ghostrider20

One of my buddies stopped over tonight, and when timing the car, I noticed the balancer thrusting forward about 1/8"-1/4" when the motor was revved. Returned back when the RPM decreased.

Is that normal, I guess I never noticed it before on anything else.


Mark

jerrybramlett

I believe the crank thrust should be to the rear and too small to notice.

ghostrider20

That's what I thought, to the rear, so what would make it thrust forward???

Mark

67L36Driver

Crankshaft end play should be .003"-.011" .

MikeM

Sounds like your buddy's engine is about to go on a weight diet. Is the whole damper moving forward or just the outer ring?

muncieman

I've seen torque converters cause this problem but you need to make sure the outer ring on the damper is not moving.

Put a pry bar behind the damper and pull or push it and see if that makes it move more than the normal amount, .003 to like .012. If it moves load the thrust on the crank or the thust bearing or both has checked out and it's time to pull the motor and repair the problem

67L36Driver

That much endplay indicates the bottom end is shot. Next, you will start to hear clicking at idle. The big end of the rods will start hitting things.

Scott Marzahl

It isn't all that uncommon for the outer dampner ring to come off and do some serious damage underhood. Some engine builders drill and countersink three bolts in a new dampner at 120 degree intervals to prevent it from coming apart at high revs.

muncieman

I've seen that done, wonder what affect that has on the ability of the dampner to do it's advertised job??

Scott Marzahl

The dampner on my 383 that I ran with NOS had that done and there were never any problems. I used the Chevy 8" modular iron dampner with the bolts not torqued down, just snugged with nylocs nuts.

henny496

Hello
I would replace the dampener. Not only will you get false readings for the timing on one that has the outer ring slip, but it can come apart.
This is why you drag cars replace them, for the same reason you replace bellhousings and cast flywheels
take care
Tom

babbah

Replace the stock damper with the Fluidampr and you will never have to worry about a outer ring problem again.

ghostrider20

The whole dampner is moving. You can noticably see it thrusting forward with revs. I doubt you would notive .003-.011 movement.

Motor sounds good, runs good.

Mark

MikeM

ro.co3

I'm assuming your running a small block and most likely the balancer is not bolted but pressed on. I had one come off awhile back doing 70mph,
lucky me no damage. Anyway pull the belts and and inspect the balancer if it moves replace it and by all means drill, tap and bolt it on. I did and have had no problems since. If you do a search on this you should find allot of info. good luck.

ctjackster

"whole dampner is moving" means it is migrating out along the snout.

give it the SHP treatment and drill / tap for a bolt, such bolts are available since they were done for the SHPs. Discussion Threads exist on doing this with engine in car, rad removed. Center punch already exists in snout.

here ya go, parts and pictures:

http://forums.corvetteforum.com/show...um_id=4&arch=1

would seem that Mark - Coves4me did this and might be able to offer some advice

Tom Piper

Sounds like the "thrust" flanges on the thrust main bearing are worn.

I saw one like this, it was caused by the clutch being held in too long and too often -- wore the thrust bearing out.


Tom Piper

Tom454

Unless the damper is loose on the crank... and is just following the belt tension as RPM changes. Grab hold of the damper & wiggle it... if it's worn bad enough to move in & out when spinning, then it will probably wiggle when it's not running. Otherwise, I'd go with the thrust bearing theory... which you can easily check by putting the tranny in neutral and forcing the crank forward/rearward (engine off).

Didn't catch which engine you have.... but the early 327's had press-on dampers and un-threaded crank snouts. I think Fluidampers require a threaded snout.

FXT

Reading this thread reminded me of the same thing concerning my '67 L-79 small block harmonic balancer. Ordered the correct new one #3817173 yesterday from http://www.gmpartsdirect.com/ .It cost $76.oo + S&H. I'm not going to flirt with disaster. Here is intersting article on balancers.....http://www.chevyhiperformance.com/techarticles/4402/

JohnZ

Good article on what "balancers" (dampers) really do, but I'm continually amazed at all the recent articles that say the pre-'69 timing index line is offset 2* from the keyway centerline. I guess they just copied what the other magazines said, and never bothered to look at the GM damper drawings to get the correct information; the index line is dead-centered on the keyway slot and pulley bolt hole center, +/- 1/4 of a degree tolerance.