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Recently I was asking for advise as to where to get my rear springs on my 62 rearched. They are the originals and appear to be in fine condition with the exception that the ride height is lower than should be.Seems that holding up the weight has taken it's time on the arch. My local spring shop which has been in business since the fifty's tells me that he can return them to there original height, however he tells me it is a cold process. I have called Eaton Spring and they also can rearch if the springs are good, but indicated they are rearched a hot process.Who's right? I am certainly far from a expert in this field. Also the car is a 250 hp, isn't there a difference in the spring rating and ride height for a 340 hp? I don't see any repro springs listed by horsepower rating.Thanks for the help.
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Re: Leaf Spring Rearch? Hot or Cold?
Gary
The vast majority of leaf (& coil) springs are SAE 5160 grade steel. It is relatively high in carbon & chromium; it heat treats in a well-behaved way by oil quench followed by tempering at ~850-1000F.
If rearch is conducted 'hot', each spring leaf would require heating to perhaps 1700F, followed by some sort of mechanical bending & fixturing so that the arch is maintained during slow cooling. The previous (factory) heat treat is lost in this process, and each leaf is now in the annealed or perhaps normalized state. If not conducted in a controlled atmoshere or vacuum furnace, decarburization of the spring steel would be likely. Once cool, each leaf would require quench & temper heat treatment to return to the original hardened state -- all the while controlling any distortions that occur during these temperature excursions. The 'General' did this well, and I suppose Eaton could, too.
If conducted 'cold', the steel will work-harden by applying a stress greater than it's yield strength, thus giving the spring a permanent set. Cold working strengthens steel, but also decreases ductility. It would be uncommon, at best, to cold work a heat treated steel part such as a spring leaf.
Personally, I would not do either procedure & would be surprised if your existing arch is not within spec. Fatique is the typical spring failure mode, and is manifested by a surface defect that propagates inward after millions of cycles finally causing a crack, then a fracture. Sagging? Not convinced this can happen in the absense of lots of heat or overpowering load of sorts. You should see other evidence if that was the case. -
Re: Leaf Spring Rearch? Hot or Cold?
spoken like a true metallurgist...
tcComment
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Re: Leaf Spring Rearch? Hot or Cold?
I agree with Jeff and will add that a common surface defect that leads to leaf breakage is a corrosion notch.
You might try new bushings and you can raise ride height with different shackles, but use the AIM procedure to measure ride height first.
All base suspension cars used the same springs regardless of installed engine. The HD suspension and brake package, which I think was only available with FI included stiffer springs.
DukeComment
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Re: Leaf Spring Rearch? Hot or Cold?
The difference in springs between HD and regular suspensions(as Duke indicated) was only a production distinction through 1959. 60-62 used only one option for front and one option for rear springs, regardless of horsepower and other options (including RPO 687)Comment
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The late Dale Pearman explained
to me he always used the hot treatment, as that was the only way to achieve proper arc AND proper hardness, if the springs were cold arched they would eventually re-sag. Since correct grooved C1 springs are not available new, proper springs can only be had by annealing, re-arching, and re-heat treating.Comment
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