[68ragtop]

So, I removed about 1/3 of a coil on these springs I have. IT only shortened the springs by about 1/4" because the the first 1/4 of the coil is essentially flat. Then I spend a good part of the afternoon blasting the coil springs, then toss them in the bead blast cabinet & have them clean as can be to paint them. Upon blasting I can see part 34P 5374 stamped into the top winding. I run the numbers & they come up as a Moog part number 5374.

Fitment would be a 1969 cutlass with a 350. Then it all came back to me....... These springs came from a cutlass I tore apart years. All along I thought they were the original springs from my 68 GTO. Nope......

Now, my goal was to lower my 68 GTO at most 1" from where it sat originally. So maybe these springs would have worked perfectly with a 90lb heavier engine, but probably not seeing a shortened them a fuzz just hours earlier. What a waste of time & materials.

Back to the drawing board....

I still don't understand why these springs I bought from coil spring specialist are so crazy stout. They are exactly what Moog calls out for wire size & uninstalled height compared to the 5390 Spring. maybe they got them too hot when they powder coated them, or just the wrong wire. but the car sat like there was no engine in it when I was test fitting panels years ago. I even threw 200lbs of sandblasting sand on the core support at the time & it barely dropped.

[68ragtop]

Going to start a new thread to see if I can understand spring rates a little better.

[HWYSTR455]

Couple comments. Front coil springs on 68-72 A-bodies are open ended on one side, closed end/flattened on the other. When you cut, you cut the open end, the side that the end goes into the control arm pocket. You want to leave some room from the spring end to the end of the pocket, the spring turns some as it compresses.

Suspension bind adds to possible ride height differences. The type of lower control arm bushings play a part in if there is bind or not.

Type of material definitely impacts the rate. Quality springs can also almost eliminate any droop or settling.

How much to cut for X drop varies, since different rate springs are effected differently by X amount cut off. Also, rate increases as the spring gets shorter. So, usually, the safest way to cut them is to do it in small increments, test it at ride height, and cut as required. Yes, it will take multiple times of assembly/disassembly.

There are very few coil spring manufacturers that have close tolerances, most are all over the place, and allow 10% variance or more. So for a 500 lbs spring, that's a 50 lbs range in either direction, meaning, it can be off 100 lbs from side to side.

Primer on coil spring tech:

https://landrumspring.com/technical/...l-information/

Coil springs are so inexpensive, unless you're doing something special, it's best to buy the springs you need, from a quality supplier. I've had great luck with Global West, and strongly recommend them. (I get no benefit from recommending them)

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[72projectbird]

I remember reading somewhere that cutting 1/2" of coil off, results in 1" of drop. I did this with a set of Hotchkis lowering springs, and the equation worked out perfectly.

[78w72]

the amount of drop on spings is not related to the number of coils... its related to the amount in inches you remove from the spring & each spring will be different judging by the coils. the rule of thumb that has worked for me on cutting at least 5 sets of springs is that the amount you cut off the height doubles the drop of the car. so, 1" cut off equals 2" of drop. on stock replacement moog type springs for 2nd gen f-body cars that was about 1 full coil.

[68ragtop]

The part that bugs me about cutting them, is that it removes the tight winding that makes them sit flat & straight in the pocket. I experimented with another spring & it will still compress & stay fairly straight. But to shorten this new one an inch, I will have to take more than a full coil off. But I need at least a 2" drop.

left one is obviously the one I cut.

[68ragtop]

Here is how it sat when I was test fitting everything. Yes, the engine was in the car Only thing missing was the windshield, interior & some other smaller misc stuff. I put 200 lbs of sand on the core support & it made almost no difference. Not sure how they could be that far off. Crazy

[78w72]

are you cutting the top or bottom of the spring? im not familiar with the springs you have for your car, but most 2nd gen f-body springs i have seen are not flattened or tight wound at the bottom end like they are at the top & they fit fine after cutting a full coil or more on my cars. the top is flat to sit in the frame pocket level. heres a pic of 2nd gen springs, the top is whats flattened.

also, be sure you are tightening the control arm bushing bolts with the car on the ground, otherwise they can bind if done when they are hanging. & bounce the nose a few times with the bolts loose before tightening. the car will settle a little bit once it gets driven for awhile, mine only settled maybe 1/8"-1/4" but some have claimed 1/2"+. changing springs isn't fun but sometimes it takes a couple tries to get it perfect.

