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 |
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