C1 Trap Door Oil Pan Identification

[Mark S.]

Seeking your expert assistance. I have (2) C1 3-Step Trap Door Oil Pans and want to be certain to install the correct Oil Pan on my 1960 270hp car.


Each Pan has the correct single long vertical crease line along with identical rivet marking locations for the side baffles and trap door.
IMG_4918.jpgIMG_4918.jpgIMG_4933.jpgIMG_4950.jpg



My questions are as follows:

Your assistance is greatly appreciated. Thank you in advance.

[David L.]

Re: C1 Trap Door Oil Pan Identification

Mark,

One pan might be GM # 3769761 (1960-1961 Corvette) and the other pan might be GM # 3789629 (1962 Corvette). In your 4th photo, the pan on the right side with the single "half moon" cutouts on the side baffles looks like the 3769761 oil pan.
According to Chevrolet Parts History GM # 3769761 was replaced with GM # 3789629 in October 1961 for over the counter parts.
I am not an expert on straight axle Corvette parts but I have done some research on Chevrolet oil pans over the years.

The link below might be helpful if you can read it.

Dave

http://www.earlycorvettes.com/corvettesite/SACE/articleswebpages/Mechanical/v4n1oilpans.pdf

[David L.]

Re: C1 Trap Door Oil Pan Identification

Mark,

Listed below is a NOS 62 Corvette oil pan (GM # 3789629) currently on Ebay for those with really deep pockets.

Dave

http://www.ebay.ca/itm/ws/eBayISAPI.dll?ViewItem&item=261040202936&clk_rvr_id=455588349393

[Bill M.]

Re: C1 Trap Door Oil Pan Identification

My guess is that the two cut out areas for the '62 pan provide a better fit of the baffle to the pan body (for a more secure spot weld.)

[Greg K.]

Re: C1 Trap Door Oil Pan Identification

From working with manufacturers, the baffle with the two cut outs could be left over parts for oil pans with two grooves used in the newer oil pans. Just a hunch.

[Loren L.]

Re: C1 Trap Door Oil Pan Identification

The one on the left gets my vote as the OEM 60-61 HP trap door. Both would probably pass judging.

[Richard M.]

Re: C1 Trap Door Oil Pan Identification

Mark, On your left pictured pan in photo #4....

Look very closely on the pan-to-block mating area on the left side(Drivers Side), between the 3rd and 4th attach bolt. There may be a date stamp visible. I have a service replacement on my '59 270hp. The date stamped on the pan's flange is 7 79. (July 1979). This one obviously not original.

P9230089.jpg P9230086mod.jpg


Below is what I believe is a original trapdoor pan which came with a '61 project. There is no date stamp on this pan.

P9230090.jpg P9230091.jpg

[Richard M.]

Re: C1 Trap Door Oil Pan Identification

I forgot...I took this one off of a 283 a few weeks ago. It's a replacement not original(I think). Painted black inside(not residue).

IIRC there was a date on it too but that I don't recall. It has the 2 grooves on each side and the two half moons on the reinforcements to clear the grooves.

P7300121.jpg P7300120.jpg

------| ------------|
------| ------------|
------V------------V

P7300119.jpg P7300118.jpg

[Bob J.]

Re: C1 Trap Door Oil Pan Identification

I'm fairly certain the rectangular oil drain plug plate is period correct for C1 Corvettes. BobJ

[Joe L.]

Re: C1 Trap Door Oil Pan Identification

Secondly, the Oil Drain Plug thread types differ as well.

Mark------


If you are talking about the thread size being different, then one of the pans must have had the oil drain re-threaded. All 1955-82 oil pan drains were 1/2-20 thread.

If you're talking about the drain flange or nut, I believe that original 1955-57 and 62-82 used the spot welded-in flange plate whereas original 58-61 used the welded-in nut. Later SERVICE pans for all 1956-82 applications used the spot welded in flange plate.

[Ian G.]

Re: C1 Trap Door Oil Pan Identification

I'm probably going out on a limb here, but after a lot of reading and examining ebay auctions and more reading, and getting the wrong pan and then finally what I think is the right pan for my early 59, here is what I think:
Rich's pan is an original 761, used late 60 to 61.
Mark's left photo appears as an early replacement 937 pan (it seems to have had two versions, same number with different weld spots, etc) (are a 629 as david suggests) and the right is an original 642 for 57 -60E like I have (which agrees with Bob's observation). From my understanding though, depending on "early" and late" 60, it could either be Rich's pan or that pan as "correct" on a 60. I don't know what early or late would be in terms of month though. I think it is a early 937 since that one has a lot of spots welds on the side, and that one appears to have them, though i can't tell with the paint.
My assumption on the extra cutouts on the 937 (or 629) is a cost-saving measure so the baffles could be used on other pans.
Please take what I think with a grain of salt.

[John R.]

Re: C1 Trap Door Oil Pan Identification

Adding to this 6 year old post. Found what I think is a unique trap door pan, at least to me. Wondering if anyone else has seen this configuration?

It's a 2 side rib, 3 smooth step, rectangular oil plug plate pan with trap door. Thought trap doors were only supposed to have 1 rib? Has all the characteristics of a 57-59 pan, but with the trap door. Huh...?