Re: Proper gas for 374 engine

Posted by Rusty O\'Toole On 2011/2/21 17:59:44

The rule I go by is the octane should look like the compression ratio. In other words today's 92 octane gas is for 9.2:1 compression engines.

Naturally this is not a hard and fast rule, just a rule of thumb. But you should be OK if your compression ratio is under 10:1.

If you notice signs of pinging or heat stress you can back off the timing, add octane booster or even a water injection unit. With water injection you can use over 10:1 on pump gas.

Look up the Thompson VitaMeter. It is a water injection unit that is period correct for your car. There are also new models available if you are not stuck on period authenticity.