850i Top End Engine Rebuild

I'm rebuilding the top end of a five liter v12 (850i) at work, and thought I would post some pictures of the progress just to show you guys. Enjoy.






Stock OHC and Rocker Set Up Makes A Nearly Hemispherical Head

Three Thou Skim

Don't Even Want to talk about the labour to re&re the engine

Awesome Corey

You're the man!

Good job!!! Thats a pertifull motor

Lookin grea!t Keep us updated.

very nice. and yes, i know how difficult these beasts can be to r&r.

thanks for thinking of us. i'm sure there are lots here that will enjoy a peek into the internals of the v12.

btw, did it overheat and pop a headgasket??


df

ps, i've got a v12 sitting in a barn waiting for the right 'recipient'...

Originally Posted by drivinfaster

very nice. and yes, i know how difficult these beasts can be to r&r.

thanks for thinking of us. i'm sure there are lots here that will enjoy a peek into the internals of the v12.

btw, did it overheat and pop a headgasket??


df

ps, i've got a v12 sitting in a barn waiting for the right 'recipient'...

No it broke a couple of headbolts and turned what was the rad cap into a geyser
Was overheating alot before it came in and the idiot continued to drive it for two days. But we got it in took the heads off and got them skimmed and they only needed three thou!! So obviously these engines can take alot of heat ay.

If the heads are still off measure the cylinder bores for roundness. They tend to oval at the bottom after overheating.
If it is a ways out a quart of oil every 100 miles or so has been one of the results seen.

Originally Posted by TerryY

If the heads are still off measure the cylinder bores for roundness. They tend to oval at the bottom after overheating.
If it is a ways out a quart of oil every 100 miles or so has been one of the results seen.

The head are ready to go on but not on as of now. The car was running before we started this and was not pushing blue out of the tail pipe, but with as much steam as there was it may have been hard to tell. Also the oil level was to spec before I started. But some very good advice, I will look into it to make sure this is not the case with this engine.

Update:
Engine bore checked, and has acceptable taper.

Engine re-assembled and getting ready to go back in.

looks quite interesting. who did you get the gasket sets from? ive strayed away from V12 cars. they are nice when they run, but a nightmare when they break. i guess if you have the money to maintain and service a V12, theres no worry.

Gasket sets are from bmw, in germany. I hate the m70b30, but thats only because it was bmw's first attempt at something as high tech as this. It had many flaws, but it had many great innovations such as the first production engine with fly by wire throttle. It was also the first car to have problems with fly by wire.
However there are some bmw v12's I would give a leg and an arm for.. Like the BMW S70/2 from the mclaren. Of course this engine shares nothing in common with the m70, it is an entirely different block and design. In fact the 6.1L F1 engine shares more in common with the s50b30 engine in my car than the 5 liter v12.

FYI This particular customer has spent over 16g in maintenance in the past year and a half.

yeah, i figured it was something high. just not quite what i'd go for, as far as cost of maintenance. probably why you dont see an abundance of these machines running around. for that matter, not too many exotics in abundance. must be nice though to be able to own one. i'll stick to my reliable 4.4 liter.

Sarting head gasket change do you have any tips on disassemble or reinstalling heads? I will be tackling this job myself and can use any help that I can get.
Thank you.

Originally Posted by CodyItaliano

yeah, i figured it was something high. just not quite what i'd go for, as far as cost of maintenance. probably why you dont see an abundance of these machines running around. for that matter, not too many exotics in abundance. must be nice though to be able to own one. i'll stick to my reliable 4.4 liter.

I wouldn't call the 850 exotic. But thats just me, that cost was not just for this job btw.

Originally Posted by semaj1

Sarting head gasket change do you have any tips on disassemble or reinstalling heads? I will be tackling this job myself and can use any help that I can get.
Thank you.

If you have no experience of this sort I say don't even think about it, you could cost yourself alot of money with the smallest error. Why is it you are doing this?

yeah heads i wouldnt recommend tackling unless you've done some before on a 4.4, you will have trouble getting the timing right and will likely have it in a shop at the end. good luck with the timing though, its a pain if you havent done it before. its not like older vehicles in a few ways.

wow!