'play' in harmonic balancer

[basherbob]

For the past several months since the GS Nationals I have been having problems with getting stranded after 15-20 highway miles. So now I am in process of replacing the crank sensor and found that the balancer bolt was loose.
After removing the belt I grabbed the pully to turn the engine and discovered I could turn the assy left / right just a little bit. The balancer is not cracked and the keyway is not chewed up. looking into the front cover the key appears to be square, not chewed or chipped and is tight in the crank. I didn't try to remove it since it was tight There is no balancer 'wobble' on the shaft and the fit is good . BUT I can turn the pully just a little bit like a click-click movement,maybe a 64th of an inch or less side to side.
Is this normal tolerance or should there be 0 tolerance just pull off staight on with no turn tolerance. I thought it strange that the bolt was only snug not tight.
The loose bolt may allow the movement as I drive causing my strange firing issue. It drives fine for a while then acts up (spits, bucks, backfires, dies) after continuous driving for 20 or so miles on the highway. After cool down it starts and drives fine, for a while.
Would a little bit of tolerance at 2500 rpm cause timing issues if the pulley is moving that way? The crank sendor was not chewed up so I don't think there was any in-out tolerance. the crank nose also looks good, not worn.
Suggestions? Just tighten the bolt down as this is normal tolerance? Replace the balancer and or the key to get rid of any twisting movement?

 

[basherbob]

By the way this is the stock 76000 never been cracked open engine. Why the bolt was loose is beyond me.

 

[Blown&Injected]

the pully is bolted to the hub - are the bolts from the pully to the hub tight?

If the hub is moving after bolting it in place to a good condition key - something seems like it is cracked.

This does not sound good to me - maybe you caught it in time???

 

[basherbob]

Yes the pulley bolts are tight. Was actually hoping that was the problem.

When I torque down the crank bolt it doesn't move which is 1 of the options. I was just concerned that it moved when first put on and the bolt is snug.

The Key is tight in the crank and I didn't try to pry it out until I found out if the movement is not in tolerance. If there should be 0 movement as I suspect the next step is to replace the key. The balancer channel is square and looks good. Nothing appears cracked.

Thanks for the reply.

 

[Blown&Injected]

If everything is right with the hub and the key/crank, there would be no click-click.

Is there a big, thick washer on the bolt?

The hub should slide onto the crank/key all the way and then crank the bolt to massive ft lbs - do a search, there are lots of good ideas on how to hold the flex plate and other stuff, like the proper amount - 200+

 

[Ebbsspeed]

Usually those things are a tight enough fit that there is no play at all, even with no bolt in. I suspect that if you did pull the balancer off you'd see some wear on the key or in the groove. At high RPM there is quite a bit of "activity" in the balancer, and if it's not tightened to spec it will eventually cause some slop at the keyway.

 

[basherbob]

Yes the big washer is there. I suspected that there shouldn't be any movement since the one on my 455 doesn't do this. I have decided to replace the key and see if that stops the movement. Will need to dig it out of the crank since it is tight in there.
Thanks for the replies. Will post results once the key is replaced.

 

[bison]

post pics of the balancer. If it is sloppy on the key it could be a future problem.

 

[Joe 1320]

I just went though this issue with a motor that Don Cruz built for me. I tried several balancers, all had a slight bit of wobble when placed on the crank snout. he insisted that when torqued to 200#, it would hold tight. Sure enough, it does. Ironic that most torque wrenches don't go over 125#.

 

[bison]

I just went though this issue with a motor that Don Cruz built for me. I tried several balancers, all had a slight bit of wobble when placed on the crank snout. he insisted that when torqued to 200#, it would hold tight. Sure enough, it does. Ironic that most torque wrenches don't go over 125#.

Try a 1/2 or 3/4 drive torque wrench

 

[S10xGN]

Try a 1/2 or 3/4 drive torque wrench

Had to borrow this bad boy, 3/4" drive, 600 lb/ft. the swing is 48" wide.