I finally had time to get the Gen 4 5.3 torn down. I removed the rods and pistons to open up the ring gap. Stock ring gap was anywhere between .015″ to .017″, not exceeding .017″ on any of the cylinders. Only the upper ring gap was modified. It was opened up to .028″ to .030″. This is done so that when cylinder temps rise, and as the upper ring temp rises and the metal swells, the ends of the ring don’t actually touch each other. This causes the piston to bind in the bore and usually results in a busted ring land or worse.
Once that was done, the rods and pistons were put back into their original bores with plenty of fresh oil lubricating the cylinders and rings. At this point I installed the BTR Stage 3 turbo cam and the new AC Delco LS7 lifters in the BTR lifter buckets. Before installing the BTR buckets and lifters I drilled a hole on each side of the bucket. This allows oil to drain back quickly rather than pooling into the buckets.
I then installed the new timing set, and Melling oil pump.
Followed by the new LS3 timing cover and sensor that I picked up from Liljohnmotorsports, as well as the L92 lifter valley cover. Originally this engine featured GM’s AFM or active fuel management. What this basically does is shuts off half the engine’s cylinders when cruising and their is a light load on the engine that doesn’t require the torque of a V8 engine. While this helps with fuel economy, the stock AFM lifters do not like aggressive camshaft lobes and are known to cause issues. The L92 valley cover is needed because the stock valley cover housed the oil control solenoids needed to control oil flow to the AFM lifters. These need to be blocked off when not used. You can do this several ways, drilling and tapping the ports under the cover or replacing the cover are the two most popular. I opted for the cover as it’s the easiest and doesn’t risk getting metal shavings into the engine.
This engine also featured variable valve timing, a feature I wasn’t interested in keeping either. Though my Megasquirt ECM could control this feature. The VVT camshaft uses a single large bolt to retain the camshaft timing gear to the cam. The majority of your aftermarket cams use the traditional 3 bolt setup. So a new timing set, camshaft gear bolts, timing cover and sensor are all required to delete this feature.
Once the bottom end was done, it was time to work on the cylinder heads. This engine came with the 243 heads, which work great on boosted applications. However the factory springs leave something to be desired. Some guys run the stock springs or upgrade to the popular PAC 1218 spring. However those are both single springs, and if a spring happens to break the valve can drop. So I opted for the BTR Platinum springs along with their titanium retainers and keepers. I also went with their chromemoly 1pc pushrods.
The springs also use a special valve stem seal and spring locator, you cannot use the stock seals or locators, they will cause damage to the spring.
With the heads done, it was time to torque them down. I used stock Felpro MLS head gaskets and new stock head bolts.
Once the heads were on I installed the stout BTR pushrods making sure to use cam lube on both ends.
Then installed and torqued down the rocker arms, making sure to lube them and the top of the valve stems. I may still upgrade the trunions on these with the Comp Cams kit.
The engine was then sealed up with the valve covers.
I started adding the front accessories.
I then installed the new Hummer LH6 oil pan, pickup and windage tray.
Then came the new harmonic balancer.