C1-56/57 pan rail fasteners

[Joel M.]

Oil pan side rails. Slotted screws or flat head hex bolts or recessed head hex bolts? Memory tells me screws but probably wrong so if hex bolts - what head config and marking? Thanks.

[Garry Barnes]

Re: C1-56/57 pan rail fasteners

Joel, you will need 14 "L" headmark 1/4-20x1/2" bolts and 4 "L" headmark 5/16-18x5/8" bolts. You can get the correct kit from Paragon. Catalog page 9. I believe they are hex head.
Garry

[Joel M.]

Re: C1-56/57 pan rail fasteners

Garry - I figured I was dreaming on the slotted screws with star washers but sure thought I'd seen used in this area when messing with 265/283's back in the mid/late 50's. Were slotted screws used for any GM oil pan retention applications during this period? Maybe six cyl? Thank you.

[Joe L.]

Re: C1-56/57 pan rail fasteners

Joel------

You weren't dreaming. 1955-57 V-8s as well as 53-55 Corvette 6 cylinders used slotted head screws for oil pan attachment. These screws had a captive, external tooth star washer. The 55-57 "corner" screws were 5/16-18 size and were of GM #839896. The remainder of the screws were 1/4-20 size and were of GM #839301.

Sometime after 1957 (1958, I think), the screws were changed to the hex head style seen thereafter.

[Loren L.]

Joe is correct - the 56 & 57 Parts Bks call

out the 1/4" as #839301 and the 5/16" as 839896 in Gr 1.428. #839896 is still in my 1971 Standard Parts Book (with a reference to Gr 1.428) and is described as "FILISTER HEAD BOLTS, with Lock Washer" and a picture showing a slotted head.

[Joel M.]

Re: Joe is correct - the 56 & 57 Parts Bks call

Thank you Joe and Loren --- Now I can pitch the " correct" repops with mental impunity.

[Clem Z.]

that is why chevy are called "stovebolts" *NM*

[John M.]

Re: Joe is correct - the 56 & 57 Parts Bks call

Don't forget that the timing cover and the plate on the back of the waterpump used the same screws. They all had a habbit of getting changed over the years!

Regards, John McGraw

[Joel M.]

Re: Joe is correct - the 56 & 57 Parts Bks call

I am also getting a flashback on the slotted screws being used in the bottom two locations on the fuel pump plate. Does this ring right? Thanks.

[Loren L.]

I don't think so - the AIM calls out #193938

for retention of the plate - that was discontinued in 10/63 and the replacement is directed to be HEXHEAD 1/4 X 20 #3817006. The AIM calls out 179840 for pump bolts and nothing I have shows this discontinued or ?????

[Joe L.]

Re: I don't think so - the AIM calls out #193938

Loren-----

GM #193938 was a hex head bolt with captive lockwasher of 1/4-20 X 7/16".

The fuel pump mounting bolt GM #179840 was never discontinued from SERVICE, but only because it was never "continued". It was a PRODUCTION-only item which was never available in SERVICE. Its SERVICE "equivalent" was GM #3751842. This was a 3/8"-16 X 1-1/8" bolt with washer head design and captive split lockwasher. It's now discontinued, too.