Well assuming you mean after the 20 minute break in with SAE 30 and proper break in lube etc..........I would stick to 3000-5000 mile oil change intervlas. First you have not one carb but two so that is a chance for twice the amount of error to creep in with requard to air fuel ratio.......So oil dilution is still going to be an issue even with a modern oil. Now if it was fuel injection with opena nd closed loop operation it would be a different ball of wax. Carb's are notthe best set up when trying to keep an oil in good shape....If it is not going to be a daily driver you need to invest in lots of fuel preservative because most fuel inthe USA goes rancid in 1-3 months because they do not put that many additives in it to keep it longer becuase a study they did towards the end of the 1970's found that most people stored fuel for less then 3 months so they cut back drasticly on antioxidents. Nothing like having a preety muscle car with rotten nasty petro in the tank! It is not like diesel fuel that still gets a lot of additives for storage. Nasty fuel is the most common problem I run into on muscle car's and people that own lots of 2 cylinder antique tractors that only run once in a great while for shows and parades etc.....
So 15W40 changed every 3-5k or every 6 months which ever comes first is a good idea. If you find it is winter and you want to take her for a spin just preheat the garage and start the engine after a couple hours in a warm garage and the 15W40 will turn over like it's summer out.You can also put one of those small catalytic heater that colman makes that screw on to a green prropane cylinder and stick it under the oil pan.
So 15W40 changed every 3-5k or every 6 months which ever comes first is a good idea. If you find it is winter and you want to take her for a spin just preheat the garage and start the engine after a couple hours in a warm garage and the 15W40 will turn over like it's summer out.You can also put one of those small catalytic heater that colman makes that screw on to a green prropane cylinder and stick it under the oil pan.
