After reading Jon's post, I would definitely check the injectors for fuel
delivery, possibly the cylinder that failed went lean due to inadequate fuel
flow.

> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com]On Behalf
> Of Jon B. Kanas
> Sent: Tuesday, May 25, 1999 11:37 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Piston Perforation
>
>
> Ken and fellow listers,
>
> I have seen this exact same thing happen to two different aircooled
> engines; once in my 912 as 201K miles and once in a 40hp VW type1 engine
> we had in our shop many years ago.  Harry Pellow (the Porsche 356 guru)
> talks a lot about this in his technical books.  It was a very common mode
> of engine failure seen in four-cylinder Porsche engines during a period of
> the early 1980's when the quality of gas was really bad.  The probable
> cause is predetonation.  You should expect that the other pistons are
> damaged also; your customer should be warned that a whole new set of
> pistons and cylinders may be required.   Pull the other pistons; inspect
> the rings and measure all dimensions carefully.
>
> What happens is that the engine is predetonating (pinging) due to
> overheating, load, bad timing, bad gas or some combination of the group.
> The piston gets so hot that it loses structural intregity. The the rings
> remain intact longer as they are made of a harder metal.  The rings smash
> the heat-softened piston ridges between the rings to bits, the bits
> eventually perforate the top of the overheated piston and get pummeled
> against the head.  These are the pieces that you found in the combustion
> chamber.  In my 912, several pieces were embedded in the head and required
> considerable effort to dislodge them.
>
> As to whether or not VW will cover any of the cost is anybody's guess.  I
> think that it would be worth the try for your customer, but keep
> expectations low.  40K miles is not acceptable wear, but it is well
> outside of the warranty period.
>
> Regards to all,
> Jon Kanas
> Longmont, Colorado
> Cultural Center of the Universe
> 303-678-0658
> kanas@qadas.com
>