How can i tell if i have a 2nd Gen LS1, the one that has all the same length head bolts?

 

Built starting 1-1-04

 

is there a block number?

 

if you have a GTO with an LS1 then you most likly do.

 

It will have the LS6 casting number 12561168 on the drivers side rear flange. Even with this stamp it could still be an 01-03 block but an 04-up will not have a different casting number than this. There is a code stamped somewhere that gives the production date, but I can't seem to find the thread with the location and breakdown.

If the heads are off you can stick a piece of tie wire in the bolt holes and see if the holes are all the same depth.

 

I found the info I was looking for but I don't have a block at work with me to verify the location. There should be a 4 digit code on the pad in front of the passenger side cylinder head. It will start with a letter followed by three numbers. The letter will be the month the block was cast, the second two numbers are the day of that month, and the last number represents the year. Ex: J025 - J is the 10th letter of the alphabet so that is October, 02 is the second day, and 5 is 2005.

 

ok, well in that case i need to buy an LS1 Gen 2 block.. anyone have one for sale.