862 vs 706 heads.
862 vs 706 heads. Cracked the block on an L33 (higher output aluminum block truck motor). It has 862 heads. I found a low mile 5.3 that has 706 heads. What is the difference? The L33 is a higher compression motor (10:1 I think) vs the base 5.3L truck motor. Is the combustion chamber vulume less on the L33 heads to get the compression bump? Also, do the L33/862 heads have bigger valves and ports? We're going to pull the cam from the bad L33 block because it's bigger than the base 5.3L truck motor cam (similar to LS6 cam specs). I'm just wondering if we need to put the L33/862 heads on the new motor too. We're going to at least have to swap the springs out for the cam swap. 862 heads are ready to go with a fresh surface job.
Last edited by old motorhead; Feb 2, 2009 at 05:27 PM.
i also have the same question about the heads... i just picked up an '06 5.3L iron block with 706 heads and i have a set of 862 heads also... i searched and this is the only thread i found. i haven't pulled the 706's off the motor yet. just wondering if theres any difference?
Those heads are the same, just different casting numbers. Same size valves and combustion chambers. The L33 gets the compression bump from flat top pistons versus a 7cc dish piston in the regular 5.3.
