Trying to get bent...

[Michael]

The strut housings on two corners of my ’78 280Z’s suspension are misaligned relative to the spindle castings. That is, the projected angle between the strut centerline and the plane of the brake rotor is off by about 2 degrees from the specified angle (~14 degrees vs. ~12 degrees). The strut housings are not bent; they just meets the spindle castings at the wrong angle. This is at the driver’s-side front wheel, and the passenger’s side rear wheel. The result is an incorrect camber at those two locations. Neither the unibody nor the various suspension linkages are at fault.

 

I have not been able to source used strut housing assemblies. So, I would like to correct the ones that I already have. To do that, my plan (actually, the original idea was Pete Paraska's) was to locally heat (with an oxy-acetylene torch) the strut housings right at their base, where they enter the casting. Then, to insert a pipe or breaker bar into the strut housing, and bend it back. The issue is, what happens to the temper of the steel, and how to restore it. And whether the bending procedure can be done successfully. No local shop wants to undertake this job; the mechanics in town feel that this idea is hopeless and that the only reasonable option is to scrap the faulty strut housings and find new ones.

 

I am looking for suggestions. Is the above-mentioned approach reasonable? Any ideas as to who might be able to do it? I don’t have an oxy-acetylene torch, or the appropriate fixtures to hold the casting in place.

[denny411]

I`ve got some struts still on a 77 280 that may be of use to you. If mine are misaligned as well, I have a torch and a 20 ton shop press that might come in handy.

Email or call me and maybe we can get together.

[Guest Anonymous]

Denny offers some good advice.. get his struts... or figure out a way to bend with a press and forget the heat....OK.. you heat the tube up and bend to correct the 2 degrees. How do you know when you have reached 2 degrees? Which direction do you push to? Plain low carbon steel can be hardened not only by dipping in water (Quench) but exposed to cool air (Quench) after heating anywhere to 1700 to 1900 degrees max. Heat the metal to only 1200 degrees and it will get no softer (annealed). Unless you have done this for years, there is no way to speculate what temp you are at by the orannge red or cherry red color. I pulled kife blades out of a kiln by use of a pyrometer many times and from that experience never could tell temperature by the color of the metal only by the dial on the pyrometer. Heat the strut tube up to "red" and bend. Have a helper handy to cut the oxygen to the torch as the red glow is almost disipated to cover the heated metal with a gas flame to cover with black soot. Hopefully this metal treatment and slow cooling will restore the temper back to the metal tube without much damage ... do not get the spindles hot even to a straw color.

[johnc]

> The issue is, what happens to the temper of the

> steel, and how to restore it.

 

If you get it hot enough to bend easily you're probably annealing the steel. All temper is gone and your back to the strength of the base metal.

 

I don't know for sure what metal is used in the strut tubes or what heat treating process they might have been subjected to. But I have cut and welded a number of them and they appear to be a low carbon steel.

 

Your best bet is to throw those away and replace them with a known good used set.

[Guest Anonymous]

John I would suggest the tubes are of a high carbon "quality" similar to bed frame rails (spring steel) evidenced by the complex spark pattern from abrasive grinding. Agreed ..toss em.... (Bed frame steel is very strnng,light and very weldable but has memory to return after deflection)

[denny411]

And I thought I was the only one who had to weld my bed frame rails

[Michael]

Update on the bent strut situation - Denny and I looked at several sets of front struts from parts cars. All of them had the asymmetry that I mentioned in my first post in this thread, though one of the non-parts cars looked to be symmetric, from the symmetric spacing between the widest part of the tire and the nearest point on the spring coils. My impression is that the tolerances on the steering angle of the McPherson struts used on Z’s is in general shabby – far worse than what’s allowable in the specs. By the way, from what I have been able to discern, there is no built-in provision for such an asymmetry. The same range of steering angles is specified for both passenger and driver side.

 

So I decided to reassemble the struts that I have, and to wait until a nicer pair comes along. Unfortunately parts cars (or any Z’s for that matter) are tough to find in the Midwest.