Ok So I was super bored with nothing to do at work this morning and I was looking over 2 different 5.3L Engines I have and I noticed they were 2 different castings #s.

12567393 Block Came with 706 Heads The block has the snow flake mark next to GM on the back leftbehind the bell housing area. I believe was from an 03 tahoe or suburban... based on casting date and what the Guy I bought it from told me.

12567392 Block came with 862 Heads The block has an Isosceles trapezoid Shape with EB cast inside of it also On the back left behind the bell housing area... was from an 02 Tahoe cause I pulled it My self

I also noticed They used different oil pans,front and rear covers, And the cranks appear to be machined different inside of the rear Piolit area...

I was wondering If any one has yet established If one is cast better then the other Like with the Old Blocks???

Any one know Were there being cast at???

SO far I have not heard of any one having core shift Issues with regards to sonic checking these or boring these out to stock LS1 5.7 spec.


I will try and Get some pictures of this stuff I am refering to.
I am not worried about the covers, pans, and Little stuff as I am sure they are all interchangable.

I was Just curious about the Block Castings them selfs....

I have not gone inside the motors to inspect the cranks But I was wondering About the cranks and why they would be machined differently in the rear piolit area? Perhaps it has something to do with the equipment The were machining it on at the different assembly plants??? I am sure it makes no difference.... But since I was bored and actually took the time to notice this crap I figured maybe I could learn something new....

 

could that be backwards? i have a 5.3 12567393 with 862 heads and the snowflake by the gm. trying to figure mine out.

 

No, Head castings have nothing to do with specific block casting numbers. 4.8/5.3 blocks cam with 706 or 862 heads. It depends on what was available at the assembly plant during assembly.