Ok 1987 IROC-Z.. 350, 5.7liters
9:1 compression i believe.

We filled the tank with 87 octane, should that be okay?

 

if i were u id just spend the extra 20 cents or so on every gallon of gas and get 92 octane gas if ur going to build a motor with good parts you might as well give it good gas to runn on.

 

but in stock form, is it alright?

 

i put 87 octane in mine... i don't have enough money to spare for the 92 octane. my car runs perfectly. i put higher octane in her when i run into some money though.

 

87 is fine. Thats what I used in my L69 (9.5:1).

And you want to use the LOWEST octane gas that your engine can live on without pre-ignition and detonation problems. The lower the octane, the BETTER the fuel burns, which means you burn more of what gets into the cylinders, which means less buildup of junk in your engine, better mileage, more power, and longer lasting parts.

Use the 87 on that engine and forget about 92+ all together.

 

As long as the motor does not knock or ping during cruise, full throttle or rolling into the throttle then you have enough octane.
A 9:1 compression ratio motor may need 87 or it may need 92 octane. Depends on a lot of other factors. ( combustion chamber design, temperature, air/fuel ratio, timing, egr etc.)

But once you have a fuel with enough octane to prevent pinging
or spark knock, more octane will not make more power or run better. Just costs more.