Indicators of a 1971 Big Block Car

[Nick P.]

My friend is restoring a 71 vette. He purchased it with a crate engine installed. The core support appears original and is for a 454. However, that can easily be replace along with other indicators of engine size such as the console plate, etc. Are there any indicators that are not as easily changed that would provide an indication if the car was originally a small block or big block? I appreciate the help!

[Patrick B.]

Re: Indicators of a 1971 Big Block Car

Does it have a rear sway bar? What is the rear end code? What is the diameter of the front sway bar?

[Mark E.]

Re: Indicators of a 1971 Big Block Car

Aren't big block half shafts shot peened?

[Ron G.]

Re: Indicators of a 1971 Big Block Car

Some indicators are suspension components such as shocks and their tags, front coil springs and their tags, the size of the front swaybar and also if they have rear swaybars. Also look for the heavy duty caps on the inboard part of the axle half shaft connecting to the outboard part of the rear end All big blocks have, automatic big and small block along with small block high-performance and all automatics are shot permed with number 31 number 31 shot. Those are just some indicators.

[Nick P.]

Re: Indicators of a 1971 Big Block Car

Does it have a rear sway bar? What is the rear end code? What is the diameter of the front sway bar?

The car does not have a rear sway bar and the front is 0.75 inches. It also appears to have original AC...which I understand was not offered with big blocks?

[Tim G.]

Re: Indicators of a 1971 Big Block Car

AC was not offered with the LS6, but it was available with the LS5.

[Stephen L.]

Re: Indicators of a 1971 Big Block Car

At some point in this era the engine designation code became part of the Vin..... don't know when that started but it's worth checking out

[Patrick B.]

Re: Indicators of a 1971 Big Block Car

3/4" front sway bar and no rear sway bar are small block attributes. What is the rear end code?

[Larry M.]

Re: Indicators of a 1971 Big Block Car

For at least GM, 1972 was the first year that included an engine identifying character in a car's VIN.

[Joe L.]

Re: Indicators of a 1971 Big Block Car

At some point in this era the engine designation code became part of the Vin..... don't know when that started but it's worth checking out

Stephen------

1972 was the first year for the engine coded into the VIN.

[Joe L.]

Re: Indicators of a 1971 Big Block Car

The car does not have a rear sway bar and the front is 0.75 inches. It also appears to have original AC...which I understand was not offered with big blocks?

Nick------


The car in question is an original small block car. No doubt in my mind about it, at all.

[Ron G.]

[Patrick B.]

Re: Indicators of a 1971 Big Block Car

The rear end code indicates whether the heavy duty caps were on the rear from the factory. Also the code would show whether the ratio was typical of a LS -5 or an LT-1.

[Ron G.]

[Mike E.]

Re: Indicators of a 1971 Big Block Car

In 71, AX was code for heavy duty 3.36, LR for regular 3.36. Why they had the two codes for 3.36 only, I have no idea.