Engine mount washers?

When I bought my 70' 911 T, the washers for the engine mounts were with convex side down.
It looked from the paint etc... that it was the original factory setup. When the clutch was replaced by a mechanic I truly trust, I noticed right away the washers had been installed the other way, the convex side up. When I ask about it, he told me there had been a note from the Porsche to turn them over. What do you think of it?
Thanks. Thierry

I have replaced my engine/transaxle mounts, and they were 'convex up' from the factory and that is the way I put them back on. The factory engineers seem to have been obssessed with noise and vibration levels in the cockpit for the last 25 years. My best SWAG (scientific wild-ass guess) is that turning those washers over might provide a slight bit more vibration isolation, but I'm not going to turn them over, because I have considered putting on 'sport mounts' or even solid mounts, as I have 100% Poly-Graphite suspension bushings, so you know why I am not too sympathetic to the factory's 'quietness' obsession!

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Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 02-19-2000).]

Thierry:

This subject was covered earlier, but once again, some observations:

1. Either way is no problem. My 1983 911SC was delivered to me at the factory with the concave side up; i.e., you could see the concavity under the bolt. This is the "stock" setting.
2. When I got serious about track and autocross events, the "trick of the day" was to change the washers to convex side up; i.e., just turn over the washers.
3. Warren is right, with the convex side up, there is more compression to the rubber, and therefore, the engine will twist less before it is restrained by the engine mounts/body.
4. Is this worth anything other than just minor, perhaps unmeasurable, vibration? There is no real answer. Only your common sense can dictate which way is best for you.

Therefore, if you wish to try to extract the maximum performace from your total package, do all the little things which might add up, includiung this change. Otherwise, if you are more concerned with the total package of a well-engineered auto, leave them whichever way you found them, or whichever way your mechanic suggests.

The difference is very very minor....Andras