1962 Series 62 - Rebuild eng. What grade of Fuel?

[malatu]

What grade of fuel would I put into a 1962 Cadillac? It has a 390 engine in it and the engine was rebuilt 2 years ago. I believe the compression ratio was 10:1. Don't know if the rebuild would have changed the ratio. Thanks!

[96Fleetwood]

My Father runs 87 octane on his '62 Deville with the 390 that was rebuilt 4 years ago. It runs fine with no issues.

[jayoldschool]

It should run hi-test (91 or 93). I run hi-test in my 65 Impala 327, but 87 in my 71 Pontiac. GM dropped the compression in all cars for 71, allowing the use of regular.

96fleet: your father likely has no problems, but really should up the octane. Those older motors with high compression are designed for higher octane to prevent spark pre-ignition (knock). That car will be so quiet that he likely won't hear mild knock (and there is no computer to retard the timing!). If he doesn't push it (big hills, passing, hard acceleration), then he won't get much knock. For the slightly higher price, the hi-test is cheap insurance.

[malatu]

Is 10:1 considered high compression?

[jayoldschool]

Yes. New motors like the LT1 get away with high compression on regular because of superior combustion chamber shape and reverse-flow cooling.