DANIEL TINDER (12/10/2012)
Ted, Would it be safe to assume that, exact static CR #s notwithstanding, if it runs ok on pump gas without having to retard the ignition, a properly prepared/assembled motor with good unposted "G" heads should not (under ordinary circumstances) suffer gasket failure?
If presented with an engine who's static CR WAS borderline, wouldn't the simplest cure (as opposed to tearing it down and starting over) be merely to retard the cam timing a bit and lower the dynamic CR? You would then have the additional "easy" adjunct of retarding/fine-tuning the distributor a tad if absolutely necessary?While detonation is a key player in the head gasket failure in un-posted heads, the actual head deck thickness is still the major consideration. The un-posted G heads simply have thin deck surfaces as delivered from the factory and as a result there is a balance point between the compression ratio and amount of head mill before gasket failures will be prevalent. A less amount of head mill and more compression or more head mill and less compression is the balancing act that must be played with the un-posted G heads. But ultimately there is a point of no return where excessively milled heads simply do not have enough internal support in which to hold the head gasket firm regardless of the compression ratio. So with that taking place, retarding the camshaft would not help. The Ford manual is pretty specific in limiting milling of the ’57 heads to a maximum of 0.010”. Once the heads became posted, the rules changed and more aggressive milling or increases in compression ratio could take place with less chance of head gasket failures.
Un-posted G heads can have posts added to cylinders 1, 3, 6, & 8 which will give these particular heads another shot at being used successfully with higher combustion pressures or save a set of heads that have already been milled.
Lorena, Texas (South of Waco)