LT1 Harmonic Balancer question!??!
Thread Starter
Racer
Joined: Apr 2003
Posts: 286
Likes: 2
From: Suffolk VA
LT1 Harmonic Balancer question!??!
Hey guys, need some advise concerning the Harmonic Balancer on my LT1. As many of you may already know the Pulley/Balancer on the modern day LT1 is not keyed on the crank like balancers usually are. I have found that this causes the balancer to slip/spin on the crank nose during hard accelerations or higher RPM operation. In my (and my machine shop guys) opinion this is a bad thing. What can be done to correct this, or is it really an issue? I don't understand why GM engineered it with out a key but I would like to fix this problem before it becomes an issue.I', all
to info and suggeestions.Thanks
Jason
Instructor
Joined: Mar 2002
Posts: 181
Likes: 0
From: Allen TX
A keyed hub can be yours for about $85
The crank should be slotted, its just the crankshaft hub that is press fit. You can either cut your own slot in the crankshaft hub (read mixed results) or you can purchase a pre-machined piece like this
keyed hub
See ya,
John
keyed hub
See ya,
John
Thread Starter
Racer
Joined: Apr 2003
Posts: 286
Likes: 2
From: Suffolk VA
Hey John,
Thanks a bunch for the link man. I haven't found a local machine shop that can Knotch my hub with confidence so this is exactly what I need, especially because the only other option I found was ATI balancer for $400!! OUCH!
Happy Hot-Rodding
Jason
Thanks a bunch for the link man. I haven't found a local machine shop that can Knotch my hub with confidence so this is exactly what I need, especially because the only other option I found was ATI balancer for $400!! OUCH!
Happy Hot-Rodding
Jason
Drifting
Joined: Nov 2002
Posts: 1,365
Likes: 3
From: Huntsville AL
Originally Posted by KyRP2NITe Corvette
Hey guys, need some advise concerning the Harmonic Balancer on my LT1. As many of you may already know the Pulley/Balancer on the modern day LT1 is not keyed on the crank like balancers usually are. I have found that this causes the balancer to slip/spin on the crank nose during hard accelerations or higher RPM operation. In my (and my machine shop guys) opinion this is a bad thing. What can be done to correct this, or is it really an issue? I don't understand why GM engineered it with out a key but I would like to fix this problem before it becomes an issue.I', all
to info and suggeestions.Thanks
Jason
The car did not vibrate the first year or so I had it. Made a couple of trips to the dragstrip and noticed the vibration shortly after that.
Since the balancer looks good, the only other possibility is that the hub has moved on the crank snout, as it is not keyed to lock it in place. I originally thought this was highly unlikely, considering how difficult it was to get the balancer off the first time, but after your comments I'm beginning to wonder if this is the case.
Have you seen one move before? Do you think my theory is valid?
Thread Starter
Racer
Joined: Apr 2003
Posts: 286
Likes: 2
From: Suffolk VA
Yes, after closer inspections and trouble shooting I believe that mine was starting to slip even before I pulled it to change the cam the first time. Thus I believe your conclusions to be correct.
By the way I took my crank gear and hub to a local tool and die machine shop and had a key way broched in the stock piece. That solved my problem and only cost me $20 (after haggling a little with the guy)
By the way I took my crank gear and hub to a local tool and die machine shop and had a key way broched in the stock piece. That solved my problem and only cost me $20 (after haggling a little with the guy)
Drifting
Joined: Nov 2002
Posts: 1,365
Likes: 3
From: Huntsville AL
That's what I was afraid of.
Does the stock crank already have a slot for a Woodruff key? I've seen that the hub is the only part that doesn't have the slot since it's press fit only. Is this right?
Does the stock crank already have a slot for a Woodruff key? I've seen that the hub is the only part that doesn't have the slot since it's press fit only. Is this right?
Thread Starter
Racer
Joined: Apr 2003
Posts: 286
Likes: 2
From: Suffolk VA
Stock Crank is cut for the key. Don't know why GM got lazy and decided not to key the hub for the balancer though..... must have borrowed a Ford engineer while all the real engineers started the LS1 design 
hahaha!
hahaha!
Racer
Joined: Feb 2001
Posts: 381
Likes: 8
From: NORTH WEST PA
Originally Posted by KyRP2NITe Corvette
Yes, after closer inspections and trouble shooting I believe that mine was starting to slip even before I pulled it to change the cam the first time. Thus I believe your conclusions to be correct.
By the way I took my crank gear and hub to a local tool and die machine shop and had a key way broched in the stock piece. That solved my problem and only cost me $20 (after haggling a little with the guy)
By the way I took my crank gear and hub to a local tool and die machine shop and had a key way broched in the stock piece. That solved my problem and only cost me $20 (after haggling a little with the guy)
I have the same high RMP vibration on my 92. So are you saying the vibration is occurring because the balancer hub only starts slipping at higher RPS ... or at some point the hub has slipped and causes the vibration because of a balance issue?
I was racing Saturday night and at one point the vibration was severe enough to pop the shifting pattern bezel out of my shifter. The vibration was there the remainder of the night but not as severe.
Thanks!!
Brian
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Drifting
Joined: Nov 2002
Posts: 1,365
Likes: 3
From: Huntsville AL
The theory is that at some point, the balancer hub slipped on the crank snout, and that cause an imbalance in the rotating assembly.
Unfortunately in my case, we found that the hub had not slipped at all. So mark that one off the list of possible causes for my vibration.
Unfortunately in my case, we found that the hub had not slipped at all. So mark that one off the list of possible causes for my vibration.
