Pontiac GTO Forum banner

1 - 12 of 12 Posts

·
Registered
Joined
·
50 Posts
Discussion Starter #1
I have one of these and i was jut wondering if it is possible to run 93 octane gas safely in this engine since it has a 8.6:1 compression ratio? (i am a little new to restoring)
 

·
Super Moderator
Joined
·
5,751 Posts
I have one of these and i was jut wondering if it is possible to run 93 octane gas safely in this engine since it has a 8.6:1 compression ratio? (i am a little new to restoring)
Yessir. It's always safe to give an engine MORE octane than it "needs".

However, the reverse is the path that leadeth to (engine) destruction. :D

Bear
 

·
Registered
Joined
·
668 Posts
No need for 93, 87 will work fine just like Jet said. Its an added expense that isnt necessary. The only way it will ping is if it is full of carbon or oil leaking past the rings/valve seals. Ive run 9:1 455s on 87 without issue, so a 400 at 8.6 is no problem.
 

·
Former Moderator
Joined
·
3,523 Posts
I don't know. I have a low compression 455 that seems to run much better on 91(best we have here) than it does on 87 and better yet when I run an octane boost with the 91. The motor was rebuilt right before I bought it. Bored .030 with a mild cam. No specs on the cam.

I guess my recommendation would be to run 87 and 93 octane and you decide what makes it run the best. Keeping in mind that 93 octane will not hurt a thing except your wallet......
 

·
Registered
Joined
·
3,376 Posts
A low comp motor that has been optimized, timing and advanced curve kit loves 93 octane. Dialing the timing up to the max will require high octane gas as the higher the octane the slower the fuel burns, thus the longer the fuel burns in the cylinder, the more power the engine will make. I time my cars by ear/feel, turn it up till it pings, then back it off a smidge. Low octane fuel burns faster than high octane, so you only need high octane if the low octane is causing the fuel to pre-ignite and try to send the piston back down in the cylinder before the piston gets over the top.
On newer cars that require 93 when you put 87 in them the computer pulls initial timing out to prevent detonation, but also reduces power out put. So, if you don't beat on your car lower octane is fine, also, on old cars dialing the timing back so it doesn't detonate is fine, it will just be down on power.
 
1 - 12 of 12 Posts
Top