LT-1 engine block code
Thread Starter
Heel & Toe
Joined: Nov 2023
Posts: 15
Likes: 12
From: Bryn Mawr, PA
LT-1 engine block code
Hello, I have a 1971 Red Convertible Base Model Corvette. I am looking to purchase a 1971 LT-1 Red Convertible Corvette. How do I know if the engine block is an LT-1?
Melting Slicks
Joined: May 2002
Posts: 2,469
Likes: 750
From: Laporte, IN
Since to 010 engine block was used for many years and different chevy models. The only way is the Suffix code has to be an original stamping CGZ LT-1 or CGY LT-1 engine in a ZR1. Plus the casting date code would be secondary verifier if the suffix code is thought to be original. The cast date is normally within weeks or days of the suffix build date but there are outside factors at Flint engine plant that may cause the cast date to be outside the normal few weeks.
Melting Slicks
Joined: May 2002
Posts: 2,469
Likes: 750
From: Laporte, IN
Personally there is an issue with the number 4 in your photo. It is not the typical font seen. Do you also have the photo of the VIN number stamped next to the suffix and the casting number on the rear of the block. Also the paint on the pad area should be removed to have a better view of the pad. Use paint thinner to remove it as to not damage the pad with tooling marks.
Pro
Joined: Nov 2014
Posts: 728
Likes: 346
From: Smyrna, TN
There are many discussions on stamps but the biggest indicator is the broach marks. If you see enough of the authenticated ones, you can tell a restamp rather quickly.
I look for other things to make sure if it is legit.
Open the oil cap on the valve cover and look to see if it has push rod guide plates.
Look at the harmonic balancer... It should be 8" diameter.
On the car itself, look for a single 3/8" fuel line on the passenger side running from the fuel pump back to the tank. If you see two lines (fuel and return) than the car is suspect...
71 LT-1's had TI ignition...If the module is missing, the wires should still be there as well as holes in the inner fender...
There are many other clues you can research to know what you are looking at...
Good luck!
