IDIBRONCO
IDIBRONCO
Wow. That's an interesting question. I haven't even been able to find one that would mill the topsGot a question for someone who might know... How big of a deal would it be to turn down pistons?
Just thinking out loud here - what if you bored a 6.9 .030" over, then took a set of cheap used 7.3 pistons(stock size) and just turned them down to the right 6.9 spec.
You'd have to re-cut the the ring grooves... but that might not be as big a deal as it seems.
I don't know whether or not they were the same casting, but other than that, I just don't see why anyone would want to bore a 6.9 to a 7.3. It would still have the 7/16 head bolts so you still couldn't use the same amount of boost as you can with a genuine 7.3 and still keep the reliability.Oversize pistons for the 6.9 are not hard to find, nor are they particularly expensive compared to standard bore 7.3 pistons.
I will also take issue with Russ about overboring the 6.9 to 7.3 just as a matter of practice. I have been in the casting industry for almost 40 years. If Ford had made new cores (and patterns to make those cores), why would they screw up and make the water jacket cylinders the same size as the 6.9? The only possible answer is that they did not make new patterns, just used the 6.9 ones, overbored them and maybe improved core location. There is not a real good explanation to go with the theory of new patterns for the 7.3, considering the carnage that cavitation has wrought. Teh cast wall thickness was just too thin.