64 SB oil pan plug

[Joe L.]

Re: 64 SB oil pan plug

Now that the original question has been answered, does anybody know whether or not these plugs had magnetic inner ends?

I have seen some (all with the circle-A) advertised as "correct big block magnetized", and "correct small block not magnetized". That makes no sense to me. I would think that they were all either one way or the other.

Joe-----


I do not know very much about this. I always thought that NO Corvette at least through the C4 era was ever originally equipped with a magnetic plug. Now, I'm not so sure. Here's why.

The 1966 edition of the P&A Catalog says this:

65-66 PASS., CORVETTE w/Sp. H/Per.(396, 427)
66 CORVETTE (427) (exc. Sp. H/Per.).......
SCREW(Magnetic) (1/2-20 X 1-5/64).....3866916

ALL, CORVETTE w/magnetic drain plug.......PLUG (1/2"-20)..........3866776

The first catalog listing is highly contradictory. However, it would seem that at least some 65-66 big blocks were to have used a magnetic drain plug in PRODUCTION. This kind of listing does not look like a SERVICE-only or accessory part type listing.

The second listing MIGHT indicate a SERVICE-only application but the "w/magnetic drain plug" implies that some other applications might have originally used it.

The 1967 P&A Catalog basically says the same thing as above except it curiously adds "F.I." after "w/Sp. Hi. Per." but still follows that with "(396, 427)".

The thing that I am most curious about, though, is what's the difference between a GM #3866916 and a GM #3866776? It turns out that the 3866916 was discontinued in January, 1970 and replaced by the 3866776. GM #3866776 was then discontinued in November, 1976 and replaced by GM #337185. GM #337185 was discontinued in March, 1986 and replaced by GM #23011420. The 337185 and 23011420 have 9/16" across-the-flats (wrench size).

But, what's the difference between a GM #3866916 and a GM #3866776? That's what interests me. They both cost $1.00 in 1966.

[Joe L.]

Re: 64 SB oil pan plug

Here's another variant (with a magnetic tip) although I don't know if it was ever a C2 production item. Notice the 3 punch dots in a triangular arrangement, which the original does not have.

Also, the head hex size is 7/8", and not 3/4" as appears (ed ?) in some C2 TIM&JG's. Head thickness is 1/4" on this one. I see the '65 guide calls for 1/8" thick, which seems to be inviting trouble. I'll have to look under my car to check and compare head thickness with what's there now.

Wayne-----


I'll bet the 3 "punch marks" in triangular pattern are a code for identifying a magnetic plug (i.e so that someone, maybe an inspector, could confirm that a magnetic plug was installed without removing the plug).