Date: Wed, 26 Sep 2012 17:44:19 -0700
Reply-To: Stuart MacMillan <stuartmacm@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Stuart MacMillan <stuartmacm@GMAIL.COM>
Subject: Re: 2.1 assemble
In-Reply-To: <BAY152-ds7A68C49664E8B6875B63EA09C0@phx.gbl>
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Wow, I knew Dennis was an expert, but he's actually a guru, several levels
above expert. Thanks for sharing your knowledge Dennis.
The complications with main bearings inside of two case halves on a boxer is
complicated. (How's that for a circular argument!)
I remember my days with air cooled rebuilds where every case had to be
align bored and stud inserts and studs installed, and they would still not
last very long. The metallurgy for the WBX case is better, but squeezing
new bearings into an old case is still fraught with risk.
It takes a good machinist to get this right, and one who will take the time
. . .
Stuart
(more than one failed VW rebuild under my belt)
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Dennis Haynes
Sent: Tuesday, September 25, 2012 6:26 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: 2.1 assemble
Part of the answer here is what happened to the engine that required the
teardown? These engine cases are consumable and a number of failures can
render them in need of work or repair.
With the case opened, carefully check the center webs where the bearings
sit. You want to see machine marks. Get a good machinists straight edge and
check all surfaces, straight and diagonally across. Both sides need
everything perfectly flat.
Put the case together empty. Snug up the bolts/nuts around the outside. Do
not install the nuts holding the bearings, just the outer flange. Get a
bright light and place at the pulley end. Take a good look at the center
webs. If you see light coming through the webs you have a problem. When you
tighten up the bearing through bolts the case will distort to take up this
space. This will pull the cylinder seats out of parallel and prevent you
from getting a proper seal at the heads. The fix becomes complicated.
Either the case surfaces have to be welded up and re-machined, or they can
just be machined and after the align bore of both cam and crank bores the
cylinders will need to have the deck height adjusted to compensate for the
new case dimensions.
While the case is tighter, you want to test fit the empty cylinders, no
rings onto the case. Again use the straight edge to make sure the tops are
level and straight across both cylinders on both sides. Only after all these
checks pass should the case be re-used.
Next is to tighten up the bearing bolts and check the bearing bores for size
and concentricity. If the engine had oil pressure problems worn main bearing
journals are the usual cause. On a running engine worn mains can be felt,
not heard. The center usually wears the most due to crank whipping and the
split bearing.
If still good, now to test bearing fit. Take case apart. Install bearings,
crank and cam by themselves. Put case together. Check that all bearings are
tight and seated. If any can be moved, you need the align bore or some luck
with one of the Loctite products.
Now you also need to test the head studs. Get some good 10 mm nuts. Place
your cylinders and heads in position and test torque the heads down. Any
studs that keep stretching or twisting need to be replaced. Keep in mind
that all internal leaks of combustion gasses into the cooling system that
are not due to a cracked head are the result of multiple stud tension
failures. ALL OF THEM! A broken stud means a tow home, antifreeze in the oil
or on the ground, and depending where it breaks a full teardown and a
dedicated machinist to remove it.
Now after all this you can put it together.
Dennis