Id'ing a LQ4 vs an LQ9
 

I bought an engine out of a junkyard for my turbo build. It is out of an 07 Van. It's a 6.0, but how do I tell if it's an lq4 or lq9 without pulling a head to check the pistons.

Thanks,
Frank

They only fitted LQ9's,

to Cadillac Escallades and GMC Denalis AFAIK.

Great! Thanks for the quick reply! That's what I was thinking, but I wasn't positive.

Frank

Your only a set of pistons away from an LQ9 spec anyway,

They were identical other than that I think (apart from small differences in the tune).

correct, vans only had the lq4

if you are going FI, you want the lq4 instead of the lq9 because of the lower CR. and it seems to me that you have an lq4.

good luck on you build.

Here is an answer to your question one person was right one is aluminum and the other has a cast iron block the one you have has the cast iron block which is better for turbocharging.

negative, no LQ4 or LQ9 was ever built with an aluminum block. The only difference is dished pistons on the LQ4 and the LQ9 i believe has slightly beefier rods. FYI, the LQ9 was also put in the Silverado SS.


Back to the OP though, you definetly have an LQ4 if its from a van.

As adam1803 said, but to add you are thinking of the LS2.

LQ4/LQ9 = Iron Blocks
LS2 = Aluminum Block

All three are 6.0L, and the LQ9 is an iron version of the LS2 but with 317 heads, versus the LS2 and the 243 heads.

later (2005) and up lq4's have the same internals as the LQ9 and LS2 sans the pistons. The LS2 internals are identical to the 02 up LQ9's I believe.

So if you don't know what the motor came out of, how else can you tell the difference between a LQ4 and LQ9?

I have a 6.0 long block, and I know its an '05 model year because of the casting date on the heads (10/04).

So how else I can I tell without yanking a head to look at the pistons?

Thanks!!!

Have a read here:-

http://en.wikipedia.org/wiki/GM_Vortec_engine

LQ4 has dished pistons, LQ9 has flat-top.

Thanks dude, but I guess I should of been more specific.....

I don't want to yank off the heads to confirm if it has flat top or dished pistons on a perfectly good long block..

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Any other way to tell the difference without tearing into the motor?

Thanks again.

Is it possible to pull out a plug and use a screw driver or something similar to feel the top of a piston? Maybe a wooden dowel rod?

Other than what these guys have already said, there is no way to tell them apart. Pistons are the only difference.

I remember seeing a thread on performancetrucks.net that showed how to identify the pistons from the bottom. It had pictures detailing the differences between the two. It wouldn't be a big deal to pull the oil pan and have a look.

If that were true it would be great since I am swapping out the truck pan for a LS2 Corvette pan anyway.

compression test. Find out the stock compression for the lq4 and lq9 and check compression. assuming you have the heads on the block that came on it.

Man, that only took about an hour of searching. It appears that the question "What's the difference between LQ4/LQ9?" is as popular on PT.net as "What cam should I get?" on here.:)
http://www.performancetrucks.net/for...ght=LQ9+piston
If you look at the pictures in this link you can see the obvious difference between the LQ4 and LQ9 pistons. I would say it's no problem to identify them this way from the bottom.

Don't mean to hijack this thread but what is the stock compression ratio on the lq4? thanks