Date: Sun, 10 Oct 2004 01:47:37 -0500
Reply-To: Al and Sue Brase <albeeee@MCHSI.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Al and Sue Brase <albeeee@MCHSI.COM>
Subject: Re: '86 Westy Oil light flickers briefly...other basic ?'s
In-Reply-To: <60C97FA0-1A50-11D9-9D63-000A959B3796@knology.net>
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Jim:
Where did you get the 4k number? I think the rev limiter comes on
on 86-87's at 5400 rpm and 91's at 5600 rpm. (I don't know about those
years in between). That's also about the same as the solid red on the
tach, right? 7200 on a Porsche must be a pretty short stroke one 2.0 or
2.2. They've got rev limiters too, abeit a little cruder than the
integrated digifant ones. I don't think ANYONE was using "stretch bolts"
per se back in the 60's or 70's, so I think the Porsche rod bolts are
not quite the same thing. Maybe "controlled stretch" is more
appropriate. ( I'm VERY familiar with the diesel head bolts- torque to
increasing numbers in 3 levels, then do 3 steps of 1/4 turn each. I'm
sure that a torque wrench would show uniform torque at each step. It
feels that way, anyhow.
I guess I'm just taking the word of others like Bob Donalds, about
the stretch bolts, but damn near every 150k mile 2.1 is either hurting
or ventilated and VERY few 1.9's are. My own 2.1 spun a rod bearing at
90k miles. I put in a set of reconditioned 1.9's and it has now done 55k
miles since, some under VERY high stress. Towed another Vanagon 400
miles in 90 degree temp, towed other cars some at 75+ mph for thousands
of miles. Still working fine.
In a previous life I reconditioned LOTS of Chevy rods using a
Sunnen precision hone and its various bits. Rods tend to go out of round
less after reconditioning. I guess the metal is sort of stress relieved
or hardened or something.
Also, measurements at rest and measurement at 5400 rpm anre not
necessarily the same. Very likely it was underdesigned, but if the
better bolts help, I guess that works for me!
Al Brase
Jim Felder wrote:
> My take on this is purely anecdotal, but I think that people who have
> ovalized big-ends have been driving too fast for too long.
>
> Porsche 911s have stretch bolts on the big-ends, too, but they don't
> "keep stretching." I got a lot more than 150K on a 911 and have a lot
> more than that on my 2.1 now, and the oil pressure is good. I never
> revved the 911 over 7.2K and don't ever rev the vanagon over 4K, the
> intended redline for both. Anyway, if the bolts were to stretch you'd
> have a double-radius circle with gaps where the separation was
> occurring (where the cap fits) and it would be very easy to spot this
> when the engine came apart. You would actually be able to put a feeler
> gauge in the gap in between the cap and the rod body. Plus, I think
> you'd definitely hear the racket and the oil pressure would drop to
> zero in a big hurry as soon as a crack opened up.
>
> If the big-ends are becoming oval, I bet it's from either
> under-designing the rod or putting more centrifugal force on it than it
> was designed to have (running it over 70 mph, say). I doubt that the
> bolts are stretching, though. If an inside micrometer or plastigage is
> used to determine that a big-end is out of round, it's going to be out
> of round whether the bolts have stretched or not, and will be out of
> round no matter what kind of bolts are put back into it. It would be
> the rods in this case, and not the bolts, that need replacing.
>
> Jim
>
>
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