Old question, new day

[Steve McMahan]

I know this question has been asked before, but the info I read didn’t give me the actions to take. So, my car is sitting too high, in the front for sure. I’ve got that ford page from the manual that shows the measurement from specific points to the ground, and the two I measured, the lower bolt of the idler arm to the ground, and the front most bolt of the front bumper, show me inches too high.

My car is a stock 73/351 car with now a 5.0 from an 87 TBird. I still have the stock front springs, all new stock suspension parts, and the only non stock part was a new Prothane upper spring seat. While I thought the stock spring was the issue, I found on the Eaton site that the same front spring was used on both 302 and 351 cars.

How do I get it closer to stock? What are my options?

 

[Sheriff41]

Try removing the upper spring seat (I'm assuming you're referring to the one on the top of the spring). The poly may be adding to the height since it's thicker than the original hard rubber piece. Beyond that, it may be time to consider cutting your springs. I think @c9zx or @Hemikiller mentioned in your earlier post on this how much cutting 1/2 a coil would lower the car. When I cut coils (using a cutoff wheel) I start with 1/2 a coil since I can always cut more, if needed.

 

[Steve McMahan]

I was hoping someone had a more scientific way to determine that process. It maybe unobtainable, but I wonder if someone has a reliable way to measure, make one spring modification, and get results within a reasonable range, like 1/4” of target.

 

[Sheriff41]

See post #6 in this thread: https://7173mustangs.com/threads/lowering-car-by-heating-springs.43567/#post-437721

 

[Steve McMahan]

Thanks

 

[AcesArneson]

Why not call Eaton and get them to make you springs that will fit your need. If you cut parts off your existing spring you are eliminating travel and your ride quality will suffer.

 

[Steve McMahan]

I agree Aces, but how do I communicate with them the ride height I want? I’m not clear what to tell them. I’ve got a stock OEM spring and the car is way too high. Here is the data I’m using to establish my correct ride height:


Either than 11.91 front bumper (mine is over 15”) or the idle arm lower bolt 10.4 (mine is over 14”) seems improbable with my stock spring and engine combo. And I have 15” tires, etc.

Also, I don’t have the wheels and tires I intend to get later. Should I do that first, then establish the height delta I need? And, I have no desire to cut the spring because I know from past experience you typically cut the wrong end, the end that gives you the moment articulation, to translate a smoother ride.

I’m wondering if I have the process out of order.

 

[Sheriff41]

There is definitely something unusual going on with your setup. If I recall, you had trouble with your sway bar installation also. What is the measurement from the center of the wheel (spindle) to the top of the wheel arch on the fender? Are the stock springs the ones that were in the car when you started your project, or are they a stock set you purchased and installed? There is no telling what a previous owner may have installed in the car, and you could simply try another set of stock springs.

Cutting up to one full coil off the saddle end of the spring will not cause a noticeable degradation in ride quality.

 

[Steve McMahan]

Drivers 16 5/8, passenger 16 7/8”

Just for the heck of it, I loosened one side of the swap bar, bounced the car, and it had zero effect.

Yes, you’re right, I’m not 100 percent certain the springs are the original, but both of the upper control arms were with the factory ball joints; same with LCA. I know that’s no proof that the springs are original, but it seems to increase the likely hood.

I’ve never cut a spring before, always just buy new ones, but I’m not sure things will improve with that.

 

[Hemikiller]

Despite what Eaton may have on their site, the 302 and 351-2V springs are not the same for all applications. The 302 w/AC uses the 351-2V w/o AC spring, but that's about it. Factory AC adds 104 lbs to the front of the car. The 351-2V was 126lbs heavier than the 302 at the front.

For reference, my 71 is 14" spindle center to wheel arch with stock replacement 71 351-4V competition suspension springs.

 

[Steve McMahan]

So, to muddy the waters more, I’ve got a 5.0/AOD from an 87 TBird with AC. I know it’s lighter than the 351/FMX w/AC, but hard to see that differance equaling almost 3”. If you were me, and I’m aiming for 1” lower than stock would have been, what replacement spring would you buy from Eaton OR how much would you remove from these springs, assuming I cut from the saddle side?

 

[Hemikiller]

If the car is completely assembled with full interior, yada, yada, then I'd start with 1/2 a coil. Easy to take more off, hard to put it back. If it's not complete, then I'd leave it be until it is. Keep in mind that the suspension ratio on the front is about 2:1. 2" at the wheel is 1" at the spring.

 

[Steve McMahan]

I do have a complete car. One question from the chart, where is Trans X? That’s what it came with OEM. I’m not sure what stock spring came with it. How do I read the chart with an FMX?

 

[Hemikiller]

C/M (cruise-o-matic) is the FMX.

 

[70cobrascj]

So, to muddy the waters more, I’ve got a 5.0/AOD from an 87 TBird with AC. I know it’s lighter than the 351/FMX w/AC, but hard to see that differance equaling almost 3”. If you were me, and I’m aiming for 1” lower than stock would have been, what replacement spring would you buy from Eaton OR how much would you remove from these springs, assuming I cut from the saddle side?

So, to muddy the waters more, I’ve got a 5.0/AOD from an 87 TBird with AC. I know it’s lighter than the 351/FMX w/AC, but hard to see that differance equaling almost 3”. If you were me, and I’m aiming for 1” lower than stock would have been, what replacement spring would you buy from Eaton OR how much would you remove from these springs, assuming I cut from the saddle side?

I cut a half coil from mine and it lowered it about 2 inches. I bought Eaton springs for a Mach 1 with a Cleveland and no A/C. My car is a A/C car but I’m running an aluminum intake with aluminum heads and headers. Also I did not reinstall the A/C so it is a lot lighter than originally.
When I installed the motor and trans it sat way too high and that’s why I cut the springs. A half coil was perfect and the car rides and drives perfectly.

 

[Steve McMahan]

And 70cobra SCJ, you cut that from the saddle?

 

[Sheriff41]

Steve, you cut the bottom coil as marked in this photo. Start with 1/2 a coil, as several have mentioned. Once you make your cut, rotate the spring so it sits in the saddle properly with the end against the stop on the saddle. The top of the spring is flat and does not need to be indexed.

 

[Steve McMahan]

So, if I have stock, I have a 7N spring, 1950#. I’ll at least measure the wire diameter to see if that matches, just to know where I’m starting. If a 302 weights 431 and a dressed 351c weights 550, and I’ve using the modern AC compressor, I’ve got excess spring capacity of about 150 pounds. Just thinking.

 

[Steve McMahan]

Got it Sheriff. I wish I had the spring compressor Hemikiller has shown in other posts, I have that really safe one that uses the spring seat, shock mount, which requires to remove the UCA to remove the spring. Just for fun to have.

 

[70cobrascj]

And 70cobra SCJ, you cut that from the saddle?

What Sheriff said but yes I did cut it off the bottom. Before and after pics, it’s actually settle a little bit more after driving it around