1966 L72 Biscayne

[mssl72]

So anything 1966 full size L72 gets my attention, so I was following this thread. The transmission discussion brought up things for me again and I found a document I had been putting together and thought I would post it.

Transmissions in these cars and the cowl tag always puzzled me some. L72 full size cars in 1966 were available with M20, M21 and M22. There was also the 3 on the tree option too. In regards to the M22 in full size cars, GM documentation says only 2 cars were produced at the factory. While close ratio transmission cars had a "2Q" as an indicator and wide ratio transmissions had a “2L”, it seems that not all plants used the same codes, especially BOP (Buick-Olds-Pontiac) plants.

I always wondered why Fisher body needed to know if the trans was close or wide ratio. I figured all they needed to know is if it was going to get a 4 speed or automatic. I had a conversation with Leigh Scott (who is a '66 Full size fanatic and retired GM 35+ year employee) about it and he said;

"All transmissions in 1966, except for Muncies, the speedo cable came out on the drivers side. The Muncie for '66 came out on the passenger side. In 1965, for the M20 Muncie, the speedo cable came out on the drivers side, the M21 came out on the passenger side, hence the reason (I believe) for the "Q" to denote the close ratio M21 and the need for the passenger side speedo cable clip on the floor pan. Old habits die hard, so that's why I think the "Q" lasted for 1966.”

He also mentioned that the rear axle gear ratio had an impact on if the trans would be close or wide ratio. It seemed that cars with low gear ratios got wide ratio transmissions. Paul (fsc66) posted documentation to reflect this as well.

So over the years I’ve kinda built a little list of 1966 L72 Caprices. The trans codes and gears didn’t always jive and I believe that Leighs reasoning on the codes makes sense.

Here are some known examples:

3.31 (DH code) and an M20 no trans code on tag (Doraville BOP plant built) 04D 16647 Caprice
3.73 (DM code) and an M21, 2Q on the tag (Atlanta plant built) 01B 16647 Caprice
3.73 (DM code) and an M21, 2L on tag (Norwood plant) 12C 16647 Caprice
4.10 (DN code), 2L on tag, wide ratio? non original M20 installed (Norwood plant) 01A 16647 Caprice
4.10 (EH code metallic brakes) and an M21, 2Q on tag (Los Angeles built) 12B 16647 Caprice

Adam, your car sounds like it’s on track. The K66 TI option is a nice piece. To see if you can locate some parts you’re missing I would contact Leigh Scott via his website. He’s a great guy, full of knowledge, and does insane restorations.

https://www.detroitautomotiverestoration.com/

I am curious if you can post some closer pictures of the air cleaner, the snorkels and bottom. What is the exhaust system like, is it original, where do the tailpipes exit? The radiator looks correct. Remove your washer bottle and take a look at the side of the radiator with a good light and see if there’s a number stamped on it. If it does let us know what it is. What is the stamping on your alternator (that pulley isn’t correct, alternator could be)?