<VV> bad crank

[William J. Meglen]

Thanks for the response and input.  I wish my friend were more computer
literate so he could respond more directly. He has read the responses and
explained his experience and processes to me, as well as his observations
that influenced his description of the problem.

On 11/17/08 18:08, "djtcz at comcast.net" <djtcz at comcast.net> wrote:

> One main bearing was worn, but the rod survived or thrived?  That is kind of
> odd.  Like most engines, Corvair  rods get oil last.
> pump>block>main bearings> into crank> rod bearings.
> cam lobes and lifters get splash and table scraps
> http://oldcarandtruckpictures.com/Corvair/1960s_Corvair_air_cooled_cut-away_en
> gine.jpg

It was noted on tear down that the wear on the bearing was uneven but not
catastrophic. The first crank was not from Clarks. Upon discovering the
uneven wear and discussing it with Clark tech a theory developed that
something was wrong!  The crank was taken to a local machine shop and "spun"
and it was found that the Journal was not ground  "true" which likely
produced the uneven bearing wear. Conclusion that the crank was bad!

> What did the worn main look like?.

Uneven wear likely induced by an untrue journal.

> http://mahleclevite.com/it_bearingfailures.asp
> What happened to that crank journal?

No damage discernible.
> 
> What crank "badness" is being suspected that can not be measured?
> Was Clark's crank checked for the same badness and found acceptable?
> Good Plastigage readings on ALL bearings and a free turning crank are
> >>usually<< sufficient, except when it isn't.  I am personally unwilling to
> take the risk of not measuring every crank journal for diameter, roundness,
> and taper and check every bearing (at least with plastigage).  The money I've
> spent on the tools would haved bought a batch of lottery tickets, but I think
> I won anyway.

Not sure if "crank journal for diameter, roundness,.. " were checked. ALL
mains and rods plastigaged and, cam housing bores checke4d
> 
> Were the case bores (mains and cam) measured for size and roundness?

Uncertain, will verify?
> 
> Where is the failed main, relative to the lifter problem?
> Is the worn GM lifter around to check out?

I think so, will check and report

Several comments questioned whether oil passages were truly unobstructed.
Friend is CONFIDENT they were clear at first rebuild and remain so.

Some responders asked about oil used after rebuild.  Presume concern was for
ZDDP content.  Doubt that it could be the problem.  The cam manufacturers
break in lubricant was used extensively and run in was according to their
specs.

Friends focus still is on the housing for the three oil by pass valves
therein.  If one were to fail would oil fail to circulate to the lifters?
While one was replaced and the other two seemed functional. What would be
the effect of their "jamming".  There is at least a suggestion by one vendor
that he rebuilds and "mods" the housing?  Why?

Bill
Gardnerville, NV