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Date:         Tue, 12 Mar 1996 15:06:13 +0000
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         "christian krahforst" <7039ckrah@umbsky.cc.umb.edu>
Subject:      Polished Combustion Chambers.....

Volks,

Well, I finally got started on the new heads (for 1600 DP). They,d been sitting awhile on a shelf at a vw repair shop before I rescued them. Fortunatey they had a coating of corrosion inhibiter. Unfortunately, there were a few nicks inside the combustion chamber and a bare corroded spot on the side of one of the chamber walls. I've heeded Bob (from account temps) Hoover's advice and polished the inside of the heads (i.e., the combustion chamber). What follows is the means by which I accomplished this task. All told it took me about 3 and 1/2 hours.

Cleaned the chambers with Gunk engine cleaning solution to remove the red-brown coating. Noticed on one of the heads, mild corrosion had set in against the wall near one of the exhaust valves. I used a die-makers' riffler file. (The type with ends curved on each end like your extended thumb during a hitch-hiking jaunt) to bring down the relief of the nicks inside the chamber to somewhere flush with the chamber walls. This tool is an excellent hand tool and I'd recommend having one in ones' arsenal of tools. I noticed differences in the quality of the aluminum casting between the two heads. One had a couple of small cavities (near or less than a cubic mm in volume) due to the casting process itself. The chambers are inherently pitted and polishing them removes the discrepancies between the two heads as well as the other benefits outlined in Bob's sermon on this very subject. The polishing begins with the use of a small electrical hand rotor (I used a Dremel tool) fitted with a flexable abrasive finisher -Cratex, extra fine. I used two geometries, a small cylinder type (0.5 cm -1 cm diameter by 3 cm long) or an extra fine disc (2.5 cm diameter). These ware readily on use, and conform nicely to the crevices around the spare plug tap and the interface between the valve seats and the chamber walls. Using the riffler file, I honed down any relief that was the result of tapping out the spark plug threads. Continue polishing until time and satisfaction meet a a happy intersection (You decide). As Bob pointed out, you can polish until .... After reaching this nirvana, chased the Dremel polishing by hand buffing the polishings using Crokus cloth (a very very fine carborundum-based cloth #J135E) to smooth out the polishing traces on the chamber walls. Keep the Dremel tool handy during this procedure as you may want to revist areas that aren't quite up to spec.

Next step, cc'ing the combustion chamber. (I'll be doing this on friday as I've got to leave for NY) :^)

christian f krahforst UMass/Boston 7039ckrah@umbsky.cc.umb.edu

'65 Deluxe


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