Opinions might differ. I use a lead substitute available in any FLAPS (friendly local auto parts store). Others might say its OK to run unleaded without the substitute. You need to consider if the engine (valves) has been rebuilt or replaced in which case there should be no problem. Why not just ask the PO what s/he used? - DB
Shouldn't be a problem. Chances are very good that you're engine has had head work done in the past 30 years since leaded gas was phased out, and no-lead friendly valve seats were installed.
The only purpose for leaded gas was to lubricate the seats. If you know for a fact that you're engine is original and has never had a top-end rebuild, there are lead additives available at the local FLAPS. (Maybe not in California, though.)
Even if it still is the original engine and heads, it will run without any problems and without accelerated wear. If the heads still have the original valve seats, they will have been work hardened by the years or hammering of the valves on them. In addition, there is a "memory" effect on engines that have ran on leaded fuel for a long time, which means that you can switch to unleaded and the seats will still be lubricated by the lead deposits from their prior life. If the P.O. ran on leaded fuel, you might have to retard the timing a bit. If you notice that the engine is pinging when climbing hills at full speed on a hot day, then you should retard the ignition timing for 1-2 degrees.
Anyway, you should check your valce clearances regularlly, especially for the exhaust valves, to determine if the valves are sinking in the seats, or if the valves are stretching (sign that they will break soon).
I ran unleaded 95RON for allmost 100000km the past 6 years (most of them was highway driving), with no problems with the original 1967 (1300) heads. When I had the engine disassembled (due to a spun rod bearing), the wear on the valves and seats was normal.
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