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what octane to use in 1973 351Q stock

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73stang:
Hello all
I'm new to this forum and would like some info. I've got a 73 mach 1 with the 351 Q code engine. It's untouched except for electronic egnition and a 750 holly 4 barrel. What I would like to know is what octane do you guys feel this engine was ran on back in the day and which do you feel it should run on today? Also, if it matters, in it I have a 1971 C-6 special that backed up the 429 from the factory and 3.70 posi in the rear.

Thanks & have a good one.

Sheriff41:
I run 89 octane unleaded in my '72 Q-code convertible with no problems.  I've replaced the C-6 with an AOD and have a 3.25:1 traction-loc (though I'd like to change to a lower gear eventually).  My dad's '71 Boss 351 only runs well on premium (91 octane).

donnie88:

--- Quote from: Sheriff41 on October 31, 2012, 02:29:49 AM ---I run 89 octane unleaded in my '72 Q-code convertible with no problems.  I've replaced the C-6 with an AOD and have a 3.25:1 traction-loc (though I'd like to change to a lower gear eventually) as shown here.  My dad's '71 Boss 351 only runs well on premium (91 octane).

--- End quote ---


Me too, 89 is the best way to go on this. 

Topless_Horse:
Run the lowest octane your engine will tolerate without pinging.  Run a tank or two of 87 octane.  Does it ping under hard acceleration?  If no, continue running 87 octane.  If yes, go to the next higher octane.  Repeat until there is no pinging under hard acceleration.

You can retard the timing a bit to make the engine more tolerant of the lower octane too, at some small cost to performance.  But your wallet will be happy.

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