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LS Rotating Assembly

   Torque specs

·         Main cap inner bolts – first pass – 15 lb ft

·         Main cap inner bolts – final pass – 80 degrees

·         Main cap outer studs - first pass – 15 lb ft

·         Main cap outer studs – final pass – 53 degrees

·         Main cap side bolts – 18 lb ft

·         ARP connecting rod bolts – first pass – 15 lb ft

·         ARP connecting rod bolts - final pass – 45 lb ft


Torque Sequence                                                                                                               

Torque Sequence

 Stay in Tune with your Engine!

Installing Crank Shaft

Once the block is clean and dry and special care has been taken to assure the main journals are dry and free of grease and oil you can proceed to install the main bearings which should also be free of grease and oil.

5.3 LS bottom end

There are 5 main bearings, each bearing is divided into 2 halves, one half will have an oil feed whole, the others will not. The center bearing is the thrust bearing, it’s unlike the other 4 bearings, it has sides that wrap around the block and cap to limit the cranks end play.

The outside of each bearing half will have an ear or tab that keys into the block effectively locking them in place.

5.3 ls rotating assembly

Place the 5 main bearing halves with the oil feed whole into the block, and place the 5 remaining main bearings without the whole into the main caps, take care to assure that all bearings are firmly seated and sit flush in the main journals. 

Apply a glob of assembly lube to each bearing half and spread it evenly across with a gloved finger. Finally, you are ready to carefully place your heavy and awkward crank shaft into the block, I recommend you enlist the help of a friend for this phase.

5.3 LS assembly

The crank shaft is now in the block but don’t pat yourself of the back yet, we still need to install the main caps. From the factory all the main caps are wisely number 1-5, 1 being the front and 5 the rear.

With the bearings installed and lubed, place the caps in their corresponding positions. Take note that each main cap has a front and a rear, a flat or flatish side and a side that tapers out toward the left and right, main caps 1-4 will have the taper pointing toward the rear of the block, whereas main cap 5 the taper points toward the front of the engine.

5.3 ls bottom end

The fit on the main caps will be tight, this is ok, don’t force them down… yet. Grab your main cap bolts and studs and place lubricant on the threads, lots of people use a 30-weight oil but we decided to use ARP thread lube because we had some.

Place the inner bolts and the outer studs into the caps and run down the threads finger tight. Using the rubber handle of a mallet tap the main caps firmly till they fit snuggly into place and run the bolts and studs down hand tight in proper sequence.

5.3 ls thrust bearing

Now take a moment to seat the thrust bearing and you’re ready to torque down the main caps.

Crankshaft Installed

Seating Thrust Bearing

With the crank installed in the block and the inner and outer main cap bolts and studs hand tight, use a prybar or large screw driver and apply firm alternating forward and backward pressure to the crank shaft.

This is easily executed at the rear of the engine by placing a prybar between the crank and block and prying the crank shaft toward the rear of the engine, then place the prybar between the engine stand and crank and apply forward pressure on the crank.

Repeat this process once or twice more to assure the thrust bearing is fully seated.  


Bearings and Crank


Torque Down the Main Caps

We made it, finally ready to torque these main caps down. First let me say it is critical that you follow the factory toque sequence, the key here is to start with the center main cap and work out from there alternating back and forth till you’ve completed all the main caps.

5.3 ls crank

The way we understood the torqueing sequence is start the first pass with the 13mm inner bolts, then the 15mm outer studs, this first pass on the bolts and studs is only to 15 foot-pounds.

Following that first pass get the 10mm side bolts and dab some RTV around the bottom of the head to insure no oil leaks down the road, torque these bolts down for a first and final time in sequence to 18 foot-pounds.

5.3 ls crank 2

Now all that’s left is the final pass on the initial main studs and bolts, this pass is a bit trickery.

What we did to guarantee consistency was draw lines across the heads of the studs and bolts in line with the engine, this allows you to visually see how many degrees have been turned.


