----- Original Message -----
Sent: Thursday, October 25, =
2001 2:44
PM
Subject: Re: B. Bobs 2.1 main =
bearings,
one more question
Bob;
OK. I measured the =
bearing ID(
in the case) and the crank's OD. Subtraction should give me the =
clearance.
What is tolerance here? How about differences in orthaganol ID =
measuments i.e.
out-of-round?
Anybody know of some =
good WEB
sites with this info?
TIA
Ken
I looked in the VW =
without
guesswork book for out of round (orthogonal) dimensions for the crank =
rod and
main journals it says the cranks on the type 1 and 4 engines can =
be out
of round as much as .0012 ths
I dont often see that kind of wear =
on 2.1
cranks they are for the most part mint or junk. I would say that =
the
crank is ok if its less than .0005 ths small or out of round more =
than
that I would consider not using it. Regrinding
has not been an option until the past few weeks I now have in =
stock some
.010 mains for a std case
The 2.1 =
blocks tend to
shift and also get smaller at the center main bore. The 2.1 main =
bearings are
made with an huge oiling depression at the case seam. While thats =
great
for feeding the crank oil that makes it realy hard to get a good =
reading at
the parting line of the case with a bore gauge. I have not =
found specs on
the 2.1 cases in any of the crank spec books or the VW info. The 2.1 =
case is
often out of round as is the the 1.9 and the type 4 case due to
the cases alignment dowel pins (not the main bearing dowel =
pins)
gaining some play over the years I have found that a block of wood and =
a wack
of the hammer can realign the case halfs so the measurements can =
be
taken. The main bearings can help (not cure) align the case as =
the case
is closed with the bearings in place. I have more than once seen the =
bearing
measurements show that the main bearing bore is still not round due to =
the
case shift. I would say that if you measure the main bearings in =
the case
with it torqued and they do not go lower than the minimum =
clearance
in any one place you are good to go. I would add to that statement =
that it is
realy hard to measure less than .001ths and be consistant every =
time so
check it more than once then check it the next day again.
Bob Donalds
http://www.bostonengine.com
as always all rights =
reserved
I =