Coil Spring 6cyl vs. 8cyl

I read that a factory supported SC/Rambler drag vehicle used, among other upgrades, six cylinder front springs with factory supplied bottom shims to restore stock height. What would be the advantage of that?

While this sounds sensible, in AMC land, where a 6 weighs nearly as much (if not more) than a 1968 and up AMC V8, and has more of its mass ahead of the front axle than a comparable V8 car, I really wonder if this is true.

I would think it more likely to be helpful if you changed springs across chassis types, for instance, it is possible that a 6 cylinder Gremlin spring would be a substantially different rate than a V8 Ambassador spring of similar vintage.  I seriously doubt there is much difference if any between a 6 cyl Gremlin and a V8 Gremlin spring.  All you need to do is look at a current NAPA spring catalog and you'll find just one part number for both.

I'd really be interested to know if anyone on the forum has AMC factory details of spring rates for various chassis.  I do remember when the Concord was launched that AMC made a  big deal about how the springs were 'computer selected'.  I don't doubt that was true, but I wonder if the 'computer' was not much more than a hand held calculator.... ;) 

jackdk wrote: 73Gremlin401 wrote: While this sounds sensible, in AMC land, where a 6 weighs nearly as much (if not more) than a 1968 and up AMC V8, and has more of its mass ahead of the front axle than a comparable V8 car, I really wonder if this is true. I would think it more likely to be helpful if you changed springs across chassis types, for instance, it is possible that a 6 cylinder Gremlin spring would be a substantially different rate than a V8 Ambassador spring of similar vintage.  I seriously doubt there is much difference if any between a 6 cyl Gremlin and a V8 Gremlin spring.  All you need to do is look at a current NAPA spring catalog and you'll find just one part number for both. I'd really be interested to know if anyone on the forum has AMC factory details of spring rates for various chassis.  I do remember when the Concord was launched that AMC made a  big deal about how the springs were 'computer selected'.  I don't doubt that was true, but I wonder if the 'computer' was not much more than a hand held calculator.... ;)  _______________________________________________________________________________ Just for instance. I am looking at my 1969 TSM on page 32 & 33 of section 12. It has almost 2 pages of springs listed for the AMC line. Wire Dia.   Load Height,  Rate lbs per inch, and they are color coded per app.  They had light, heavy, WAC (withA/C)  springs for 6 cyl, springs for 8 cyl. I see about 10 or 11 different springs  listed just for 1969 models...

OK - this is the kind of info I'd enjoy seeing.  The question in my mind would be just how big a difference in spring rate there is between the 6 and V8 applications, and if there were meaningful differences (remembering the original poster's question) between the two, or within the groups.

I wanted to lower the front of my American , The original springs were shot, when I took then out one of the springs was almost 4" shorter then the other, Anyway I took out the 6cly.and put in a 401, the shop that ordered the springs said there were only two available, V-8 and 6 cyl. with air cond. so I to thought that the V-8 would be much heavier, I got the 6 cyl, springs and the car looks like an old gasser with front end way up in the air and no bounce, I can't even get the shocks in they are so far extended. Has any one cut front springs to get the correct height ?

First and foremost the discussion is covering a 43 year old car that aftermarket has been supplying parts for most of that time.
And 43 years old also defines a front suspension re-design that took place that actually altered to some extent what could be gotten away with. Trunnions have some mechanical properties that ball joints do not have and visa versa.
I am not familiar with how to deal with trunnions as to ball joints? Starting with, how many years do you think the factory (speaking of taking it to a dealer and having the "Dealer" install 6 cylinder springs apply) actually had a stock room full of part numbered springs.?
And the probability that was actually done after X number of years went by.  Or from another standpoint, if the thing needed springs where did they come from?  Choices? A wrecking yard with the gimme a spring that fits? Or a spring shop, wind me one that fits? or??? What ever reason you cn think of.
Taking NAPA as a source of aftermarket springs, they used 5 part numbers from springs in NAPA stock to fit springs to all AMC cars from 1970 to end of production with the exception of ALL WHEEL drive models and Pacers.
So what spring do you think you are going to find under a 43 year old car with any degree of confidence?
My experience says sort of twisty round looking ones.
And as spring rates are effected by wire size and the number of coils and a few other variables, there is no guaranty at all what may happen or something specific might be on a spring removed from any one car of unknown heritage.
My have owned more than a few ball joint front suspension AMC cars and rebuilt the front ends of over 2 dozen of them. If I have needed a spring and had access to a junk yard with AMC cars in them I have gotten a matched pair from something, brought them home, routinely cut about half a coil out of the top of them and installed them in what ever I was working on.
Why?
First of all, they fit. That pretty much tracks what NAPA says, all 5 of their part numbers can be pretty much found one way or another in the front of an AMC car.  The lightest being a small 6 Gremlin no options and the heaviest a full blown AMBO fully loaded.
Why did I need a spring? Damage to the ones on the car. Rust, accident, what ever, the things are 40+ years old.  They stopped being pristine a long time ago.
The weight difference? Not enough to get upset about.  After 40 some odd years the objective was to go down the road more or less up right and to get the nose out of the air.
The last done by taking about a half a turn out of the top.
Basic rule of thumb, one coil = 3 inches of height.
A rule of thumb that holds true pretty much across the board based compression rate of so many pounds per inch.
That hold constant or close enough to be workable across AMC models and pretty much anything else with ball joints.  Trunnions having a slightly different mechanical response.
That also says that if I am pulling a set of springs from an AMBO to put in a Gremlin, an AMBO being heavier I probably would take 3/4 of a turn rather a half a turn.
In general, to make something work, close is good enough.
After all considering the parts sources them selves, close is gonna be about as best as you can get.
Unless you pay good money for the best in the business, but you have to ask to some extent are they better than a ball park estimate?
As to cutting springs.  DON'T USE HEAT.  Heat destroys springs. Torching them is not a good thing.  A cut off tool works well, quick and efficient and does not have heat.
Is there a down side? Yes there always is, you have to pay attention to the new now altered size. It is not perfectly square any longer.  There will be a little more bow to a compressed spring and you want the bow towards the tire, not the inner fender well. It rubs there.
A half a turn gets the nose out of the air.  A primary objective. It is not that the tail is too low, the nose is too high.
How far out of the air is dependent on exactly how much you want it to drop down and where it ends up. It is after all an estimate.
I personally like a nose down rake.  But if I am looking for level it make take pulling the spring a couple of times.
Is there any great loss? None that I can see, cutting a section out increases the spring rate, stiffens it up as they say, but road ride is un-detectable as to it's change.
How far can you go?
As far as you are comfortable with.
Through a mistake I made not detecting that the car I was working on had really the wrong springs in it before I started or they already had been modified, I have gone down 6 inches from factory height with out a detectable ride problem.
There were others before I discovered I was 6 inches down, but no show stoppers.
I obtained replacements from a wrecking yard Concord and took a half a coil out. That was more reasonable.
The point? After 40+ some odd years, the factory part numbers are long gone and junk yard parts will work with a little work.  So will other sources.  But the fact still remains, NAPA has 5 part numbers that cover ALL AMC APPLICATIONS except Pacer and Eagle. from 1970 up and I am not going to get real emotional over a nuance that no longer exists.