Re: [E36M3] M3 -Valve spring retainer questions...

[Skip Bogard <skip.bogard@xxxxxxxxxxxxxxx>]

>  While the head is in a zillion piece I'd like to update/upgrade the valve
>  spring retainers since I've heard the ealier (02/95) production heads have
>  some problems in this area.   Which retainers do I need to buy?

Rob, You need BMW P/N 11 34 1 432 453  seen on fiche 11-085, the part description will be
"Upper Spring Plate".   And, it was implemented in 10/95, not 2/95

The old BMW P/N was 11 34 1 703 218A, but you can't buy it anymore.

Rob, I am curious to know two things if you can please: 
  1. if the old ones taken out are "silver" 
and 2. if the new ones put in are "blackened".

Usually the nitriding process turns metal black, but not always.  Alledgedly the new ones are
nitrided.   They might be blackened, depending on what kind of nitriding was done.  Answering this question would be a
good "visual" way to detect whether a '95 head has been rebuilt with new & improved parts.  Actually, any noticable
color difference would be useful to report.  Many people
who have missed a downshift have done the update.  So, to not buy a '95 M3 if it is pre-9/95
production may be a missed opportunity.  Personally, I'm looking for a '95 violet coupe, non-lux.
But I'd want to know it's head pedigree, it it can be visually determined easily with little
teardown.

Also, try to measure your old retainers for "cupping".  This would be the result of
the soft retainers.  Compare them to measurements on the new retainers (measure
to .001 or .0001 with best micrometer you can find.)  Hope it's not so obviously cupping that
it's visual!

The new BMW retainers are about $2.70 list price.   If you want, you can buy titanium retainers (but not from BMW) for
about $16 each.  If you want to get really spiffy, I know a company that can harden titanium.  Titanium would give you
about 300 more RPM redline.  It weighs about 1/2 that of steel.

Titanium is very strong, but it relatively soft (hardness of ~28 Rc).  Coated titanium exists, but the coating wears
off.  Ion nitriding of titanium produces a hardess of > 70 Rc, but only with a penetration of 25 microns.  Ion
implantation produces the same hardness, but only 10 microns thick.  A process called Diffusion Hardening (DH) is brand
spanking new.  It can harden to > 60 Rc to a depth of 250 microns.

I have seen actual pictures of a differential housing for a German Super touring car (titanium) hardnened with this
process.  It has also been used on such parts as a slip yoke with power steering pulley pump (also Titanium).

Best of luck

- - Skip Bogard, and I might pompously add my
  Society of Automotive Engineering # 6103028501
  '95 M3, with Titanium retainers, blueprinted head,
          all the stnd. intake mods, fast as stink, so 
          eat your heart out when I drop you after our
          completed pass.   

Rob wrote:
> 
>     Okay guys and gals,
> it looks like a local shop is going to weld/machine my cracked M3 head to
> get me back on the road for waaaaaay less $$$ than buying a new or used
> head.....
> let's hope it works!!!
> 
>  While the head is in a zillion piece I'd like to update/upgrade the vave
> spring retainers since I've heard the ealier (02/95) prodution heads have
> some problems in this area.
>  Which retainers do I need to buy?
> 
> Thanks
> Rob
> motor@domain.elided

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