Ironembraced

The L92's will make more power than the 243's...short answer, yes.

But ONLY at high RPMS. The 243's offer the LQ4 more power at low/mid range.

You will not be able to bump up your compression as you will with the 243's.

Jim_PA

iTrader: (9)

http://sdparts.com/details/gm-perfor...parts/12576063

These are LS2 heads (799 or 243 castings) but do not come with the sodium filled valves.

Check around with your local GMPP dealer, they gave them to me for the same price.

t_raven

iTrader: (12)

Ah good to know. I like the idea of the L92s because at some point I'd like to stroke the short block. For now I just want to get it running as cheap as possible. I guess I'll keep an eye out for a good deal on some 243s and LS6 intake.



Thanks for the link. I didn't know 799s were basically the same as 243s

Damian

iTrader: (89)

LQ4's have valve reliefs in the pistons. You can mill the hell out of the heads on that engine and not have any clearance issues. FWIW.

Ironembraced

I am curious to know exactly how much...I keep finding threads saying .030 was very tight space.

I'd like to get some 243s and mill them to 10.5:1 compression on my LQ4.

Squirts11

iTrader: (14)

True, in regard to PTV clearances. Also, I thought I'd add that milling much more than .030-.035" might affect intake/head port alignment (although this isn't always the case, as some mill more than .060" and just alleviate any intake sealing issues with other gaskets or additional RTV). While the 243 and 317 castings are usually considered identical in design (other than camber size), you wouldn't have identical products after milling a 317 casting to mimic the stock 243 chamber size (72vs63-can't remember exact specs).

PTV is affected by head gasket thickness, deck height in relation to how much (if any) the piston protrudes from the block, valve size, chamber size (milling) and camshaft duration and ICL, not max lift. Max lift occurs closer to BDC, and isn't a factor.

GMCtrk

iTrader: (23)

I've never seen an LQ4 with valve reliefs. Maybe only on the very late ones.

GMCtrk

iTrader: (23)

LQ4 right, LQ9 left

LQ9-LQ4pistonsrods5.jpg?t=1260330988

Ironembraced

Yeah, I was kind of curious what they mean by valve reliefs on the LQ4. Was just assuming we're talking about the center dish.

By the way, most LQ4 pistons that I have seen do not have that cross-shape to the dish. My LQ4 is from a 2005, and the center dish has no cross. (or valve relief indentation)

WS6SP33D

iTrader: (2)

Yes you would benefit from the install of 243's, But send them to A.I and it will be a hella benefit.

fheckro

I can modify pistons or buy them so that is not so much a factor. What i am really curious about is how much meat can i lop off the heads before they become too fragile to handle the added compression. I want to build the LQ4 motor I have to it's max potential ... and like everyone else would like to do it the most economical way possible. I want the highest compression possible to run on race gas. Keep in mind i am running a Carb. My thinking here is use the best flowing head with the smallest chamber and cut them to the limit. Do whatever i have to to run my Texas Speed cam with .603 lift. TO get my name in the record books and keep it there i am thinking i will need close to 500hp; on gas;with no power adders or computers. Is this possible?

Fred

Not Me

iTrader: (7)

After reading the whole thread I was wondering I have lq4 or lq9. Not sure witch one because I have not taking the 317 off yet. But I have 243's, ls6 cam,fast 90mm intake, 90mm intake, fast fuel rails, and ls6 injectors. How much hp and torque will that make an will a stock 4l60e hold it.

99fbodyTA

this....no brainer to me

the_merv

iTrader: (88)

Came across this thread doing some reading...some bad info in here..

I have yet to see a factory LQ4 with "valve reliefs" in the pistons...all the ones I have seen are dished. That pic above the piston on the right is a 5.3l Piston...you can even see it's smaller in the pic compared to the one on the left.

kinglt-1

iTrader: (26)

some lq4's did indeed come with valve reliefs for one valve.

https://ls1tech.com/forums/generatio...t-pistons.html

the_merv

iTrader: (88)

Interesting...I see there are from the newer ones with VVT...all the stuff I've messed with was 2005 back..makes sense.