mightybird

Ok fellas what is the biggest advantage of going with a ls3 vrs the ls2? this engine will have stage 1 prc ls6 head on it. I have yet to spec a cam I kinda wanted to wait till i got the short block at my house. but the idea is to run boost so far this is where im at.

Tainted

iTrader: (9)

ls3 hands down. more displacement, larger bore, badass flowing heads and intake, most recent technology. what more could you want?

BTW no ls6 heads for ls3!!! the stock heads outflow the ported ls6 ones you have.

gnx7

iTrader: (28)

yes yes and yes

LS3 with stock LS3 heads/intake and a good sized cam will make around 500rwhp.

Mike454SS

iTrader: (4)

Yeah...stock LS3 heads are pretty dam great compared to older GM castings.

The difference from say the LS6 to the LS2 wasn't as big a deal...they went up 0.3 liters but they used the same heads on the new engine that they used on the old one...when they went to the LS3, they opened up the bore even further, which really helps flow a lot, then they completely changed the port design...which really helps move a good bit more air. LS3 ports almost look like they're stolen from a big block.

mercccc

i did the opposite of what most are telling you and was happy with the results. i used my prc 5.3 heads that i allready had on top of a used stock bottom end l92. i think the 126 traps for a 3700 pound car were decent for the money spent.

mightybird

well i do agree the ls3 heads are much better but this is what i have for now. I will buy a forged bottom end ls3 short block and use my heads and intake till i save up more money for the better heads and intake.

mightybird

What are the flow numbers of the ls3 heads? if i remember right these heads i have flow numbers in the 320-330cfm range at 600 lift

mightybird

looks like the ls3 heads flow 307cfm at 600 lift stock http://s2performance.net/ls3heads.html

Tainted

iTrader: (9)

Without milling the ls3 heads down, you will lose some compression. Your heads have a much smaller chamber than the l92

mightybird

i was wrong the prc heads i have flow 313 cfm at 600 lift so this should be interesting.

bww3588

iTrader: (49)

The ls2 bottom end and ls3 top end is a very stout combination. Once it's all said and done, you basically have an l76, which is a very good engine.

mightybird

im going with a forged bottom end ls3 and will run my prc heads till i save up for some prc ported ls3 heads i plan to run the kypt turbo kit on the car as well.

mercccc

You are correct. I think we are looking at 11.46:1 with these 62cc 5.3 heads. I did exactly what the op is doing. Use what we had at the time and save for better heads down the road. It still should be a solid setup.

Mike454SS

iTrader: (4)

I misunderstood your original post. I thought you meant an LS2 with 5.3 heads versus an LS3 with LS3 heads...given the same heads on both, go for the LS3 if price is reasonable just to have the bigger bore, but it's not really going to be a major difference.

lstvr

I have LS3 bottom end, with modded Dart LS1 heads sat on the top...