5.3 ls torque spec



Again, still moving in sequence turn the inner 13mm bolts an additional 80 degrees, I like to think of this as just under a quarter turn.

Finally turn the outer 15mm studs the oddly specific 53 degrees, or what I call a bit over and an 1/8 of a turn.

5.3 ls engine

The crank shaft is installed, and all the bolts are torqued to spec, turn it over a couple times buy hand, it spins over freely and effortlessly, the only resistance you feel is the weight of the crank.

 5.3 ls engine 2

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Main Bearing Cap


Rods and Pistons

With the crankshaft in place its time for the repetitive job installing the piston and rod assemblies. This is a v8 with 8 pistons so naturally there are 8 rods bearing, each bearing consisting of 2 halves, 1 half with an oil feed whole and the other without.

Like with the main bearings each rod bearing half has a tab that keys in to the rod and cap locking the bearing in place.

5.3 ls gen 4 pistons

Install the rod bearing halves with the oil feed whole into the rod side, this will allow oil to travel from the crankshaft through the connecting rod and into the piston and rings, install the remaining rod bearing halves into the connecting rod caps.

5.3 ls connecting rod spec

I recommend doing this one at a time because rod bearing caps are not interchangeable, any mix up here will lead to significant problems. To start go over the cylinder bores with some fresh motor oil to assure they are well lubricated and protected against corrosion.

I like to begin with cylinder 1, turn over the crankshaft till it’s at bottom dead center relative to cylinder 1.

5.3 ls crank spec

Before placing the rod piston combo into the bore take a moment to apply assembly lube on the rod bearing surfaces.

I also like to take this time to rub some motor oil on the piston skirt and rings to insure it slides in smoothly.

5.3 ls block

With the engine up right and turned so that cylinder 1 is perpendicular to the floor, this assures that the rod doesn’t slide against the cylinder wall, slide the first assembled piston and rod into the cylinder bore, note that the top of the piston has an indent or dot, this marking always points toward the front of the engine.

5.3 ls block 2

[also worth noting the gen-IV connecting rods have a dimple on one side, the dimple always faces the rear of the engine.]

The piston should be in its bore but sticking out the top now, I find it easier to work the first oil retention ring into the bore by hand, going around it perimeter till the piston drops in.

5.3 ls piston bore

At this point we used a variable size piston ring compressor, this tool can be frustrating but has the benefit of working for multiple bore sizes, stay calm and take your time.

Position the piston ring compressor around the piston and slowly tighten till it fits snug around. Using the handle of your mallet smack the piston dead center firmly.

5.3 ls block 3

This takes a bit of feel to get right, but it should slide right in, if it fails to slide into the bore re-position the ring compressor and try again.

Occasionally the rod bearing comes off the rod, if that happens clean it up and reinstall after the piston is fully in the bore.

5.3 ls got ya

Awesome the piston is in its bore, turn the engine upside down and slide the piston down the bore till the connecting rod journal meets the crankshaft.

Make sure the connecting rod bearing is still fully seated and sits flush in the rod, and install the rod cap and torque to spec.

5.3 ls block 4

Repeat this on cylinder 2 and again in till all 8 pistons are installed, rotate the crankshaft to bottom dead center when necessary so you don’t strike the crank with the connecting rod when installing the piston.




ARP Rod Bolt Torque

We used ARP rod bolts in this build and the installation torque specs are a bit different from stock.

arp rod bolts

Like the main bearings we squeeze some ARP thread lubricant on the rod bolt threads before running them down finger tight.

Take your torque wrench and tighten the 12 point 3/8 connecting rod bolts alternating back and forth till you achieve 15 foot-pounds.

Then following the same procedure torque the rod bolts to 45 foot-pounds.

We loosened the bolts and executed this torqueing process again to assure initial bolt stretch wouldn’t distort the final torque value. 



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