Vanagon EuroVan
Previous messageNext messagePrevious in topicNext in topicPrevious by same authorNext by same authorPrevious page (December 2002, week 3)Back to main VANAGON pageJoin or leave VANAGON (or change settings)ReplyPost a new messageSearchProportional fontNon-proportional font
Date:         Sun, 15 Dec 2002 23:24:44 -0600
Reply-To:     John Rodgers <j_rodgers@CHARTER.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         John Rodgers <j_rodgers@CHARTER.NET>
Subject:      Re: Top Overhauls
Comments: To: Stan Wilder <wilden1@JUNO.COM>
Content-Type: text/plain; charset=us-ascii; format=flowed

Stan Wilder wrote:

> When dealing with a 4000$ crank I've seen them chrome plated to bring > them back into specs.

Can't say I've seen that done on a crank, although it may well be a process used. I have seen them ground, re-nitrided, and oversized bearings used.

> Some aircraft came with chrome cylinders and that was a standard process. > Although I think the chrome cylinders tended to run a little hotter.

I always thought they ran a little cooler, once the rings are broken in. The matter of chrome barrels vs. steel barrels are an interesting one. You prol'ly know that the steel barrels are expected to take the wear more so than the rings. In the chrome barrels, gray iron rings are used -soft- so the rings wear more than the barrel. There has been more than one engine on which the repairman improperly matched the rings to the cylinder type, and seized the engine shortly after startup. Chrome to chrome or steel to steel doesn't work well. I had an old Cessna 195 (Actually a military LC-126) with a 7 cylinder 300 HP Jacobs engine in it with chrome cylinders when I went through aircraft mechanic school many, many years ago. Bought it for a song because of a cracked case. The case was magnesium and everybody said it couldn't be welded. Well I found a spare case for $200, and got my instructor to allow a rebuild of the engine in the school program. I really got my education going through than engine and airframe in the school.

Anyway, the barrels were sent out, bored to oversize then re-chromed back to spec. I though that was a really slick thing to be able to do. While they were out , new valve seats were installed, and when they got back, in the school shop I was able to install new guides and ream them to spec. Strangely the valve stem wear was all within spec except one. I got a new one to replace it with. Did an aircraft grind on the valves and seat faces, lapped them in, and put it together. Pistons were fine. Put in new rings and bearings, Everything down inside the case was ok, just had to be reassembled. New seals and all.

It was a strange beast. The engine had a magneto on one side and automotive distributor on the other. The first time it was fired up after then engine was installed, it belched once and caught fire. Snuffed it instantly by killing the mixture and opening the throttle while still cranking. Sucked the flame right up. It was exciting for a few moments. The manual was unclear as to how to set the distributor timing and we (me and the instructor) set exactly 180 degrees out, so it fired when the intake valve was opens. really caused some excitement for a few moments. Reset the timing, fired her up and it ran like a charm. Went through the ground break-in then wen out and flew the thing. Never had a minutes problem as long as I had it. Good airplane, good engine.

> In VW engines the #2 main bearing can be worn more than the #1 or #3 and > your crank can be in near perfect alignment. Its just the way the bearing > is loaded at high RPMs that causes excess wear at this point. > You couldn't measure this wobble on a cold crank ........... it only > deforms / bends under heat and stress.

> When crankshafts are set up on a grinding machine they are measured for > straightness before the grinding process is started. In effect a bent > crank could be machined back to tolerances if it is out only 2/3 > thousandths. > In short; there really isn't a good way to evaluate your main bearings / > crank without splitting the case and spinning the crank between fixed > centering arbors. > In any event that your engine lost oil pressure immediately, I'd split > the case. If the oil pressure edged down slightly over several thousand > miles I'd investigate the rod bearings for abnormal wear on the #2/#3 and > be wary of the mains.

I wonder if counter balancing and dynamic balancing of the complete rotating assemblies would help this problem, i.e., counterbalanced crank, balanced with rods, pistons, flywheel.

I asked Bob Donalds about using different rods on the 2.1L to get around some of the stretching problems in the lower end of the rod. If the rod gives, and gets out of round because of the bolts or whatever, then I would think a substitute would be in order. I have heard that with a little work chevy rods could be used, but I'm not up on that hot rodding stuff so don't have a clue.

Anyway, I like my flat four, and don't intend to do a conversion. I would rather modify what I have. It fits the hole, and is matched to the van. Just a little more "oomph" would be nice, and I see no reason it cannot be gotten, without everything going to hell in a hand basket. I have a basket case engine I want to rebuild in 2003 and would like to have some mods done before I start. It would be fun.

John Rodgers 88 GL Driver


Back to: Top of message | Previous page | Main VANAGON page

Please note - During the past 17 years of operation, several gigabytes of Vanagon mail messages have been archived. Searching the entire collection will take up to five minutes to complete. Please be patient!


Return to the archives @ gerry.vanagon.com


The vanagon mailing list archives are copyright (c) 1994-2011, and may not be reproduced without the express written permission of the list administrators. Posting messages to this mailing list grants a license to the mailing list administrators to reproduce the message in a compilation, either printed or electronic. All compilations will be not-for-profit, with any excess proceeds going to the Vanagon mailing list.

Any profits from list compilations go exclusively towards the management and operation of the Vanagon mailing list and vanagon mailing list web site.