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Date:         Fri, 1 Jan 2010 12:44:21 -0600
Reply-To:     John Rodgers <inua@CHARTER.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         John Rodgers <inua@CHARTER.NET>
Subject:      Re: 1.9 Compression?
Comments: To: Stephen Cebula <sfcebula@YAHOO.COM>
In-Reply-To:  <607852.16231.qm@web111414.mail.gq1.yahoo.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

I csan only relate some things done on opposed 4 cylinder and 6 cylinder aircraft engines, as this is what I have worked on most - but their resemblances to the van engines - both air and water - are uncanny.

On the aircraft engines - we always ran the engine to get it to operating temperature. THEN, a differential compression test was run. Same as a leak down test. The engine was turned so the cylinder was at TDC on the compression stroke, and with a regulated air supply, and a dual gage regulator - compressed air was pumped in to the cylinder. Once loaded, the gage regulator was closed, and the cylinder gage was watched for several minutes and compared to the regulated pressure gage. The cylinder pressure would nearly always be lower slightly or a lot, depending on wear - than the regulated pressure.This gave a really good comparison. This was done on each cylinder. You want to do this on the engine while at or near the operating temperature - because all the fits and clearances will be at optimum at those temperatures. This is where your engine runs, so it needs to be tested where it runs.

Checking end play is also important and checking crank wobble is also important. This is a bit more problematical, because there is a pulley mounted on one end, and the transmission blocks access on the other. But typical check of crank wobble is usually done with a dial indicator.

At the minimum, you should definitely get that leak-down test , and do it at operating temps.

Regards,

John Rodgers Clayartist and Moldmaker 88'GL VW Bus Driver Chelsea, AL Http://www.moldhaus.com

Stephen Cebula wrote: > I'm looking at an 84 Westy on Saturday. The guy want $6500 for it. It looks really clean but has 170K on the original motor. He sent me a copy of the compression test he had done in 2007 when he bought it. It shows 140psi on all 4 cylinders. I'm planning on having another one done when I go look at it. What would be an acceptable number? I've heard 145-190. > > Thanks, > Steve > > > > > >


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