Is anyone else interested in a bronze pilot bushing? - PeachParts Mercedes-Benz Forum

junqueyardjim · #1 06-21-2010, 10:34 AM

I am thinking of having my local machine shop make me a bronze bushing for a pilot bearing on my 1985 617. I am thinking of having 10 made, though I don't have a cost at this time. The bearing for the 240D was six or eight bucks and I expect we will have to spend more then that. But it seems to me from the research done on this forum that there is no correct bearing for the 85 617 with a bore of 34mm in the tail of the crank. Therefore a bronze bushing would be the way to go.

Stevo · #2 06-21-2010, 11:07 AM

I would be interested as I now have an "85" with a few miles. I don't know for sure that the regular bearing wont fit but I'm not going to pull the tranny to find out. you can probably count me in. Thanks for coming up with this, good idea.

junqueyardjim · #3 06-21-2010, 12:04 PM

Well I just talked to a person at Bearing Headquarters, Indainoplace, and he said that on the commercial market there is no other bearing that is close. The next one down in size has a smaller ID and is narrower also. So the choice is to go bronze or brass bushing or remove the crank and get it reamed to 35mm. That sounds like a lot of work or do you think I could find a mobile machine shop to come and ream it out in my shop. That 35 mm is a bit under and inch and half. and the bore is less then 3/4 inch deep after the tapered inlet. Do you think a person could drill out the one mm of stock in one pass and keep it straight or is it stupid to even consider doing it by hand.

TnBob · #4 06-21-2010, 12:53 PM

Pls add me to the "I will take one" list.

Stevo · #5 06-21-2010, 01:28 PM

Someone around here whittled one down to fit in the hole, but that doesn't sound fun.

aaa · #6 06-21-2010, 04:37 PM

I'm in.

JB3 · #7 06-21-2010, 05:11 PM

a number of people have had success grinding the 1mm off of the stock pilot bearing. I think someone even took the bearing to a machine shop and had it done.

With a bushing in this application where a bearing was originally intended, I would be concerned with heat, how much heat do you thing would be generated by the constantly spinning hardened shaft against the bronze?

junqueyardjim · #8 06-21-2010, 06:02 PM

You show me a car running with a ground down pilot bearing and I will show you a junker. Get real, grinding off a half mm from a hardened bearing shell. It can't be done. I would rather go with the correct bearing, that is true. Yet many vehicles have had bronze pilot bushings. Remember, the only time it is in use is when the clutch is disengaged, like when the pedal is in. Not much use!

JB3 · #9 06-21-2010, 06:09 PM

Quote:

Originally Posted by junqueyardjim

You show me a car running with a ground down pilot bearing and I will show you a junker. Get real, grinding off a half mm from a hardened bearing shell. It can't be done. I would rather go with the correct bearing, that is true. Yet many vehicles have had bronze pilot bushings. Remember, the only time it is in use is when the clutch is disengaged, like when the pedal is in. Not much use!

I know winmutt has one off hand, he seems to have no complaints so far. You should PM him and see if anything untoward happened and how he went about doing it.

Wait, so you don't let your car idle for hours while you sleep at a rest stop?

junqueyardjim · #10 06-21-2010, 07:02 PM

You make that statement about letting your vehicle idle at night when you are sleeping. Not me, I don't sleep in my car, if I didn't have the bucks for a good motel, I would stay home. But even so, idling that vehicle for hours puts no load on that pilot bearing. If the clutch is engaged, (let out for slow learners) the flywheel, pilot bearing and input shaft of the transmission all turn at the same speed and the pilot bearing is turning, but not carrying any load. Next thing you will be trying to tell us is that Winmutt had his boy carve the bearing down a half a mm with the steel cutting blade of his Swiss army knife, when you know that if you rub it gently with toilet tissue you will get in down eventually and you will have a smoother looking bearing.

JB3 · #11 06-21-2010, 07:13 PM

You are right! shame on me for forgetting power flow! Fortunately, it was an idle joke, I thought, but you seem to be taking it awfully seriously.

#2- Relax with the scathing contempt and sarcasm, HE said thats what he did, I have no reason to believe that he did not find a way to do it successfully. Im not saying a bronze bushing is not a good idea, im just pointing out that other people have done this other ways as well, for options reasons.

Personally, I have not tried to grind down the outside of a bearing, but if you have one, it can apparently be done successfully. I have some ideas on how I would do it, but I would be worried about keeping it round and not taking too much off. Is this better or easier than making a bushing? I don't know.

I am also interested in a bushing however when you do a run. I also have an 85, and the same problem

panZZer · #12 06-22-2010, 04:37 PM

I like the idea of a bushing that could have a roller bering pressed in-is there enough room to do this with the bigger 85 hole?

Stevo · #13 06-22-2010, 07:10 PM

Quote:

Originally Posted by junqueyardjim

I am thinking of having my local machine shop make me a bronze bushing for a pilot bearing on my 1985 617. I am thinking of having 10 made, though I don't have a cost at this time. The bearing for the 240D was six or eight bucks and I expect we will have to spend more then that. But it seems to me from the research done on this forum that there is no correct bearing for the 85 617 with a bore of 34mm in the tail of the crank. Therefore a bronze bushing would be the way to go.

I need to ask you this, please dont take offense, this shop, you know these guys for a long time? From a mechanist point of view, is making this fine a tolerance thing (all of them) a everyday sort of job or what? Such skinny little walls and all

How big of a deal is making such a bushing for those in the know?

JB3 · #14 06-22-2010, 07:40 PM

A machine shop guy I was having stuff done with told me a decent flat tolerance is within 5 thousandths of an inch.

He said they regularly take stuff down that far, and i was having him bore some things out where only a few thousandths needed to be removed for a sliding tolerance.

I found on wikianswers that a thousandths is .0254 of 1mm

I figure if 5 thousandths is only .0254 of 1mm, and they get that fine all the time, making something correct within a mm should be an easy job for any machine shop worth its salt.

Stevo · #15 06-22-2010, 08:12 PM

So we are not asking them to split the atom, Thanks, It would be nice to have a solution to this bearing problem. Seems they made a few goofy changes in 85.