[JonEQuest]

Originally Posted by bbnks2

Replace the rod if you can. Theyll.need to be balanced though.

I already got a replacement rod from a friend but it is just a little out of round for my liking. the sizes I got from measuring the others at 3 places were typically:

Rod #1 was 53.467, 53.441, 53.594 mm
Rod #2 was 53.467, 53.518, 53.569 mm
Rod #3 was 55.885, 53.213, 53.340 mm (this one is obviously bad)
Rod #4 was 53.619, 53.594, 53.594 mm
Rod #5 was 53.518, 53.467, 53.594 mm
Rod #6 was 53.594, 53.341, 53.314 mm

Then the one my friend gave me measured: 53.797, 53.441, 53.645 mm

Which is better than the trashed #3 but still seems a little out of round. I just don't know if it is within specs because the deviation is described as +/- 5 "g" and I don't know what a "g" is.

Measurements were taken with a standard micrometer and then converted to mm from inches. I may have been a hair off on some of the numbers since I had to keep sliding it on and off the journal and make a decision on the actual number I wrote down.

[bbnks2]

Originally Posted by JonEQuest

I already got a replacement rod from a friend but it is just a little out of round for my liking. the sizes I got from measuring the others at 3 places were typically:

Rod #1 was 53.467, 53.441, 53.594 mm
Rod #2 was 53.467, 53.518, 53.569 mm
Rod #3 was 55.885, 53.213, 53.340 mm (this one is obviously bad)
Rod #4 was 53.619, 53.594, 53.594 mm
Rod #5 was 53.518, 53.467, 53.594 mm
Rod #6 was 53.594, 53.341, 53.314 mm

Then the one my friend gave me measured: 53.797, 53.441, 53.645 mm

Which is better than the trashed #3 but still seems a little out of round. I just don't know if it is within specs because the deviation is described as +/- 5 "g" and I don't know what a "g" is.

Measurements were taken with a standard micrometer and then converted to mm from inches. I may have been a hair off on some of the numbers since I had to keep sliding it on and off the journal and make a decision on the actual number I wrote down.

Journal? you mean rod bore?

"g" refers to grams... you have 6 rods. They are paired in weight classes at the factory. If you grab a rod from another set, you need to balance the assembly to within a 5gram variation. Like balancing a tire weight variations will cause vibrations. Balance by removing material from heavier rods.

Rod bore should be no more than .0005" (half a thousandth), or .0127mm, out of round imo. You really need a decent bore gauge to measure the rod bore. If you're using some cheap probing device, and then measuring that result (like in the video below even this digital caliper is not very accurate) with a caliper then you might be introducing a lot of error.

The caps need to be torqued to spec (use your old bolts) before you measure. You do not want the bearings in place when doing this. Rod bearings are actually not round. They are eccentric so you'll always show out of round if you measure with the rod bearings in place.

rod specs per tis:
https://www.newtis.info/tisv2/a/en/e...rings/AlznYERj

[JonEQuest]

Originally Posted by bbnks2

Journal? you mean rod bore?

"g" refers to grams... you have 6 rods. They are paired in weight classes at the factory. If you grab a rod from another set, you need to balance the assembly to within a 5gram variation. Like balancing a tire weight variations will cause vibrations. Balance by removing material from heavier rods.

Rod bore should be no more than .0005" (half a thousandth), or .0127mm, out of round imo. You really need a decent bore gauge to measure the rod bore. If you're using some cheap probing device, and then measuring that result (like in the video below even this digital caliper is not very accurate) with a caliper then you might be introducing a lot of error.

