Date: Thu, 24 Feb 2011 16:44:21 -0500
Reply-To: Joe Luther <jluther@ALFONS-HAAR.US>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Joe Luther <jluther@ALFONS-HAAR.US>
Subject: Re: air cooled piston weight/cylinder question
In-Reply-To: <BAY152-ds114C9CF8244E26D5A5D41A0DB0@phx.gbl>
Content-Type: text/plain; charset="us-ascii"
The mounting shoulder of the cylinders measure within .004" total deviation
within the 5 cylinders I checked using a .0001" indicator on our surface
plate. I checked over the soft shim that was sitting on the shoulder area
of the cylinders being sure it was fully flat on the shoulder. I also
checked 4 points on each cylinder to see how flat they were but I was slave
to the flatness of the bottom surface of the cylinder, which I stoned and
cleaned. The soft shims threw a little variation in there too but they go
with the cylinder.
Unfortunately, the cylinder that goes with the matching Mahle piston I found
last night has some unacceptable problems within the bore that I didn't
notice last evening. If the piston and other cylinder measure out ok one to
another, I may end up using the Mahle with the 'odd' cylinder.
Alternatively, I can look at the other piston and cylinder from the 84k
engine and see if it's a Mahle and the bore is ok. Hopefully tonight.
I have a set of bore/inner mics and an outer mic to check the cylinders and
pistons. It would probably just be for informational purposes since I am
probably going to reuse these parts unless they are really bad but it will
be interesting to see how they hold up.
I do have a question on the total seal second rings....if they eliminate
blowby don't they also increase compression and add more stress to the case
mounts? Isn't a little blowby working in our favor if the case is a weak
point as you mention? I'd rather have a little more case life and a little
less compression, it's an aircooled brick more or less so I don't expect
neck snapping performance. I drove a diesel Rabbit (NA, not turbo) for 7
years so I'm used to glacial 'acceleration'.
Thanks as always for the comments.
Joe
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf Of
Dennis Haynes
Sent: Wednesday, February 23, 2011 11:02 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: air cooled piston weight/cylinder question
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.
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
