Gas octane
Thread Starter
Racer
Joined: Sep 2005
Posts: 399
Likes: 0
From: Fleetwood PA
Gas octane
Now that my 283 270hp is on the road, what is the lowest octane that should be run in it? Or should I just go from high test lower till it pings? Also, it probable matters what it was set up on, I guess.
Le Mans Master
Joined: Dec 2004
Posts: 5,232
Likes: 419
If I remember correctly the 270HP engine is the same as the FI engine mechanically. That engine has a 10.5 to 1 compression ratio. Without the modern control systems that allow for detection of pre-ignition and given the relatively high compression, I would just stick with the high test. Why would you want to try a lower octane, it's not like there is much of a cost differential?
Le Mans Master
Joined: Jun 2004
Posts: 9,015
Likes: 331
From: Southeast Missouri
I think you're on the right track with your thinking, just go down to the lowest octane you can run without significant pinging under load, that'll be the lowest octane you should run in my opinion. Anything higher will be OK as well, just won't be worth paying any extra at the pump for the higher octane.
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
The 270 hp engines used flat top pistons and had an advertised compression ratio of 9.5-1 I think for most/all years. The FI engines used domed pistons and the their advertised compression varied between 10.5-1 to 11-1 I believe.
I don't see any reason the 270 hp engine in stock configuration including timing won't run well on 89 octane fuel.
I don't see any reason the 270 hp engine in stock configuration including timing won't run well on 89 octane fuel.
