BLACKND

iTrader: (5)

Hey guys, sorry to barge in on your section of the world, but with the recent developement of these motors, I was just wondering if anyone has really done any major mods or done any testing and tuning?

I am a major contributor on the Performancetrucks.net part of LS1Tech, and the 4.8/5.3 truck guys over there are constantly looking for upgradable parts from the ls1/ls6/ls7/etc..... Just wondering how closely related the LS4 is to the truck version of the 5.3. Are you guys running an electronic throttle body or is it cable driven. I was looking at some pics of the LS4 online earlier, and noticed the intake manifold. It resembled the ls1/ls6, and was wondering if anyone knew what exactly it was, or if it is an LS4 specific part altogether.

Thanks in advance for your help. Looking forward to you guys getting some good numbers out of those things. The 5.3 is quite a capable motor.

LS4 GXP

I don't know a whole lot about the LS4 yet, but it appears to be much closer to the LS2 than any other motor. It's an electronic throttle body, and the heads are actually the LS6 heads I believe (243 cast on the heads) I'm really not sure about the intake manifold.

GXP Lover

Yeah, it's the 5.3 truck with LS6 heads. They shortened the motor, mainly by the moving the accessories closer to the block and shortening the cam shaft to make it fit under the hood. Someone indicated they put new rockers on and they seemed to work, but no official word as to what improvements it makes yet.

There is at least one ECM tuner out there, Vector Motorsports and another was looking into it. The vector will get another 20 hp out of the motor.

Anyway, lots of info at clubgp.com (GXP thread) and LS4wbody.com. A lot of interest is out there, we just don't have anyone leading the charge right now...

Hope this helps...

ChipC

LS4 and the LH6 (DOD/AFM in TB/Envoy) are basically the same motor. Block may vary on mounting points and accessory drives are different. The camshafts are the same length as other LSx engines. Heads are LS6 heads, same as LS2. This is a GenIV architecture LSx. Vector Motorsports and DHP are in beta on PCM/TCM.

Chip

GXP Lover

I forgot which was actually shortened. The Crank was shortened about 13mm and from that, it was assumed the cam has been shortened. As far as I know right now, it has not been confirmed if the cam is shortened or "regular" length.

Chip have you been able to confirm the length is the same?

ChipC

Actually, Lightfighter was the one to confirm the cam. He also measured the block. It is actually the same length as the LS1 blocks. It seems all of the length savings came from accessory drive and the crank (nose and flexplate mount). The timing chain, gear, and crank sprocket are also the same parts shared with the LS2.

Logically, if you change the camshaft much you mess with the valvetrain geometry and possibly head design. We already know the heads are shared between several GenIV LSx engines.

Chip