Date: Sun, 11 Feb 2001 20:07:44 EST
Reply-To: Wolfvan88@AOL.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Robert Lilley <Wolfvan88@AOL.COM>
Subject: Re: 2.1L Oil pressure problem: Rods: SYMPTOM NOT CAUSE:UNBALANCED
crank the ...
Content-Type: multipart/alternative;
<<< Well there seems to be a lot of "hype" there..the counterweights will help
the MAIN bearing life as they will have lower loading...>>>
If you look at a T1 engine, almost ALL need to have the case line bored
because the case saddles have been pounded oval by the crank flexing, even
engine that have not turned over 4000 rpms or driven hard. Gene Berg, along
with others, looked into the problem and determined that the addition of
counterweights stopped the saddle being pounded out and greatly increased the
life of the bearings. The crank in a T4 engine is longer and stronger than
the T1 crank and does not have the case problem due to the elimination of the
magnesium, but bearings still wear. Now, those building stronger T4 engines
are going to counterweights to increase engine life, power and reliability.
In the WBX engine the case is aluminum and the journals do not wear as much
as the T1 case, BUT bearings were made for an oversized case saddle, so VW
knew that the case COULD wear similar to the T1 case and require line boring
(IF it was ever done I do not know). So if the case could wear and increase
the journal distance, then the bearings could wear and cause an oil pressure
problem. The addition of counterweights was done to balance the rotating
force of the heavy crank journals.
<<<as far as the flex?..errr... how does adding weight to the throw of the
crank PAST the edge
of the main bearing reduce flex? if the crank was flexing enough to change
the position of the rod relative to it's journal, then the center main would
have to move some ungodly distance.>>>
Remember that the clearance between the bearing is SMALL .010 mm. As the
bearing wears the clearance increases. As the clearance increases, the crank
has more room to flex out of a straight line.
Think about a washer, if the load is unbalanced does the washer run smooth?
No, it starts to vibrate and shake. The more unbalanced the greater the
shake. The crank is the same way. When you look at a crank, the center two
rod journals are on the same side. The weight of those journals cause an
unbalanced condition when the crank is rotating. The higher the Rpms, the
greater the center wants to flex due to the greater centrifugal force, like
the unbalanced washer. The center main saddle and bearing keeps the crank
from flexing, when the bearing is new, the flex is minimal, as the bearing
wears, (the crank is harder than the softer bearing material) the flex
increases. Acceleration and Rpms determine the wearing out of the bearings.
The faster/harder you push the engine the faster the rate of wear. Other
factors include (but not limited to: Type of oil, how often it was changed,
overheating of engine).
The crank does not need to flex much before the rod journals are not exactly
perpendicular to the crank journal. When the rods are even slightly off, the
rod bearing and the rods suffer from wear. The power loading of the rod
during the ignition phase causes the rods to hit one side of the rod first
and then the down force on the rod causes the rod to be forced sideways as
the rods wants to equalize across the bearing surface. The sides of the rods
wear and this also causes the elongation of the rod as it twists sideways in
the journal. It does not take much to start the process, then the force
grows as the wear increases.
The counterweights balance the weight of the journals. Think about a seesaw
that is equally balanced, also think about the washer that is perfectly
balanced, no vibrations and all the parts last longer.
This is the same principal with the counterweights. The counterweights
increase strength of the crank to spin at a higher RPM and not damage the
bearings. The crank can be better supported by the oil pressure because the
crank does not want to constantly go out of line on the heavy side of the
crank. The vibrations in the crank are eliminated because it is no longer
flexing due to being unbalanced. The flywheel and pulley are heavy to absorb
these vibrations and prevent them from quickly damaging the engine bearings.
(Many with T1 engines remove the stock steel pulley and replace it with a
light weight aluminum pulley, soon they end up rebuilding the engine due to
bearing wear that the heavy pulley slowed down)
<<<Your Type 1 blew up NOT because of what you DID but because what you DIDN'T
do..Yes, you can bend rods whacking them with a hammer..stretching the bolts?>
>>
Yes, YOU CAN, stretch the nuts but not bend the rods.
