Another couple newbie-type questions! As a little background, I had a 1971 Cutlass convertible (green) back in the early 80's, sold it for our house fund after I married, always told my wife I wanted another one when I retired. The retirement happened last year and the 1970 Cutlass Supreme convertible happened this past weekend, after a long search.

I of course know the previous owner, and he knew the one before him, but after this all I know is that it was purchased new at Blanchard GM/Oldsmobile dealership in Weston, Ontario, as it came with the owners manual/packet. What is best VIN# search source to possibly find out more info as to where this car has been after it left Canada? It doesn't make a whole lot of difference, I suppose, but just curious.

The second question-the car was restored at some point-I have no records but the gold paint still looks new on the engine, the bay is really clean, it runs strong and shifts smoothly and the Matador red paint is still shiny, and interior is too good not to have been redone.. I know the OEM motor was built for leaded gas, and I would assume that the valves and seats would have been changed out to hardened ones for unleaded gas during the rebuild, but what is best way to know for sure? The previous owner ran unleaded, but he didn't drive it but 3500 miles in five years. I am planning on running premium but wondering if I should use a lead additive also?

I won't be driving the car much either, but will definitely be putting more miles on than previous owner.......

 

There are plenty of fuel discussions on this site. The results are that these cars run fine on unleaded and hardened seats are unnecessary unless you are racing or doing heavy towing. Additives are not needed but some people insist on using lead replacements, I don't.

 

I don't think there is such a thing.

 

Never ran into a rebuilt 1960s engine that needed the additive...

My experience with the lead substitute alone was that it bothers the original untouched engine. In the sense of making it ping and have run-on more than without. If you try one or want to go that route. Get an octane booster that includes a lead substitute additive. But I doubt you need it. That's for an original non-rebuilt high-compression engine that doesn't have its timing pulled back.

If your 1970 Cutlass Supreme Convertible has the lower compression 350, it will still appreciate the premium. My 67 330 2bbl did not like any gas under 91 octane. But again, that's a non-rebuilt engine thing...

 

Also note that the pistons used in the rebuild make a difference. Aftermarket cast pistons are typically short on compression height, so even with the replacement 6cc dished pistons for the 10.25:1 compression engine, the actual compression ratio will be well below the advertised number - like around 9:1 or so.