According to the documentation I have, the head was changed along with the pistons. The precombustion chambers were made smaller, and I'm guessing that the spots in the head where the precombustion chambers go into had to be altered slightly to match. The exhaust valves were also made slightly thinner, BTW, to accomodate the taller "B" model pistons, and there were also fuel system changes (notably different injectors, and the IP was changed internally to adjust the timing schedule).Agnem said:Due to the pistons.... not the head.
If you have the 6.9 Liter Diesel Engine Update (published by Ford in October 1985) document that was posted on TDS a couple of years ago, take a look at the Appendix (the 4th file as they were originally presented), pages A1 to A4. If you don't have them for whatever reason, let me know and I'll be happy to either E-mail them to you or put them up on my server and make them available for download. It's a total of 4 .pdf files that come up to 5.15 MB in size.
I know it's a moot point for this thread, since GreenBeast looks to be dropping that 7.3l in this truck, but I thought I'd at least post the info for posterity...