[68ragtop]

Originally Posted by 78w72

are you cutting the top or bottom of the spring? im not familiar with the springs you have for your car, but most 2nd gen f-body springs i have seen are not flattened or tight wound at the bottom end like they are at the top & they fit fine after cutting a full coil or more on my cars. the top is flat to sit in the frame pocket level. heres a pic of 2nd gen springs, the top is whats flattened.

also, be sure you are tightening the control arm bushing bolts with the car on the ground, otherwise they can bind if done when they are hanging. & bounce the nose a few times with the bolts loose before tightening. the car will settle a little bit once it gets driven for awhile, mine only settled maybe 1/8"-1/4" but some have claimed 1/2"+. changing springs isn't fun but sometimes it takes a couple tries to get it perfect.

The images I posted are of the bottom. Yes, they fit into the lower arm pockets, But are still normally wound tighter at the end so the spring sits straight. the pocket it only as deep as the coil thickness. The other side is ground flat. This had polyurethane bushings. They spin 360 with next to no resistance

However, this time around I am installing std rubber, I will leave those loose until I know its sitting were I want it.

I am trying to avoid taking it apart again for fear of scratching something. I have over 100 hours in repainting the chassis parts & frame. I filled & smoothened every last mark & rust pit this time around. More than likely, it will come back apart, But I want to miss as close as I can. I thought about just ordering another set of springs as they are very inexpensive, but thats going to be just as much of a gamble. Might as well start with what I already have I'm thinking.

[78w72]

ok just checking which end you were cutting.

[HWYSTR455]

So you're sure you don't have any suspension bind?

Ok, those springs are way too high of a rate, period. That thing could be an off roader. Even if you did get the ride height to where you want it, no way will it ride properly.

Just buy the correct springs, or better springs, screw the place you got this set from, and go to a known-good supplier. And buy a matching set of 4. Just get a set from Global West and be done with this. $300 and all your struggles will be a thing of the past. If you're not sure about ride height or rate you want, call them.

I would suggest not going back to rubber bushings. You WANT no resistance, they should spin freely, the suspension should articulate with no bind. That way you can tune with springs and shocks.

And to all on the thread, there's no way you can use any 'formula' of how much drop there is by how much of a coil you cut off, period. The rates of springs are all over the place. You think you will get the same drop by cutting a half a coil on a 500 lbs spring as you would on an 800 lbs spring? Of course not.

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[AG]

I cut a half a coil of f my Moroso 240#/in drag springs and it dropped the front end 2.5", car weighs 3520#.

[78w72]

Originally Posted by HWYSTR455

So you're sure you don't have any suspension bind?

Ok, those springs are way too high of a rate, period. That thing could be an off roader. Even if you did get the ride height to where you want it, no way will it ride properly.

Just buy the correct springs, or better springs, screw the place you got this set from, and go to a known-good supplier. And buy a matching set of 4. Just get a set from Global West and be done with this. $300 and all your struggles will be a thing of the past. If you're not sure about ride height or rate you want, call them.

I would suggest not going back to rubber bushings. You WANT no resistance, they should spin freely, the suspension should articulate with no bind. That way you can tune with springs and shocks.

And to all on the thread, there's no way you can use any 'formula' of how much drop there is by how much of a coil you cut off, period. The rates of springs are all over the place. You think you will get the same drop by cutting a half a coil on a 500 lbs spring as you would on an 800 lbs spring? Of course not..

just a few comments &/or questions about your post, not trying to argue, just stating my experience...

how do you know the rate of his springs just by looking at the pic? the height the car sits at is mostly due to the springs free standing height, not the rate. in theory, you could have a solid rod in there & the height the car sits at will be determined by the height of the rod. so with that being said, he can cut the springs & remove say 1 full coil, that will only increase the rate a certain percentage based on the number of coils the spring has, if it has 10 coils & 1 coil is removed it will raise the rate ~ 10%. of course that isnt exact just a general estimate.

if they were stock replacement springs, which im guessing they were, then the rate is not too much or causing the issue, its the springs height making the car sit that high. example, moog replacement springs use 1 part # to cover numerous cars including many 2nd gen f-bodies, they are a stock rating but on my car & every other car ive seen them installed on over the years, they make it sit way too high, like a 4x4, at least 2"-4" above facotry height. again its not the rate causing that its that they are too tall for 2nd gen cars. cutting 1 full coil, which happens to be 1" off the height drops the car almost exactly 2", this "formula" has been used for a long time on these cars & works for many other cars too. as i mentioned above, i have done this no less than 5 times on my own cars so i know it works. PTFB has said it for years as well. so to all on the thread... you can use that general formula if you have a spring that sits too high, but be carefull & take off a little bit at a time untill you are comfortable with what it does on YOUR car. after doing this a bunch of times, i do agree that paying more for a name brand performance spring with a claimed drop is probably better/easier than creeping up on the height you want by removing them 2 or 3 times.

