QSPres

iTrader: (15)

........knowledge. What did you think I was going to say?



Situation:


Standard bore 03' LQ9 motor. 00' Camaro front accessories. Going into a 1970 GTO.


Question:


Which heads would be the best for a street application? By street, I mean power steering, A/C, etc.


L92 (with intake), LS6 (with intake), stock (with LS6 intake).


I know the L92's need special rockers and valves, so let's assume I get a set complete. Will the compression be too high? I have seen the flow numbers on the L92's, and while impressive, for a street car, they seem a bit much, plus it seems I'll probably have to overbore my block?

ArcticZ28

iTrader: (14)

Well, that all depends on what your goals are. L92's would be a bit overkill for just a fun street car. But, if you're lookin for all the hp you can get, L92 is a good route but it will certainly cost a lot more than an LS6/LS6 setup.

brad8266

iTrader: (23)

LOl @ thread title.

QSPres

iTrader: (15)

Yeah, the L92 set up is way too expensive. The guy wants almost $600 for the used valves and rockers...



Are the LS6 heads much better than the LQ9 heads?

ArcticZ28

iTrader: (14)

LS6 performs a tiny bit better. You would be better off putting your money toward having your 317's ported.

QSPres

iTrader: (15)

That I can do, thanks!



How about intakes? LS6, Aluminum, F.A.S.T.?

ArcticZ28

iTrader: (14)

All depends on your goals and money. FAST 90/90 wil lnet more hp, but costs more. Either way, aluminum sucks.

QSPres

iTrader: (15)

How much more in the low/mid RPM range (street driving) than the LS6? Is there a substantial low rpm airflow increase?

cws T/A

iTrader: (3)

[QUOTE=QSPres]Yeah, the L92 set up is way too expensive. The guy wants almost $600 for the used valves and rockers...



You can buy fully assembled L92'S for $800

Use your LS1 exhuast rockers and get L92 offset intake rockers for $70

the L76 intake flows 323 cfm through the as cast L92 heads

Bare L76 intake cost $290

ArcticZ28

iTrader: (14)

The L92 is just too much overkill for his app though with stock bore. The L92/76 setup flows more but is more upper RPM biased. The Fast 90/90 will also flow more than the Ls6/ported TB like I said, but again, you won't gain much down low, if any at all.

QSPres

iTrader: (15)

Thanks guys, and if you get a chance, check out my other post titled "accessories question".


Thanks

cws T/A

iTrader: (3)

The big 260cc intake ports are making killer torque. Tested on a stock LS2 engine in the GMHIGHTECH magazine that has 10.5:1 scr with 64-65cc heads , the 70cc down on compression L92's still made the most hp and torque .Torque is what matters the most on the street , I read it where it even says this combo would be great for a heavy streetcar.

Comparing them to the other graphs of the same LS2 shortblock ,232/234 .600'' 112 cam the L92's vs all the aftermarket street heads , L92's hold their own .

Fwiw -15% figureing drivetrain loss from 546flyhp / 494flytq would endup around 464rwhp 420rwtq , dcr was probly in the mid to low 7's .

Thats friggin sweet, imagine ported milled L92's , bound to gain 20 hp from a bump in compression and porting. More tweaks could have 500rwhp 440rwtq .

http://gmhightechperformance.com/tec...gine_l92_heads

ArcticZ28

iTrader: (14)

I'm gonna have to disagree on this one. Looking at this GMHTP dyno graph...



The torque is nothing stellar down low at all (disregarding the spike). My 408 with ported 317's flowing 320/220, LS6 intake, stock tb, and 244/248 cam (8.0:1 DCR) was making 425tq at 3k rpm with KR issues. That is a very peaky tq graph. The Tq/Hp is gonna have a lot to do with the cam, not just the heads though, so take it for what it's worth. My point is, properly ported 317's (of which you can easily get for under $1k) along with a 90/90 certainly wouldn't be surpassed by an L92/76 setup as shown in these GMHTP tests.

(BTW, this argument is very poorly put together, but I'm running out the door... I'll check back later tonight to clarify as I can already find a few things to nit pick on myself...)

cws T/A

iTrader: (3)

All the graphs look like that even the AFR's /Trickflows .

cws T/A

iTrader: (3)

This is a 408 , but damn look at the torque at 3200rpm .. 450 at the ****'kin tires , flatter than an anerexic models chest

stock casting L92 heads, REV valves, L76 intake, 36lb. inj, NW90, 11to1, Kooks 1 3/4 LT's w/cats, 3.73, Textralia, LSK 231-235 110+0


http://img291.imageshack.us/my.php?i...vl92l76gz9.jpg

Doesnt even hit 6500rpm ,this engine will probably run for 100,000 miles .

Irocss85

iTrader: (1)

that graph would be ideal for this guys heavy *** GTO. and, I think the fast 90 loses torque down low, to gain up high. not a good trade off for a car like this, AND its a helluva lot more expensive.

ofcourse your not gonna get a torque curve like that out of a stock short block though, what is the LQ9 motor, like 362CID? I think Id do the L92/L76 myself if I were you. thats just MHO

QSPres

iTrader: (15)

The car is going to weigh around 3500-3600lbs with me in it. Not exactly heavy compared to the F-bodies and new GTO's...



I understand the L heads will make slightly more power with the right cam and induction set up, but, for the $, plus the fact that 11:1 and A/C don't go well together on pump gas, plus I don't want to have to overbore the motor right now, leads me to the conclusion I'll just have my buddy port my stock heads and get a LS6 intake.



Thanks everyone for the great information!

ArcticZ28

iTrader: (14)

I think that's the best decision, personally. The L92/76 is good for a 4xx displacement engine, but I really think it wouldn't benefit you for your stock LQ9.