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Old 01-17-2011, 03:54 PM   #1 (permalink)
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LQ4 build advice

I just acquired a 2003 LQ4. It has about 200k on it and I will rebuild it before it goes in my jeep. I have done a fair amount of reading and have found some good info but most of it is for street/strip cars, not 4x4s, hence this post.

My main concerns are #1 reliability/durability and #2 power.

I know these motors are capable of big power but what is a realistic # to shoot for for a DD/weekend trail runner. I would be happy with 400hp but would really like to shoot for 500 if that is a realistic goal for a motor that I want to be reliable for years.

What have you put together that has worked and what kind of numbers are you making? Also I cant find much info on the crank, should I replace it or just have it turned, or???

I have plenty more questions but this will be a good enough starting place for now and see what kind of responses I get. I would like to do this on budget but only want to do this once so I am willing to spend now to save later.


Also what other sites or sources are out there for info, and are there any "rebuild kits" for these motors that are worth looking at? I figure the top end is going to be pieced together with different parts but where do I look for a kit for all my seals, bearings, gaskets, etc etc?

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Old 01-17-2011, 04:06 PM   #2 (permalink)
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Went there with these items (except I did it all at one time):

L92 heads
L76 intake
LS7 injectors
Walbro 255lph fuel pump
tune
cam by Patrick Guerrera Motorsports ($425 total)
stock lower end
----------------
$2000 @ 500hp or so

Stroker with Scat Crank
Mahle Pistons (4.065")
machining
HBeam rods
---------------
Another $2000 max @ 650hp
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Old 01-17-2011, 04:34 PM   #3 (permalink)
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LS1tech.com is a very good site to find all the info you seek about this engine. Almost everything that is avalible for an Ls1 or an Ls6 will fit on your Lq engine
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Old 01-17-2011, 05:26 PM   #4 (permalink)
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Originally Posted by whitebrowithafro View Post
Went there with these items (except I did it all at one time):

L92 heads
L76 intake
LS7 injectors
Walbro 255lph fuel pump
tune
cam by Patrick Guerrera Motorsports ($425 total)
stock lower end
----------------
I would go this route as well. The L92 heads flow really well.

But WAP since your rebuilding it, I would stroke it to a 408. And use flat top pistons for more CR.

Texas speed sells stroker kits for $1700 bucks
http://www.texas-speed.com/shop/item...d=886&catid=88

Well worth it. With the heads larger stroke you should see 500HP at he wheels easy!
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Old 01-17-2011, 06:59 PM   #5 (permalink)
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Thanks for the advice. I was thinking of doing the L92s and L76 but wasnt sure how well that worked for wheeling vs high rpm racing.

I am all about more power but would stroking it decrease the reliability? If not then I woulds seriously consider it. I dont want to build this motor and think later down the road it need more power.
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Old 01-17-2011, 08:23 PM   #6 (permalink)
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Thanks for the advice. I was thinking of doing the L92s and L76 but wasnt sure how well that worked for wheeling vs high rpm racing.

I am all about more power but would stroking it decrease the reliability? If not then I woulds seriously consider it. I don't want to build this motor and think later down the road it need more power.
The 408 stroke is just adding a 4''crank so its not that much. Some of the larger stokes 416ci etc have more of a problem as its just too much and the pistons end up hang to far out of the block. And have the reliability issues, but the 4'' will be fine.

I think a L92 truck intake would be fine and you would gain more torque on the low end.
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Old 01-17-2011, 08:30 PM   #7 (permalink)
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Stock crank, forged pistons, H or I beam rods, studs, and boost! Leave your static compression higher than a normal FI motor, around 9.5-1 to 10-1, then run lower boost - turbo or Roots style blower, it's allllll good!
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Old 01-17-2011, 09:42 PM   #8 (permalink)
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This is the motor that was discussed in post #2. Specs are exactly as listed with a TH400 behind that combo. Not bad...

**scroll ahead to 1:08 in the time sequence.

YouTube - 1/8th mile drag: KOH rig
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Old 01-17-2011, 10:03 PM   #9 (permalink)
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is that with the 650hp or 500hp setup?
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Old 01-17-2011, 10:39 PM   #10 (permalink)
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650hp
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Old 01-18-2011, 04:05 AM   #11 (permalink)
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If your #1 is reliability, then you might want to re-think 500HP goals. Sure the head swap is painless, and the 408 stroker kit isn't much worse in terms of reliability, but start adding radical cams/springs and higher compression to that equation and your reliability will go to shit. (i.e. No free lunch.)

