56' 331 Hemi - octane gas?

Discussion of the 331-354-392 HEMIs.

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flynnstone
Posts: 3
Joined: Fri Jun 13, 2014 11:38 pm

56' 331 Hemi - octane gas?

Postby flynnstone » Thu Jul 17, 2014 10:03 pm

I just picked up a 28 Ford with a 56 331 Hemi which originally was in a grain truck. It's running ball&ball carbs and the truck intake.

Just curious what octane fuel is required for this motor?

George
Posts: 636
Joined: Wed Aug 25, 2004 4:12 pm
Location: Fl

Re: 56' 331 Hemi - octane gas?

Postby George » Fri Jul 18, 2014 7:45 am

According to this site it is officially 7.5 C/R, and some hemis, when measured, have measured up to close to a full point lower than posted C/R, so it could be anywhere from 6.6 to 7.5. Should run on 87 w/o any problems. If you're where Sunoco sells 85 it would probably be good on that.

Rob
Posts: 208
Joined: Thu May 05, 2011 10:15 pm

Re: 56' 331 Hemi - octane gas?

Postby Rob » Sat Nov 22, 2014 3:31 pm

It would run on 79 I bet. lol

George
Posts: 636
Joined: Wed Aug 25, 2004 4:12 pm
Location: Fl

Re: 56' 331 Hemi - octane gas?

Postby George » Sat Nov 22, 2014 7:58 pm

Rob wrote:It would run on 79 I bet. lol
Probably. hemis can run a point higher C/R on the same octane as a wedge, so what octane would be needed on a 5.6-6.5 wedge engine?


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