Ford Repair: 5.0L HO Roller engine ford mustang, combustion chamber, ford mustang

Question
Steve,There is alot of theory on running a high compression engine on the street using pump fuel.How much compression can I get away with running on pump gas, 93 octane, and does camshaft grind/cam timing come into play here?And what is the combustion chamber size of a stock 5.0L HO cylinder head and how much horsepower can this head really support with some port work? This engine may be EFI or carburated with auto or manual shift. Any help would be really great. Thanks, TB

Answer
Tony-

  I'd say to be safe I wouldn't go much past 10:1 compression on 93 octane.  You could probably get away with 11:1 if you played with the timing a bit.  Since a full point of compression only equals about a 4% increase in power, it's just not worth risking it in my opinion.  There really is no specific 5.0L cylinder head.  The most sought after heads for Mustangs and other 5.0Ls usually ends up being the E7TEs (a truck head, ironically).  The factory listed specs for the E7's as far as combustion chamber size is 60.2cc-62.2cc.  On a good day with these heads ported to the max, bigger valves, and a radius valve job I don't see them making a whole lot more than 400hp with the right backup equipment (internals, cam/exhaust/intake/etc.).  They're about as good as factory heads got for the 5.0L, but they're still a bottleneck.  Hope this helps.

Steve