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Date:         Sat, 21 Jul 2007 11:33:42 -0700
Reply-To:     Mark Drillock <drillock@EARTHLINK.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Mark Drillock <drillock@EARTHLINK.NET>
Subject:      Re: scratch on heads mating surface for cylinders
Comments: To: David Kao <dtkao0205@YAHOO.COM>
In-Reply-To:  <354022.96417.qm@web82709.mail.mud.yahoo.com>
Content-Type: text/plain; charset=us-ascii; format=flowed

There is no way that a pressure or leakdown test can mimic the nearly instantaneous pulse of 1000s of psi that the sealing ring sees every time that cylinder fires. It may leak only occasionally and only when the thermal stresses of combustion are high and the pressure cycles are 1000s of times per minute. Plenty of waterboxers pass the static compression and leakdown tests but can barely make it around the block before blowing coolant out with leaking combustion gases once the engine gets hot.

If the scratch is deep, the head can be machined to remove it. No need for a replacement head just yet.

Mark

David Kao wrote: > The rings (head gaskets) are made of stainless steel. The heads are Aluminium. > I think the rings will not compress. It is the heads that may yield to the > extreme torque. But the torque is only 38 ftlb. It's enough to seal if all > surfaces are clean and flat. Minor scratch may be fine. But if you can not > eliminate the scratch by lapping it seems the scratch is deep. > > The only way to find out is to assemble the engine and do a pressure test > or leak down test. Any leak into the cooling chamber means replacement of > the cylinder head unfortunately. Whenever combustion gas is leaked through > the head gaskets into the cooling chamber it will push coolant out of the > cylinder head and raises the engine temperature by cooking the coolant. > The temperature sensor will feel it. The temperature guage will show it. > > David > > --- Benny boy <huotb@VIDEOTRON.CA> wrote: > > >>Hi Pascal, unless it's very deep and long enough so it larger than the ring >>itself, i would not put nothing there, combustion temperature are so high >>that most product will melt. >> >>That ring/head gasket will compress and sould fill the gap, but again, if >>not to deep. >> >>Ben >> >>On Sat, 21 Jul 2007 13:28:13 -0300, Giasson, Pascal (DNR/MRN) >><Pascal.Giasson@GNB.CA> wrote: >> >> >>>I have some small scratches on my heads, I think they got there from >> >>removing the metal gasket that goes between the cylinders and the heads, but >>not sur as I was really careful when removing them. Anyway I tried to >>remove them with lapping compound and laping them with the cylinders, but no >>luck. Is there a sealant that I can use or maybe JB Weld? Thanks >> >>>Pascal >>>'84Westy >> > > > > > ____________________________________________________________________________________ > Be a better Heartthrob. Get better relationship answers from someone who knows. Yahoo! Answers - Check it out. > http://answers.yahoo.com/dir/?link=list&sid=396545433 >


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