Date: Wed, 23 Feb 2011 11:02:27 -0500
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: air cooled piston weight/cylinder question
In-Reply-To: <34558E2E1F314DA9B5018B3A646C12D3@alfonshaar.local>
Content-Type: text/plain; charset="us-ascii"
Pistons and rods should be generally to within 5 grams. Rods also should be
balanced end to end. One of the things to also check on the pistons is the
ring lands, (side of grooves). These do wear especially the top lands.
If using cylinders from different sets a measurement that has to really
carefully checked is the deck height. As the cylinders are placed on the
case you need to make sure the tops are both at the same height and level.
Any deviation will result in the seal between the cylinders and head
failing.
As for how long these engines should last there are a number of folks that
have gotten really good service out of them. Having been around VW's and
always having a Bus I paid a lot of attention to the Vanagons when they
first came out in '80. As they hit the used marketplace quickly they had one
thing in common, engine failures. Many did not make it past warranty.
Waited for water cooled my first Vanagon being an '84.
With all the air cooled busses trip preparedness often included a valve job
to be sure an exhaust doesn't break. Now maybe I do an oil change and check
all the belts and hoses.
Having dome a number of air cooled engine repairs, the common failures are
dropped valve seats, burned top gaskets, melted-burned pistons, worn
cams-collapsed lifters and the case pounding out at the base of the
cylinders.
The last one is the usual cause for the head gasket failures.
It is common for these engines to show need for overhaul considerations
somewhere between 60 to 120K. A lot depends on type of use. They don't like
extended high speed use in warm temperatures. Hill climbs and lugging bring
death quickly.
One thing that also needs to be working is the EGR valve system. EGR lowers
peak flame temperatures which both reduces NOx emissions and piston-head
temperature.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Joe Luther
Sent: Wednesday, February 23, 2011 9:53 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: air cooled piston weight/cylinder question
I got a chance to weigh the piston/wrist pin assemblies on our digital
postal scales here at work, they are accurate to .1 oz. The wrist pins are
rather tight to the pistons at the moment so I decided to weigh them with
the piston since they will move with the piston anyway.
The KS piston I thought should be heaviest because of the "+" on top
actually turned out to be the lightest by a large amount.
Here are the weights converted to grams -
Mahle pistons marked with 93 97 - :
677.55 (1# 7.9 oz)
680.39 (1# 8.0 oz)
686.05 (1# 8.2 oz)
KS piston marked with 93 98 + :
660.55 (1# 7.3 oz)
Just goes to show that what you see isn't always what you've got. I've
really wondered if someone worked the top of that piston a little, it looks
very different under the scope than the others from a surface finish
perspective.
The other engine has 2 cylinders removed due to the head problems, maybe one
of those pistons is a match for the other Mahles. Hopefully I'll get a
chance to look some evening this week.
Joe