Don't get me wrong, I dig high performance LSx motors, but let's get real. At 500-600HP the priorities flipped and HP is #1 while reliability (Durability) slipped to #2.
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Old 01-18-2011, 05:31 AM   #12 (permalink)
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WTF-J that is a big part of this the reason I started this thread was to see if 500hp was a realistic goal for a 6.0 while maintaining reliability.

whitebro, that is sick!! deff makes me want to go ahead up my goal from 500 to 650!!

I think I want to stay away from boost right now, thats just more $ I dont have and its not needed to reach the goals I am looking for.

Thats great info on the stroker kit. I will have to weigh my options but since I am doing a full rebuild anyway if I have the $ I will prob go that route.

Are there any off the shelf cams that would work well with my application or am I goin to have to get a custom grind?
What do you guys think about getting the rotating assembly balanced? Any reason not to?

I read the thread on LQ4 cam suggestions, and basically I am looking for the same thing, good bottom to mid range with as much lope as possible without affecting things negatively.
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Old 01-18-2011, 06:54 AM   #13 (permalink)
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I wanted to get good power from my LQ4, but still maintain reliability. I kept the 317 heads and just added a GMPP LS Hot Cam and LS6 Springs. I have the Walbro 255 pump, LS1 Intake, TB and Injectors and custom made headers. This is what mine did on the dyno with 39" tires. 290 HP at rear wheels, estimated at 400hp at crank. I have heard great stuff about Texas Speed, so you may tray them for a cam also
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Old 01-18-2011, 09:27 AM   #14 (permalink)
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Remember also that the LQ4 has dished pistons so if you rebuild it get the LQ9 flat-tops and run 93 gas and you'll pick up HP via the higher CR.

Get the bottom end balanced, that is a component to longevity at high HP.

As for the cam if you go L92 heads you need a cam for those heads.

Check out these cams. The L92 cams are toward the bottom
http://www.vincihiperformance.com/ca...s%20truck.html



Will a 500hp stroker motor see 200k miles probably not. The more HP you run the longevity goes down that's a given. If its not your daily drive I wouldn't worry.

I doubt you'll break the bottom end or have any real problems. Since 500hp isn't that much for these motors. If you have the right tune it should last, I would be more worried about the trans lasting.
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Old 01-18-2011, 09:50 AM   #15 (permalink)
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Horsepower TV did a build a while back on an LQ4 making around 500hp on an engine dyno. If i remember correctly, it was done with a new cam, rockers, 90mm Fast intake and injectors, and a Howell tune. Might be worth looking into.
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Old 01-18-2011, 09:52 AM   #16 (permalink)
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More great info^^^^

I talked with John at Tx speed shop, please tell me if you guys see any reason to shy away from the advice listed below, whether it be due to a more cost effective route or what ever the reason.

He recommended doing the 408 stroker kit and balance everything, run weisco pistons, and upgrade to the arp 2000 bolts, shoot for 10.5-11:1 CR. Send in my 317 heads and have them cnc ported and do new valves and springs, basically rebuild the heads with a port job and better parts. Keep the truck intake and run a good cam (we would narrow that down later down the road) and I should be at 6-620 crank hp. With the money I save keeping my intake and just having my heads redone it will pay for the stroker kit, and I will sacrifice some top end but he said is should pull strong to about 6,000 rpms and drop off hard by 6,500 but with shorter runners of the 317s I would have better low-mid range then the L92s and with the port job my LQ4 heads would flow close to what the L92s do.

So, what would you change and why? I figure if his estimate is high (though I would hope it would be realistic since this is what they do) and I only make 500hp, with the forged internals it would be no problem to run some N02, he said with that motor it would take a 200hp, no problem.

I like the above recipe because it seems very cost effective and I get forged internals and a 408ci motor.
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Old 01-18-2011, 10:19 AM   #17 (permalink)
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They expect that much power with the stock intake and 78mm TB? That's awesome. I'm building an lq9 right now and was under the impression that it would be best to upgrade to a 4 bolt 90mm intake. I'm building around a 90mm trailblazer ss truck intake.

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Old 01-18-2011, 11:00 AM   #18 (permalink)
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Exclamation Caution!!!!!!!!!

Too many people on here dont know what they are talking about and try to promote shops and companies products and labor skills without knowing all the facts. U can't make decisions by what you read on some forum or article. U should make decisions in person and face to face and from seeing proven results. Make sure you trust and know who u r dealing with before you drop money on parts and labor. DO IT RIGHT THE FIRST TIME!!!! It may cost more up front but nowdays more than ever you get what you pay for!! And you get the level of work done from who you choose to get the parts and labor from!!!!

Good Luck to everyone and HAPPY NEW YEAR!!!!!!! 2011
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Old 01-18-2011, 11:52 AM   #19 (permalink)
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The 90mm TBSS truck intake is what I would get if you can find one used. Worth a few more HP with the 90mm TB.

