Thread: Bought a Fat Man M II. What now?

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Early this summer I bought a Mustang II FatMan Stage III hub to hub kit for my '34 roadster.

Since the bodywork took more time than I thaught it would (surprice! ) I haven't done anything with the frame and suspencion yet.

During the last months' however, I've heard quite a few bad things about Fat Man Fabrications. The crossmember is of a poor construction, the overall quality is not what it used to be etc etc.

Since I have this kit ready to use I will stick with it. But are there anything I can do during my chassiswork to avoid problems? (Yes I know about following the mounting instruction and think before I weld. Probably think a lot during the mounting, I suppose.)

Do you guys agree on what I've heard, or have I just paid attention to people who don't know what they're talking about?

Sorry you didn't check for opinions first, but that's water under the bridge now.

Personal opinion here, others may differ. I've never been fond of the clunky look of the FM crossmember stuff. More substantively, if yours is like the ones I've seen in the past I don't like the smaller frame contact surface of the lower crossmember section. I have a strong affinity for Heidt's stuff, and like the way it wraps fully up the inside of the frame rails to the upper suspension "hats". I think it reinforces the chassis better as well as having a better "look". The upper shock mounts on a Heidts are a nice conical shape, the FM looks like a piece of pipe with a washer welded on. Probably not much difference structurally, but again, the Heidt's appears to be more professional.

If you've got any concerns about whether or not what you've read about the construction quality being diminished it would be a good idea to take the pieces to someone with equipment to check for cracks, week welds, etc. Suspect welds can be redone as long as the adjoining metal is intact.

Ok. Good to have some others opinion.

To me the welds look nice and the overall impression of the kit is good. But I'm just an amateur and there are no hot rod builders here were I live.

I've also read about problems with the rather narrow crossmembers ability to support the lower A arms during hard braking. This problem is supposed to excist not only on the FM crossmember.
The braking forces will pull the A-arms backward, of course. From a side wiew all the aftermarket M II crossmembers are narrow, so the forces can either bend the lower A-arm mounting bolt, or even worse, cause crossmember brekage in the lower A-arm mounting hole area.
On my FM kit a pipe with a triangulated piece of metal is encosed. It is supposed to be welded in on the rear side of the crossmember to fill the gap between the crossmember and the "legs" on the A-arm.
The other manufacturers must have similar solutions, since none of the aftermarket crossmembers are wide enough to fill the gap between the "legs" on the A-arms.

But according to some people this is not enough.
Have you heard about this?
(Excuse my bad technical-english language.)

I'm not saying this is a fact. I've just read about it in some other hot rod forums.
But then again. Some people seems to have their biggest task in life to write bad things about FM, Heidt's, TCI and the other well known manufacturers.

I'm with Bob on the Heidt's stuff, IMO best there is. Even on the Heidt's I add a peice of 1" DOM tubing to the inside of the crossmember with the lower A-Arm bolt going through it, then a couple of small triangular shaped gussets on the inside tubing much like the gusset on the outside peice. Once the inner tubing is in place, I fabricate a peice of 10 ga. to cover the opening in the lower crossmember on the ends and tie it in to the lower side of the frame rail. A friend of mine put a Fat Man's in his '34 Plymouth, used the same procedure on it. He's been driving it for about 5 summers now with no problems.

Originally posted by staleg
But according to some people this is not enough.
Have you heard about this?

The internet is a wonderful thing. Yes, you and I have probably read the same posts, or some repetition of them.

Dave's suggestions are certainly a wise modification if there's any concern. That being said, I have to wonder about some of this theorizing. The lower bolt, for instance, is fully encased in the through tube, unlikely that it would bend without bending that whole tube structure. In a severe braking situation as is supposed in the noted fear stories the forces against the lower control arm would be to the rear, and if the x-member were too weak, rotating upward. Going to the rear would have to "fold" the gusset you described first, and then the crossmember structure. It's conceivable I'll admit, but just doesn't seem likely. In my personal experience, limited I will admit, I've probably known maybe 100 cars with this kind of setup. Never once have I seen such a failure. I think I stay as tuned in to the hobby as much as most folks do, and I've never heard of this type of failure ever happening in reality.............only in theory. Given our surplus of blood sucking lawyers, and the willingness of juries to award rediculous sums of money, if any real world examples of this type failure existed, successful companies such a Heidt's would be HIGHLY motivated to develope a cure.

If there are any real examples of the failure imagined I'd be curious to know if it were really the design of the lower arm mount, or the surrounding structure or workmanship of the installation that may have been more at fault.

I'm with you, Bob. I've really pounded on some of my cars with IFS fronts, including "hot lapping" a '34 coupe on a dirt track late one Saturday night.......but we won't get into that story here......

I would bet that the majority of component failures are actually the result of poor welds and/or poor worksmanship.

I can't imagine a braking situation that could possibly break the lower A-Arm mounting, I guess he was running a lot stickier tires then I have ever had on a hot rod. However, I have seen just a normal road bump break a "bird poop" weld, or one that was ground excessively in the name of beutifying the chassis...... If these peices are susceptible to breakage, I'm just plain lucky, I guess........

Is it possible on your installation to add another bracket off the frame so that the rear a-frame pivot is held in a double shear?

Originally posted by halftanked
Is it possible on your installation to add another bracket off the frame so that the rear a-frame pivot is held in a double shear?

I've seen that suggested before. Again, it would be "cheap" insurance though maybe unnecessary. Don't know what you're picturing in your mind, but for the sake of discussion, a single "strap" wouldn't do it, it would need to be a two sided deal gusseted to the rear.

I too would seriously doubt that you could break that gusset under pavement braking. If there is any cause for concern you could always go with a standard Mus II lower arm and a strut rod.
IMHO if any front end is reinforced like Dave suggested it would be supper strong.

If you go to www.hotrodders.com They have a whole thread devoted towards the mustang 2 front ends. Both pro and con.
There is a lot of good and valuable information. Its under the suspension title.
Hope this helps you.