Date: Mon, 31 Jan 2005 20:27:55 -0500
Reply-To: ROBERT DONALDS <donalds1@VERIZON.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: ROBERT DONALDS <donalds1@VERIZON.NET>
Subject: Re: wrist pins/boston bob
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Mike, Jimt and fellow vanagon types
The wrist pin noise is not what it sounds like pun intended The term wrist
pin noise is a piston slap unless the bushing comes loose in the rod and the
piston rattles around then its just called engine failure
Wrist pin noise or piston slap is heard when the piston does not transition
from one side (skirt) to the other just before the piston reaches
TDC..Pistons are made with an offset wrist pin hole the offset is in the WBX
piston is 1MM with this offset the piston gently transitions the piston
unless of course you install the piston backwards. Other things that can
cause a piston to not transaction are damaged pistons or tight fitting rod
bushings . Most con rods also have an offset top to bottom the top sits a
little
to the left or right depending on what side of the engine we are talking
about. When the rod is installed backwards it can touch the wrist pin boss
of the piston and hold a little side pressure on the piston and this
prevents the piston from transitioning and you can hear that for sure. I had
one fellow bring in an WBX engine that he had taking apart more than once
tiring to find the rapping noise with no luck I was brought in for the
autopsy it was the rods on backwards
The air cooled bug engines can have a wrist pin noise if the rod bushing is
worn but its minor AND WOULD LAST FOR EVER most water cooled engine may
have as much noises but the water jacket is a great noise damper
One other thought about wrist pins is that if the bushing is damaged when
the piston pin is installed then the bushing can come loose over time the
signs of bushing damage is that the piston does not float on the con rod
after it installed this is hard to check when the cylinder and piston go
onto the rod at the same time with little room to wiggle the piston on the
pin.
I think that the chances are that its not a wrist pin noise but more likely
a lifter, rocker or crank rattling around in the case. Loose main bearings
are common in the 1.9 enignes at about 20 to 30Kwhen the block is not align
bored at the time of the rebuilding or reassembling. If you suspect the
main bearings are loose in the case check for exsessive crankshaft endplay
its a dead giveaway for loose mains
yes I ramble what's your point
going faster miles an hour with the heat on
I remain
Bob Donalds
Boston Engine
http://www.bostonengine.com
----- Original Message -----
From: "Mike Miller" <mwmiller@CWNET.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Saturday, January 29, 2005 2:58 PM
Subject: Wrist pins
> Volks, especially engine volks,
>
> A friend has a 85 van with less than 30k on a rebuilt engine. Mechanic
> says
> that the new noise in it is wrist pins, dump it.
>
> What are the chances it is wrist pins with that many miles?
>
> Is that an engine killer with van engines, or like piston slap in the
> early
> Audi 5 cylinders, let them slap?
>
> TIA
>
>
> Mike
>