& just going by the number of coils you cut is pointless unless you know the amount in inches each coil is worth off the total height of the spring. a half coil on one brand spring is likely much different than another brand spring.

[HWYSTR455]

No that's fine, I don't mind being asked to explain better, or even challenged. Getting the info out there is the key.

Ok, free height. Well, generally, free height should be spec'd to the application, and generally, is in a 'range'. If the free height is way off, you would have to compress the heck out of it to even install it. So I guess, technically, it could be too tall of a spring. Some companies even include 'dead' coils, extra coils, specifically for trimming to meet a particular application. And that could be the case, because it seems the original poster ordered springs base on wire size and height, and not by application.

"They are exactly what Moog calls out for wire size & uninstalled height compared to the 5390 Spring. "

But I am assuming the free height is correct. The comment 'compared to' makes me wonder if it is actually a 5390 spring, but I'm thinking no.

I'm still asking if there's any binding, because this also is a key statement/piece of info:

"This had polyurethane bushings. They spin 360 with next to no resistance

However, this time around I am installing std rubber, I will leave those loose until I know its sitting were I want it. "

Is it in fact loose? And loose enough to where it's not binding?

Indications it's a rate issue:

"I put 200 lbs of sand on the core support & it made almost no difference. Not sure how they could be that far off. "

Only way I can think of that this wouldn't indicate a rate issue is if the coils are already at coil bind, or close to it. It would have to be a gross free height difference I would think, but I guess it's possible. You would have to compress that spring like at least 3 or 4 inches to cause the suspension to remain completely extended.

Honestly, the springs in question are of unknown specs. They were ordered by free height and wire diameter, not by application. I still say just order the right/quality springs. Moog is not one of those brands, as you too have experience with.

.

[78w72]

i agree free height should be spec'd to application, but as far as moog & some other cheaper OEM replacements, if you do a search or call an auto zone, they will give you the same part # for many different cars. as of about 5 or 6 years ago the moog #5006 was a very common part# that covered multiple cars from a 78 400 firebird to a 78 305/350 camaro. i gave up trying to figure it out & just bought the moogs, after installing them the car sat way too high. thats when i researched cutting them on other t/a forums & learned about the formmula of cutting half the amount you want dropped. i cut 1 full coil, (1") & sure enough it dropped ~2". went through the same thing on my next 81 t/a WS6, both cars were more of a stock resto so didn't want to buy performance springs at the time. 3rd car i did recently is a 72 firebird & i decided to go with a PTFB GT kit, the front springs were estimated at a 2" drop & were much bigger coils & spring rates, installed them & they are exactly what PTFB said & sit very close to my other cars with the cut moogs. so i know each car will be different but in my experience & many others ive read about, the formula mentioned is a pretty accurate starting point for cutting springs.

i hope 68ragtop figures it out & reports back with results.

[Sirrotica]

Second Gen spring length, proportionate to height ratio is .6, so the 50% cut in length to height is within 10%. I've always cut the springs and followed Herb Adams instructions for heating the last 1/2 coil and flattening it so it was the same as the portion you removed. The last 1/2 coil is dead anyway. I've cut springs since the late 70s using Mr. Adams instructions and never had any problems with temper or breakage. After all Herb Adams was the designer of the T/A suspension, he might have a clue of what can be done to improve the suspension on second gen T/As

I have a 73 T/A that I used this method on in 1979 and it still has the same springs in it currently, no problems. These were MOOG springs for a 1979 WS6 with 403 and A/C, cut down 1/2 coil when they were brand new. I've cut plenty of springs old and new, for road cars as well as race cars, using this method, and not one problem. My .

[68ragtop]

I know sometimes these threads get difficult to jump into because they get long winded, but just wanted to clarify a few things as I revived the OP, but didn't start it & some details got lost as I had some details in another thread.

