in the block where the oil plug goes.

I thought of reinstalling a brass plug with some good thread sealant and cap the whole mess off with some sort of epoxy.

I would appreciate your thoughts and ideas. Thanks.

 

Had this problem before... clean the area with brake parts cleaner.
Install the proper steel plug with liquid Teflon sealer.. No tape !
Then fill the hole up to the deck with " ultra" silicone sealer , grey or black work the same.. " ultra" sets very hard.
It will not leak , I promise.

Sent from my SAMSUNG-SM-G891A using The H.A.M.B. mobile app

 

If I remember right it was a Pipe plug. In the photo it looks like a smooth hole with no threads. Maybe it should have a soft plug in it. Personally I'd go talk to Archie for the easiest way and sound advice. I'm pretty sure you know who he is.
The Wizzard

 

they used non threaded plugs in the earlier engines, and threaded plugs in later ones, in that position., right?

 

Yes, I just can't remember when they did and when it stopped. Permatex sealer on a soft plug and 3 stake punches should do it.

 

I thought it was a solid plug, not a normal soft plug.

 

I can go in the shop and look at several SBC motors but they all are 350's. I can see that motor posted is a 283 or 327 and I just can't be sure what it used. Archie Somers is my local go to GM machinest and I know MAD 034 is close enough to him to do a drop in. MAD 034 is no stranger to Chevy stuff either but when in doubt ask the best person you know and Archie is where I would go.
The Wizzard

 

I don’t know about the real early blocks but I built a 301 from a ‘57 block and that one (and all the later ones) was tapped for 1/4 NPT. The top of the hole is not threaded, the threads start where you can see them in the photo, and the pipe plug was one of those square female hole ones. I bet somebody got gorilla and removed it without dripping candle wax by the threads and letting it wick in to help release the plug.
I would chase the threads with a pipe tap and maybe even try to cut two or three more threads. In any event, put sealer on the pipe plug as suggested, but be careful, don’t over tighten it, those remaining threads will be weak.

 

Thanks for the quick responses! the engine is a 1957 283 and the hole was fully threaded 1/4 NPT (I think). I like the idea of a soft plug as a fix. Interesting info as the top of the hole may have been smooth and just the bottom threaded -- I do see what appears to be threads up high however. Archie's shop is close by -- I will give him a buzz.

 

I was just out looking at the 350 blocks. That hole is smooth bore down 3/8" then the pipe threads start. Same as your block looks to be. The faint threads may just be a witness mark from removing your old pipe plug. The top of the plug in my motors is totally below the deck surface.
The Wizzard

 

Very interesting. I appreciate the look!

 

It looks like someone shit in their mess kit. (Screwed up.)

 

Got the motor back together with the help of the guys above and a little of my own common sense (very little). I ended up tapping the hole a bit deeper which allowed me a little more clearance up on top. After installing a new hex pipe plug with thread sealer I drove in a shallow 17/32" soft plug on top with a dab of RTV for extra insurance.

I've got about 50 miles and no leaks to be found. I am a happy guy -- thanks all.

 

The Wizzard is correct. The same as my 350 block. 1/4" npt thread, sealer (just about any will work) and tighten the shit out of it..... otherwise you'll have oil drizzling out on the floor..../ highway....

 

Locktite is the best thread sealer going . It will seal bad threads also

 

Good job!!!
Another block saved.....