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Old 04-29-2012, 08:42:49 PM   #1
DCL70
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1970 Oil Pan Bolt (aka plug) marking

I would like to know the correct marking (or markings) on the oil pan bolt (aka plug) from original 1970 Camaro engines made in Tonowanda. According to my 1970 Chevrolet parts catalogs the GM part number is 3923420 in Gr. 1.456 and is described as "1/2"-20 X 13/16" - non-magnetic". The gasket is listed as GM # 3921989 ("nylon 1/2" I.D. X 29/32" O.D.).

I have a bolt from a 1970-1974 oil pan with the letter "A" inside 2 concentric circles with 9/16" hex head (actually a washer-head) as shown in the link below. The threads are 1/2"-20 by about 0.50" long. The end of the bolt does not have any threads and measures 0.41" in dia. and 0.34" long. The net length of the bolt measures about 0.84" (13/16" = 0.81"). The "smushed" nylon washer measures about 0.92" in dia. (29/32" = 0.91").

BTW, the main bolt that holds my 1970 factory Hurst shifter onto the transmission has the letter "A".

I assume the oil pan plugs installed on 1970 Z28 engines from Flint had different markings.

I would appreciate any comments after the next oil change from those with original engines.

I also have a oil pan bolt from a 1969 oil pan that is almost identical. The marking is in the shape of a "dog bone" of "bow tie" with rounded corners.

Dave

http://imgur.com/a/syoJz#0
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Originally from "Narragansett No. 6" in the Bay State

1970 Camaro SS350 w/Muncie
(real long term project, 1990 to ????)
1966 Corvette 327 w/Muncie (1980 to 1995 restoration)
1994 Camaro Z28 w/6-speed M.T.
1998 Chev. S10 w/4.3L & 5-speed

Last edited by DCL70 : 04-29-2012 at 11:53:41 PM.
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Old 05-14-2012, 07:53:15 AM   #2
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Did an oil change yesterday on my 70 LA-built SS350. Looks like I need to get a new nylon washer for next time.
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Andy

70 SS L48 Forest Green Auto
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Old 05-14-2012, 09:07:45 PM   #3
DCL70
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Andy,

You oil plug looks exactly like the one that I have on a 1969 oil pan. I assume your engine was built in Tonowanda.

According to my 1970 Chev. parts catalog the nylon washer should measure 1/2" I.D. and 29/32" O.D. (0.91")
My original washer measures about 0.94" O.D., 0.50" I.D. and about 0.065" thick.

I found a suitable replacement nylon washer made by Dorman (part # 65270, M12-1/2"). It actually measures about 0.99" O.D. . 0.55" I.D., and about 0.065" thick.

Thanks for your reply.

Dave
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Originally from "Narragansett No. 6" in the Bay State

1970 Camaro SS350 w/Muncie
(real long term project, 1990 to ????)
1966 Corvette 327 w/Muncie (1980 to 1995 restoration)
1994 Camaro Z28 w/6-speed M.T.
1998 Chev. S10 w/4.3L & 5-speed
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