I have searched and im still confussed on what to get. I have a turbo 350 trans in my iroc now. So what lq4 would i have to get to make my turbo 350 bolt up and work. I also have a 7004 trans i could use.

You can use any of them. With the later ones, you need the flexplate spacer.

So with the early lq4, it will bolt up no problem, the later ones after 01 will need the spacer.

It's the crank itself that is the issue between the early and later blocks. The early block cranks will work with SBC style trans (700R, TH350, LT1 style T56, T5, etc). If you want a newer block to work with an older transmission you just take the motor apart and put one of the older style cranks in it or you can use a crank spacer for the flex plate. I actually have a crank from an older block that I would sell for reasonably cheap if you wanted to go that route. I put an LS2 crank in mine because I wanted to use an LS1 T56.

What year did they switch to the new style crank? was it 2001 or.

Yep, 2001.

(heads)99-00 have iron you can pick up cheaper, and go straight to LS6 heads or aftermarket right away. The newer versions are LS6 design with lower compression 72cc cambers, that are good for boost (I plan)

(blocks) some caddy's and ss have aluminum versions (sweet)

Tci makes an adapter for the cranks, I believe, not sure (i used a 04 6.0/4l80e)

Or TCI's flexplate.

Does the same crank issue, apply to the LQ9 as well?

I don't think there were any LQ9s before '01, the development of the LQ9 came hot on the heels of the LS6. The main difference is the LQ9's got flat-top, coated-skirt pistons instead of the LQ4's dished pistons. LS6 #243 heads on an LQ4 gets you comparable results.

From what I understand, no. LQ9's were only made AFTER 2000 I am pretty sure. They all had alum. Heads, and the wierd crank blocks had iron heads.

From what I was reading, researching between LQ4 & LQ9, both were iron bock/aluminum heads.

The 2000 LQ4 had iron heads.

LQ9 Applications:

* 2002-2006 Cadillac Escalade
* 2002-2006 Cadillac Escalade EXT
* 2003-2006 Cadillac Escalade ESV
* 2003-2007 Chevrolet Silverado SS
* 2004-2005 Chevrolet Silverado and GMC Sierra Vortec HO Edition Only [Badging on truck](B4V)
* 2006-2007 Chevrolet Silverado and GMC Sierra VortecMAX Option

Well crap my LQ4 had iron heads AND flat top pistons?

the lq9, had the top and skirts coated...

all alum. headed lq4s have coated skirts...

both are heavier then ls1's so not good for high rpm's (6200+)

Ya I wouldn't rev a stock block that high regardless...

I buzz my stock LS1 to 7K on the regular.... three seasons now

Patriot Gold Valve springs are the ticket

I've got the PRC's from Texas Speed

So the 99-00 have crappy heads compared to later. Is that why some of the lq4's were rated at 300hp or was that because of different cams.

I'm not sure. The guys on LS1truck.com would be able to tell you though.

compared to the alum heads, they are not as good. and they are way heavier. stock 317 go for good prices, and are same intake runner as 243 castings. 71cc chamber. very good heads for the money. although the 243 and 799 are very similiar, they all share the same intake and exhaust ports, the 243 and 799 have smaller chambers at 65cc and usually go for more than 317.

y not bro? they will take some abuse, if fortified with arp rod bolts and if the cylinders are in healthy condition.
although 6000+rpm may be alot to ask for from a worn stock motor.

i turn my dd to 7k when i have to and its a .060 over lq4
the engine has around 13k miles now and been in car around 3 yrs.now.
if anything it took its toll on my t56

Ya I meant stock as in BONE STOCK. The rod bolts are weak on a factory block. I will spin mine to the high heavens because the peak on my cam is something like 6,400 RPM plus I have lighter rockers, forged internals, and ARP bolts.

243 and 799 is that what the 99-00 had. Can you still make decent power with them?

IIRC, 243s were some of the stock castings on LS1 engines, so I'd say yeah, they can flow halfway decently...

243's are LS6 heads.