[Stan65]

mgarblik,

It was a bit of a head scratcher. I did not use retaining compound or pin it as the interference fit was the same as a correct bearing one the bearing shell resizing was set.

I assume the same as you as to the one being exactly .005 over the others and perfectly concentric.

I made the mandrel in a few thought out steps.

First drill and tap for pipe plug. Didn’t want to cut slots until the hole was tapped.

Next cut slots, kinda ugly, just did it on my band saw as I don’t have a cutter for my mill. (Will be ordering one in the near future and would have used with my indexing head to make it more exact)

Put back in lathe and marked position for #1 chuck jaw in case I needed to remove it. (I didn’t which ensured concentricity when I reduced the OD)

Turned the OD of the mandrel for a nice slip fit of the bearing while leaving a shoulder for the bearing to seat against.

Not sure it was necessary, but I also reduced the diameter of the mandrel on the chuck side to help with the expansion when the pipe plug was tightened. I used ARP lube on the threads to help eliminate gaulding.

It didn’t take much pressure from the pipe plug to hold it nice.

The dremel wasn’t ridged enough and wanted to chatter on one of the test bearings. I was able to just use a new ceramic cutter insert and it machined really nice.

Long winded reply, but I’m pretty proud of this home fix. I feel like this is as good as original without any “might be ok” worries.

Thanks!
Stan.

I ult




and never removed it from the lathe chuck

[tom s]

2X for spray weld the bore of that bearing and line hone the cam tunnel.Tom

[Shiny]

Originally Posted by mgarblik

I am glad to hear the entire repair came out great. ....

Yes, thanks for sharing the issue and your solution! Nicely solved!

I have to wonder just what caused the issue with that one cam bore with no sign of the bearing spinning? ....

I have no idea how they machined these bores, but it doesn't make sense to me that a factory would use a different set-up for each journal. Wouldn't they all be machined by the same tooling in the same operation? Maybe the block was damaged during assembly or there was a casting defect that forced a repair? Was there a "standard" flow for repair operations and/or a dedicated machining center for repair operations? Anything like this would make more sense "offline" IMO.

[Stan65]

Shiny,

Agree, they wouldn’t have stopped, track in the block, reset the dimensions for the cutter, then took it back apart on the line.

You could see the original machining marks on the bore, and they looked exactly the same on #4. There the engine had never been apart so my only speculation is it was repaired during assembly not block machining.

Be curious if anyone on this site work at the engine plant?

Stan

[Stan65]

Another update,

I just checked to see if my setup would knurl the shell. It could and I was able to get .005 over.

Gonna throw this bearing in my tool box.

[steve25]

Nice deal!

[Shiny]

Originally Posted by Stan65

Another update,

I just checked to see if my setup would knurl the shell. It could and I was able to get .005 over.

Gonna throw this bearing in my tool box.

Wow, that looks great! You do nice work.

[mgarblik]

The mandrel you made is the heart of the successful repair. It enabled you to do two different operations as needed without slipping and ruining the ID of the bearing. That's impressive. Also, it was rigid enough to turn the OD of the bearing with a cutter, rather than grinding. And knurling was a good second choice option in a real pinch.

Having .010" oversize bearings is a really nice insurance policy for us Pontiac engine lovers. Last chance for some of the engine builders out there to chime in if your willing to stock a set or two of the OS cam bearings. I will wait another week and call Durabond to try and force them into production. So let the forum know if interested and how many sets you would want. Just my best guess, thinking they will be $50.00-55.00 a set. This is based on when Butler last had them a few years ago.

Impressive repair.

[Stan65]

mgarblik,

Thanks for the compliment. My job for the past 30 years has been a trouble shooting and continuous improvement in manufacturing. So I can usually think out of the box.

I’m in for 2 sets even though I don’t need them now. I will put them on my shelf and they may save the day for myself or someone else in the future. I would say it’s possibly the last run they will make based on how long they have been on national back order and the limited interest now.

Hopefully a few others will step up.

Thanks,
Stan

[Shiny]

The pipe plug as an expander was a great idea.

That custom mandrel with the shoulder looks like factory tooling! Nice use of your skills, experience, and cleverness. I don't wish a problem like that on anyone but seems it found the right guy to drop on.

Mike

[PAUL K]

Originally Posted by Shiny

The pipe plug as an expander was a great idea.

That custom mandrel with the shoulder looks like factory tooling! Nice use of your skills, experience, and cleverness. I don't wish a problem like that on anyone but seems it found the right guy to drop on.

Mike

I agree with everything said..... And now I know where to go next time we need a slightly oversized cam bearing

[Stan65]

Paul,

Least I could do. I have a +.005 knurled one in my tool box now.

Stan