Intermediate Shaft Bearings

[Nohawkscott]

My machine shop guy just told me that they pulled the oil pump shaft and bearings out of my block in order to vat the block. This is something I really didn’t think would need to happen since we discussed leaving these bearings in place and using his non-caustic cabinet to clean the block.

I’m not opposed to replacing these bearings but I had been told it wasn’t a can of worms worth opening, now he’s telling me he’ll just reinstall the old bearings since they still look good??

is there any particular insights regarding this shaft and bearings I should share with him? This shop see’s mostly domestic stuff so they might not be completely aware of potential issues with just driving some bearings back in..

or maybe I’m overthinking this?

[digger]

i think they are "line" reamed from factory so if you remove them they will likely not go in concentric anymore so you're probably better to replace (especially if they are not ultra low mileage) and have them line bored and honed in situ once they are pressed in.

[Nohawkscott]

Does this sound about right?

[digger]

I have seen that process mentioned before and it apparently works ok but it isn't how i would do it as a first option (i would have it line bored to size after pressing in if they have equipment to do so and then hone. Since it is a flexible sleeve so not guaranteed to be perfectly concentric after pressing it in an honing it wont correct that). In any case the shop should be able to tell you what to do as they are supposed to be the experts. There usually multiple ways to skin the cat

[Nohawkscott]

That makes sense to me digger. I’ll get some new bearings ordered and talk to the machinist tomorrow about their plan.

In your experience is it a normal scope of work to replace these bearings during a rebuild if an M20 or are the originals usually left in place?

[digger]

That makes sense to me digger. I’ll get some new bearings ordered and talk to the machinist tomorrow about their plan.

In your experience is it a normal scope of work to replace these bearings during a rebuild if an M20 or are the originals usually left in place?

Normally left in place if they are in good condition but given the age and mileage these things are hitting there does seem to be issues with them flaking away from fatigue so these threads do pop up every few months

[Nohawkscott]

Well, got the block back today and I was handed the box of new intermediate shaft bearings I bought! The machine shop owner then tells me he reinstalled the old bearings because they look brand new! This has me extremely concerned. He went on to tell me that after reinstalling the originals bearings, the shaft wouldn’t fit and he used scotchbright on them until the shaft fit. I doubt he could remove too much material with scotchbrite but man, Ithis sounds sketchy to me

[zaq123]

Well, got the block back today and I was handed the box of new intermediate shaft bearings I bought! The machine shop owner then tells me he reinstalled the old bearings because they look brand new! This has me extremely concerned. He went on to tell me that after reinstalling the originals bearings, the shaft wouldn’t fit and he used scotchbright on them until the shaft fit. I doubt he could remove too much material with scotchbrite but man, Ithis sounds sketchy to me

yes, extramely. Also scotchbrite and any part of the engine that see oil, is a disaster waiting to happen. Aluminum oxide and other abrasives dust in it will clearance everything else that you'd rather not to clearance.

[Nohawkscott]

I’ve absolutely flooded these bearings with brake cleaner today because of my concern about leftover scotchbrite debris. Literally sprayed 6 cans of the crap today, shop smells explosive and toxic right now.

This situation has me so bummed out. If the owner of this machine shop wasn’t such a nice old fella I would’ve been less pleasant. Needless to say, I’ve stopped short of putting the main bearings and crank in but I did gap all the rings today at least. I guess my next move is to borrow a dial bore gauge and measure the clearance between the shaft and the re-used bearings. And figure it out from there…

[Nohawkscott]

Pics of the reinstalled used bearings..

[Nohawkscott]

Does anyone have a roundabout idea of how much these bearings compress once they are installed?

[zaq123]

Does anyone have a roundabout idea of how much these bearings compress once they are installed?

they don't compress evenly on the whole circumference so it's impossible to say what you are asking. New bearings are not exactly round and become round once installed from what I understand. What your machine shop did (reinstalled old bearing) was done before and not a concern. I just don't understand why the shaft didn't fit after the reinstallation. Did you ask him what clearance they did?

[digger]

to me there is risk that they don't go back to the same position which could affect alignment/concentricity and also roundness might not be maintained. Roundness is easy to measure with dial bore gauge but alignment is not (without a CMM). i would want that verified by some means.

[Nohawkscott]

they don't compress evenly on the whole circumference so it's impossible to say what you are asking. New bearings are not exactly round and become round once installed from what I understand. What your machine shop did (reinstalled old bearing) was done before and not a concern. I just don't understand why the shaft didn't fit after the reinstallation. Did you ask him what clearance they did?

Interesting. The re-installation of these bearings is not a concern? I plan to take some measurements when I get back home to determine the actual clearance. I don’t think this is something he did.

[Nohawkscott]

to me there is risk that they don't go back to the same position which could affect alignment/concentricity and also roundness might not be maintained. Roundness is easy to measure with dial bore gauge but alignment is not (without a CMM). i would want that verified by some means.

thanks for the feedback digger. This is a valid concern. I spoke to another machine shop (Engine Performance and Machine) in Longview,Tx. I showed in pictures of the used bearings that were installed and he thought they looked too crappy to be reused. His thoughts were to order some aftermarket bearings and he said he would make them work. All these machine shops around here seem to think this is no big deal?

would it be wise to remove the existing bearings and measure the OD and ID to get an idea of the compressed dimensions?
Im thinking that the used bearings could be used as a reference to what the new bearings should be reamed to…