krwyellowZ28

iTrader: (10)

I've searched a couple different forums without a definitive comparisson or opinions on swapping out the stock 317 heads for a set of 243/799's on an LQ4. Second hand experience has shown how 317's on a turbo 5.3 will drop the compression too much and make it a gutless dog out of boost, so I was wondering if the compression bump on the 6.0 would help or hurt the overall performance for the combo. The main reason I'm asking is because I have an extra set of LS4 243's that are just sitting around... I'm only asking b/c they're here and didn't cost me anything.

My build is a '96 Impala SS, 2006 LQ4/4L80e, twin GT35 ebay specials, LS6 intake, probably start out with the LS6 cam I already have, and a 3600ish stall. The goal is 700whp and good torque out of boost to move this boat down the highway. Whichever heads I go with will get a home PnP job. Since the runners are almost identical, this really comes down to the compression change... will it help or hurt?

Thanks for your opinions.

Ryans99ls1

iTrader: (16)

Run as much compression as you can. If you have the fuel and tuning ability to support the raised compression, do it. If you are considering E85, definitely do it. If you are octane limited (93 or lower with no meth), lower compression is your friend.

If it were me, I'd put the 243s on

Blackpanther99

iTrader: (8)

You already got the 243s, those will work great.

krwyellowZ28

iTrader: (10)

My bad, I should've mentioned it will primarily be running 93 octane due to availability of E85, have a fairly large IC, and most likely add a little meth on top to be safe. I'm tuning it with EFI Live and plan to use a dual tune switch for E85 on days I know I need some more power. Chances are, I'll tune it on E85, get hooked, and not switch back.

Blackpanther99

iTrader: (8)

Order some E85 You wont regret it.