# 68 2bbl 400



## 68goatragtop (Mar 19, 2011)

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)


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## 68greengoat (Sep 15, 2005)

Your engine will thank you......


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## 68goatragtop (Mar 19, 2011)

haha ill take that as a yes thank you.


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## ALKYGTO (Mar 29, 2010)

With that compression ratio you should be able to run 87 octane, every penny counts.


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## BearGFR (Aug 25, 2008)

68goatragtop said:


> 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. 

Bear


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## 68goatragtop (Mar 19, 2011)

WEll thank you guys from your input i really appreciate it!


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## jetstang (Nov 5, 2008)

There is no reason to run 93 octain on a 8.6-1 motor unless you have an advanced curve kit in it or are running a bunch of timing to it. If you have it at stock timing it will run just fine on 87. If it doesn't ping, it doesn't need better gas.


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## 68goatragtop (Mar 19, 2011)

oh ok awesome thanks again!


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## Thumpin455 (Feb 17, 2010)

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.


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## 68greengoat (Sep 15, 2005)

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......


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## 68goatragtop (Mar 19, 2011)

ill test it out


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## jetstang (Nov 5, 2008)

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.


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