Date: Thu, 24 Oct 2002 10:03:03 -0500
Reply-To: Stan Wilder <wilden1@JUNO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Stan Wilder <wilden1@JUNO.COM>
Subject: Re: Engine Balancing
Content-Type: text/plain; charset=us-ascii
I agree with Mr. Bulley on his statement that you should balance any high
performance engine.
Even if you don't plan on a professional balancing job you should have
the new pistons and your rods checked. This can be done on many 'less
than 40$ digital scales' that can read in +1/-1 grams.
If you are shooting for a zero balance it is best to use a three or four
beam balance scale unless you have a very accurate and expensive digital
scale.
Often you can selectively mate rods to pistons to achieve Zero balance
without sending your parts out.
This procedure is effective but not the ideal balance.
My post was for the purpose to tell folks that in most situations it
wasn't out of balance that caused the rod or main bearings to fail; a
major problem in most thrown rod events.
I'm not advocating that a novice start balancing his own engine, just
that simple checking will bring bigger problems to light before you
reassemble your engine.
In all honesty I thought that some of the engines I disassembled might be
Junk Box engines with mismatched pistons, cylinders, rods etc; however
that was not the case so far.
Since many of these vans are 20 years + in age there is always a good
chance that you got a patched up engine that could contain parts from
various engines combined to just get the van back on the road.
Stan Wilder
On Thu, 24 Oct 2002 07:31:00 -0400 "G.M.Bulley"
<gmbulley@BULLEY-HEWLETT.COM> writes:
> Though Stan is correct that the flat four is balanced well-enough, it
> is
> far from perfect. If you like to keep your motor rolling for >130k
> miles, or if you are doing any 'performance' work on your motor,
> failing
> to balance your motor is like using a toilet-paper oil filter.
>
> It costs $100-$200 more for a 0-gram race balance on a type 4. The
> crank, rods (set and end to end), pistons (set), flywheel, and fan
> should be both static balanced, then rotating parts spin balanced.
> Though Stan mentions 'a gram off here and a gram off there' as being
> no
> big deal, I would disagree. Cumulatively, these grams can be an
> annoying
> vibration on the road, and shorten the useful life of the motor.
>
> If you are revving close to or above redline, 0-balance is
> critical.
> Either way, once you have it done and enjoy the Honda-like
> smoothness,
> you'll never go back to unbalanced rebuilding.
>
> Bringing your ideas to life,
> G. Matthew Bulley
> Bulley-Hewlett
> Business: www.bulley-hewlett.com
> AIM = IExplain4u
> Phone: +1.919.658.1278
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On
> Behalf
> Of Stan Wilder
> Sent: Wednesday, October 23, 2002 10:37 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Engine Balancing
>
> Over the years I've acquired and rebuilt about ten Air Cooled Type
> IV
> engines.
> It has always been my standard procedure to disassemble engines and
> maintain all of the parts together.
> The purpose in this is to have all of the parts and investigate why
> the
> engine failed.
> Some things just jump out at you like dropped valve seats, crank
> bearings
> that missed the pins, cylinder head gaskets cut by leaks, burned out
> rod
> bearings.
> Many of these things lead you to believe that the single thing
> caused
> failure.
> I've seen engines with a dropped valve seat and a valve stem just
> hanging
> on by a thread on an opposing head.
> If you can evaluate the mileage on the engines by crankcase stains,
> cylinder head stains, carbon deposits on pistons and valves and rod
> bearing wear, cam shaft wear, roundness of the rod big ends / crank
> shaft
> bearing bores and you can find the cause of failure is related to
> several
> things.
> Each engine is a special case and we all know something has to fail
> first.
> In many cases the first failure crippled the vehicle but had this
> part
> not failed there was another in line to kill the engine.
> Part of my evaluation is to weigh each piston assembly and rod to
> see
> how
> close they are in weight.
> My first adventure with this was at Allied Fastener that weighed
> some
> parts on their very precise fastener counting scale.
> I doubted the results because the pistons and rods were very close
> in
> weight, never more than one gram difference.
> I considered that the law of averages was fighting me but after
> buying
> my
> own electronic scale, I've weighed OEM, Cofap, Mahle and Japanese
> pistons
> and never had anything more than one gram out. (scale has +1/-1
> accuracy.)
> With rods I seldom find them more than two grams out even after 20
> years
> of use and several reconditioning. The proper way to weigh rods is
> ......... weigh each end. Even with this more critical weighing
> process
> the rods were still within one gram on each end. (Weighing both ends
> not
> much of a trick, fixed rod from scale center mark, weigh one end,
> turn
> the rod around and weigh the other end.)
> Example: Rod nut 6 grams.
> It shows why the big end of rods balances: IE 1gr is a lot of steel
> and
> reconditioning rods seldom removes much steel.
> Now that I've got you yawning .................. engine balance in
> VW
> engines is very good, I've never found a VW engine that was far
> enough
> out of balance to cause engine failure.
> I'm hoping that this has answered the age old question "Why do
> Waser
> Boxers Throw Rods?".
> If they are as precise as Air Cooled : It ain't the balance.
>
> Stan Wilder
>
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