vikingray

Hi...Nubie here so be gentle.......I got a 1999 GMC Sierra SLE 2500 dirt cheap because of bad LQ4 motor which is all iron. I can turn it a little backward but forward it hits something and locks up. Loosened all rocker arm bolts and could turn cam when locked up so it NOT in top end. Thought it may be TQ converter bolt had backed out but didnt see anything with cover off. Thinking its a broke rod or busted piston. Found a 06 LQ4 from a Denali...My question is.....Of these two motors what combo would be best to put together for the truck. Im thinking the crank from the 99 and pistons and rods from 06. Heads (aluminum) from 06 with a small tow cam. New rings and bearings, etc.... Anyone have any suggestions or anything to watch out for when using parts from these engines!!! Want best combo for good motor but NOT looking a race motor . will have PCM redid after and maybe shorty headers. Thanks

G Atsma

Use the WHOLE 06 LQ4. The old one has no advantage over the 06. Drop it in, hook it up and send it.

Che70velle

iTrader: (6)

The 99’ LQ will have a longer crank flange than the 06’
Not sure how this will affect the flywheel/converter setup, but something back there will be different. 06’ might even be a Gen4 engine, so the knock sensor locations, cam sensor location, and type will be different, along with the reluctor wheel...if in fact the 06’ is a Gen4, which it should be by then. Do your homework before you dig in too terribly deep.

G Atsma

ALL LQ4's are Gen III made thru 07, so sensors are the same. Isn't there a spacer available to adapt the late crank to the older configuration?

blsnelling

iTrader: (4)

The '06 LQ4 will have better rods and pistons than the '99.

Che70velle

iTrader: (6)

True. But...Sierra Denali went to LQ9 in 05’. If the engine came out of a Yukon Denali, then it’s an LQ4. Hence why I said to do your homework. Depends on which Denali model. Could be Gen3 or Gen4 as I posted.

G Atsma

My point is, if it is designated LQ4 or LQ9, it will be Gen III. There are no Gen IV LQ4's or LQ9's. Gen IV went to a different designation.

00pooterSS

iTrader: (40)

I agree homework needs to be done to confirm

But from what I recall the 06 denali is going to be an LQ9 and a gen 3

I believe you can just slap the spacer kit on the crankshaft to space out the flexplate to make up for the difference in crank length

As for swapping pistons and rods and such, there's no point in doing any of that.

One easy easy thing to look for on the 06 motor to confirm if it's gen 3 or 4 is look for a sensor mounted in the front timing cover. If there isn't one it's a gen 3. Just slap that dude in the truck. If there's a sensor it's a gen 4 and you'll have to do some converting. But again, I'm pretty sure the 06 is gonna be a gen 3 straight swap in deal, except crank length. If in fact the 99 motor had the long crank, which it sounds about right that it would being in a 2500 it should have a 4L80 long crank iron head setup.

Again, homework needs to confirm, but I believe all trucks stayed gen 3 till 07 and that was when the half ton trucks changed. I think the big trucks kept gen 3 for a while..?? I dunno that's out of my wheel house.

I didn't know the sierra got the LQ9 but the Yukon got the 4. Freaking weird. Either way no reason to swap any engine internals. The newer engine is as good or better. Nothing better at all in the 99 motor.

matts01z71

From Wiki; (For 2005-2006 and 2007, "Classic body style" Sierra Denalis were equipped with a 6.0L 345 HP V8.)

Do the Denali, probably an LQ9, should have flat tops and floating rods. A great place to start. At least a stage three truck cam from someone, tuned.