Re: Timing Questions. smooshed valves

[Jason <jtcst20+@pitt.edu>]

At 12:45 AM 12/22/97 +0000, Ryan Schuermann wrote:
>why didn't 
>VW go with a pointy piston or something that would allow the valves 
>clearance at any position of the piston? Is it physically impossible 
>to make such a piston in a 16v setup?

	Good question.  Well, I know (unfortunately from experience) that BMWs
have the same problem... even with their 2-valve per cylinder engines, so
it's not a problem that's exclusive to multivavle designs.  
	Judging by the fact that the 8v doesn't have this problem, it's probably
the fact that the compression ratio is so much higher on the 16v engines.
The stroke is the same, so that means that for there to be a higher comp
ratio, the combustion chamber must be smaller. And therefore, the valves
would need to be further down- i.e. closer to the piston at TDC.  That's
probably why there's not enough clearance.
	How often do you all change the belt?  My dealer recommended 45k
intervals... is that too anal?


	And now for the anectodal story:  (And the reason why Jason is so paranoid
about his timing gear)

	My friend Mike had 60,400 miles on his 325. (A beautiful 1988 with that
lovely 2.7 liter inline 6).  I kept telling him to change the timing belt
at 60k, so one morning he called me up, and asked me to meet him at his
house.  He wanted me to follow him to his mechanic, as he was going to have
his timing belt replaced. 
	I met him at his house, and he went outside to his car.  He turned the
key, and instantly, before we even heard the starter turn the motor over,
we heard this horrible thump and subsequent crashing noise.  He released
the key.  He had it turned for *maybe* 3/4 of a second.
	As much as I hated doing this, we got out a rope and had my shining, brand
new Corolla (Towing capacity 1000lb) tow this 3200lb bitch 18 miles (city
driving) to the shop.  The result (besides taking 50,000 miles off the life
of my clutch..) was a $1500 valve job, as he had bent 6 valves... mind you
his car never even STARTED... and I've heard the Scirocco is even worse-
you'll bend all 16 of 'em if you really get it bad.
	Moral of the Story?

	CHANGE THE TIMING BELT ON YOUR 16v!!

	Jay


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