<<<Man, you'd have to be swinging that sledge hard enough to knock the whole
thing into the neighbors yard! (and clear the 8 foot fence!)...It is not
uncommon for a top end rebuild of ANY engine to become a TOTAL rebuild in
short order.. an "iffy" bottom end will put up with the pressure that leaking
valves and rings can produce..go back to "as new" power and the bearings
just give up..chevy six or the type one four, it makes no nevermind ..
You didn't perhaps, as others have done, rebuild the top end after the thing
dropped a valve? People DO that and don't think about the bent rod.>>>
NO, the engine was running fine. I simply wanted MORE POWER. My 1300 cc
engine was slow... All I could afford at the time was to have the heads bored
for the 85.5 cylinders, gasket set and a set of pistons and cylinders. I
used a hammer and a 3/8" extension bar to hammer the piston pins out. That
was enough to slightly stretch the threads on the nut, ONCE the torque of the
nuts was LOST (it is only 33 lbf ft), it does not take much to back the nuts
off. Once all was put back together, it ran perfectly. I was cruising at 60
and just outside of Wilson, NC there was a loss of power and a loud metal
noise like a hammer. I tried to make it to Greenville, NC, but just before I
got outside of Wilson the engine locked up. When I looked at it, the rod
nuts had backed off on one rod and the cap came off. The rod was not broken,
just the cap came off and bent the bolts and damaged one piston (MY BRAND NEW
ONES...)
I rebuilt my first engine on a picnic table at an ex-girlfriends uncle's
autoshop. He would not let me inside to work on a bench.
I also did not have the engine rebuilding experience as this was my first
attempt. I followed my father advice, just enough to get by, and I did that,
by the third time I followed MY advice and did what was needed to do it
right. It lasted three years and was running fine when I sold it.
Then comes my T4 engine, I did it right except for the heads, I cut some
corners and had a local shop redo the seats. At 57,000 a sinking seat caused
a valve to drop. For my next T4 engine, I had the seats done by Mark
Stephen's (before he went bad...)
along with other head modifications. The "do it right" approach was done to
my WBX. I took all the know problems with the T1 engine, the T4 engine and
the WBX and applied known industry fixes to try to prevent them from
happening from my engine.
<<<Ok..So..counterweighted crank? Sure..it can't hurt..take a bit of weight
off
the flywheel too and retain the nice idle..
rebush, resize and balance the rods? there is no other way..the loading on
the rod and it's strength are the main reasons that the 2.1's blow...Notice
the "racing" top rings? a whole bunch thinner to prevent ring chatter at the
high piston speed on the 2.1's.
these and stretch bolts are more of the "band aids" of which I spoke.. They
KNEW that the rod was overworked and that is a way to make sure that the cap
stays on the rod..>>>
Stock rods in a properly setup street engine can take about 150 HP and go to
6500 rpms and live a long life. It is the flexing of the crank that leads to
bearing wear and than leads to rod failures.
<<<As far as "why did they stop growing the stroke?"..simple..piston speed is
one and rod angularity is the other...even with "shorty" slipper skirt
pistons (not known for their longevity in "street" engines) most "big" type
one's get wider...long jugs and/or barrel shims..
You can't make the WBX WIDER (ok, you CAN, but remember production tooling
and all that?)
so to pack more stroke in the WBX "box" you'd get REALLY crazy rod angles and
even MORE loading......
I'd be more tempted, if I HAD to worry about it, to use something like a
chevy rod, combined with shorter skirt pistons..but these don't exist as it's
a piston with the conbustion chamber in it...>>>
This is what I have been saying: the WBX IS a DE-TUNED RACING engine...
No longer stroke? NOT TRUE!
VW could have gone to longer stroke IF they wanted to but was too cheap and
would cost them too much. There is a company TODAY that MAKES A 2.5L
COMPLETE DROP IN UPGRADE KIT for the WBX. It is basically a drop in to the
STOCK WBX CASE. It is a much longer stroke with 98 mm pistons, plus heads,
cam, rods, barrels.
Adding counterweights will increase overall engine life and give you many
more benefits, so ask yourself: Do I want to spend less than a 10th of a
penny a mile to greatly increase the life of my already expensive engine?
<<<2.1's? great torque-..keep the RPM under, oh 4 grand and it will be FINE...
>>>
I normally keep it under 4 grand, but sometimes I like to get to speed
faster...
Robert
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