Hans

Looking through the spark plug holes with the piston down might show the valve imprint in the piston surface if the both met.
Used pistons will have an darker surface, the imprint might have left fresh marks.

Leak down test can be done without the belt on it.
Set the pistons half way and lock the crank.
Connect up air and rotate cam to close both valves as required.
TakeCare

mumzer

will a car with bent valves even idle properly?!! anyone have any first hand experience?

Dave951M

No, bent valves will not idle correctly, and running it any more than necessary may even lead to more damage. Having repaired these in a number of Fiats, one way we used to check, this is with solid tapets, was to put the pistons even with each other and gently turn the cam. You could feel each resistance as the lobes moved. Any "weak" spots usually indicated a problem. Then the leak test, then the head removal, then the valve job, for reassembly, reverse. As for how many valves were bent, play the lottery. I saw one once where the belt failed at 7k rpm, no bent valves, none. I also saw one that failed at idle, 7 of 8 got whacked. At least on these cars, we aren't cursed with the dreaded "auxilary shaft error". If the aux shaft is out of time on a Fiat, a lobe that drives the mechanical fuel pump will hit the crank and blow out the side of the block. Back to Porsche, try the leak down and you'll know really quick just where the bad ones are.

Leakdown test- I like Hans' method, very easy to do.