Stock Bare TBSS Intake Manifold is P/N 12580420.


Porting the 317 would be very cost effective.
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Old 01-18-2011, 12:00 PM   #20 (permalink)
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that koh rig sounds like money. that thing was haulin ass
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Old 01-18-2011, 12:25 PM   #21 (permalink)
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I agree that there is way too much MIS information on the interweb. Building a 500hp engine without any valve train upgrades brings the funny to me. Sure it can dyno queen some good numbers, but how many times before the stock stuff pukes and your spending the money twice to make it right.
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Old 01-18-2011, 12:36 PM   #22 (permalink)
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I agree that there is way too much MIS information on the interweb. Building a 500hp engine without any valve train upgrades brings the funny to me. Sure it can dyno queen some good numbers, but how many times before the stock stuff pukes and your spending the money twice to make it right.

I agree but there really wouldnt be anything stock about the valve train. We didnt talk specifics but besides the cnc port job we discussed aftermarket valves, springs and pushrods.

Will the trailblazer intake bolt to the LQ4 heads or would one need L92s? I also plan on bigger injectors, and if using the truck TB I may port it, or scrap it all together and go with a larger one. I have not problem doing a different intake, heads, and or TB. I only want to do this once, but the money saved on L92 heads (tx speed shop prepped, not stockers) and and intake to go with it I can pay for the stroker kit, have as good as if not better bottom end, and not give up much on top. I dont want to turn this motor past 6,000 anyway so thats my reasoning with leaning towards using modified stock heads. If I come across a deal on L92s (or similar) and or an intake I will snatch it up but unless I am wrong so far it seems dollar for dollar what John said may be the best way to go for me right now. I am still a ways off from ordering anything, I just want to make sure I only have to do this once.

Oh, and Bo185, I will be running an np435 so I am not to worried about the trans making it.

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Old 01-18-2011, 08:46 PM   #23 (permalink)
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To be more specific... the stock L92's came with double PAC valve springs & titanium retainers - $1068 shipped to my door from Scoggin Dickey. PAC makes valve springs for virtually everyone (or so I've heard), so hit the source and save some money.

More info:
Stock rockers
Chromoly pushrods
ARP head bolts
LS7 fuel rail (LS7 injectors are shorter)
Fuel pressure reg - Mallory
ARP rod bolts

The machine work was:

Balance assembly together (crank, rods, pistons)
Sonic the block for wall thickness
Line bore mains
Deck the block
.065" over cylinder bore and hone
Final wash, oil galley flush and port blow out

The 317 heads seem alright, but the L92's flow within 10% of LS7 heads (stock). Easy fix there should you desire it. 317 heads are desirable on LS1tech.com for the LS1 turbo crowd. If you sell those and take the $400 head port money. You are almost in reach of the L92's.

All in all - The cam is probably the most important thing in a motor. Patrick Guerrera (link : http://www.guerragroup.com/camshaft_help.htm) is the man when it comes to designing these. He can explain dynamic compression ratio vs static compression ratio. Static is what everyone refers to. 12:1 compression seems high, but its how the valves work with it. Patrick does just this.

Have you ever heard of anyone tuning shocks with the same valving in desert racing? I'll answer that... NO. No motor is exactly the same. Get a cam with the specs you know. Whatever you go with, just set some money aside for Patrick. Give him all of the details and tell him what you want. Lopy idle, and more high rpm hp, or stable smooth idle with high torque, or a mixed bag of whatever. Just let him know. He is very personable, and worked with everything I had, and wanted. The dyno numbers were 392 ft/lbs and 387 hp. At idle, the car at 320 ft/lbs The torque curve peaked right away and carried, until hp took over - then it fell off.

All good... would go that (patrick) route again and again.
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Old 01-19-2011, 05:39 AM   #24 (permalink)
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whitebro, you said stock rockers, stock for what?

Also, if I was go the L92 route how does the L92 intake compare to the L76?

One of the biggest reasons I like the idea of using the 317 heads and truck LQ4 intake is that it all bolts together just like it is. I have HEARD one changing to the L92s and L76 or other intakes that there can be problems using the stock LQ4 water pump and other accessories. Dont know how much truth is to it but though I dont mind mixing and matching parts, using what I got would take a lot of guess work out of the equation.
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Old 01-19-2011, 05:59 AM   #25 (permalink)
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Heres another question(s).

IF I went with the L92 heads what intake would you want to run? L92, LS3, L76??? And which one is best? Which one is the easiest to bolt on to an LQ4?

I am finding some good deals on diff head and intakes but dont wan to bite until I know that I now what combo to run.

PS it looks like the L92 makes more power than the L76, whats the advantage of running the L76 intake vs the L92?? And where does the LS3 intake fit in all this?
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