GM LS Engine Build - Short-Block Assembly

Short-Block Assembly
Here's where the fun starts. After returning the block to our shop, we cleaned it one last time with hot soapy water and then began the assembly. We'll spare you the details of the half day we spent measuring bearing clearances. While aluminum block motors need a little more clearance, we aimed for the more traditional 0.0025-inch rod and main bearing clearance spec along with a proper crank endplay and rod side clearance. Assembling the short-block is not much different from building any small- or big-block, but there are some minor details that change. LS engines are actually very easy to assemble.

We carefully set the new 4.00-inch stroke Scat steel crank with its early 24X reluctor wheel into the main journals. Note that we replaced the stock main bolts with ARP main cap studs.
We carefully set the new 4.00-inch stroke Scat steel crank with its early 24X reluctor whe
Before we installed the pistons, we slid the Comp cam in place to make sure it would slide into the new bearings without interference. If there's a problem, it's best to discover it before the pistons are installed.
Before we installed the pistons, we slid the Comp cam in place to make sure it would slide
We chose a set of 4.010-inch-bore Mahle pistons that are fitted with 1.5, 1.5, and 3mm oil rings. The oil control rings require a support rail, since the wristpin protrudes into the oil ring land. The oil rings are so small they must be installed very carefully. The rods are Scat 6.125-inch I-beams.
We chose a set of 4.010-inch-bore Mahle pistons that are fitted with 1.5, 1.5, and 3mm oil

Since we went with a 4.010-inch bore, we needed a new ARP tapered ring compressor to slip the pistons into place. We learned that those tiny oil rings demand a quick hand when installing the pistons or they can pop out in the transition between the ring compressor and the block.
Since we went with a 4.010-inch bore, we needed a new ARP tapered ring compressor to slip
With all the Clevite bearings in place, we carefully stretched each rod bolt to the spec using an ARP stretch gauge to ensure the rod bolts were at their optimum tension. We can't place enough emphasis on this step.
With all the Clevite bearings in place, we carefully stretched each rod bolt to the spec u

LS Assembly Tricks
There are some specific differences in assembling a typical LS engine, including a couple of required oil gallery plugs, the front and rear covers need a little attention, and there's a cool technique to installing the oil pump. None of these steps is difficult, and you can bolt on all these parts without expensive specialty tools. Let's get to it.

Next we took the time to degree the Comp hydraulic roller camshaft to make sure we had the cam in correctly. This required a special LS1 crank tool from Powerhouse to mount the large degree wheel and to turn the crank forward and backward without the wheel getting loose. We used a Comp adjustable cam gear that made degreeing the cam much easier.
Next we took the time to degree the Comp hydraulic roller camshaft to make sure we had the
The oil pump is driven off the crankshaft and installed after the crank and cam are in place. A new pump must be aligned to ensure proper clearance. Tighten the four oil-pump-to-block bolts to a snug fit against the block. Then slowly turn the crank over several turns. This will align the gears and allow you to torque all four bolts.
The oil pump is driven off the crankshaft and installed after the crank and cam are in pla
We wanted to check if this trick really worked, so after spinning the engine, we removed the cover and measured the clearance around the gears with a pair of 0.002-inch feeler gauges, which is the spec. The shortcut worked perfectly.
We wanted to check if this trick really worked, so after spinning the engine, we removed t

We inserted the dumbbell oil diverter into the back of the block on the driver-side oil passage lubed with a little engine oil. This must be done before the rear cover is installed. We also installed a small steel oil gallery plug in the front of the block on the driver side. Do this before installing the front cover.
We inserted the dumbbell oil diverter into the back of the block on the driver-side oil pa
We installed the rear cover gasket and slid all the bolts through the cover and the O-rings integrated into the gasket. The rear cover main seal uses a white plastic spacer that helps stretch the seal so it will slip over the crank flange. We positioned the entire assembly over the crank flange but just snugged the bolts for now-there's another step before these bolts are torqued.
We installed the rear cover gasket and slid all the bolts through the cover and the O-ring
GM specs an expensive front cover alignment tool, but Ken Duttweiler told us to just use a dummy front balancer hub. We cut the three legs off the original truck balancer to leave just the hub. Then we used a flapper wheel to hone the hub so it would easily slip over the crank snout.
GM specs an expensive front cover alignment tool, but Ken Duttweiler told us to just use a