ranchracer

I'm in the process of rebuilding an aluminum block 5.3 (factory code L33) out of a 2006 GMC 2500, and my machine shop is looking for specs on the head bolt torque values prior to installing the deck plate and honing the cylinders. I've only been able to find one published spec for the heads bolts on the 5.3, which is 22 ft pounds first pass, 90 degrees second pass, additional 70 degrees third pass. My machinist is concerned that's way too much for an aluminum block.

Does anyone know if there are distinct torque specs for the aluminum block, or does it use the same specs as the standard iron block? Local Chevy dealer couldn't help, and the AERA gave him those same published specs.

07NBSChevy

iTrader: (1)

I don't recall GM using an L33 5.3 in a 2500, nor a 2500 using a 5.3 in 2006. But anyways, my shop manual specs for Gen3 Aluminum Block Engines, including L33, LS1, and LS6, are as follows....

On an Aluminum Block Gen3 LS Engine using TTY OEM bolts.
-First Pass with M11 Bolts in Sequence at 22 ft lbs.
-Second Pass with M11 bolts in Sequence at 90 Degree's
-Final Pass with M11 bolts in Sequence, *Excluding the Medium Length Bolts at the Front and Rear of Each Cylinder Head*, at 90 Degree's
-Final Pass with M11 Medium Length Bolts at the Front and Rear of Each Cylinder Head in Sequence at 50 degree's.
-M8 Inner Bolts in Sequence at 22 ft lbs.

ranchracer

Thanks, this is exactly what I was looking for!

Sorry, meant to type 1500, not 2500. The L33 was a rare option in the '05 to '07 Silverado and Sierras. It was a vin code "B" and in marketing materials was referred to as the Vortec 5300 HO. Besides the obvious difference of the aluminum block, it also used the 799 casting cylinder heads (identical to the 243 casting on the LS2 and LS6) and the flattop pistons from the 4.8L motor. This bumped compression from 9.5:1 to 10:1 and resulted in slight bumps in hp and torque. It was only available on extended cab 4x4 1500s during those three model years.

Thanks again for the confirmation on those torque numbers.

07NBSChevy

iTrader: (1)

No Problem

I do know what the L33 is tho, haha. I used to have one in my 06 Extended Cab. I think it had 310 Hp and 335 Tq Stock. Very good motor for performance in mind.

Good luck on the build and just make sure your builder follows the specs to a T, you can strip those easily. I have stripped a head bolt hole on a LS1 by going a tad over.

MaroonMonsterLS1

Just Go sloppy mechanics style and just reuse the stock bolts and rip em all to 65 ft lbs and call it a day