NOS327

iTrader: (30)

was looking at a suburban for the wife this evening and noticed the 5.3L in it had 243 heads. Both sides, clear as day.. Is this correct? ..just wondering if somebody has been into the motor.



Engine apparently is an LC9 if anyone can break that down

Thanks,
TJ

ISMELLRICE

iTrader: (22)

from what i have read before some 5.3's did come with 243 heads

SLP4CamaroSS

iTrader: (16)

my 2007 sierra 4.8 has them also nothing special i think all the newer 4.8 and up got teh 243

01ssreda4

iTrader: (96)

Yep, it turned into the go-to head for the Gen 3 and up motors. Lots of trucks got them.

2nd Gen Fl 'bird

iTrader: (13)

Good heads, just doesn't have the sodium filled/hollow stem valves like the Z06 243 head.

NOS327

iTrader: (30)

yeah, I got the same heads on my '06 GTO donor motor for my chevelle swap, that's what caught me off guard.

Anyway, thanks guys.

Full-Force

iTrader: (11)

My guess was it was an easy way to improve power and lower compression at same time.

rdkonkel

iTrader: (4)

Did the intake port change at all on the heads. I have some older cathedral port motors but haven't dealt with the L92 heads. Saw the '07's have the newer style intake with the 4 bolt throttle body. Just wondering

awd39chevypickup

so whats the differance between these cas numbers and 863 number?

01ssreda4

iTrader: (96)

The 241/853 LS1 head is a 67cc chamber and (I think) around a 200cc intake runner. The 243/799 casting is a 64cc and around a 210cc runner. More compression and the potential for more flow volume is why they perform better. Because the port is somewhat tweaked, they produce better results when ported as well, as opposed to a standard LS1 or 5.3 head. Valve size is the same for all 4 of these heads. I don't know much about the 5.3 heads except the chambers are likely around 62cc, they have smaller valves, and they flow like crap in stock form. I really don't think they are that great of a head when ported either (from what I've seen).

For flow: 243/799 > 241/853 > 5.3
For compression: 5.3 > 243/799 > 241/853

And the 317s are basically the same as 243/799s just with 72cc chambers (more deck thickness) for really low compression. A favorite among the boosted applications.