'89ChevyMadneSS

iTrader: (3)

searched and came up empty...

ive got an '03 lq4 block ya see... if i were to get a set of lq9 rods and pistons used or cheap or what have ya (block has to be torn apart anyway) would they drop right in? i know bore, stroke and heads are the same but i didnt know if the cranks were diff or rod bearing etc etc were the same are there only certain years that are interchangable? i think that since ive got to pull it apart anyway and it needs atleast on piston that the 20hp or w/e would be well worth the money. any thought or input welcome

StrokerAce03

iTrader: (7)

LQ4 and LQ9 blocks and cranks are the same; as well as the heads. The only difference is the LQ9 uses flattop pistons and beefier rods. I think they upgraded the LQ4 to the LQ9 and ls2 rods in later years but I'm not positive on that. If you can find the LQ9 internals cheap; I'd say do it.

blown3qtr

The bobweights on the crank might be different due to the different weight of the beefier lq9 rods and pistons. You could always have the rotating assembly balanced. As far as size, everything will fit.

A lot of useful info in this link although its soon to be out dated.

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

Steve Bryant

iTrader: (1)

blown3qtr is right. The bobweight of the crank is wong for the LQ9 pistons and rods. You could have the crank/rotating assembly rebalanced though. Another thing that I would do is to mic the pistons and the cylinders to make sure that the piston to cylinder clearance is acceptable. You'll also need to scuff hone the cylinders before reassembly. Use new rings, plus main and rod bearings and be sure to plastigage them all.

One last thought. If your existing pistons are in good shape, I wouldn't fool with the LQ9 pistons to raise the compressions a few points. It won't make over 20 more HP and you'll have to use premium. I'd just get a little bigger cam and spend a some money on pocket porting your heads and a good valve job. That will mean a lot more to you at the end of the day.

Steve

TurboGibbs

iTrader: (6)

Off topic kinda but on the different cranks. I know for a fact that a 5.3 and a 6.0 LQ4 has the same casting # on the cranks, or at least the ones I have are the same. From visual inspection I can't tell any difference in bob weight machining. Can anyone confirm for sure, as in you know there is a difference because you've balanced the different cranks yourself of have specific knowledge from GM? I would assume they would balance them descent from the factory and the counterweight machining be a little different but who knows? The 5.3 and 6.0's share the same piston pin height yet the bore size is much smaller on the 5.3 so the pistons pretty much have to be lighter. Anyway, just thought i'd throw that out here.

blown3qtr

I would also like to know. ttt.