1969 350/350 Oil Drain Plug

[Steve M.]

I have a 350/350 October 1969 build and wanted determine the correct oil drain plug. When I purchased the car it had a 'modern' oil plug. I have picked up several plug and would like opinions on if either is correct. One is a 9/16 " wrench with a D in a circular depression in the center, outer flange is approximately 7/8" in diameter and 1/8" thick. The other is similar size but has a raised A in the center. Any comments appreciated.
Thanks, Steve

[Joe L.]

Re: 1969 350/350 Oil Drain Plug

I have a 350/350 October 1969 build and wanted determine the correct oil drain plug. When I purchased the car it had a 'modern' oil plug. I have picked up several plug and would like opinions on if either is correct. One is a 9/16 " wrench with a D in a circular depression in the center, outer flange is approximately 7/8" in diameter and 1/8" thick. The other is similar size but has a raised A in the center. Any comments appreciated.
Thanks, Steve

Steve------


The flanged, 9/16" across-the-flats (wrench size) drain plug is correct for all 1969 and later Corvettes. I believe it's also correct for most, if not all, 1968's, too.

As far as headmarking, there were at least several. "A" was one of them. I don't specifically recall seeing a "D" but I have little doubt they were also used during 1969. "D" is a period-correct headmarking.

You can still purchase one of these drain plugs from GM under GM #3921988 although the headmarking probably won't be period-correct.

Speaking of these drain plugs, I sure wish that GM or someone else like Dorman made one of these things in 1/2-20 thread size but otherwise configured for use with the rubber seal used on many later metric-sized drain plugs. This would solve the problem of drain plug leaks which plagued Chevrolet engines for years. I'd use one of these things regardless of what headmarking it had and regardless of whether it's configuration slightly differed from the originals. See attached photos of what I'm referring to. These things are THE NUTS! ABSOLUTELY. POSITIVELY. PERIOD.

If I were replacing an oil pan drain plug flange plate in any C3 oil pan, I'd use a plate tapped for M12 X 1.75 thread and, then, use the plug described. Yes, its head configuration is slightly different than original C3 plugs but I prefer NO LEAKS to nuances of configuration.

[Steve M.]

Re: 1969 350/350 Oil Drain Plug

Joe,
Thanks for the infromation.
Steve

[Sal C.]

Re: 1969 350/350 Oil Drain Plug

Joe, try NAPA part #704-1925. I think it is what you are looking for.

[Joe L.]

Re: 1969 350/350 Oil Drain Plug

Joe, try NAPA part #704-1925. I think it is what you are looking for.

Sal-----


Thanks; I'll give that one a try.