70 Convertible 351C FMX sits way too high after restoration and new springs

[Rcodenewf 44]

 rcodenewf

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Joined Jul 21, 2000

650 Posts

 Discussion Starter • #1 • 25 m ago

This is the second set of springs i've installed in this freshly restored car. First set if put in were Moog 8534: .670 diameter/Free height 14.69/ install height 11.00/ load 1578 with a spring rate of 428 lbs/in. The car wouldn't move up or down as it was on axle stands..lol.

Then i switched them out for a pair of 8234: .620 diameter/ Free height 16.31/ install height 10.5/ load 1668/ with a spring rate of 283 lbs/in.
There is no difference. There are no shocks in this car yet. I realize it will settle somewhat after driving but there's over 3 inches above the tire!
Tires are 245/45ZR17.

Ive included a pic of the side profile of the tire as well as a pic of the undercarriage showing the steep angle of the lower control arms.
I recall having to change the springs twice on my 69 fastback to get the front right but this is over the top.

From the floor to the fender lip i have 30 3/4" !

I know forum members have run into this before but this seems kind of excessive? thanks..John

Note: I've loosened the entire front end to eliminate the possibility of the suspension being in 'bind'. No luck.

[dream car 12]

Check this from CJ Pony, and read the reviews.

https://www.cjponyparts.com/scott-drake-contour-coil-springs-1-drop-mustang-1967-1973/p/CSC6773/

[Mach1 Driver 560]

If you buy good springs they will last the life of the car- talk to Eaton Detroit Springs. They can set you up, or make custom springs. They will say you must have all the weight on the car- it must be completely assembled, and driven for 500 miles. They even want to know if your car has AC, because of the added weight. Since they don't know how high your car is, everything is measured from stock ride height and adjusted for changes like aluminum heads and intake manifold. Following is how Ford measured stock ride height. This is from the Osborn Chassis manual (thanks for pointing this out RPM), which even has a chart for differences in ride height based on gallons of fuel in the tank.

Ride Height

Ride heights are measured from the ground to the highest most point of the wheel well opening (which should be though the center of the wheel).

To measure:

1. Place car on level ground

2. Push front end down approx.1 inch and release slowly

3. Measure at the center of front wheel wells at the center of the wheels.

4. Raise vehicle front end approx.1 inch and release slowly.

5. Measure at the center of front wheel wells at the center of the wheels.

6. Average up and down measurements. The difference between right and left should not exceed 1 inch.

7. Repeat 2-6 for the rear. The difference between right and left should not exceed 1 inch.

Curb load requires the following:

a.    Full tank of fuel (6x20=120 lbs)

b.    All engine fluids at full

c.     Spare tire with wheel in design position

d.    Front seat at rearmost position

e.    Jack and components in design position

f.      Tires inflated to 24-psi front and rear (for ride height evaluations only)

g.    6.95-14 tires

E70-14 same as 6.95-14

7.35x14 add 0.20

F70-14 add 0.30

FR70-14 same as 6.95-14

C78-14 subtract 0.10

E78-14 add 0.20

F60-15 add 0.30

For Mustang with standard suspension (see Chassis manual):

Front: 27.02 tolerance +1.00 / -0.70

Rear:  26.76 tolerance +0.60 / -1.15


See chart for variation in fuel loads versus ride height

[Rcodenewf 44]

Dreamcar: I read over the reviews and the results varied. It would appear that the springs maybe did drop the car ballpark 1" as a few customers stated...certainly not the drop i'm looking for to get this car down. The general consensus of those springs you referred to is that they are not a soft ride. The ride of this car doesn't have to be 'soft' but certainly not harsh.

Mach1driver: I like #2 in the procedure you listed. "Push front end down approx.1 inch and release slowly".. you can't push this car down 1/4 inch..lol.

Thanks for the suggestions though...John

[jmlay 80]

When the lower control arm to chassis bolt was tightened was the car setting with full car weight, engine and trans included, or was it on a jack or jack stands?

[Rcodenewf 44]

I backed it off after i installed the engine and trans. Car is 95% assembled. Only thing left is seats carpet and the convertible top ..the framework is installed.  That certainly won't bring it down 3 inches.

John

[Mach1 Driver 560]

12 hours ago, Rcodenewf said:

Mach1driver: I like #2 in the procedure you listed. "Push front end down approx.1 inch and release slowly".. you can't push this car down 1/4 inch..lol.

All you mention is that it is freshly restored. What have you done to the upper, and lower control bushings, strut bushings, stabilizer bushings and spring perches? This much resistance is coming from some combination of the bushings and springs.

Eaton claims that 95% of all ride height issues are because the car is incomplete (springs support weight and it isn't all there), and the car hasn't been driven 500 miles.

I'm sure you've heard this, but our suspensions are from a Ford Falcon and have been the butt of many jokes. It works MUCH better with roller or spherical bearings instead of rubber bushings. I did a search for the video of the suspension moving while driving, but I can't find it. Its a real eye opener and will convince you to change to a different type of strut rod. The video below is about Open Tracker Racing products:

Edit, here is the "before video" with stock parts. Watch the strut rod bushings compress in each direction and the wheel move. All of that is removed with a strut rod mod from SOT, OT, and others.  

 

[Rcodenewf 44]

I agree wholeheartedly with you Mach1driver. Upper and lower control arms..strut rod bushings..spring perches..idler arm..upper isolators have been replaced..100% new. All moog except spring perches which are SD.

I also agree that the car has to be 100% assembled ( i watched the Eaton video) and the fact that that the car has to be driven 500 miles but...looking at the pics i think you'll agree that it won't settle over 3 inches. Maybe im wrong.??

John

[Mach1 Driver 560]

It is kinda looking like a AA/Gasser and I agree that its unlikely to come down 3 inches. Do you have gas or hydraulic shocks? Gas shocks might account for some lack of travel. Since no one has talked about it, is the end of the spring touching the tab on the spring perch, with the flat end of the spring up and an insulator on top? 

[Rcodenewf 44]

Good day Mach1 driver: there are no shocks in the car yet. Haven't purchased them.  Yes the bottom coil is up against the tab and the top fully seated in the insulator. Thanks 

[Mike65 475]

Rcodenewf, many years ago I replaced front springs in a 68 j code (302) GT Coupe I owned & I installed big block front springs instead of small block front springs & the f/e sat exactly like the f/e of your 70 Convertible. Double check the front spring rate.

 

[RPM 1,190]

 

[Midlife 814]

Good advice there!

[Rcodenewf 44]

yep..it is. I like the fact that he explained the fact that whatever is cut off the spring will be double at the wheel..makes sense ...forgot about that. 

I guess In the interim i'll put the seats in  and fluid..other than that the car is pretty much complete and i know those few additions won't bring these coils down any.

Then i'll calculate and start trimming. Interesting though in his video he talks about a 620 coil for the early mustangs being in the 13" range.. I'm assuming he's talking about freeheight. These springs have a 16.31" free height.

I might drop him a line and see what he thinks and maybe what  he can supply. Or maybe i'll cut as is in his video.

..John

Edit: I just sent him an email.

[Rcodenewf 44]

Mike65...according to the list on rock auto they are correct for the car??

John