my 2012 5.3 has the 799 heads and flat top pistons for 9.9 compression.

 

I know I'm new here, but someone should add that all the heads are cast the same as far as head bolt bosses are concerned. Its the blocks that's different. I had some confusion with this when I bought head bolts that fit the newer engines when I needed the older bolts that fit my block.

 

good info

 

Gen iv rectangular port castings are 5364, 0821 and 823... The ls3 came with sodium filled valves in 0821 heads... The 5364 were the earlier castings on the l92, the 823 and 0821 were used on most of the 6.0l (L77, L96, L76 etc) as well as most of the later 6.2 truck engines... The lc9 5.3s typically have 243 castings and the lmg 5.3, l20 4.8 most of what i have seen have been 799.... This is from what ive seen the past few months working at a chevy dealer....

 

Anyone know the specs on the 823 heads ?

 

https://www.performancetrucks.net/fo...e-823s-434453/ Theres some info in here

 

 

This video does a decent job of comparing heads.

706 / 862 pope hat heads - Every 4.8L & 5.3L V8 before '06 ... except the L33
61.15cc combustion chamber, 200cc holy intake port, 70cc oval exhaust port, 1.890" intake valve, 1.550" exhaust valve

243 / 799 pope hat heads - 5.7L LS6 (hollow valves), 5.3L L33, 6.0L LS2, most 4.8L & 5.3L after '05, 6.0L LFA & LZ1
64.45cc combustion chamber, 210cc holy intake port, 75cc D- exhaust port, 2.000" intake valve, 1.550" exhaust valve

821 rectangle heads - 6.2L LS3
68cc combustion chamber, 260cc rectangle intake port, 90cc D- exhaust port, 2.165" intake valve, 1.590" exhaust valve

716 / 364 / 823 rectangle heads - 6.2L L92 L9H L94, most Gen4 6.0L
70cc combustion chamber, 260cc rectangle intake port, 90cc D-port exhaust port, 2.165" intake valve, 1.590" exhaust valve

Don't know for sure which rectangle port head was used by the L99? I'll make any provable corrections as needed.

 

Are you just trying to get your post count up by regurgitating stuff that's already been posted in this thread?

 

I have never heard of cathedral heads referred to as “ pope hat heads”.