862 casting number. heads
 

Off a 2004 5.3 liter. The casting numbers are 862, does anyone know the specs for these heads? Combustion chambers. Valve sizes. Anything that would help. Wanting to see if I buy these and port and Polish them if they would be much better than my stock 4.8 liter heads off 2008 4.8. Any help would b appreciated

They will all end up flowing about the same in the end due to the CNC program being pretty much identical on all the LS1 style heads. The 4.8 heads probably have a smaller runner though thinking more about it...

So the 862's ported will definitely better than the imported 4.8's? I mean yes that makes sense LOL! Do you know anything about combustion chamber sizes? I need to get a compression ratio

You should take a look at the casting number on the heads that are on your motor. You should either have an 862 casting or a 799. If there is an 862 casting on the motor right now then obviously you have just purchased the same thing. If it is a 799 casting it is actually and LS6 head which will flow a little better then a 862 casting will once ported. 4.8l motors don't have heads specifically made for them, the runner will be same size as on a 5.3l truck head.