Porsche Repair: unleaded fuel, combustion chamber, valve job

Question
I am just about to own a 911 sc '78. This car comes from Germany, and apparently in good shape but there is something that worries me.
The owner (not the german, next one) says it´s been adapted to unleaded fuel (and uses it normally) in Germany but has no catalytic converter.. I´ve seen lots of bills of the reparations that have been done to the car. After hours translating from german, well.. trying, I found no reference to cylinder heads modified or changed.
Then I found one from 2000 in wich they defined the car as adapted to unleaded fuel since 1993. It comes from an authorized service in Germany, and that´s why I tend to believe it really is. That year pistons and cylinders where changed. I´m lost.
Are the original cylinder heads prepared for unleaded fuel..? Will I damage the engine using that fuel if nothing has been done?
How could I know what has been done?

Answer
Hi Juan,

Sounds like a car to have some fun with.  You're right to be cautious...let's review.

In the olden days, espcially here in the US, and then elsewhere around the world, gas was leaded.  The lead-based emissions caused the industries (both oil companies and car makers) to be completely shaken to their core and pushed in another direction.  Only inleaded fuel would be used from then on.

The impact on auto engines primarily affected the cars of that era, the 1940's, 1950's and some 1960's.  The real problem is the valves.  The edges that meet and seal the combustion chamber were actually lubricated by and happy with lead in the leaded fuel.  Those older valves were not lubricated and their edges burned with unleaded fuel.

"Converting the car to unleaded" usually meant a valve job and replacement of the valves to the new materials.

Obviously, the German market must have had leaded fuel much longer than the US, but Porsche certainly knew how to build cars that could run either fuel as soon as the US made its move.

In any event, the valve job is what you should be looking for IF you believe the car was made to run on unleaded fuel rather than both.  As a reminder, the unleaded valves were happy with either fuel.

Your 1993 reference to changing the pistons and cylinders makes me feel the same way you do...the car probably was converted at that point (opr earlier)...So, they replaced the p[istons and the cylinders but used the old heads??? Sounds odd.  But how do we know for sure?

I would sure suggest talking to the people who made that 2000 statement about 1993.  What did they base that statement on.

Short of that, if the car is unconverted and using unleaded fuel now the problem will show up as burned valves and will really affect the compression ratios.  So...What are the compression ratios?  If the car is unconverted is it possible to even but leaded gas in Germany anymore?

Dave