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Discussion Starter · #1 ·
Greetings All,

I am trying to make an IFS decision and can not find any comparison information. I am building a 37 Pontiac 4 door sedan. My plan is to replace the stock suspension with a Fatman front Clip. What I am trying to decide on is whether to go with the standard coils or the coilover setup. It is a fat fendered car so all the polished aluminum is moot. However are there any handling differences. I have heard that the coilovers are easier to adjust height. How much easier and can standard coil systems be adjusted. Also I am looking at the car weighing in around 3600 lbs. I am sure this will factor in as well. Any help would be greatly appreciated.

I appologize if this topic has already been covered and I missed it. I have looked all over this site and other and can not find a comparison.

Thanks,
Rob
 

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Yes, coil-overs are easily adjustable for height and coil springs pretty much aren't at all.
The big question and "problem" is how far down is that new FM crossmember going to dump your car. The crossmember pretty much decides ride height in a gross sense, the coil-over adjustment allows a little tweaking. Problem I see is that many, if not all, of the makers are now doing the crossmembers to drop the car into the ground and shove the tires up inside the fenders which can easily cause range of steering problems.
The depth the frame goes down inside the crossmember is a critical dimension.
In other words, how much drop is built into the crossmember itself?
 

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In todays word I would set it up with coil overs. That allows for easy swapping of shocks, coils, or even if you ant to add air suspension down the road. Also keep in mind that mustang II designed suspension are designed to be run at ride height with the lower control arms parallel or close tp parallel with the ground. You do not want to bandaid a bad install by adjusting the suspension outside of its designed partameters.
 

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Actually, since "looks" aren't the issue, I'd do coil springs & gas shocks.
1. Ecomonically, they are less expensive. And the shocks can be replaced if your "out on the road".

2. Most Mustang II coil-over shocks don't have as much stroke, so I wouls ask how much stroke does the coil-over have and the Mustang II suspension. Also ask how much is down travel & up travel.

I would only consider a coil-over if it had 2.5" up and over 1.25 downtravel.
 

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I'm with bluejacket. The coil springs will ride a little better too -- larger diameter always does. Coils aren't that expensive or hard to mess with if you decide to change ride height. It's not something you're going to do often!

Chassis Engineering, Inc. (http://www.chassisengineeringinc.com/) has bolt-on IFS for 38-39 Chevy with adjustable spring towers (spring jacks). How close it that to the Pontiac, I wonder? They have universal kits, but don't show the adjustable spring tower with it. Would be worth a call to see if they make the adjustable tower in a weld-on universal application if adjustability is important.
 

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I am no suspension/shock/spring expert but have tinkered with them for years. I like the KISS method of doing things (Keep It Simple Stupid) so will add my simple stupid input. When you are talking coil over vice coil and shock, my simplicity says you are only talking the location of one with respect to the other. A big coil spring with the shock located inside of it is basically a coil over with out adjustment. Usually, it is bigger but I have seen some very small coil springs on lighter cars. A coil spring with a shock located out side of it is very common and is almost always utilized in the rear because of shock changing issues with the axle housing being in the way. Rear coil overs are most commonly installed in the front or rear of the rear axle. Changing/installing a coil over on the side of the road does not present a big challenge in my mind. To me, the coil overs make for a very clean installation in tight quarters, are just as functional and reliable and changing one out/replacing does not present any problems for me.

Trees
 

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It's possible, with a smaller mean coil diameter, to juggle the wire diameter and number of coils and thereby maintain the same spring rate. For instance, with a 25% reduction in mean coil diameter, the same spring rate and stress level is maintained if the wire diameter is reduced by 9% and the number of coils increased by 62%. This would mean an increase in free length of almost 50% to maintain the same compressed height.

Incidentally, let's not forget "weight jackers," as used by our friends with circle track cars, offer a means to adjust the standard springs.
 

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I don't know what kind of front end a US built 37 Pontiac wore, but here they got a coil spring IFS which was a great improvement over the awful DuBonnet 'knee action' ifs of 35/36.
A friend has a 39 Poncho we rebuilt the stock IFS in back in 1978 or '79. It's still good. The lower wishbone has a seperate 'bolt in' spring seat - perfect for fitting with a 'weight jacker'. If it is a double wishbone IFS, why not just rebuild it? The geometry is little different to the pinto (sorry-mustang 11) as most of the engineering principles Billy describes were common knowledge prior to WW2 - tyres have seen more improvement than suspension.
Glad to see ya on deck Billy, I was worried. Ian.
 

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Discussion Starter · #11 ·
Old vs. new

I had contemplated rebuilding the original suspension but talking to other rodders convinced me it might not be such a good idea. I plan to replace the engine with an Olds 455. The general consensus I found was the stock suspension would not work well with the power and Torque involved and also the stock setup would not work well with modern tires and wheels. I might have been fed a load of bull. Unfortunately, when I decided to get into rodding I was not a gearhead by any means. I have read any book I can get my hands on dealing with all aspects cars and I have learned much over the last year but still rely on the experience of others rodders to cover things I can't find in books. I appreciate everyones feedback

-Rob
 

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trees said:
I am no suspension/shock/spring expert but have tinkered with them for years. I like the KISS method of doing things (Keep It Simple Stupid) so will add my simple stupid input. When you are talking coil over vice coil and shock, my simplicity says you are only talking the location of one with respect to the other. A big coil spring with the shock located inside of it is basically a coil over with out adjustment. Usually, it is bigger but I have seen some very small coil springs on lighter cars. A coil spring with a shock located out side of it is very common and is almost always utilized in the rear because of shock changing issues with the axle housing being in the way. Rear coil overs are most commonly installed in the front or rear of the rear axle. Changing/installing a coil over on the side of the road does not present a big challenge in my mind. To me, the coil overs make for a very clean installation in tight quarters, are just as functional and reliable and changing one out/replacing does not present any problems for me.

Trees
Physically changing the coil-over isn't exactly what I meant. It's availablity. My local parts stores like Napa, Advanced Auto, Murray's and Auto Zone don't stock coil-overs. Sorry I didn't make my thoughts clear.
Thanks Tony. My mind also went blank in the middle of typing. :embarrass
 

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Someone with more weighbridge time than me may have more idea, but I'm guessing a 37 Poncho straight 8 weighs as much as a 455.
Mu 2 front ends were designed with a 302w as the big hoss. You can set up a prewar f/e with -30' camber, 3-4 degrees caster and 1/8 toe just like a 90s front end.
 
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