I recently purchased a 1970 big block (454/390 - LS-5) and was wondering what type (octane, lead, etc) of gasoline do I need to use. Do I need to add any additives for octane level or lead, etc.? The car has very low mileage and is all original condition. I don't just wanta to put anything in it but rather want to make sure I use the correct gasoline so I don't cause any damage. Incidentally, I only drive it around the block once or twice per month.

Congrats on your new toy!!!

Anyway that you can find out what the previous owner was using for fuel? If you have the orginal valve seats you will want to use leaded fuel or a lead additive that contains teflon. If the seats have been replaced with hardened seats then you can run the unleaded fuel with no problems. The good news here is that, even if you don't use leaded fuel or the additives, as often as you drive it it would take a very long time to do any real damage. As for octane, I would use 93 octane as a minimum. Higher octane levels are usually attained by mixing 93 octane with a racing fuel (usually 100 to 112 octane). You can calculate the octane by using a weighted average (I can email you my spreadsheet for this). Using octane levels between 95 & 100 will allow more advanced timing (noticably more power), and a smoother running engine in general. You can probably run on 93 octane but the engine will probably have to be "de-tuned" (timing is retarded) to do this. For more discussion check out a long running thread titled "High Octane Fuel, Anyone??" in the Fuel, Emmision, & Exhaust forum.

PS: these cars run a lot better if take them for occasional long drives. Its a heck of a lot of fun too!!

Thanks for the detailed reply. I will take your advice on the fuel as well as taking that occasional drive.

This is a great time of year for that long drive since your feet won't burn off from the engine heat!