65 vette dude

It might be a good idea to keep that tach under 6K with A/C. Back in 1970, I bought a new Z/28. Living in South Florida, I, and the sales manager tried everything to get it made with A/C....... GM refused. They said that the LT1 was proven to smoke A/C compressors at high rpm. After I got delivery of the car......I understood what they meant.

macs65

Someone told me that if you mark the inside of the rear tire and the half shaft at the same location, then rotate the tire forward one revolution counting the how many times the half shaft turns it would give you a rough idea of the gears. for instanse one revolution of the tire to 3 and a 1/2 revolutions of the half shaft would equal a 3.50 gear. Don't know how true this is?? Maybe a more experianced member will chime in and advise.

C2Racer

That works but it's easier to just get out and run about 50mph, get the rpm and find an online calculator. There's quite a few of them.

C2Racer

The L76 has a larger pulley on the compressor to reduce it's rpm's. They apparently are rare?

hope2

exactly correct if it is a positraction rear.

65 vette dude

Rare as hens teeth. A friend has a 65 L76, with A/C, and looked for over a year for one for judging.......he never found one. LIC's does reproduce it, he bought it, and it passed judging.

Powershift

Macs65 needs to count the revolutions of the DRIVESHAFT not the halfshaft, If he counts halfshaft revolutions his rear end ratio will always be 1.

Larry

hope2

your right obviously, i assumed driveshaft.

JohnZ

Nope. Midyears didn't use the "ratio tags" - they were only used on some C1's, and there's nothing stamped on the top of the midyear diff; the ratio codes and assembly date are stamped on the bottom of the diff housing, between the strut rod bracket and the spring retainer plate.

JohnZ

Yes, they're extremely rare and expensive - here's what they look like.

hope2

my recollection is (some) A/C solid lifter cars had lower redline for simple reason belt might come off.

JohnZ

Nope, not on midyears. The only other solid-lifter Corvette with A/C was the '72 LT-1, and that application DID have a lower redline than it did without A/C, but the engines were identical - the idea was that the owner would respect the redline.

macs65

Sorry my error, the term should have been driveshaft.