<VV> RE: installing a cam?

[Andy Clark]

Bob, see my interleaved comments.

Andy
----- Original Message ----- 
From: <BobHelt at aol.com>
To: <slowboat at mindspring.com>; <virtualvairs at corvair.org>
Sent: Saturday, April 14, 2007 2:28 PM
Subject: Re: <VV> RE: installing a cam?


>
> In a message dated 4/14/2007 11:20:21 AM US Mountain Standard Time,
> slowboat at mindspring.com writes:
>
> It's not  like the "tight spot" was "tight", in the normal sense
> of the word, it's  that upon crank rotation I could detect a slightly
> increased resistance to  rotation in one spot.
>
>
> Hi Andy,
> My apologies for dragging this out so long. Please understand that I mean
no
> disrespect to you. This is mearly a technical discussion in my view. I
> understand your experience, but let's look at the logic here.

No offense taken, Bob. This is interesting to me and, I hope useful as well
to the VV folks looking on.
Especially if it helps them decide if the "quickie" case separation
procedure advocated here is valid or not.
>
> Here's how I see this problem. Please comment. You and others have
describe
> this problem as the "dreaded tight spot". As I understand  this, you could
be
> rotating the crankshaft by hand and encounter an increased  drag at some
> point. But this increase ceases as you continue rotation. This same
increased drag
> would reoccur on each rotation of the crank at the same point.  Now, here,
> we're talking about slight increases in drag, not bending the crank  or
> something.

This is exactly what I experienced; a slight increase in drag at the same
spot on every revolution.
>
> If this is the case, then here's my thinking.
>
> This must be caused by the crank, and only the crank,  or some  attachment
> (eg, a gear) to the crank. Only the rotating device can cause this
intermittant
> drag. If it were the crankcase, or a function of the torquing  sequence,
then
> something would be out of alignment. This would cause a STEADY  increased
> drag. In other words this would contact the crank in a uniform manner,
pressing
> on it and increasing the drag, but in a constant manner.

As usual your logic is impeccable. In my post I did not try to explain it,
for I don't know how to. I just shared my experience, and related it to the
caution specific to this event in "How to Hotrod Corvairs", that many of us
cut our teeth on waaaay back when <G>. Before I started the torque sequence
again from scratch using a pure X pattern, I checked the cam and crank gears
very carefully for damage or foreign matter that could interfere with
rotation. There was none, nor any indication of excessive run-out (dial
indicator on both face and circumference of gears). The second attempt to
torque the case together resulted in a smooth rotation through all 360deg.
Had it not done so, the crank would have come out for close checking.
>
> To me, this can only mean some out-of-round condition on the crank or a
bent
> crank.
> Either way, I can't see how retorquing or changing the sequence could
repair
> these conditions if they exist.

After reading your excellent analysis, me neither. I just know that I
experienced a tight spot. That engine susequently went into Orange Julius
and regularly turned 7K at autoslaloms and 8K on tracks with longish
straights like Riverside and Pacific Raceways in Solo I and SOVREN events. I
surmise therefore that the crank was not bent, otherwise I would have had a
grenade at those revs. However, that's purely an anecdotal conclusion.
>
> Your comments?
>
> Regards,
> Bob Helt

Sorry I can't shed more light on the subject, Bob. I still have the build
records for that engine somewhere in my archives, but I doubt that they
would be much help. You see, I took what was said in HHC as gospel,
experienced what the book said I might, used a different torque sequence, as
they recommended, and went on. Since the "bible" said it was possible that
this could happen and that it was due to slight case twisting (if I remember
the words correctly), I did not spend a lot of time pondering the whys and
wherefores of it. That would have been in the mid 70s, and I was a lot
younger. I was probably more focused on getting out on the track, and not on
revalidating what a Corvair expert said was so. Knowing what I know now, and
with the benefit of 30+ more years, well.....call it the folly of youth.

Best Regards

Andy