pjburges

Has anyone ever blown the bearings out in their balance shafts? Mine failed after a reseal at right about 1000 miles. The balance shafts threw metal from the bearings into the engine and blew out the main and rod bearings and left some deposits on the cams. (This is a 16V).

Ill get some pictures up, but it grooved both the balance shafts about 1/8" deep and very nearly spun the bearings closest to the counterweights. There isnt much left of the balance bearings except lots of large finger sized flakes of babbit floating around. The block and casing were both hammered in the area that held the bearings, though not spun out.

Anyone ever had this happen? Seriously considering after this total rebuild Im about to have to pay for/ do - just deleting them. What horse ****.

Worth adding is that the bearings were perfect 1000 miles ago when I did the reseal.

carlege

was the Balance shaft belt over tightened

pjburges

There are 2 bearings on a balance shaft, one at the front, one at the back. It was the bearings over the counterweights (back) that failed. The metal wash from them took out the front ones.

Luis de Prat

Yikes. That's definitely a first for me. Really sorry to hear and hope you get it sorted as painlessly as possible!

docwyte

Time for an LS1!

PorscheDoc

I've seen it happen in a couple of turbos to the upper balance bearing. Never had a full failure as I caught them making some slightly odd noise, pulled them apart and they were done. Replaced them with new and never had a problem again.

savvas944

Have you thought of cutting the last counterweight of and plugging the oil hole,thus reducing the spinning weight by half?Broadfoot racing do it for their racing 16 valve engines, for more bearing reliabilty.

I have personally removed them on my 951 track car and on my 968 without noticing any adverse effects
but then i have rebalance the cranks to a higher accuracy level.Beleve me the improvement in , acceleration is worth it, after getting rid of 9.5 lbs of spinning weight at twice the engine speed.

You may consider also that it was not the balancer shafts which they failed first ,but the conrods
as the sfafts are fed with oil from the gallery ,and the spend oil drops back in the sump,does not go buck into the conrod journal.

pjburges

I may rebuild this engine, and sell it to someone who needs a spare for a racecar. It is a nice engine with a fresh head. This is a big pissoff. I've got a 283 SBC with aluminum heads and intake that is just begging to be put in lol.

Im undecided on deleting the balance shafts, especially if Im going to daily drive this motor rather than sell it to someone who will put it in a racecar or just not care. I am worried the shafts have damaged the block and housings. Still need to measure that. Everything else in the motor looks alright for having had a decent amount of metal in the oil.

Chris White

I don’t mean to pick on you but….
You said that you did a reseal 1000 miles ago – you don’t need to remove the balance shaft to do a reseal.
You also said you looked at the condition of the bearings…sounds like you reused the bearings. Reusing a shell type bearing is never a good idea.
Did you install the cap in the right direction? Did you swap the right / left bearing caps?

There are a lot of possibilities for the bearing failure and most are due to taking them apart. Failures of the bearings in the balance shafts are very rare – even though the shaft spins at up to 13,000 rpm.

Also – previous lister have a very good point – the oil for the balance shaft bearings comes from the crank – not to the crank. Any shrapnel would have fallen back into the pan and should not have made its way through out the engine. Time to rethink the failure mode – the balance shaft bearings could have been damaged by debris from something else failing.

pjburges

All my rod bearings look about right for a 100K motor, and the mains look a little scratched from the metal contamination, but none of them through the babbit. The head doesn't seem suspect either.

I pulled the motor from a parts car to put it in mine, so while had it on the stand I did a reseal on everything, and replaced those little clear plastic washers on the fronts of the balance shafts, so yea I pulled them, and whatever I did while re-assembling was likely my fault because I did not put something back together properly.

Both shafts failed the bearing over the counterweight. I didn't switch housings, or remove the shells from the block or housing when I did it. I know at least everything went back in the way it came out. There was tons of metal caught in the lower front balance shaft housing, in the pan, in the filter, and on the pickup screen. The chunks were large corresponding to the lost material on the balance shafts, there is not any real damage to any other bearing in the motor.

Can you re-install a balance shaft and get it crooked in there?

pjburges

Here's a picture of the block at the counterweight side where the bearing shell would be. Does anybody think this is re-usable?...or did I toast the block? You can see where it looks as if it was hammered and traces of metal are embedded in the aluminum. Its my understanding that this assembly is line-bored, and no oversize balance shaft bearings are offered anyways...

Charlie

If you pulled the balance shafts could you have switched them when you put them back in the housings?

2bridges

so it appears from the pic the area of contact is the small C shaped on upper left?
Pics are sometimes hard to tell, but Is that the only area of contact?

If so it certainly does not look like a big deal to me. In terms of surface area under the bearing that is a very small percentage of material. Looks like the primary bearing seating surface is all in tact

rlm328

If the only damage block damage is where the balance shafts reside, I only have one thing to say, Ya don't need no stinkin dampeners. Replace all of your internal bearings, probably rings, and put it back together.

Chris White

I can’t tell looking at the pics – there is supposed to be an alignment dowel that locates the balance shaft covers – if it wasn’t there then you could have an alignment problem.

Anything happen to the other side?

BTW – I have to take back one comment – I was thinking about the balance shafts that have the separate caps when I said that you don’t have to open up the bearing son a reseal, you must have the integral bearing caps – in which case you do have to expose the bearings to do a full reseal – sorry about that!