1sicss

iTrader: (3)

Ok so I made up my mind and decided that I do not want to drive my car anymore due to the car burning more oil than I thought after I swapped camshaft. Im pretty sure its the valve seals cause I did the mistake of leaving the stockers on while swapping cams, anyways I dont really see myself vesting time or money in the stock heads for no extra power really piisses me off. I see that a guy on the forum posted 799 castings as the same as 243's is this true? Also a guy here at the local machine shop has some 4.8 casting which are 8xx I forgot the casting number as it's almost like the stock cast number on my stock ls1 heads are these heads any good? I know some of you may say get prc from tsp but really dont have the cash at the moment and also where could I get the centerbolt valve covers with racks since I have the 98' ls1 and each coil pack is bolted seperately in case I do come up on different set of heads. Long story short which heads out perform stock ls1 heads?

Isolde

iTrader: (4)

4.8 heads add compression, but have smaller intake valves.
799s are the same as 243s, with the better flow and the improved chambers,. And they add a little compression.

remauto1187

iTrader: (1)

The 799 is the casting number for vendors that make heads for GM and as he said they are identical to 243 castings. The 799/243 will NOT add compression to your LS1 unless your heads have a larger combustion chamber. They will if installed on a 4.8/5.3l though. The 243/799 will outperform your original heads and get you the perimeter bolt valve covers as well. The heads you probably ran into on the 4.8l are the 862 castings which also come on the 5.3L's . 862 heads have 61cc chambers and the 799/243 have 65cc chambers.

Isolde

iTrader: (4)

The 4.8 heads were nominally 61.15 cc, the 243s were nominally 64.45 cc, and the LS1 heads were nominally 66.67 cc. So switching from 66.67 to 64.45 does gain compression. This is exactly why the LS6 was 10.46:1 rather than 10.19:1

01ssreda4

iTrader: (96)

An LS1 head i.e. 241 has around 67 cc. So both the bolded statements couldn't be correct.

BIG_MIKE2005

iTrader: (116)

^^This. Also slappin a 67cc head on a 5.3 motor is not gonna give you comp. its gonna take it away cause your added a larger chamber head to a smaller bore block. Kinda like sticking a 317 head on a stock LS1. Thats why people use the 5.3 head with a smaller chamber to get a comp. bump on a stock LS1.

So basically his entire post was false information.

BADD SS

iTrader: (4)

Contradicting yourself in the same paragraph???? BTW 243/799's will add some compression on an ls1, but lose it on a 4.8/5.3. And they dont have perimeter valve covers...

Isolde

iTrader: (4)

But the OP of this thread made it clear that it's a 5.7, not a 5.3 or 4.8. The 4.8 / 5.3 heads were in question, for a 5.7L engine.

PREDATOR-Z

Just change the valve seals, that would be cheapest to put you back on track. Can be done while in car too.

PREDATOR-Z

Please delete this post, there is nothing true about it.

dawgs74

easy peezy........

G Atsma

Replying to a 7-yr old post.....

dawgs74

off topic though. .....I gotta 99 lm7 5.3 I was gonna rebuild and swap out to 4.8 flat tops......I have a set of aftermarket 64cc chamber heads ,any guesstimate's on what my compression should come out at?

dawgs74

I know......someone is bound to read this and maybe help......you could have just told me it was synthetic oil......(gf-4 oil) ......thanks in advance

KCS

iTrader: (20)

dawgs74

lol.....Yea that's kinda what I figured