Originally posted by Pony
The MII was never designed or engineered for that kind of weight and stress and that now we have failures. Just look at what the front end was on: Pinto's and Mustang II's, hardly a Hi-Po front end design no matter how many coil-over shocks, etc, you throw at it.
Not true. I've heard this argument over and over again and it is based on a lack of understanding of how the Mustang II IFS was designed. People think Pinto and Capri (both light weight cars) but fail to remember that many Mustang II's (Cobra and Mach I) came equipped with the 302 and 4 speed.
A Mustang II equipped with a 302 loaded down with air conditioning put much more stress on the front suspension than most street rods would ever think of. What most people fail to understand is that this IFS was designed to have the engine mounted directly over the crossmember. When it comes to street rods, most typically mount the engine with the front crank dampener at the crossmember. This lowers the percentage of weight the front suspension has to support dramatically. That's why most cars running big blocks or Hemis only need 4 cyl. springs when using a Mustang II IFS. Because the engine is mounted further to the rear, the center of gravity (fore and aft) is moved rearward a significant amount and the front suspension simply doesn't need to support as much weight as it was originally designed to carry.
I know Jon didn't like Gary Heidts letter but Gary was correct. There are literally thousands of these systems (manufactured by many companies) on the road today. When you take into consideration the majority were installed by shadetree mechanics and the fact that some people insist on modifying Ford's original design by eliminating the strut rods, its a miracle there haven't been more failures. Of all the traversing of the internet I've done I have only read discussions of three people who experienced failures. Two were the result of using strut rod eliminators and one was a strut rod bracket that broke off the frame under braking due to poor bracing/welding.
When a Mustang II IFS system is installed properly, using stock Mustang components, including strut rods, they are very safe for all but the heaviest of street rods.