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My 71 project car had newer aftermarket coils (unknown origin) installed and a new set of 550 lb coils in a box. No motor originally, so didn’t see ride height with the unknown coils.
When car got running, installed the 550 lbs coils. Fender height was a low 26.75” to ground but looked good with 245/60-15 tires that are ~26.5”. Unspring, the 550s are 12” high with wire diameter of .692”.
But, ride was harsh. Have a small block and lots of engine aluminum. QA1 adjustable shocks on a soft setting helped just a little.
To soften the ride, just put in the "unknown" coils. They are 12.5” tall and have a smaller wire diameter of .651”. Not sure if these are 460 lbs coils and online research shows inconsistent dimensions for 460s across vendors. Given they are only .5” taller than the 550s and have a .041” thinner wire, figured ride height could be OK.
It is not OK. Ride quality is better, but after driving a short distance, fender sits at 27.75” dvr side and 28” on pass side which looks terrible. Made sure the tops were seated correctly in the cups, but the bottoms did not end in their cups.
Questions:
Is the rule that to drop a fender by some amount you shorten the coils ½ of that amount valid? So, for my ~1” drop I’d need to take .5” height off the coil?
As the unknown coils have flat tops and bottoms, is there an issue when cutting a lot of coil off for a little (.5”) difference in height?
Could the first approach be to cut and clock the tops and bottoms to sit in the cups as indicated by the shape of the A arms, and lose some height that way?
Know a lot of people cut coils for ride height, but haven’t read anything about if cutting the bottoms off flat end coils will work as expected.
Thanks in advance, Brian
(Here is an example of “flat end” coils referred to above)
You are correct.
Global west explains it well.
If you want to drop the fender lip 1", cut the coil wherever it is 0.5" less.
So if they truly measure 12.5", cut them at 12.0"
Do not worry about the half closed coil on the end, or if it is exactly a 1/2 coil or 1 coil or whatever.
Make sure you put the top of the coil back in the frame in the same spot.
Your old springs appear to be uncut VBP 550# or F41 springs.
Your new ones appear to be Moog 5758 springs.
The "specs" call for a 12.94" height, but it only matters what yours are. They do vary a little anyway. Measure carefully.
IIRC I believe this 1" for 2" ratio only works because the end is half closed. And on GMs only. https://www.globalwest.net/video-tri...obal-west.html
Last edited by leigh1322; Mar 9, 2023 at 09:22 PM.
BEFORE you cut anything...please check the rear lip clearances.
Sometimes the rear diagonal spring bolt-nut can be tightened or loosened
to adjust the opposite front fender gap as needed.
You may not have to cut coils if adjusting the spring bolts works.
I cut my first set of coils in 1990 on an S-10. The rule then was 1.5 coils for a 3" drop........fast forward 23 years and my 69' 427/400 was nose high with new Moog springs in the front.......cut one coil and it dropped 2".......
Will cut them this weekend and post before and after pics.. Going for 1" drop with .5" at the spring, which will likely be a good chunk of a coil due to the flat ends of the coils..
Cut the coils which are assumed to be Moog 5758s. Wanted a 1” drop to 27” fender height, so measured .5” down on the spring which equated to about ¾ of a coil.
But saw how the original flat bottom didn’t align with the graduated cup or groove in the lower A-arm, and sat on the high section of the groove. Noticed that with the cut, the end of the spring would sit in the groove adding another ~.25” of spring drop. So, backed off on the cut to a little more than half a coil, and the cut spring ends fit perfectly in the top and bottom grooves ends, where the drain holes are.
The measurements (with pics below):
With the VBP 550lb springs (12” tall, wire of .692”) – fenders were 26.75” on 26.5” tires
With uncut Moogs (12.9” tall, wire of .651”) – fenders were 27.88” or right under 28”
With cut Moogs – fenders are now 26.625”
So, missed the target of 27” sitting .375” lower than that. Not a lot, but means floor jack can’t easily get under front spoiler, and have to set wood on the garage floor to get up the driveway into the garage without scraping exhaust. Also, lukewarm on front rake look.
The thinnest rubber spacers online are .375” so would add .750 of an inch at the fender to total 27.375" – too much . They do say “trim to fine tune height” but not sure how it's possible to get them to .25” thick to get .5" at fender.
Bottom line: The "half distance on the spring equals the fender" rule is only good if the pre-cut and post-cut coil ends are in the same vicinity in the lower a-arm groove. Otherwise, the cut coil end deeper in the groove will affect fender height which happened in my case.
Cut the coils which are assumed to be Moog 5758s. Wanted a 1” drop to 27” fender height, so measured .5” down on the spring which equated to about ¾ of a coil.
But saw how the original flat bottom didn’t align with the graduated cup or groove in the lower A-arm, and sat on the high section of the groove. Noticed that with the cut, the end of the spring would sit in the groove adding another ~.25” of spring drop. So, backed off on the cut to a little more than half a coil, and the cut spring ends fit perfectly in the top and bottom grooves ends, where the drain holes are.
The measurements (with pics below):
With the VBP 550lb springs (12” tall, wire of .692”) – fenders were 26.75” on 26.5” tires
With uncut Moogs (12.9” tall, wire of .651”) – fenders were 27.88” or right under 28”
With cut Moogs – fenders are now 26.625”
So, missed the target of 27” sitting .375” lower than that. Not a lot, but means floor jack can’t easily get under front spoiler, and have to set wood on the garage floor to get up the driveway into the garage without scraping exhaust. Also, lukewarm on front rake look.
The thinnest rubber spacers online are .375” so would add .750 of an inch at the fender to total 27.375" – too much . They do say “trim to fine tune height” but not sure how it's possible to get them to .25” thick to get .5" at fender.
Bottom line: The "half distance on the spring equals the fender" rule is only good if the pre-cut and post-cut coil ends are in the same vicinity in the lower a-arm groove. Otherwise, the cut coil end deeper in the groove will affect fender height which happened in my case.
Thanks for the data Brian.
I have been working hard on a spreadsheet for these springs.
I am very curious as to your options on your beautiful vert!
383, Al heads?, 4spd? auto? AC? etc
I think a .375" spacer may just take you back up to 27.25" if that is what you are looking for.
But I think it looks fabulous just as it is. I like a little down front rake.
But for an in-between spacer, Summit and Global West have aluminum spacers that could be "shaved" if you want thinner than that. https://www.summitracing.com/search/...-in%3A0-375-in
C3 Coil Cutting Conundrum
