BHJ Balancer

scskydivin

SCCoA Member
So, my HB bolt broke off, again.
It's a BHJ. I've had it on for 8 years. The motor has been rebuilt 6 years ago. New pistons, rings, & bearings. Crankshaft, camshaft, and connecting rods all checked & cleaned. Heads were rebuilt & resurfaced. The odometer stopped at 232,000 2 years ago. It's still my daily driver. Car has ran fine.

A month ago, the hb bolt backed out & broke off. I replaced the bolt with a new one and went on my way. No lock tight on the threads. I also didn't get under the car with a screwdriver in the flywheel to stop the motor from turning when I reinstalled it. That was a dumb move on my part. So, this morning when I heard that "clunk" and seen the bolt bouncing on the road behind me, I knew what had just happened. Lucky me, I've got a spare new bolt on the shelf here. I decided I was going to do it right this time. Got the lock tight, and i crawled under the car to hold the flywheel still while tightening the bolt up. Guess what I noticed? The BHJ has an 8th of an inch to go on the crankshaft and I can wiggle it by hand, easily. I can pull the BHJ off the shank with a little effort and put it back on the crank. All the way to an 8th of an inch to go. I've also noticed the key way in the BHJ is slotted, with 2 different sizes, one bigger than the other. The pictures I've found on here have all shown the keyway as one size all the way across the hole. I'm startin to stress here a bit. Any one have any insight?
 
does,nt seem right could u have installed it with a

worn key :eek: then it was able 2 wobble and wear the key way:mad: u could cut some shim stock .0001-001 :confused: get a new key and refit it tighter:p if the crankshaft snout is worn u will have 2 maybe drill set screws in the balancer 2 tighen in it .:rolleyes: I woulld mike all parts 2 check the wear ..then do what u can 2 reinstall :cool:
 
Yeah, upon further inspection, it looks like the balancer is no good. The key hole is worn and made the one side a bit larger. I'm gonna order a new balancer today. I'll inspect the key on the crank this evening when I get home from work. It looked good last night, but then again, it was midnight, mad, hot & sore. I couldn't see the worn key hole. I post a pic of the worn BHJ as soon as I find the camera~computer cord in the remaining moving boxes.
 
Neither the key nor the bolt are there to hold the balancer on the crank.
The balancer is supposed to have an interference fit. Without that, the key nor the bolt will be sufficient to retain the balancer.

If you can install and remove the balancer by hand you have two options.
#1 - replace the balancer.
#2 - have a machine shop check if they can sleeve the balancer and bore it to give you back an interference fit.

Which one will cost more, I don't know. My guess is it would be a wash.

This assumes that your crank snout is not worn down such that even a new balancer would not have the interference fit. In such a case, you're stuck with sleeving if possible.
 
Well, found the camera box right on top of the last moving box marked "desk"! The pic of the BHJ is self expanitory. The crank has a little dirt on it.
 

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That looks like the balancer was pressed onto the crank-shaft without proper alignment causing it to be forced over the key stock.

That likely also deformed the hub of the balancer, leading to it's loose fit now. my guess is the balancer hub inside is no longer concentric and may have egg shape now.
 
That looks like the balancer was pressed onto the crank-shaft without proper alignment causing it to be forced over the key stock.

That likely also deformed the hub of the balancer, leading to it's loose fit now. my guess is the balancer hub inside is no longer concentric and may have egg shape now.

I thought the same thing at first but on closer inspection I don't see any material pushed up at the end of the wide area so that makes me think that it was not misaligned.

It's true that the press fit is intended to primarily hold the balancer, but without a retaining bolt it is plausible that it may have moved on it's own. Clearly the press fit is gone and nothing will fix that now.

I also wonder if maybe it wasn't put on with insufficient press in the first place. Remember the early BHJ's were finished undersize so that final honing was required to install them. I've seen before where over-zealous machinists, or perhaps inaccurate measurements resulted in loose fitting balancers. Lack of a proper press fit doesn't spell the end of the balancer, at least not at first, but it does mean that the significance of a properly torqued bolt becomes more a functional part of the final product than it would have been with proper press fit.

Since this one is now worn loose, I would also be concerned about material transfer to the crankshaft and a resulting problem when installing a new balancer.

Sucks either way.
 
Got the new BHJ on w/o a hitch. Car runs good n' smooth. I took great care on installing this, just to make sure I didn't shortcut anything. I had everything so clean from the teardown, that my hands were hardly dirty after the installation was done. New front seal, RTV on the keyway and a thin amount all the way around the inside. Knocked that in lightly with a piece of wood. Shot a couple coats of 500 degree clear coat on it and let it hang overnight. Put it on nice n slow with the installer tool I rented from the auto parts store. New bolt was torqued to 130 ft lbs. I'll keep a close eye on it. If this thing has an issue now, I'll be pulling the engine, so I can get to the rotating assembly. I hope, of course, that I don't hafta do that. Not that I wouldn't mind a set of those serious rods and those big boy pistons from SCU, which would then need to be accompanied by a matching cyl head/cam set up, it's just not on my 'to do list' right now....
 
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