Date: Sat, 10 Apr 2004 18:09:41 -0400
Reply-To: ROBERT DONALDS <donalds1@VERIZON.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: ROBERT DONALDS <donalds1@VERIZON.NET>
Subject: 2.1 con rod notes from Boston Bob
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Doug in CA <vanagon@ASTOUND.NET> wrote:
What is up with the rods in the 2.1s
Is it as simple that they are getting pounded oval and the bearing spins, so you just need to re-size them back to factory and everything is AOK?
Doug, Mike, Zoran and other fellow vanagon types
let me start with some shameless self promotion
I have located new German rod bolts that fit the WBX rods these are not bug or 1.9 bolts but work with no grinding
and I am now offering rebuilt 2.1 rod sets for $140 exchange this includes the new bolts
they are weighted sets and ready to hang on the crank. I also have a large selection of vanagon main bearings and this includes the 2.1 20 case std crank mains 025 198 471A that have not been seen in this country for a few years
I also can measure and alignbore if needed all air-cooled and water-cooled flat 4 blocks
please visit my web pages and read the other article on 2.1 rods
http://www.bostonengine.com
please consider me for you engine rebuilding needs
Boston Engine where you get more than engines and engine parts
I wrote and never finished these rod notes a while ago yes they ramble and could use some
cleaning up but I offer them the way they are for now due to time restraints.
You've reminded me about the testing and clearance checking I've done
with rebuilt and used bug and WBX con rods. So I spent this morning going over my notes on con rods
and con rod bolts. I also took a random sample of used 1.9, 2.1, one
rebuilt 1.9 rod and a used bug rod. I torqued them up with and without bearings and
measured them. I also brought in and measured a set from one 1.9 core engine had
only 65k miles on them they measured consistently what I would consider
round but .0005ths to big according to the maximum listed clearance range
and .001th larger than the spec I use to get the rod bearing to crank journal clearance I
want of .0015th. This got me thinking about bearing sizes. Do the original
German Kolbenschmidt bearings measure thicker than the more common
replacement Brazilian Mahle or metal levi bearings and is this part of the
difference in clearances we see when rebuilding engines and checking
clearances. Incorrect clearances with new parts and parts that are within spec
are not uncommon and are called tolerance stack up when all the
parts measure within tolerance but the clearances is incorrect.
The new bearings I pulled of the shelve and the old 1.9 bearings with 65k measured
the same within a couple of 10ths of a thousandth so they are consistent this time.
when I install the bearings torqued and check the ID of the
rod bearings in the 1.9 low mileage rods they where just to big to suit my preferences in clearances for
the rod bearing to crank journal.
Now that I am measuring bearings I found a used 2.1 con rod bearing
that had the copper showing opposite the beam of the rod this
bearing measured 001th thinner at the warn copper area. I then assembled torqued and
measured the 2.1 con rod that I took the bearing from the rods big end measured smallest of
all rods I checked opposite the beam of the rod in the very same place
where the copper was showing. The rod also showed .001th cap shift the cap had
moved sideways all the other cores I had selected for the mornings
testing. This decreased the bearing clearance at the parting line the in the used 2.1 rod to
less than .0005ths at 45 degrees from the parting line and to 001ths
opposite the beam. I would have thought the rod would become larger
opposite the beam. The end results of cap shift and the rod bearing wear is that the
clearance of the rod bearing increases over time and the symptom of this is
that at a warm Idle the oil pressure light comes on even with a thicker oil.
And that my friends is the only warning you get before you throw a reused rod with new bearings threw the
block and with only a few thousand miles on a reassembled engine ( I did not say rebuilt did I ).
The rod bearing to crank clearances that the federal mogul master spec book
used by crank grinders and engine builders listed a range of oil clearances
from .001ths to a wear limit of .003ths. The max limit of .003th from my
experience is that this is to much because the high mileage engines I have taken apart
with symptoms of the oil light coming on at a warm idle have typically only one
clearance out of spec and that was the rod bearing to crank with a clearance of 003ths and often more
Other notes
The rod bolts are serrated there the two halves of the rods come
together making for a tight fit and to prevent the misalignment of the machined rod
halves. The rod bearings are always slightly thinner at the rod parting
line to accommodate for a slight shift in the cap and to hold oil and is an aid in
oiling. The oil pump cover gasket that comes with the German gasket set has the same part number
as the bug but if measured you will se its thicker than the bug gasket and the engine will have a lower oil
pressure at an idle if used.
My conclusions are that all the bug , 1.9 and 2.1 rods I measured had
distorted over time and the miles. the 2.1 rod took the prize for most
distortion. Its my opinion that the stretch to yield bolt is responsible for this
The 2.1 rod has 5 distinctions from the bug and 1.9 rods.
The first is that the 2.1 engine makes the most power
2) It also uses a different rod bolt of the stretch to yield type
3)the 2.1 is the only rod that gets smaller opposite the parting line
4) they throws themselves threw the block with little or no notice.
5) the rod angle is greater due to the longer stroke of the crank
I have spent thousands of dollars on micrometers and gauges so I can know exactly
what the clearances between the bearings and crank are. Yes I've used plastagauge
and that was fun but it won't show you the out of round of the rod and crank
journals or the cap shift that I saw when we put the rod on the rod gauge. Plus don't
you feel better knowing that the rod bearing to crank journal clearance is exactly
0015ths almost all the way to the parting line on the rod. that is what has worked for
me so well for the last few hundred engines with no rod bearing failures.
That's that will get you all the way home
going faster miles an hour I remain
Bob Donalds
Boston Engine
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