Apocolipse

iTrader: (1)

Hey,

I have a L33 from a Sierra with the stock harmonic and flexplate on it. I am converting it over to a 6 speed in a car and I need to know more about its internal balance.

I was told that the engine is balanced factory with the stock flexplate ASSAMBLY / harmonic as one unit. Will I be able to take the flexplate off, and match its balance offset with a new flywheel, and be done?

Is the balance done on the flexplate? or is it including the stock torque converter as well (which I do not have)?

I am thinking of taking the whole assembly out and getting it fully balanced. Get a new harmonic, flywheel, and clutch assembly... balance the crank, rods, pistons etc, and then neutral balance the fly / harmonic.

What are your suggestions when it comes to this? I am running the motor to 6500ish but it is mainly a street car / random road race car for a few track days.

Thanks a ton!

wildcamaro

iTrader: (15)

If the engine is factory sealed still I would just thrown a clutch and pressure plate on it and go, of course you can balance the rotating assembly but it should already be good to go unless something was replaced/changed...

Apocolipse

iTrader: (1)

The engine has never been touched. Pulled straight from the truck. I have read that some have a vibration issue if the flywheel is not properly balanced with the assembly but it did not really make sense to me. Can I not just get a neutral balanced fly and call it a day?

bww3588

iTrader: (49)

The ls engines are internally balanced with zero balanced flex plates and balancers. As long as the fly wheel is zero balanced, you won't have any problems. Just don't forget the pilot bearing.

A torque converter has nothing to do with balance as it is full of fluid and moving parts. It balances itself.

Apocolipse

iTrader: (1)

Ok, so its just the vettes that are balanced as an assembly after its all built then? The rest rely on the factory tolerance of the parts when assembling the bottom end?

I believe the vettes are balanced after its put together because they are more prone to harsh vibration due to their torque tube / rear mounted trans setup. Makes 0.5oz feel much bigger than in a regular car.

This is what I have been reading when searching. Just want to make sure I am close. I was debating pulling the bottom end out and getting it balanced at a good machine shop to get it even closer with a zero balanced fly and harmonic...

2muchboostNY

iTrader: (8)

Thanks for the thread...this was a similar question to the one I had a few days ago in a discussion with some old school muscle car guys. They had said the same as above.

Also, sorry to thread jack a bit but it may also answer this question if you had it, whats the part # for the Pilot Bearing needed for the conversion? Doing a very similar build and want to make sure I buy the right part. Thanx in advance and OP GL on the build.

Apocolipse

iTrader: (1)

No worries on the jack, I will need to find that information out as well one of these days.

I am more curious if it is worth taking the full rotating assy out to be balanced properly or how close GM spec usually is.

bww3588

iTrader: (49)

If you're not changing anything internally as far as the crank, rods or pistons, don't touch it. Benefit over cost is not worth it.

wildcamaro

iTrader: (15)

If using an old school 4 speed use an ls7 pilot, other than that I would assume an ls1 pilot

Apocolipse

iTrader: (1)

Nothing is changing inside. The engine was from the junkyard and the clowns liked putting the weight of the motor when resting onto the front harmonic balancer. So as a precaution I am changing the main bearings in case they got distorted from the weight. Debating changing the rod bearings... but don't really feel like re-torquing the bolts lol and I have heard horror stories about swapping to arp.

I am running a C5 so I assume that's the ls1 pilot.