Thinking about installing an BMW M6 engine in my Z

[Careless]

8 hours ago, Captain Obvious said:

Really seems like an un-German "afterthought" design.

IMHO- quite the contrary. if I were to count the number of cars I was under or half-way into when I said "How did someone get a pay-cheque for designing this?", I would say German cars top the list. Completely unnecessary parts with exaggerated importance in a lot of places. Most of their "afterthoughts" are the product of subsequent "overthoughts". If anyone would like to give me a good reason as to why Porsche would use self-tapping sheet metal screws to secure cam phasing solenoids to the cylinder heads on some of their more recent engines- I'd like to also know what time and day of the week they decided that a common DIN metric threaded fastener wasn't sufficient enough as it was for the passed 30 years when used for the same purpose. I don't think I'll ever get a good enough reason as to why that is. 

In this case, BMW could have easily designed these shims with material near the oiling hole just a smiiiiidge longer and bent over the between the main cap and the oil hole flange. It looks like it would fit there without issue and prevent it from spinning... I'm actually not surprised it's done this way... as per my comment above. They're great engines when they're running in tip-top shape- but there are certain things I would never forgive an engine designer for implementing.

BMW has other types of shims for other motors, apparently. They span from one side to the other:

I wonder if they will work as is. Even if they don't quite fit across the crank like on this particular motor, I'd use these instead and just cut it to an appropriate legnth so that it has a tab to bend over. Should be easy with tin-snips/shears.

Edited September 2, 2017 by Careless

[grannyknot]

8 hours ago, Captain Obvious said:

Looks like they included a tensioning device in later years, but the early ones used shims?

I actually have one of those later tensioning devices from a 7 series but they are just a spring loaded arm that quietens down the chain, I wouldn't want to rely on it.

4 hours ago, Zed Head said:

 Probably doesn't matter since you're rebuilding, but sometimes the obvious thing isn't really what it seems.

Neither me nor the engine builder could find anything else it could be, the oil pump is working perfectly, there are no obstructions in any of the oil feed lines, if I hadn't just noticed the faint circular imprint on that shim I was ready to accuse the builder of not replacing five of the bearings.

[grannyknot]

4 hours ago, 240260280 said:

,2,3 do look very lean, or they were simply not receiving the lubrication oil on the walls that burned naturally in 4,5,6 to colour them?

I still have no idea why those first 3  look like that compared to the other 3, you call it lean looking, someone else told me they were too rich. To me it was just an oily surface feel, the valve guides on those cylinders feel and look the same as the other 3 that is, virtually no wear.  The exhaust ports were all identical as well, no visual difference.

4 hours ago, 240260280 said:

ou trace the oil passages to confirm the slipped shim could have put less oil in the from half of the motor vs the rear half and cause the burn pattern we see on the cylinder domes

That shim was partially covering the only oil feed out of the pump so whatever percentage of oil it was stopping the entire engine had the same amount restriction.

 

20 minutes ago, Careless said:

BMW has other types of shims for other motors, apparently. They span from one side to the other:

The are 3 feet on the oil pump, one of the shims is like the long one in your post and goes under 2 of the feet, the single shim that I so expertly placed goes under the 3rd and most important foot.  I will certainly be making modifications to that shim that prevent it from shifting again.

 

 

[Careless]

Are the holes on the long shim identical on the one side so that you can use another long one and just cut it a bit longer than the short one so it can be bent over the edge between the main cap and oil pump mount? 

In any case, I am glad you found out that what seemed to be the cause of the bearing failure was as apparent as it turned out to be and the shim seems like a dead give-away to me- that's a good thing IMHO! Having to rebuild an engine again sucks, but I'm sure you agree that not having a single clue as to why it f'd off in the first place sucks even more!

Edited September 3, 2017 by Careless

[grannyknot]

13 hours ago, Careless said:

Are the holes on the long shim identical on the one side so that you can use another long one and just cut it a bit longer than the short one so it can be bent over the edge between the main cap and oil pump mount? 

No they are different but that's good idea, I could get a second long shim, modify it to fit and have lots of extra material to play with.

14 hours ago, Careless said:

Having to rebuild an engine again sucks, but I'm sure you agree that not having a single clue as to why it f'd off in the first place sucks even more!

Yes, as a few others have also mentioned. I would much rather look like dimwit #2 and know why the engine failed than rebuild it again not knowing the cause.

 

On 9/2/2017 at 2:22 PM, 240260280 said:

1,2,3 do look very lean, or they were simply not receiving the lubrication oil on the walls that burned naturally in 4,5,6 to colour them?

You know Philip now you have me thinking about the piston rings again, all the rings and cylinder walls looked good so I moved on to other possible causes. I'll get the builder to check the ring to wall clearances while he's in there.

[240260280]

Good!   Something just does not seem right with such a defined transition.

[grannyknot]

No word yet from the engine builder on when he thinks he'll be finished, he is going to go with a good used crank instead of repairing the original. All of the connecting rods are still good and usable.  I finished rebuilding the head, everything is clean and flat, fresh valve seals and lapped the valve seats while I was at it, ready to go.

 

[Careless]

did you happen to rock any of the valves side to side or manage to check the openings of the valve guides at all with a caliper or something to check stem clearance? I was wondering if the front 3 cylinders had poor valve guide clearance, which can contribute to a tiny bit of oil getting in even if the valve seals are new.

[grannyknot]

I did the rock test on all the valves, almost all of them felt new with virtually no wiggle, 2 exhaust valves had a weeny bit more wiggle than the rest, one was on cylinder #3 the other was on #5. Pointing to the rings at the moment.

[grannyknot]

While I'm waiting on the engine I have started a little project to modify the stock lower control arms and the T/C rods to allow me to adjust camber and caster but with out loosing the stock rubber bushings that dampen out so much road noise and vibration. I got the T/C rods finished today, the dia. of the T/C rods are about 10/1000ths" too big for a 5/8"x 18 die so had to skim a bit off first on the lathe.

The rods look true but they are not, had to fiddle with them in the chuck to minimize the wobble, probably could have done it with a double cut file. In their fully closed position now they are the stock length and there is about an 1.25" of usable adjustment, should be plenty.

 

[Careless]

Chris, did you thread the side that was welded + turn it a few threads into the coupling nut or turn it down in diameter so it has a peg that slides partway into the coupling nut- or did you weld them face to face?

Edited September 21, 2017 by Careless

[240260280]

Great solution!

Another way to skin the cat would be to cut a reverse thread into the other end to make a turnbuckle-like adjustable solution and forego the welding.

Edited September 21, 2017 by 240260280