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Rebuilding the head on the M6

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Da_Hose
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Rebuilding the head on the M6

Post by Da_Hose » Thu Dec 06, 2018 4:19 pm

I have finally torn into the dreaded head rebuild, thanks to a blown Victor Reinz head gasket. NEVER AGAIN VR !!!!!! [-X

I am not closely documenting the process this time, as my big rebuild document details how to accomplish the task. I will update this thread as I go, and add pics. if something unusual, or super cool comes up.

This time around, I will be having a local shop that I trust skim the head to make it lazer straight. I will also replace the exhaust valves this time, with the brand new set I still have wrapped in paper, and I will have the seats/valves cut to 3-angle. When it goes back together, the one thing I am debating is whether to use an original BMW head gasket, or Cometic MLS, but absolutely not a cutting ring HG.

The beloved bundle of snakes took the usual, dreaded couple of hours to remove, although it was easier now that I have a lift. Given how much bloody heat actually comes off those bad boys, I have decided I will have them ceramic coated as well.

While everything is apart, and there is TONS of room to get at all the parts in the nose, I will do the AC condenser upgrade as well.

I accept all good juju folks, and hope to have everything back together by end of January. Yeah ..... nothing goes quick, or is easy with an M. :roll: Such a love/hate relationship. :-({|=

Jose
1987 M6 - My dream car

bpoliakoff
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Re: Rebuilding the head on the M6

Post by bpoliakoff » Thu Dec 06, 2018 5:24 pm

Jose, What about contacting VAC in Philadelphia about the gasket? A friend on Bimmerforums who is doing a mega $$thousands build on an M motor in Australia has bought most of his "head" parts from there and after much research his head gaskets for sure
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
flickr.com/photos/bertsphotos.

brickwhite
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Re: Rebuilding the head on the M6

Post by brickwhite » Thu Dec 06, 2018 5:43 pm

I didn't think you could skim a s38/m88 head?
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bpoliakoff
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Re: Rebuilding the head on the M6

Post by bpoliakoff » Thu Dec 06, 2018 9:53 pm

I am curious as to why you would think that. I would think any head could be skimmed and if a problem could be adjusted with head gasket thickness which I know VAC, amongst other providers, can supply in various thicknesses. I know many years ago, and I mean many, it was not a problem when I did an early Ferarri motor and I would think clearances there are as sensitive as on an "M" motor.
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
flickr.com/photos/bertsphotos.

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Da_Hose
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Re: Rebuilding the head on the M6

Post by Da_Hose » Fri Dec 07, 2018 5:13 pm

Heya Bert,

My machinist in Napa is a well known dude in his world. He was president of the machinist/engine builders association for a bit, and has great contacts all over. On his recommendation I bought valves and springs for my M10 build from VAC, and we are happy with the stuff, but I have heard some troubling things about VAC of late. Has to do with a recent change of ownership (sadly, the founder passed away). Granted, what I have heard is second hand info., but it's reliable enough to cause me some concern as to VAC continuing to function at the high caliber their reputation stands at right now.

At any rate, the OEM is for sure a known good quantity, and Cometic continues to have a stellar reputation among high end engine builders, but I will definitely check out VAC's MLS. I had completely forgotten that they made one.

brickwhite - Maybe you are remembering that an S38 doesn't really have a specification written for what you can machine. BMW only states a minimum head thickness value, BUT there also is NOT a variable head gasket thickness. So the implication would be that if you shave the head, there would be no way to "fix" the problem of lost head thickness. As Bert points out, you can just shave it a touch, then make up for that thickness with the head gasket.

From what I understand Bert, Ferrari motors (especially the early ones) are built with manufacturing steps that essentially make each engine a freaking one-off. My machinist was sent a broken cam cap off a Dino (I think) that he had to measure and replicate exactly, because on that engine the caps were all bolted on, then machined in-situ. So every freaking cap has a different offset, on every engine ever made for that car. 8-[ That is why Ferrari's are such a pain to work on. Every damn one is "off". #-o BLAH! I'll take our German car precision any day of the week.

Jose
1987 M6 - My dream car

bpoliakoff
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Re: Rebuilding the head on the M6

Post by bpoliakoff » Fri Dec 07, 2018 7:10 pm

Hey Jose I am out of the No Cal car scene for 40 years when we used to race at the old Cotati air field, but drive down to Infineon Raceway and look up Dodge Riedy who has a shop there. I have known him since the mid sixties when he was a 16 year old kid. He knows his stuff and could be another great source.

As to the early Ferarri, to be honest, it was like putting 2 6 cylinder Chevys together. Other then the overhead cams, by modern standards, it was not a very sophisticated motor.We short blocked it on my dining room table. Worst part of that was my ex wife wanted to grab the crank shaft and have a lamp made out of it!! She was totally with the program. The base for our coffee table was an old Ferarri block. Wife #2 doesn't see things that way.
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
flickr.com/photos/bertsphotos.

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Re: Rebuilding the head on the M6

Post by clipper47 » Sun Dec 09, 2018 2:39 pm

Why would you have not kept wife #1 ? Any woman who would to put up with an engine block (even a Ferrari) on a dining room table would be a real gem.
Dave
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bpoliakoff
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Re: Rebuilding the head on the M6

Post by bpoliakoff » Sun Dec 09, 2018 8:19 pm

She didn't want to keep me.!! Oh well, ended up on the better side of good with #2 except she makes me keep the garage clean!
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
flickr.com/photos/bertsphotos.

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