'63 Stripped Oil Pan Drain Hole

[Norm B.]

When draining the oil on my '63 in order to pull the pan and replace the gasket I had that "Oh s**t" moment when reinstalling the drain plug when I just knew it was not going to snug up. My first thought for repair is Helicoil but are there any other or better options? It's a 340hp oil pan and the engine is currently out of the car, on a stand, and the oil pan was coming off anyway.

Norm

[Harry S.]

Re: '63 Stripped Oil Pan Drain Hole

When draining the oil on my '63 in order to pull the pan and replace the gasket I had that "Oh s**t" moment when reinstalling the drain plug when I just knew it was not going to snug up. My first thought for repair is Helicoil but are there any other or better options? It's a 340hp oil pan and the engine is currently out of the car, on a stand, and the oil pan was coming off anyway.

Norm

Potential solutions:

1) As you said a helicoil
2) Purchase a larger drain plug that will self tap a new set of threads into the pan
3) What is on the welded on the inside of the pan, a nut plate or a nut? Grind off the nut or nut plate and spot weld a replacement.

I had the same problem on my 63. I ground off the nut plate and replaced it with an NOS nut plate.

[Peter M.]

Re: '63 Stripped Oil Pan Drain Hole

Norm,
There should be a 1 and 3/8" by 7/8" flange that was spot welded inside the pan that the plug screws into. They were available from GM for service, I think the part number was 3723008.
I don't know if your FLAPS has them. I may have one in my tool box if you need it.
Kind regards

[Mark E.]

Re: '63 Stripped Oil Pan Drain Hole

Norm,
There should be a 1 and 3/8" by 7/8" flange that was spot welded inside the pan that the plug screws into. They were available from GM for service, I think the part number was 3723008.
I don't know if your FLAPS has them. I may have one in my tool box if you need it.
Kind regards

What an impressive car guy- knows the part number AND may have one in the toolbox.

[Joe L.]

Re: '63 Stripped Oil Pan Drain Hole

Norm,
There should be a 1 and 3/8" by 7/8" flange that was spot welded inside the pan that the plug screws into. They were available from GM for service, I think the part number was 3723008.
I don't know if your FLAPS has them. I may have one in my tool box if you need it.
Kind regards

Peter------


The part number was GM #3723008. However, it was discontinued without supersession in July, 2013.

[Harry S.]

Re: '63 Stripped Oil Pan Drain Hole

Here is what it looks like.

IMG_1071.jpg

[Harry S.]

Re: '63 Stripped Oil Pan Drain Hole

Installed...

s-l1600 (5).jpg

[Peter M.]

Re: '63 Stripped Oil Pan Drain Hole

Thanks Mark and Joe.

[Mark E.]

Re: '63 Stripped Oil Pan Drain Hole

The design of #3723008 highlights why these things leak. It's not enough for the threaded hole to be sealed. The flange of the drain plug must also be sealed against the surface of the pan.

[Patrick H.]

Re: '63 Stripped Oil Pan Drain Hole

You might also look at a Time-Sert rather than a Heli-Coil.
Better product.

[Joe L.]

Re: '63 Stripped Oil Pan Drain Hole

The design of #3723008 highlights why these things leak. It's not enough for the threaded hole to be sealed. The flange of the drain plug must also be sealed against the surface of the pan.

Mark------


The seal at the oil plug flange is the only seal that matters. Unfortunately, despite repeated attempts GM never came up with a seal that worked 100%.

GM #344690------metal and asbestos composition

GM #513975------nylon

GM #3765650----nylon

GM #3921989----nylon

GM #14079550--rubber/tin

GM #14090908--rubber/tin

Later with metric thread plugs:

GM #3536966----rubber; used with compression controlled plug GM #11562588

NONE of the above work to 100% prevent oil seepage at the plug. NONE!

Below are photos of the GM #14090908 which is the latest and currently available seal for SAE thread plugs. Also shown is the GM #3536966 and with the GM #11562588 plug.

DSCN3703.jpgDSCN3704.jpgDSCN3706.jpg

[Mark E.]

Re: '63 Stripped Oil Pan Drain Hole

Mark------


The seal at the oil plug flange is the only seal that matters. Unfortunately, despite repeated attempts GM never came up with a seal that worked 100%.

GM #344690------metal and asbestos composition

GM #513975------nylon

GM #3765650----nylon

GM #3921989----nylon

GM #14079550--rubber/tin

GM #14090908--rubber/tin

Later with metric thread plugs:

GM #3536966----rubber; used with compression controlled plug GM #11562588

NONE of the above work to 100% prevent oil seepage at the plug. NONE!

And this explains why it's so common the threads strip- folks trying to stop the leak by over-torquing.

[Dick W.]

Re: '63 Stripped Oil Pan Drain Hole

And this explains why it's so common the threads strip- folks trying to stop the leak by over-torquing.

I have used Loctite PST on the threads of oil plugs for years. Might leak somewhere else but not there.

[Joe L.]

Re: '63 Stripped Oil Pan Drain Hole

I have used Loctite PST on the threads of oil plugs for years. Might leak somewhere else but not there.

Dick-----


I've tried that, too. It did not work for me. And, the seepage was definitely originating from the plug.

[Terry M.]

Re: '63 Stripped Oil Pan Drain Hole

All Corvettes mark their spot.
Just like they all leak.
Not to worry.