The caps need to be torqued to spec (use your old bolts) before you measure. You do not want the bearings in place when doing this. Rod bearings are actually not round. They are eccentric so you'll always show out of round if you measure with the rod bearings in place.

rod specs per tis:
https://www.newtis.info/tisv2/a/en/e...rings/AlznYERj

THANK YOU! That makes sense now. All I needed was a little clarification on the 5 gram thing. I figured out with the last engine rebuild (my first) that bearings are not round and they are cocked into place then even after tightening they are still always a little out of round. I have a bore and caliper but just used the caliper for my initial measurements. I noticed that the rod bore (correct term, thanks) are a hair skinnier closest to the bolts than across the top/bottom span. My main concern was consistency between all the parts. I definitely need a better rod replacement. I will reuse the original piston but will probably use my friends jewelry scale and measure the two rods when I get another one. If they are not the same, hopefully the new one is heavier and I can dremel some weight off of it.

[rulermark]

Some food for thought, they threw a starter at it because it probably wouldn't start based on all the damage you have found and ignored the engine noises leading up to it initially because direct injection motors are noisy.

[JonEQuest]

I agree they probably burned up the original starter because the trash in the bearings added a lot of drag. Except for the rod #3 that spun enough to make it so loose you could grab it and wiggle it all around.

[JonEQuest]

UPDATE I took my original N55 crank to a very good machine shop that does work on car, aircraft, ship and industrial parts so they are the best. They said the crank was slightly warped and started cracking when he tried to straighten it. So I brought him another N55 crank that had spun rods but was given to me free. That one was worn beyond what could be reground. N55 crankshafts are $1,600 new and ~$1,100 used and scratched like mine, so fuck that.

Now onto plan B. I ordered a very good condition N54 crankshaft (I know its wrong) for $450 and I am making that work by replacing the front main crank bolt (N54 are different). The rear N54 is 8 bolt flywheel vs. the 6 bolt N55 flywheel. Luckily I have a spare N54 flywheel. Then I had to drill the 6 bolt N55 magnetic reluctor ring into an 8 bolt configuration. I think this is going to work just fine and having a forged crank is not going to be a bad thing. Putting the engine back together this weekend and still have to polish the camshafts that have scoring so depending on how that and family time goes I may be running just after Christmas. I will keep y'all updated on my hybrid N54/N55 engine.

[weehe126]

I still have mine if you are interested.

[JonEQuest]

Originally Posted by weehe126

I still have mine if you are interested.

Originally Posted by weehe126

I still have mine if you are interested.

I am still considering that if this does not work. I just figured a good forged crank for $450 shipped was hard to beat since I had the N54 flywheel laying around.

[MightyMouseTech]

Originally Posted by bbnks2

OK so you have no idea and you either made it up or copied it from somewhere. Thanks.

That valve doesn't cause any issue with low oil pressure. Find something else to blame. I've never seen anyone show low oil pressure in an N55 either... Except at the track where the pickup runs dry.

Happens often in freezing temps. BMW is currently tracking problems with seized N55 in freezing temps due to lack of oil.

[fatty335]

Originally Posted by MightyMouseTech

Happens often in freezing temps. BMW is currently tracking problems with seized N55 in freezing temps due to lack of oil.

MMT, can you elaborate?

[bbnks2]

Originally Posted by fatty335

MMT, can you elaborate?

There was a reddit thread that popped up last winter when -30f temps swept across parts of northern USA for almost a week straight. A "BMW Tech" posted showing a bunch of N55's needing engines in their shop. One had been sitting in their lot waiting for service and seized up on them when they pulled it in for service. They dropped the oil pan and found it was frozen.

How that happens I do not know, but, I'd say the engines being N55's probably has more to do with the N55 being the current bulk of every engine sold and still under warranty more so than anything else. N55's seizing up because of freezing wouldn't really be relevant to seizing up after OFHG work or just seizing for no reason either so this specific scenario doesn't explain much at all. There are only a slim few reasons why a cars oil would freeze.

I'd love to see anything that shows what BMW is tracking. People are STILL trying to file class action lawsuits over S65 failures. I believe one case has moved toward "discovery" or at least got approved by a judge to move forward. After all this time, and literally hundreds of people tearing down engines to change bearings, they still can't prove anything or build any kind of case.