[b-man]

The entire balancer is cast iron including the hub.

That was an easy diagnosis, there’s nothing else in that region that could have broken off and poked through the very front of the pan.

[AJD1964]

Question is, what usually causes this.
I was surprised at how easy it was to get the balancer bolt loose. It slightly turned the motor and threaded right out. No way was that 160 ft lbs.

[Formulas]

under torque on install causes this, when not enough torque is applied the key on the crank hammers back and forth in the balancer hub eventually cracking it

[besserspat]

Originally Posted by Formulas

under torque on install causes this, when not enough torque is applied the key on the crank hammers back and forth in the balancer hub eventually cracking it

Man, its quite funny last month I was timing a friends car that he just bought a 86 Cutlass Supreme, that has a 454 and th400 swapped by the previous owner and sat 10 years.

A parts bin special kinda deal with mismatched "hi-po" parts . While timing it I realized there were no bolt holding the damper in place... I told him to get one ASAP before he shears the key and destroy the engine.... Im sure he still hasnt put one in... So ill guess Ill keep one of my spare 454s in the shop in case he calls crying...

Peter

[steve25]

That’s true for certain!
That balancer gets wedge and firmly held in place between the bolt and the crank gear and then there is no load on the keyway groove.

In fact the rear of the cam gear is something to always check.
The chamfer in it must be deep enough to allow the rear face of the gear to sit flush onto the face of the crank.

I recall a good number of years ago there was a aftermarket gear and chain set in which this chamfer was not cut deep enough and you could not even get both gears in close enough alignment to get the chain on.

[sdbob]

I was doing something to my 65 421 years ago.i noticed a crack in the keyway of the balancer. So I make sure now of 160 ft lbs. Never noticed one since. Also I mark a known good balancer so I can just look and see if has moved due to deterioration of the rubber.

[AJD1964]

The crank key is trashed where the balancer was, but still ok at the timing gear. Can the key be replaced? Timing chain and gears look good. Nothing left of the timing case seal. I did pull a mangled piece of really thin gauge metal sitting at the front of oil pan.

Gonna go to a local cruise in today and enjoy the ‘64. Only had a chance togo to 2 events this summer. Grandkids now! I’ll begin prep for removal later in the week.

[steve25]

Yes, the key can and should be replaced.
Put some punch marks in the new key if need be so you have to tap it in .

[mgarblik]

Balancer/crankshaft nose is a common failure point on the Pontiac engine. Most aftermarket replacement balancers have about a .001" light press fit to the crankshaft. This is important. As mentioned, if the bolt torque isn't maintained, the key cracks the cast iron hub and the rest is history. To avoid this, when drag racing the Boss Bird, we attached the hub with a longer L9 strength bolt to get extra thread engagement. Also purchased the hubs unfinished and honed them to a .002" press fit. Used locktite and 235 ft. lbs. final torque. No issues with this set-up. On a stock Pontiac balancer, I make sure there is a at a minimum a zero fit. Should NOT slide on by hand. Then I use locktite and 160 ft. lbs. minimum. 180 ft. lbs. preferred.

[VCho455]

I've had this happen to me twice over the years. One the nylon timing gear was destroyed (Who said nylon timing gears were all bad? ) and the other time it happened while starting the engine. Huge deafening, backfire, both mufflers ballooned, and one end of the timing chain was hanging out of the oil pan. Bummer day!

I now check every used balancer I use for cracks before I install it. And I install it as mentioned with Loctite and 180 ftlbs of torque.

[Dragncar]

Mic your snout, call Darrin at Nightmare, give him your snout measurement and he will send you a proper press fit BHJ balancer with the 4 bolt holes. Not cheap, but Made In The USA and as good as they get.
The bonding issues they had awhile back are a non issue. Since they changed their bonding process they have not had a single one come back. Cost them a lot of business in NASSCAR but they are fine balancers.

[AJD1964]

Got motor out yesterday, and is on a stand.
More pieces of balancer and timing cover seal were found at bottom of oil pan. But I was hoping to find more balancer pieces as only about 30% of balancer hub was remaining in the pan.

At least from a bottom up inspection, I only see evidence of fresh dings on the piston skirts and the crank in the front 2 cylinder locations. Not sure what to do about the small dings. All cylinder walls look good, and no dings on any connecting rods. but I’m not a pro, and wonder what to do next.

Please review photos if interested. Opinions valued.

[AJD1964]

More pics

[steve25]

I think you lucked out!
All of those nicks can be polished out and you do not have to be concerned with any balance issues.

Time to take the pump apart a see how the gears and the gear case walls look like.
Any signs of crap getting in there and it’s time to look at main and rod bearings, and with signs of trouble there if it where me I would strip the block down so t it can get hot tanked in case any metal grit is lodged in old oil in the galleys.

[johnta1]

I'd just take the high spots off with a fine file on the pistons. The crank maybe the same, but not as critical.
Possibly check the bearings for any scoring?
Any pieces stuck on the oil pump screen?

[AJD1964]

Originally Posted by johnta1

I'd just take the high spots off with a fine file on the pistons. The crank maybe the same, but not as critical.
Possibly check the bearings for any scoring?
Any pieces stuck on the oil pump screen?

Nothing on oil pump screen - it was clean

[AG]

Check a few rod and main bearings before you button it up.

[Formulas]

some pieces may be resting in the lifter valley

[mgarblik]

Could you post a few pics of the crankshaft nose? And also let us know if the key came out easily and had a nice snug fit in the keyway? I would make sure the nose is smooth and not dinged up. Chances are the keyway is high on the edges where the key was beat up. Once cleaned up and happy with it, I would lightly oil the ID of the balancer and see if it slips on. I would do this without any key installed. This is to determine in a deformed keyway is providing the interference. It should go on with some interference. A large shot filled hammer or a block of wood and a large ball peen hammer should be needed to get it on more than about 1/2"-3/4". If it fits snug like this, remove with a puller. Then install a new key. Put your timing cover on with a new seal, lube the rubber with grease. Torque the bolt with locktite to 160-180 lbs. and your good to go once again.

[geeteeohguy]

Agree you lucked out. The piece hit the piston when it was down, which kept it from going up the cylinder and hurting the wall. Dress down the burrs, keep it clean, inspect a couple or all bearings (only should take an hour or so) and button it up.

I would change all of your core plugs (they look terrible and about to fail) and I would ditch that Fram oil filter for a Wix or Baldwin.