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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Sat, Jul-04-2015, 04:43:54 PM   #11
terraphantm
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Default Re: Rod bearing journal diameter

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Originally Posted by m3 hal View Post
Isn't there only 1 size of rod bearing anyway, making measuring pretty much useless unless you're looking for reasons to rebuild?
True. Just the standard and +.25 sizes are offered. And if I needed the +.25, I'd probably buy a new crank or a new engine
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Old Sat, Jul-04-2015, 04:51:15 PM   #12
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Default Re: Rod bearing journal diameter

even a "same size" bearing will differ from one to the next, that is why you blueprint everything and then try to match the best bearing for a given journal size, probably using more than one set and selling the ones you don't use

then again like I said, seems these are getting swapped out as standard practice without issue, soo...

If you do go through with measuring and all, would be nice if you posted what numbers you came up with

I'm still saving my lunch money for the Sunnen stuff
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Old Sat, Jul-04-2015, 05:00:23 PM   #13
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Default Re: Rod bearing journal diameter

You'd still need to pull the motor if you want to make measurements that precise. Plastigage is the only way to measure them with the engine in the car and I doubt it's accurate enough for sorting tolerances in same size bearing shells, and it only gives you a clearance at one location on the bearing.
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Old Sat, Jul-04-2015, 05:11:28 PM   #14
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Default Re: Rod bearing journal diameter

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Originally Posted by m3 hal View Post
You'd still need to pull the motor if you want to make measurements that precise. Plastigage is the only way to measure them with the engine in the car and I doubt it's accurate enough for sorting tolerances in same size bearing shells, and it only gives you a clearance at one location on the bearing.
his motor is out..
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Old Sat, Jul-04-2015, 06:01:24 PM   #15
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Default Re: Rod bearing journal diameter

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Originally Posted by SliM3 View Post
Journal Dia.
1.928" (48.983 mm)
Can go up to 1.9288" (48.991 mm)

Clearances:
Min. 0.00118" (0.030 mm)
Avg. 0.00197" (0.050 mm)
Max. 0.0027" (0.070 mm)
Exactly what I was looking for, thanks. Mine all fall between 1.9281" and 1.9283"

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Originally Posted by terraphantm View Post
It hasn't really proven to be a problem on the S54. I don't know if the difference in crank wear comes down to the crank being forged or something along those lines. I agree it's ideal to measure everything... but that's not practical for most. And the cost of having someone else do it approaches the cost of finding a low mileage complete engine somewhere else
A forged crank will be stronger than a cast one, but strength and hardness are not the same thing, and hardness is more relevant to journal wear. No idea if the S54 crank is any harder than average.

Quote:
Originally Posted by m3 hal View Post
You'd still need to pull the motor if you want to make measurements that precise. Plastigage is the only way to measure them with the engine in the car and I doubt it's accurate enough for sorting tolerances in same size bearing shells, and it only gives you a clearance at one location on the bearing.
You can get a compact 1-2" micrometer around most of the rod journals pretty easily with the crank still installed. Plastigauge is really to verify oil clearance, it's a supplement to your initial measurements. And buying a mic is a pretty small expense compared to some of the tools used for far more mundane maintenance tasks on these cars.
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Old Sat, Jul-04-2015, 06:07:17 PM   #16
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Default Re: Rod bearing journal diameter

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Originally Posted by GasolineCologne View Post
You can get a compact 1-2" micrometer around most of the rod journals pretty easily with the crank still installed. Plastigauge is really to verify oil clearance, it's a supplement to your initial measurements. And buying a mic is a pretty small expense compared to some of the tools used for far more mundane maintenance tasks on these cars.
it's not really complete without a dial bore gauge on the rods, but I suppose there's no way to do that with the crank in place. A spec on the crank helps though
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Old Sat, Jul-04-2015, 07:55:20 PM   #17
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Default Re: Rod bearing journal diameter

The rod big end should be 2.0866". Measure each bearing shell thickness, add it to the BE, and subtract your journal diameters to verify clearances. Back it up with a plastigauge reading if you need a little more assurance.
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Old Sat, Jul-04-2015, 08:01:52 PM   #18
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Default Re: Rod bearing journal diameter

There are actually 3 different rod bearing sizes. Yellow is most common. Then White and I think Green. I'm not at home so going from memory.
I just recently rebuilt an S54 with coated Red and Blue bearing shells. I used a mic to check the crank for dimensions and roundness. Then I used plastigage to check clearances. Everything worked out in spec. I had purchased a used, polished crank and a used rod as well so I was concerned.

My old crank had a spun rod journal. There is a local company that will be or already is doing a type of metal build up that would be suitable for cranks. My plan is to get the crank fixed and see if it is a useable procedure.
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Old Sat, Jul-04-2015, 08:22:45 PM   #19
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Default Re: Rod bearing journal diameter

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My old crank had a spun rod journal. There is a local company that will be or already is doing a type of metal build up that would be suitable for cranks. My plan is to get the crank fixed and see if it is a useable procedure.
I've heard of basically welding to add layers of metal, turning it back down to size, rinse and repeat to repair damaged cranks. I think it was even mentioned in my engine repair textbook. But it takes a very skilled machinist a lot of time to do, so it's not cost effective for cars. I've only hear of it being done on heavy industrial equipment where a replacement part would be incredibly expensive.
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Old Sat, Jul-04-2015, 08:39:04 PM   #20
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Default Re: Rod bearing journal diameter

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Originally Posted by GasolineCologne View Post
A forged crank will be stronger than a cast one, but strength and hardness are not the same thing, and hardness is more relevant to journal wear. No idea if the S54 crank is any harder than average.
It must be pretty hard (and consistent). I've never seen any non spun bearing cranks need the alternate size.

BMW's procedure during the rod bearing recall (2001-2002) didn't require any measuring, and it would have been super expensive for them if that resulted in engine failure at any sort of significant rate (especially as all the cars that were involved in the recall got bumped to a 100,000 mile engine warranty). That was a LOT of engines getting bearing swapped.
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Discussing Rod bearing journal diameter in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)