LQ4 verses LQ9

[00fxd]

Hi all. How much better is the LQ9 over the LQ4? If I had a choice of an LQ4 with 10.000 miles or an LQ9 with 55.000 miles for the same price which should I go for? Both say '03 -'04 in years.
Opinions PLEASE.
Thanks, Frank.

[4OfaKind]

Hi all. How much better is the LQ9 over the LQ4? If I had a choice of an LQ4 with 10.000 miles or an LQ9 with 55.000 miles for the same price which should I go for? Both say '03 -'04 in years.
Opinions PLEASE.
Thanks, Frank.

I think the only difference is in the heads. Both the LQ4 and 9 use the same block, bore, crank, and pistons. The 9 makes more hp and that is due to the heads being slightly better I think. So your choice would be based on what your goals for the motor would be.

If you just plan to do a conversion and drop the motor in w/o too many changes, go w/ the lower mileage LQ4. If you plan to increase the power considerably which would require alot of new parts like cam forged rods and pistons, go w/ the better performing LQ9. My .02

Mal

[93Polo]

Both have 317 casting heads. The LQ4 has a more dished piston for lower compression and some sources say the LQ9 gets stronger rods.

[00fxd]

Thanks guys. I should have been more descriptive with my uses for this engine. It will go in a Mid Year Corvette that will be run hard on occations.
I understand that there may be better rods in the 9, dished pistons in the 4 and I have read that the 9 has LS2 heads.
I will probably run Camaro exhaust manifolds [unless that is strongly recomended against] to easily hook to my sidepipes and a LS1/6 style intake.

[93Polo]

The LS2 head is a 243 casting which is the same head used on the Ls6. You can find the casting # on the top corner of the heads.

243s and 317s use basically the same port design but the chamber is larger on the 317.

Casting Number 243
Head: 2001 LS6 5.7 Litre Passenger Car
Material: Aluminimum
Part Number:
12564243
Combustion Chamber Volume: 64.45cc
Compression Ratio: 10.5:1
Intake Port Volume: 210cc
Exhaust Port Volume: 75cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches

Casting Number 317
Head: 2001+ LQ4 6.0 Litre Truck
Material: Aluminimum
Part Number:
12572035
Combustion Chamber Volume: 71.06cc
Compression Ratio: 10:1
Intake Port Volume: 210cc
Exhaust Port Volume: 75cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches

[4OfaKind]

Both have 317 casting heads. The LQ4 has a more dished piston for lower compression and some sources say the LQ9 gets stronger rods.

Polo,

I stand corrected thanks. So either engine would work. I would go w/ the lower mileage LQ4 if the prices are the same.

Mal

[00fxd]

Thanks, Guys.
So there's no huge advantage to get the better rods, heads [poss] and flat tops and running it as is?

[4OfaKind]

Thanks, Guys.
So there's no huge advantage to get the better rods, heads [poss] and flat tops and running it as is?

I don't think so, No.
You said you were going to run it hard at times. To me that means start with the lower mileage LQ4, less wear already. If you are happy with the 325 hp of the stock LQ4 motor cool. I personally don't think the extra 20 hp of the LQ9 is worth the extra wear. If you want more hp, how much more? Because then since no truck motor has forged rods/pistons, even slightly stronger powdered metal is still powdered metal. So parts would need to be changed and you still have the higher mileage block. With price being the same to me lower mileage is a big advantage.

Mal

[93Polo]

I'd go LQ9 for the extra compression. My LS1 received heads and cam at 65k. It is over 90k and still running strong. The miles were not babied either.

Powdered metal rods can take quite a bit of abuse. A few 355 LT1s with blowers locally had stock crank and powdered metal rods running at ~600rwhp. The rods bolts are the weak link in the earlier LS1s not sure about the trucks. I would swap to ARP bolts since you will have the motor of the car.

[00fxd]

Good advise, Thanks guys.

"I would swap to ARP bolts since you will have the motor of the car."
Can you change rod bolts in these engines without re-sizing??

[93Polo]

Good advise, Thanks guys.

"I would swap to ARP bolts since you will have the motor of the car."
Can you change rod bolts in these engines without re-sizing??

Yes that was my understanding. The rods have a cracked beam design which allowed you to swap the bolts without resizing but also be sure that they go back together the exact same way you took them apart. Ls1tech has had some topics on it. If you can not find it in a search let me know and I will try to dig it up.

[00fxd]

I will look, Thanks Polo

[93Polo]

I was playing around on Ls1tech and http://www.ls1tech.com/forums/showth...=423651&page=2 has some info on the rod bolts

[00fxd]

Thanks Polo, good thread. It makes sense to me that because they are not interference type press fit bolt and nut assemblies, but are Lemans style capscrews that there should be no issues.

[justanova]

I am pretty sure the lq9 has full floating wrist pins, I read that somewhere like a hot rod magazine a while ago when they covered all the diff. between the lsx engines.

[00fxd]

Interesting........ Thanks.

[Samckitt]

What did each of these come in? For some reason I was thinking the LQ4 is what is in my '03 1500HD & the LQ9 is what is in the Silverado SS. yes/no?

[00fxd]

Silverado SS and Caddillac Escalade as I understand it.
Frank.

[93Polo]

Thanks Polo, good thread. It makes sense to me that because they are not interference type press fit bolt and nut assemblies, but are Lemans style capscrews that there should be no issues.

No problem I lurk in the suspension area just trying to add some info to the form

[justanova]

http://www.automotiverebuilder.com/ar/eb040538.htm

Rods
This whole family of engines was designed with three different bore sizes and two different strokes, so GM only needed two rods, a long one and a short one, to cover all four different displacements, but they ended up with three different rods anyway. These rods are all powdered metal forgings with cracked caps and they all had press-fit pins, except the ones used in the 6.0L LQ9 engines that came with full-floating pins. And, it appears that all the Gen III/Gen IV motors (a Gen III motor with "displacement on demand" is called a Gen IV motor) went to full-floating pins in '05 according to some car magazines.

I did a little research to back up my previous statements. some good reading in there that explains pretty much all diff in the gen 3 eng.