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Need coil spring/ride height help
#1
OK, I guess a made a classic mistake. When I replaced the front suspension on my 73 vert I installed a set of Scott Drake 1" lowering springs and KYG gas-adjust shocks. Ride is so harsh its almost like a solid suspension when I hit bumps - jars the whole car. I just spoke to Eaton Springs for their help. Their stock spring is rated at 292 lbs, their performance spring is rated at 362 lbs. According to Scott Drake spec the spring I put on is 600 lb.!!!! going to go with Eaton performance spring but need help with how much drop to get. They offer -1, -1.5, and -2 in springs. Problem is, I like the stance of the car with Drake springs but I think they dropped the car more than 1". To find out what to order, I need to find out the factory ride height. I'm running 225/60/15 BFG's on the front and it measures approx 25 inches to the fender lip the way it sits now. Any help or advise would be much appreciated. Got to get these thing changed before it knocks everything on this old vert loose.
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#2
You can go here to get the factory ride heights
https://www.7173mustangs.com/thread-unde...#pid298050



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#3
I recommend that you ditch the Gas A Justs before going to different springs. If you want a more factory ride, try the KYB Gr-2s, they're about $80 / set of four from RockAuto. I just swapped mine out last weekend and the ride difference is amazing.

As far as Drake's springs, I seriously doubt that they are 600lb rate. any time you see a spring listed as "620", it's because the wire diameter is .620", not because they have a 620lb rate. I bet the tech gave you some bad info. The 73 Mustang springs were all right around 300lb rate for non-CS cars, and upwards of or slightly over 400lb rate for CS equipped cars, equipment load out and engine dependant.

If you give me your original engine, trans type, A/C, P/S or not, I can get you the original Ford part #.

What did you use for rear springs?


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#4
(07-19-2018, 11:59 AM)Hemikiller Wrote: I recommend that you ditch the Gas A Justs before going to different springs. If you want a more factory ride, try the KYB Gr-2s, they're about $80 / set of four from RockAuto. I just swapped mine out last weekend and the ride difference is amazing.

As far as Drake's springs, I seriously doubt that they are 600lb rate. any time you see a spring listed as "620", it's because the wire diameter is .620", not because they have a 620lb rate. I bet the tech gave you some bad info. The 73 Mustang springs were all right around 300lb rate for non-CS cars, and upwards of or slightly over 400lb rate for CS equipped cars, equipment load out and engine dependant.

If you give me your original engine, trans type, A/C, P/S or not, I can get you the original Ford part #.  

What did you use for rear springs?

The 600 lb/in rate was what is listed in the catalog for spring rate. All I know is that its way too stiff for this car. Your factory rates above are very similar to the information I was given from Eaton.

1973 convertible, 351 2v, FMX, A/C, power steering.

I think you are right about the KYB shocks combined with these springs. That was also a recommendation from Eaton. I have not changed the rear springs but am running the KYB shocks on them too and and they're Ok on the rear. 

Looking for a little stiffer feel for the front, just not bone-jarring. Thats why I though The Eaton 362lb springs might be a good compromise - something between factory stock and CS equipped spring rates.
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#5
I see that in their catalog, again, I have my doubts. I'd like to get some measurements on those to see what they match up to.

Stock springs for your car:

C9OZ-5310-F - 8.5 coils, .630" wire, 16 5/8" free length , 1900 lb load

Moog crosses that as the 8350 spring, but the specs are off - 16.64 free length, .65 wire and 2117 lb load for a 345l lb/in rate.

A closer replacement is the Moog 8330 w/ 16.625 free length, .620 wire. 1809 lb load and a 290 lb/in rate.

Competition suspension spring for your car is Moog 8356 - 15.05 free length, .650" wire and 1900 lb load, with a 418 lb/in rate

I've always jsut trimmed my coils to get the ride height I wanted. The "1" lowering springs" are so arbitrary as to be completely useless. Drop an aluminum intake and set of head on a car and it's going to ride higher. Most of us has reduced the weight of our cars in some respects.


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#6
(07-19-2018, 09:46 PM)Hemikiller Wrote: I see that in their catalog, again, I have my doubts. I'd like to get some measurements on those to see what they match up to.

Stock springs for your car:

C9OZ-5310-F - 8.5 coils, .630" wire, 16 5/8" free length , 1900 lb load

Moog crosses that as the 8350 spring, but the specs are off - 16.64 free length, .65 wire and 2117 lb load for a 345l lb/in rate.

A closer replacement is the Moog 8330 w/ 16.625 free length, .620 wire. 1809 lb load and a 290 lb/in rate.

Competition suspension spring for your car is Moog 8356 - 15.05 free length, .650" wire and 1900 lb load, with a 418 lb/in rate

I've always jsut trimmed my coils to get the ride height I wanted. The "1" lowering springs" are so arbitrary as to be completely useless. Drop an aluminum intake and set of head on a car and it's going to ride higher. Most of us has reduced the weight of our cars in some respects.
Thank you for this information! I really appreciate your effort.  As to the car - It does have an Edelbrock intake and I have replaced the factory air with a simple Sanderson style compressor and system from Classic Auto Air. My estimate would be at least 100 lbs off the nose. The guy at Eaton also asked specifically about modifications from factory. Based on this information, he suggested springs for a non-ac car. He also suggested, as you did, that the best thing would be to buy stock springs and cut them to get the ride height I was looking for. They even have a tutorial on their website for cutting springs. Basically, they say cut, drive hard, check ride height, repeat as needed. Problem is, I have gotten older and have health issues that prevent me from doing this myself and I'm afraid that hiring a shop to go through this would be cost prohibitive. 
Tomorrow I will try to take some measurements from the frame as shown in my shop manual, probably at the front bumper arm mounting hole. According to the diagram, factory spec is 11.91". According to Marti, car came with E70/14 which is real close in diameter to the 225/15 on the car now. Hopefully, this will give me some idea of how much the car is lowered and I can go from there.  At this point, I am willing to give up some in ride height for improved ride.  Never ridden in a car with CS suspension so I really don't know how stiff a 418 lb rate is, which is why I am leaning toward Eatons 362 lb spring as sort of half-way between stock and  CS specs. Also will ditch the Gas-adjust shocks. Eaton suggested Qal (sp?) adjustable shocks which are ridiculously expensive or Eldebrocks as an alternative. I'll probably go with the lighter KYB as you suggested. 
Again, thanks for your help. I'll try to take some measurements of the Drake springs when I get them off - #coils, wire dia, and free length as close as I can and relay the info to you.
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