Date: Fri, 27 Dec 2002 19:51:20 -0800
Reply-To: jbclem <jbclem@EARTHLINK.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: jbclem <jbclem@EARTHLINK.NET>
Subject: Re: diesel rods weights
Content-Type: text/plain; charset="iso-8859-1"
Brad,
On gasoline engine VW rods, the numbers are to make sure you keep the rod
caps matched up with the other part of the two piece rod. Since the two
circular holes(eyes) in the rods are resized(honed) with the rod pieces
bolted together, when you take the rods apart to replace the bearings you
need to have a way to reassemble them so that the individual rod caps are
mated with their original partners in the same orientation that they were
honed. When you have four sets of rods (8 pieces) laid out on a table and
you're cleaning them and moving them around, it is possible to mix up these
matched pieces. So you should have two pieces(rod and rod cap) with the
nunber 64 on each piece, two with the number 74, etc...and when reassembled
the numbers have to be on the same side, ie right next to each other when
the pieces are bolted together. If you marked the rod pieces before you
disassembled them that'll work as well. As I remember, the convention was
that the numbers were on the same side as the knotches(that designated which
way was up when the rods were laid out on the crank in a certain horizontal
manner). This was for gasoline VW engines, and looking in a Bentley vanagon
manual at the diesel engine there is no mention of the numbers but you are
told to mark the rod and the cap before removing them for the same reason.
Orientation-wise, for diesel connecting rod installing, the Bentley
mentions this: "casting marks and retaining lug for bearing shell face
toward intermediate shaft", along with a picture showing the casting marks.
I hope you have a Bentley manual, these things(rod orientation and rod cap
matching) are important both for the balance of the engine and future rod
bearing wear.
Sorry I can't be more specific, I've rebuild many gasoline VW engines but
not one diesel. But given how much more stress is going to be on the
crankshaft system in a diesel engine, I'd say these things are even more
important. What do you do if you overlooked all this? Get out a bright
flashlight and a mirror and look real hard to see if you can spot any marks
that make sense, and hopefully you've got the numbered caps assembled
correctly. As for the rods without numbers, if there are no marks at all
and you have no idea if they are assembled correctly, then you have to find
someone who has rebuilt enough VW diesels to know what exactly how important
this is, and what you can get away with. If you used a set of rebuilt rods,
they probably came assembled correctly, so if you put them back together the
way they came then you might be ok, but call the machine shop that did them
and find out how they mark them. In my case, in rebuilding a gasoline VW
engine, if I somehow found out I have put a rod cap on backwards, even if
the engine was all together I would take it apart again. I'm so paranoid
about things like this that I don't think I even had this particular
problem.
Let us know what happens.
John
----- Original Message -----
From: "Bradley Flubacher" <flub@ADELPHIA.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, December 26, 2002 11:33 AM
Subject: diesel rods weights
> I just finished assembling the bottom-end of my engine that I'm
> rebuilding and noticed numbers stamped on the connecting rod caps. Are
> these weights? Do I have to take out the pistons again and weigh them
> each to make sure I have the weights correct? I saw one had the number
> 74, one had 64, and two had no numbers on them.
>
> Brad
>
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