LT1 engines are balanced with flywheel and front damper installed. If an engine from a manual shift car is put in an automatic car, will there be any balance issues changing from a stock manual flywheel to a stock automatic flywheel?

 

You'll need to match balance the new flywheel.

 

The front damper is neutrally balanced and isn't an active part of the engine balancing. The flex plate and the flywheel should nominally have the same amount of imbalance out of the box, but match balancing is the most accurate way. That assumes, of course, that the clutch assembly is accurately neutrally balanced.

RACE ON!!!

 

This is true of LT's? Then why do I have to match weight locations of old and new dampners when replacing?

 

As CFI said, LTx dampners are neutrally balanced. That's why the hub is an interference fit and has no keyway.

 

When hub is removed, it must go back in the same position it was removed from as to not effect the balance. GM did not put keys in them because they are cheap. LT's are externally balanced that is why you must match balance the flywheel/flexplate and the front dampner with appropriate weights.

 

You are mistaken.

 

If you remove a hub from an Lt motor. You can't just put the hub back on anywhere you please like you are saying. You have to put the number one cylinder at top dead center. On the hub there is an arrow cast in that has to be in the 12 o'clock position when reinstalled in order to be in the correct location. The dampner can only go on the hub in one position. Weight must be in its appropriate hole on dampner. Why do you think this is? I guess it has nothing to do with balance, huh?

 

This has been explained to you. An LTX is externally balanced by the flywheel/flexplate. It is neutral in the front. That's why it is called a dampner and not a balancer. You can reinstall it in any position although putting it back in the original position is not a bad idea. Some may have been drilled to "fine tune" an engine. In theory, it is not necessary.

 

 

Maybe three people telling him will get his attention.

 

All,

On this same subject, I'm in the process of replacing the 3 seals in the front engine cover (95 LT1, 6 spd, btw). I have everything off (also replacing water pump, Opti w/MSD unit, plug wires, etc.
The damper/balancer/pulley piece is off & I note to re-align the arrow on the back of the damper with the arrow on the crank hub.

Picking up on a reply here, there is no key on the crank ? Re-align at 12 o'clock (TDC) you said. Is there a mark on the cover ?
Naturally, I assume the cam will follow & properly align the dist. rotor.

I know I'm asking obvious questions, but this thing scares me a little...

Thanks for your help.

KLS

 

Put the hub back like it was as best you can. The dampner will only go on one way. The dampner has nothing to do with the timing.

The opti will only go on one way also. Be sure and not force it. Your FSM explains it well.

 

Even though the crank isn't keyed. You should be able to see a witness mark in the hub where the crank is cut. This will help you to realign, if you want it in the same position. There is no mark on the timing cover, unless you left one.

 

Here's a little fact. The dampner is neutrally balanced. Small weights are added to fine tune the overall engine balance. If you buy a new dampner, per the factory service manual, you are supposed to install the same number of weights in the same location in the new dampner as the old one.

Hope this helps.

 

Thank you, that is what I have been trying to say. There are 12 little holes around the dampner so you can install weights gm p/n 274584. Yes before you install weights it is neutrally balanced. But have you ever seen one come from the factory with out them. Nope. By commenting that you could drill it to fine tune it I assumed you have never seen one as it already has holes. I am pretty sure Uncle Lenny has gotten his answer by now so I will stop trying to get my point accross.

 

By the way, Speed of Heat, what do you drive. You haven't filled out your profile.

 

To ensure that the new dampner is match balanced to the old neutrally balanced one.

 

I've seen the argument over the LT1 damper being used to balance the engine assembly many times over the years.

As far as I can find out from doing research in it, it is my belief (for what it is worth) that the LT1 damper has holes in it to allow the balancing of the damper by itself before being put on any engine.
According to some of the after-market torsional damper makers, dampers with elastomer that is used to bond an inner (hub) ring to an outer ring cannot be made of perfectly balanced components because the bonding of the rubber is not perfectly concentric. (In other words, if both rings were perfectly balanced before the bonding of the rubber, since the bonding is not perfectly concentric, the rings will be positioned so they won't be balanced anyway).
Therefore, the holes around the damper are to allow the damper to be perfectly balanced after the bonding takes place. In other words, the damper is supposed to be neutral balanced before putting it on the engine.

Some sources of information:
http://www.vibratechtvd.com/VISCOUSTECH.htm

In particular, about half-way down:
-------------------------------------------------
Elastomeric Dampers

In elastomer dampers, the outer inertia ring is fixed relative to the mounting hub through a ring (or rings) of elastomeric material (usually rubber). These units must be balanced after assembly to correct imbalance due to any offsets between the inertia ring and the hub that are created by the imposition of the rubber ring between them (note the large balance holes on many of these dampers). An elastomer damper that is not balanced out of the box is not self-correcting at any speed.
---------------------------------------------------

Because of this research, I believe that the LT1 elastomer damper is neutral balanced, and the lack of a keyway in the hub goes a long way in agreeing with that. If anyone in their right mind thought the damper position was critical to the balance of the engine, they would provide a way to insure the position.

However, you will read many things on-line that differ with this -- it is up to you to decide what you believe, like I have.

Tom Piper

 

Couldn't have said it better.