M20 Int. Shaft Bearings

[boogle2]

Hey Guys,

Been doing a ton of research and part ordering in prep for my m20 pull and rebuild for my turbo project.

I already ordered my intermediate shaft bearings, but was curious. How will hot tanking the block destroy them? Will they expand too much relative to the block? Or will the hot tank destroy their surface?

Did a bunch of searches but couldn't find the actual reason behind the replacement.

Any machine shop / engine shop worth its salt should be able to turn these down and fit them, correct?

[Northern]

Isn't it just because the hot tanking removes nearly all the grease from the bearings?

[SkiFree]

The hottanking process uses some pretty caustic chemical. It'll literally start to dissolve the bearings (increasing their inside diameter and irreversibly roughing the surface finish).

And OP, don't just drop the "oh and can you size these bearings for me too?" on the machine shop. You need to talk with them about it so they can include it in their estimate for you. Many shops "worth their salt" that could easily do it, will simply refuse. The reason being that it isn't an efficient part of completing the job and then there is the added liability.

[nando]

what I did back in the day was filled the bearings with grease and left the shaft in there when they tanked it. I let the shop know about it so they wouldn't leave it in there too long. as far as I know they're just fine, never had any issues with it.

[Cabriolet]

OP, you will get the bearing. the issue is that they are the wrong size.
bmw doesn't not have the correct ID for the bearing, you must have them machined to fit.
people will tell you to no do this, yada yada yada, you cant machine the shaft bc the gear wont fit though the inner bearing.


9 out of 13 m20s i've ripped apart the outter bearings are shot. the bearings are a harder outer material and the inner a soft material.

[wakeboardr42393]

I had my block machined. They hot tanked it and did everything else, then asked me to bring in the int shaft bearings. I ordered and brought it, and the engi e shop had my engine for half of a year, and they were stuck. They even tried to make tooling and ordered a second set of bearings. No luck. I now have a block without bearings. And this shop is a reputable shop tbats been in the area for decades. They do racng engines for some big time people, too. I've called like 30 places around Ohio and not one had any clue, most said they would not be able to do the bearings. Many of these shops were German or bmw specialty as well. The only place that said they'd be able to do it, painstakingl, is metric mechanic. (Who, by the way, has left a great impression on me- I will be using them in the future). So, I recommend leaving them in. Or at least talk to the shop beforehand and confirm that they can do the job correctly. This is a pretty vital part of.your engine.

[boogle2]

I talked to the machine shop I have been discussing with here in Calgary about these, and they didnt seem to be phased at all. I discussed the whole sizing the bushings in place, once they were pressed into block and that there was some stand-off between them, and he just laughed like I thought he was an amateur. I brought up that I had heard this type of work seemed to be an issue for other shops, and he said that there isnt too many people that do his type of machine work anymore that are true machinists.

He said he would ream the bushings, and then finish with a fine grit to clean it up. He stated he would have no trouble getting it to within 1 or 1.5 thou tolerance.

Thoughts? Should I be skeptical?

[akorcovelos]

My engine builder is an old school machinist who builds only race/competition engines and it took him two tries to get them right. 3 seasons later and no problems, but he did say it was a b*tch to get them sized correctly.

[boogle2]

Apologies for the thread revival, but just to be certain about the tolerances for the IMS bushings, they are to be no more than 2 thou than the IMS? Is this correct?

[noid]

11 11 1 264 196 - BEARING BUSH
11 11 1 280 863 - BEARING BUSH

'Secret' part numbers that dont come up in realoem.

[Cabriolet]

Apologies for the thread revival, but just to be certain about the tolerances for the IMS bushings, they are to be no more than 2 thou than the IMS? Is this correct?

you will need to have the bearing machined to fit. complete and under hell to get done right.