Date: Wed, 14 Feb 2001 21:00:06 -0500
Reply-To: Robert Donalds <bostneng@FCL-US.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Robert Donalds <bostneng@FCL-US.NET>
Subject: Re: 2.1L Oil pressure problem: Rods: SYMPTOM NOT CAUSE:
UNBALANCED crank the Problem
Content-Type: multipart/alternative;
I disagree
the 2.1 cranks dont flex and in the hundreds wbx of engines I have
dissasembled and
rebuilt (unlike the bug crank) I have never seen any sign of a wbx crank
flexing
or the edges of the rod bearings showing any wear
All 2.1 rods do however show out of rod at the big end
the 2.1 engine uses a stretch to yeld con rod bolt this is a bolt
is torqued to a
certain ft pds of torque then it is given a 1/2 or a 1/4 turn this puts
it into a yelding
or a stretched state
the 1.8 and 2.0 vw golf jetta engines use these also on there rods
and heads
you use type 1 info to make points about a completely different
engine and crank
apples and oranges
your ideas dont match what I have experianced and vw engines is all
I do
all day every day for the last 30 plus years
Boston Bob
Bob
Wolfvan88@aol.com wrote:
> <<<...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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