Date: Sun, 11 Feb 2001 13:18:19 EST
Reply-To: Wolfvan88@AOL.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Robert Lilley <Wolfvan88@AOL.COM>
Subject: 2.1L Oil pressure problem: Rods: SYMPTOM NOT CAUSE: UNBALANCED
crank the Problem
Content-Type: multipart/alternative;
<<<...The con rods are the same on the 2.1 and the 1.9 but the bolts
aredifferent I blame the stretch to yeld bolts for the distortion of the2.1
rods. the1.9 engines never throw rods and the 2.1 are well known for
throwingrods...>>>
Why do you blame the bolts as the problem for causing the rod distortion?
This does not make since. If the bolts stretched ANY AT ALL would they not
come a part in a few miles NOT THOUSANDS of miles or NEVER AT ALL.
Once in my past when I did not know much about the T1 engine, I did a top end
rebuild on my 1300 cc 66' bug engine. I went to 85.5 mm pistons. I simply
banged the old piston pins out and put on the new pistons. I did not know
that that would STRETCH the rods bolts. In about 40 miles, one of the rods
let go and destroyed my engine. The bolts came loose and backed off the rods
allowing the cap to come off and locking the engine.
If this is what you say is happening, the rod bolts stretch allowing the big
end to be distorted, would not ALL the 2.1L engines rods FAIL and have rod
nuts coming off left and right EVERY 2.1L engine that was ever made BECAUSE
if the bolts stretch then the nuts would back off.
I see the distortion is due more to the uncounterweighted crank COMBINED with
the LONGER stroke that is putting increased stress on the rods causing the
distortion AND the increased bearing wear. The crank flexes during running
and with the longer stroke the angle on the rods is greater due to increased
travel thus bearing wear and engine failure as the bearing can no longer
support adequate oil pressure and a rod overheats and the rod then breaks
apart.
Bob, I think that you are looking at the symptom and not the cause of the rod
problem.
You have to ask "Why did VW go with the 76 mm stroke in the engine and not
any larger?"
There were a lot of racers using larger strokes in the T1 engine and some
developed ways to make the softer stock T1 case live 200,000+ miles by just
changing the crank slightly.
Could it be that during their testing any longer stroke on the stock crank
caused early engine failure and the 76 mm stroke gave an adequate 100,000 to
150,000 mile life expectancy with the stock crank which was normal for an
engine in that time period. They built in a predetermined engine failure time
to ensure new car sales or revenue from replacement engines.
During my engine modification development, I have talked with several machine
shops: RIMCO, Demello Machine Shop and my local machinist, FAT performance
and others to name a few. When I asked them about problems that had surfaced
on the list: Broken cranks and rod failures, I was told that crank failures
were rare and not a problem and the rod problem was not with the bolts. The
rod would break before the bolts would. It was when the rod got over heated
due to bearing failure and causing oil pressure loss and the rod seizing to
the journal. The bearing failure is due to unequal stress across the face of
the bearing causing one edge or side to wear before the other side.
The solution to the rod problem is not just changing the rod bolts, it is
more than that I think. By simply adding counterweights to the crank, it
will hold the rod in perfect alignment at any RPM by eliminating the crank
flexing. This eliminates any side stress on the rods that comes from the
crank flexing as the engine rotates. The rod bearing can support the oil
film equally across the face of the bearing rather than on one side and the
bearings last longer, up to or more than double the normal life expectancy of
the bearing.
Adding counterweights cost @$150 (my costs about two years ago, could be more
now...)
$150 / 150,000= 0.001 cost per miles $150/ 300,000=0.0005
So ask your self: "Is it worth .001 cents to get an extra 150,000 miles out
of your bottom end?"
The other benefits of the counterweights: Smoother engine, more power across
the RPM range, can handle faster take offs without damaging bearing, can
lighten flywheel to further increase take offs and improve low end power.
Proof in is the Gene Berg Enterprises engine track record and the MANY T1
engine that have properly built and matched engine and in my engine...
Feel free to disagree...
BTW the Bug rod bolts cost only $0.88 each from my FLAPS
Robert
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