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Howdy folks,

I always knew I was nursing a cracked head for about 4 years. #4 cylinder to be exact. The oil never got contaminated and I mostly drove her gently. Mostly. Anyway, the head gasket finally blew. I'm now upgrading to a 1984 M90 head. The previous cracked unit is a 1979. I did all my due diligence to make sure it's going to fit.
http://www.firstfives.org/faq/cylinder_ ... ad_faq.htm
^ I love this article.

This post is just to document some obvious stuff that didn't seem so obvious to me at first. Watch the rocker shaft clocking, there are grooves cut so that the head bolts and oil holes line up so all the journals and rockers get oil pressure. I also had to machine a new aluminum plug for the end of the rocker shaft. A nice tight fit installed with a thin coating of JB weld.
I measured the thickness of the head and the machinist got back to me verifying that about .010 inch had been removed and AERA (American Engine Rebuilders) does recommend the thicker head gasket so I'm going with the Elring 2.10mm head gasket. 1 valve did weep alcohol on a static test so I gave it a 15 second fine valve seat grinding even with the new valve seal still installed (probably a no-no but I think it should be OK?)

I'm going to get back to this post later. Please comment because I have been taking my sweet time on this repair and the head is still on my kitchen table.

https://imgur.com/gallery/Y2ed0

Pulling ferrous crud from coolant passages by Matt Squirsh, on Flickr

Found some weird ferrous "rings" in the coolant passages, looks like they were just artifacts of the original iron casting. I extracted these rusty bits in pieces. Also, vacuumed the cylinder walls with a 2mm rubber tube attachment.

Prep by Matt Squirsh, on Flickr



Orange Stuff by Matt Squirsh, on Flickr

At least I didn't paint any of the engine parts a stupid color. Oh wait...

You could have even gone this far!!

viewtopic.php?f=2&t=29098

Good work Matt!

I just did my HG on my '80 euro but now have an odd sound coming from maybe the Throwout bearing. will have to pull the trans sometime this winter...

Hey, I recently got a head gasket replacement and I noticed my piston tops were just flat. Yours looks like there's some hump (or is that a recess?). Is that for added compression?

So what's with the cat? Did that inspire the color choice?

Finally, I like polished aluminum look. One day when I have unlimited time, maybe I'll give it a shot.

Song, those pistons are not dished, they are raised, called the "piano top", commonly used in the Euro M30B34 "dirty" motor

The CR is rather high on these engines, I seem to recall 10:1

But this does bring up a question for LandShark, what year is your 6er or I guess more important, what engine is in the photos

It's possible that the Euro M30B32 also used this type of piston

But in the actual M90, the pistons would be flat topped, producing a CR of 9.3:1

Song, I'm surprised that your pistons are flat topped in the US version M30B32 Motronic, mine are dished in the M30B32 L-jet, producing a lowly CR of 8:1

I don't have a clue what I have besides cryptic stories from the previous owner of the full overhaul that was done by a mechanic in Italy. As far as I can tell, they went through everything since I see the same red RTV squeezed out of every seam. The block is original 1976, same VIN as the car. If this was some budget hotrod build, well then great, I guess.

Holy crap, that's a lot of time on the sanding and polishing. Glad you showed me that.

Plates are NLA. I'm a former aircraft mechanic and was just itching to safety wire something.

Safety wire on cam gear fasteners. by Matt Squirsh, on Flickr

Timing was far too advanced in the video. Things are happy now.

https://youtu.be/ysBFjeNiAp4

Did you cross-drill the bolts yourself?

Maybe that engine is the euro b34 with piano top pistons. Just going by what I've heard about it on the interwebs. Not sure what other indicators are. If it is thats a nice little surprise for you.
I agree that posting on firstfives is great.

Sorry, I just reread your post saying its the original 76 block so it couldn't be a b34 Ignore me

I used just a vise and a drill press. Some websites sell ready to go drilled head bolts. 1/16" or 3/32" bit.

The later cars don't actually use a lock plate, fyi.

I hope you cleaned up the deck of the block a little bit... but maybe you have already begun reassembly?

Found some weird ferrous "rings" in the coolant passages, looks like they were just artifacts of the original iron casting. I extracted these rusty bits in pieces. Also, vacuumed the cylinder walls with a 2mm rubber tube attachment.

I just thought I would mention those rings you pulled out with all that crud are dowels or rings that stay in the block to line up the head when replacing the HG and head

Hey guys - my head gasket needs replacing, at the very least (8/86 635Csi). I don't see oil in the coolant, but need to dig deeper to see if there's other damage. If I DO NOT need to just replace entirely with another B34 head (worst case scenario the head is cracked), what do you figure the job would cost in parts if I do the work myself?

I've been reluctant to work on the car myself for kinda big stuff, but $3K from a shop to do it is the last straw. I've been lucky to be able to throw money at it, but no more.

With a headgasket and some other piecemeal gaskets, $100. If you find a worn cam and need to disassemble the head you may as well do a valve job as well and you could be into it $800 even working on it yourself.

IIRC, the M90 was replaced in 1982. I might be incorrect though. This is what I have:

1984 - 3430cc M30 Motronic DME II 92x86, 10.0:1 218bhp/5200rpm
224lb.ft/4000rpm

http://www.bmwcoupe.se/images/stories/e ... ngines.pdf

Jens6er wrote: ↑Tue Jan 02, 2018 10:17 pm Hey guys - my head gasket needs replacing, at the very least (8/86 635Csi). I don't see oil in the coolant, but need to dig deeper to see if there's other damage. If I DO NOT need to just replace entirely with another B34 head (worst case scenario the head is cracked), what do you figure the job would cost in parts if I do the work myself?

I've been reluctant to work on the car myself for kinda big stuff, but $3K from a shop to do it is the last straw. I've been lucky to be able to throw money at it, but no more.

I had my head gasket replaced by a shop in Santa Cruz, CA about 3 months ago. All in the cost was $1,800. I wrote about it in my project thread if you wanna read more. About $290 was for the gasket and related bits.

viewtopic.php?f=25&t=25858&start=525

LandShark wrote: ↑Tue Nov 14, 2017 3:28 am I don't have a clue what I have besides cryptic stories from the previous owner of the full overhaul that was done by a mechanic in Italy. As far as I can tell, they went through everything since I see the same red RTV squeezed out of every seam. The block is original 1976, same VIN as the car. If this was some budget hotrod build, well then great, I guess.

Ah. Just read this bit, so it's not an '84 as I posted...

SenorShark wrote: ↑Fri Mar 02, 2018 3:46 pm IIRC, the M90 was replaced in 1982. I might be incorrect though. This is what I have:

1984 - 3430cc M30 Motronic DME II 92x86, 10.0:1 218bhp/5200rpm
224lb.ft/4000rpm

http://www.bmwcoupe.se/images/stories/e ... ngines.pdf

And yes, being a 1976 block it would have to be a hotrod build. The 635CSI didn't come until 1978. CR on a stock '76 would be 9.0:1 if it was a 630CS or 633CSI, US (630CSI) was 8.0:1