Engine Failure #2; less catastrophic

[scribb]

Been out of the picture for awhile after Covid sent my business for a spin and automotive activities went on a back burner. In the meantime--bad news. My 2UZ rebuild with Kelford cams seized before I got a chance to finish tuning it. Nothing dramatic--it just sounded like a stall after I started pulling away from a stop sign. I thought the alternator had failed or something, because there were no other sounds, sights or smells.

Just got the report from the builder. It looks like one of the valve keepers--or locks--failed in #4, and dropped a valve into the cylinder. They were stock valve locks, which Kelford said should be no issue with the 208-B cams. Builder said it looked like another keeper in a different cylinder was close to failing as well. Builder said it looks like there was an indentation in the shim under the keeper.

Good news is the damage is light--just a piston head to replace and a bit of machining before they put the motor back together. The question is, why did the valve locks fail? Are the 208-B cams too much for the stock ones and should upgrade to chromoly? Or is there something else we're getting wrong in the setup? We've followed Kelford's recs so far.

Thanks as always for any insights.

 

[Zuffen]

Some photos of the keepers would help.

Do you know if they we installed correctly?

 

[scribb]

Here's the keeper that failed. Is this just a matter of switching to chromoly? Or does that just shift the pressure to the next weakest link?

Thanks for your response!

 

[ivan129]

Stock collets (keepers) work fine with high lift cams and heavy valve springs. Something has been wearing against the top of the collets and forced them apart and down the valve stem causing the valve to drop. Possibly a damaged bucket. I wouldn't be blaming the cams. By the looks of the amount of wear this has been happening for a while. I'd be looking at the engine builder / assembler who may have fitted a faulty bucket.

 

[scribb]

Stock collets (keepers) work fine with high lift cams and heavy valve springs. Something has been wearing against the top of the collets and forced them apart and down the valve stem causing the valve to drop. Possibly a damaged bucket. I wouldn't be blaming the cams. By the looks of the amount of wear this has been happening for a while. I'd be looking at the engine builder / assembler who may have fitted a faulty bucket.

Key question--I believe stock valve springs were used, not heavy springs. Would that contribute to the issue?

 

[ivan129]

No, using stock springs would not have caused your problem. If the heads had been dismantled for a valve job, then I'm certain the wear on those collets, on that valve would have been picked up as it would have been happening for sometime. I'd go as far as saying that who ever installed your cams didn't inspect the valve stems.