[rotorwrench]

All of the SUMB French engines were army truck engines. Near all of the engines that were purposed for big trucks were relieved. Trucks always needed some help in keeping them from self destructing under hard use. Since gearing made up for the lack of horse power, they needed a change from the stock automobile design to improve long term work performance. Relieving was the fix that FoMoCo engineers settled on since the flathead is so limited with respect to what can be done to it that won't take more away from it's capability to function in order to effect a change. In later years they did more modifications to the heads. The 8RT heads are a good example of a low compression head but when pulling a full load in the old F6, it really made the difference between the roughness of detonation or running smoothly. It was all about warranty consideration and reliability to keep the customer coming back for a new truck every so often. The big F7 & F8 trucks were the first Fords to get the new 317 Lincoln Y-block in 1952 so that they could get away from the flatheads. Even the Lincoln 337 wasn't up to the task well enough for the big trucks so it was finally dropped for the OHV engines.

Relieving was such a mainstay for the old aftermarket aluminum heads with crow foot chambers(that are still available to this day), that it's been viewed by so many to be the performance way to go that it is doubtful that there will ever be an agreement between folks that are all for relieving and those that don't use large reliefs.

Barney Navaro was one of the guys that played with the bent 8 long after most folks were adjusting there rocker arms. He preferred a small relief that basically just made a smooth ramp from the valve seat edge to the edge of the cylinder wall. After all those years of both seat of the pants experimentation and using science to effect meaningful changes, this was what he settled on.