mitchcole

I just pulled off the hub and damper from an LT1. There's no keyway on the crank. Is this supposed to be so?

Can I just slap the parts back together any old way?

96GS#007

If you take a look at the hub, you'll notice a cast in mark or arrow between two of the fingers. With the #1 piston at TDC, the arrow should be at 12 o'clock. While it probably doesn't matter, that's how the engine was balanced when assembled.

89'Bowtie

When I built my 96 motor, there was no keyway for the hub. I do not know about earlier models. I am open to being wrong on this one, however I don't remember any alignment marks on the hub-crank relationship. There are no timing marks on the LT1 units so there is no need for any alignment. Again, Its been a while.

The only thing indexed is the hub-to-balancer bolts. It can only go back on one way.

Good Luck, other chime in here if I missed anything.
89'

89'Bowtie

96'GS Brought up a good point. Its alway best to put things back on the way there came off.

However, wouldn't the "balancer" assembly be installed after the rotating assembly has been independently balanced without the "balancer"???

BrianCunningham

There was a thread about this a while back. Some LT1/4 are rebalanced at the factory after it's all bolted together with a special machine. So you need to get it back on as close as you can get it. Which is what I did, my car runs fine.

You can get aftermarket keyed hubs, the supercharger guys need it to keep the drivebelt from slipping.

Strick

Check your Helm's Service Manual for hub installation. You have to find TDC and put the arrow at 12 o:clock or something like that. It's important to put it back on in the same position as it came off because of the damper's effect on the external balancing of the engine.

93Quasar

I've been told by several reliable sources that the harmonic balancer is neutral balanced. Yes there are holes, yes there are counterweights. But those are there to get the unit neutral balanced. No casting, or machined part for that matter, is ever perfect, so it can't be designed to be made neutral. Therefore, it is spun afterward to get it neutral and weights are applied inside the holes. Have you ever heard of anyone having to match balance an aftermarket balancer or underdrive pulley set? The only external balancing done to the LT motor is to the flywheel - most of which comes from the large cast in counter weight - not the small pins.

However, having said that, I would still agree to put it on the same way it came off. There is a cast pointer on the hub that should point up at TDC. There is also a cast pointer on the balancer. Just line up the two pointers.

mitchcole

So - I didn't mark it as it came off and the crank moved around a bit trying to get that dam hub off...

The book says to put #1 at TDC - that's what I'll do. even on the exhaust stroke - the crank will be in the same spot.

HammerDown

There have been a billion threads on this. The harmonic dampener for LT1 cars is balanced to the engine it's installed on in the factory. Why would the service manual tell you to put the weight in the same hole on the new balancer as the old one? That would mean that the "casting imperfections" of the new balancer were EXACTLY THE SAME as the old balancer, which is highly unlikely.

Next time you have the balancer/dampener off, flip it over. You'll see a bunch of partially drilled holes in the outer ring. Now, compare yours to another balancer/dampener from another car. They will be different. THIS is how they neutral balance the dampener; the weights are added to BALANCE THE CRANK.

Not trying to be an a-hole about this or anything, but there's a lot of misinformation going around on this subject and it ends up leaving people with vibrating engines.

By the way, this is how they are (were) balancing Z06s at the factory. Only difference is the Z06s have screw-in weights, so they're a lot easier to change.

So bottom line, if you take the hub and dampener off the engine and aren't taking the rotating assembly to the machine shop to be neutrally balanced, put everything back on the way you found it. Otherwise, you're going to have vibrations. And not the good kind.

93Quasar

OK, then please take my comments above as my opinion only and not as known fact. I have never had a problem with vibrations resulting from switching to underdrive pulley sets (with built in balancer for LT1) that were not match balanced to the original crank balancer. If the stock balancer was not neutral, then I should have had problems - but didn't. Either my stock balancer was neutral, or I got lucky.

HammerDown

I'm not familiar with the underdrive pulleys with integrated balancer for the LT1. Is it a balancer like the OEM unit, with a rubber ring sandwiched between the inner and outer pieces? Or does it have some kind of internal damping mechanism (like a fluid damper, or a ball bearing assembly)?

What may happen on a lot of cars is that reinstalling a balancer in a different position does not result in increased vibration because the engine was pretty well balanced to begin with. Those weights they use in the holes aren't very heavy. If there's just one weight in there, then moving it around a little probably isn't going to affect things much. However, if the engine was a "shaker" from the get go, changing the balancer position will have a noticeable effect.

The manufacturing variation on these engines was pretty much all over the board, it seems. Wouldn't surprise me if you had one that didn't really need any weight on the balancer to get it balanced.

Timmy!

With the amount of sludge and dirt that was on mine when I took it off, I don't see how it's going to make too much of a difference if you clean it off and reinstall it.

Michael Maaser

I just pulled off my 95 Vette harmonic balancer Hub,the cranck has a keyway the hub don't??? Is that rite
?

Michael Maaser

Lt1

STL94LT1

^^^ Yes.

Michael Maaser

Thanks