Thinking about installing an BMW M6 engine in my Z

[Zed Head]

If you haven't thrown it away yet you could cut open the oil filter and compare the clean side of the filter medium to the dirty side.  That information, combined with the flow paths, should give a good idea of which bearing surfaces saw bearing shell particulate matter.  The cylinder bores and pistons get their lubrication from splashed or thrown oil, unless the BMW engine has squirters.  Pretty much everything else gets filtered oil, I believe.

[grannyknot]

1 hour ago, Zed Head said:

If you haven't thrown it away yet you could cut open the oil filter and compare the clean side of the filter medium to the dirty side.  That information, combined with the flow paths, should give a good idea of which bearing surfaces saw bearing shell particulate matter.  The cylinder bores and pistons get their lubrication from splashed or thrown oil, unless the BMW engine has squirters.  Pretty much everything else gets filtered oil, I believe.

I still have the filter, it is a cartridge type. One of the guys in our local Z club works for a trucking/fleet reliability Co and said they have oil and oil filter analysis, he wants me to bring it over so they can dissect it.

[Careless]

what did the previous guy actually do when he rebuilt the engine? just resurface the head and check the clearances and replace bits and pieces? any head work? 

for 1, 2, 3 oily cylinders- use flashlight in the intake and exhaust ports. check for oil or sludge build up on the valve stems or on the backs of the intake valves. perhaps leaking valve seals or worn valve guides.

One thing i noticed in your head/block photos... that head gasket (whatever make it is)... before you reorder it or use the same style, have a look at what the OEM BMW one looks like. The block and head pattern for those areas on the exhaust side seems to differ from the gasket, and if those pockets are used as cooling chambers to be filled with oil- I can see the head-gasket being "poorly" designed in that regard. If they are to be filled with coolant, I'd say they are even worse. The OEM BMW gasket is designed with a lot more attention paid to that area of the engine.

anyways- forget all that. when we turboing this thing? 

[grannyknot]

I figured out what was blocking the oil feeding the bearings, there is a thin metal shim/gasket that mounts between the block and the foot of the oil pump. The main oil feed flows through that foot, somehow the gasket shifted before being tightened down and blocked about half of the flow and even though the gauge showed good pressure there wasn't enough to protect the conrod bearings the way I was driving the car.  However there was enough oil to protect the cams, the valve guides and six of the seven main bearings. I hate when I have to say this but all the glory for this screw up falls completely on my shoulders, with the engine hanging from the the engine hoist I should have laid on my back to torque those bolts instead of on my knees with my head upside down, I just didn't notice it.

I met with the engine builder today, he says the crank is bent and that it is actually cheaper to replace it with a good used one than fix the original, it seems that when other owners of my engine get theirs rebuilt they go for the later model crankshaft from the 3.8L engine and so there is a glut of 3.5L cranks on the market, my builder has 3 of them on the shelf. And the moral of this story just shows me to always stay original and never modify, it's cheaper!

[wheee!]

Nice detective work. Feels good to get closure and be able to move ahead...

[Patcon]

Glad you found it. It always makes me nervous to have a major failure and never find a definitive cause

[Captain Obvious]

Wow. Glad you found something! It always makes me nervous not to have what I believe is the smoking gun.

So that shim is supposed to just stay in place with no locator pin or pressed in boss or anything? Just pinched by the bolt nearby? I don't like it.

What's that shim's purpose? That's a gasket between the block and the oil pump?

[grannyknot]

1 hour ago, Patcon said:

Glad you found it. It always makes me nervous to have a major failure and never find a definitive cause

Agreed

8 minutes ago, Captain Obvious said:

Wow. Glad you found something! It always makes me nervous not to have what I believe is the smoking gun.

So that shim is supposed to just stay in place with no locator pin or pressed in boss or anything? Just pinched by the bolt nearby? I don't like it.

What's that shim's purpose? That's a gasket between the block and the oil pump?

The shims job is to adjust the the tension on the oil pump chain, new chain, new pump you only need one shim, a worn chain and pump you need to stack a few. Certainly not one of their best designs and I managed to find the worst possible position for it.

[Captain Obvious]

Got it. I did a little digging and found people on BMW forums talking about installing different thickness shims or multiples to adjust the tension. Really seems like an un-German "afterthought" design. Looks like they included a tensioning device in later years, but the early ones used shims?

And to design the system without interlocks or locating pins or something such that you can easily do exactly what you did. Just surprising. Could they at least have put the shims on other feet that don't have oil holes or do all the feet port oil? Certainly not poka-yoke. Haha! It's always easier to second-guess someone else's design decisions.

Anyway, glad you found a smoking gun. I would have never been comfortable with the engine ever again if I hadn't found something definitive. The guy with the Viper will be happy to see your rear again.  

[Zed Head]

Cut the shim with two "ears" on the side and bend them over and you'll have a self-locating shim that will probably hold itself in place also.

Curious though, and just to be rigorous - are you sure that the mislocated shim reduced flow enough to cause the problem?  Often those big passages connect to smaller passages and can't flow that much anyway.  Probably doesn't matter since you're rebuilding, but sometimes the obvious thing isn't really what it seems.

[Diseazd]

4 hours ago, Captain Obvious said:

Got it. I did a little digging and found people on BMW forums talking about installing different thickness shims or multiples to adjust the tension. Really seems like an un-German "afterthought" design. Looks like they included a tensioning device in later years, but the early ones used shims?

And to design the system without interlocks or locating pins or something such that you can easily do exactly what you did. Just surprising. Could they at least have put the shims on other feet that don't have oil holes or do all the feet port oil? Certainly not poka-yoke. Haha! It's always easier to second-guess someone else's design decisions.

Anyway, glad you found a smoking gun. I would have never been comfortable with the engine ever again if I hadn't found something definitive. The guy with the Viper will be happy to see your rear again.  

I agree with you Capt.  ......if it were me, and I was going back with that shim, I'd super glue it down so it couldn't shift.....Creepy design.

[240260280]

Chris, I am sorry to see your loss.  I am glad your are tracing (pun) the problem.  For the photo below:

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?

Did you 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?