I started a frame/ nut/bolt restoration on this 68 GTO 15 years ago. Around that time I asked questions on this forum about new springs & a few people recommended coil spring specialties, & thats who I ordered my springs from. My intention was not to find the cheapest springs, but to find some I could purchase, install & the car would sit right, the first time around. When I called coil spring specialists they seemed very knowledgable & they asked every question about the car. So I ordered all 4 springs. They also had powder coating options that I went with.

I didn't realize until years later into the project that these springs were really stout. I just figured it was lack of weight at first. So, here I am doing EXACTLY what I was trying to avoid in the first place. To me, going to another mfg & ordering more springs is just going to be a crapshoot. The last mfg was highly recommended & I believe they still are today. So I felt why not try to modify them & see if I can get them within reason.

As far as free specs, they match Moog 5390 specs to a tee, so I am guessing thats these where mfg under those numbers, but someone the wire used was different than oem. The picture I posted above was without the extra weight. Nothing but sheetmetal on the car & no interior. From my notes though, I was about 2" to high when I had it loaded down. in the pict I think its even higher. The picture is about 4 years old, I was all I could find for a visual. No coil bind. room al the way around & I think maybe 1/2"-5/8" spacing between the coils when installed? I might have a picture of that. Just guessing from memory.

As far as the Bushings go, I went with oem style as I changed the scope of the car. I tore everything back apart last year & am re-restoring the chassis to bring it to a higher level. Filled flaws in the frame. Road rash, left over rust pits, etc. So thats why I am going away from the energy suspension parts. No doubt they would function better, but the car is no longer going to be a driver.

As far as ride quality, Not to concerned. I would be ok with it being a little stiff as long as it sat right. I would rather have it sit 1/2" lower than original height over 1/2" high. So I think even if I found something really close out of the box, there's a good chance I would be taking it apart & trimming them if its even a little too high. Just a personal preference I suppose.

Again, the thing I keep tormenting myself with is getting rid of that last tighter winding & how that impacts things. Some say it make no difference, but these springs were wound like that for a reason, right? My thinking was it was to insure they would stand straight in the pocket & not want to arc outwards, & maybe ever run on the shock?

Thanks again for all the input, its appreciated & I am reading everything I can.

[Sirrotica]

The springs in a 68 GTO and a Second Gen T/A are essentially made the same as far as the flattened bottom coil to fit in the spring bucket. The way HA cut the T/A springs would work the same as a 68 GTO application.

I Googled Herb Adams front spring modification and found a page from one of the old magazines showing step by step instructions on how he cut and flattened the bottom of the spring by heating it so after the cut it appeared the same as the spring before the cut. This is the same procedure I have followed in the past....FWIW

https://www.bing.com/images/search?v...x=1&ajaxhist=0

[78w72]

following the herb adams procedure linked is a great way to do it... but, not doing that works fine too. myself & many others out there over the years have just cut the springs & not flattened the bottom. mine sit perfectly fine & are not crooked at all, dont hit the frame or the shocks & the slight increase in spring rate is a good thing IMO. so if you can heat & flatten the end properly try that, if not it will still function right with no issues. also be sure the spring is "clocked" right on the lower control arm, the end is supposed to be between the 2 drain holes & equal on both sides.

if you dont want to buy new springs i think you will be fine cutting them based on the 1:2 ratio. also i dont measure the drop at the factory location at the front rocker, i measure at the center of the wheel well lip, inline with the center cap, basically the gap between the top of tire & bottom of fender lip.

as for the poly bushings, they may function better than stock rubber but they will start to squeak, i used the energy suspension on my 78 t/a & after a few years they squeak, the grease wears out & you cant get new grease in there without taking them apart... unless you have a zirk fitting which i dont think control arm bushing have. rubber is fine for a fair weather street car that see low miles.

best of luck!

[P@blo]

I cut my moog 590 coil springs 1 full coil and followed the Eaton spring cutting instructions. They clearly stated that do not heat the spring for any reason so I cut and installed.

Herb Adams was a great engineer but there are threads out there of his rear mod on a leaf spring cars breaking the mounts. There's just not enough material there after relocating the leaf spring pivot point. Too me this is dangerous giving marginal improvements at the expense of safety.

Same case where herb suggets heating a coil spring after cutting to lay it back down. If you think of how hot the metal gets 2 or 3 inches on either side of the spot you heat you have changed the way the spring will now function.

Something worth considering is the spring is in a compressed state it will already be "laying flat" when installed. Once located in the pocket the spring also stays put in relation to the inspection holes as well.

No heat on a coil spring and a torch should not ever be part of the coil cutting equation.