[BOB MILLER]

I'm rebuilding my A code 1965 mustang GT. I just got it on my friends death. Should I use two barrel pistons to make it more driveable on todays gas? My machinist says I would have to use octane boost to use the car on a regular basis with 4 barrel pistons.

[Dave]

From looking at one of my good reference books, I would sure agree with your mechanic. The 4V's were running 10 to 1 compression while the 2V's were at 9.3. Good luck!
Dave

[rodbender]

I run my bike ( Harley stroker) at 10:1 (89 + octane)and my brother runs 10+:1 in his 69 Mach 408 however premium only. I've experienced no detonation. I wonder if location has anything to do with it? Okay, after looking my 65 shop manual ( page 8-50), codes A,C,D were all 9.0:1 A & D of couse being the 4bbl. The hi-performance sported 10.5:1 and the good ol' 260, 8.8:1. The shop manual designates chamber volume at 52-55ccs. But then you go to page 8-82 and you get the figures Dave has for the compression.

[RedGTvert]

I don't see any reason you would need to run octane boost on 10:1 compression if it is tuned properly. You will probably need to run premium though.

Is this going to be a daily driver?

[yellowtonka2]

10:1 on premium can easily be done with out any issues my 289 is right around 10.5:1 and it does well on 93 octane no detonation

[Cobra6]

I rebuilt my '65 A - code with the higher compression stock pistons, and it runs great - but I do have to run 93 octane fuel.

[dodgestang]

Christ, I run just shy of 11:1 in my 410 in my 65 fastback and it runs just fine on 93. Even runs the quarter in 11.5 on 93!