Using a 6.9 head gasket on 7.3

[icanfixall]

Some of you know the 6.9 head gasket has a couple of coolant passages that are open compared to the 7.3 head gaskets. This is why both Mel and I feel the 7.3 engines run hotter than the 6.9 engines. I also feel the engineers had to heat up the heads so the 7.3 engines could pass the smog rules for that time long ago. Here are some pics showing the differences. The gasket on the top is of course the 7.3 and the bottom one is the 6.9... See the small piece of gasket material that did not punch out completely on my finger. I suggest checking the gaskets very closely for just this problem. These are Fel Pro gaskets too.

 

[PwrSmoke]

Just to add relevant material to this, the September '87 Ford 7.3L Diesel Book (CGE-429) which highlighted the changed and difference from the 6.9L says:

"The cylinder head lower corner coolant passages on the 7.3L have been plugged. This change is introduced to eliminate lower corner gasket coolant seepage during cold start engine warmup. In accordance with this, the mating passages in the cylinder block have been plugged as well"

That is the only mention of why this was done, so it wasn't because of any particular design feature or cooling advantage, just to eliminate a seepage issue.

Further:

"Fire ring I.D. increased to 4.22 inches from 4.14 inches on the 6.9L. This is a result of the larger bore diameter of the 7.3L."

Didn't somebody measure the fire rings of 6.9 vs 7.3L and find they were the same? My question is: If the same, was it the larger or the smaller dimension?