This has been my go to spring for years, requires cutting to get ride height right. Works good as a performance front spring on the street.

NAPA AUTO PARTS

You will want to leave it about 1/2" 1" high because it will settle.

I have Maier 620's on the front of my 68 big block, but at 1" drop I think they will be just about where you are now.

The above spring is 70 Mustang Mach 1 428 auto w/ac it was the heaviest spring available in a Mustang ,cut to fit.

 

Thanks for responding. I am willing to give up some drop for ride quality. Being a big block spring, wouldnt that be a firmer ride than a small V8 spring?

 

Honestly I would say no , you look to be very close, if not on the bump stops.

Do you have a 351w or c ?

I should have asked what spring do you have now?

I have used that spring in my 67 289 car cut to 8 coils, -1 1/2 . My 64 Comet with a 351w -2 coils , that car was low. My current big block 68 -2 coils.

Do you have lowering blocks in the rear , are you planning to raise the rear too?

What shock are you using ?

I'm sure you know spring change ride / ride height questions are near #1 in post count here .

Before you make a change make sure you know whats under the car now. If you have a 720lb race spring and 5 1/2leaf rear spring then going to a 4 1/2 rear and Grab-a-Trac front will raise it and soften it up some. If you already have the G-a-T stuff then a call to Eaton for stock Mach 1 parts would be the way to go. If you have KYB shocks no firm spring will ride nice IMHO.

 

My car is an M code with 351c. Yes, I plan to raise the car all the way around. I am running stock springs with 1.5 coils cut, rears are de-arched 2" with 1" drop block. Am running KYB GR3's all the way around

 

do you know if it is hitting the bump stops as it is now?

I have a friend with a Boss 302 that is set up like the stage 3 mods from the chassis manual the ride is only bad when it slams into the bump stops , his car has Koni classics all around but I think the key for his is the 15" tires and wheels.
Our cars with low profile tires seem to ride harsh.

Pull the lowering blocks out of the back and decide if the rear sits where you want it. If not your going to have to replace all 4 springs. Now you will have to decide how you want it to sit. Stock? Call Eaton give them all the info on your car and it will sit like a stock MACH.
Lowered but the rear higher than your set up less blocks ? 4 1/2 leaf mid eyes with a not 620 front spring cut to fit. ( for the money the spring I linked is the way to go, you have to trim to fit any way)
But my GUT feeling is if the car is not on the bumps your problem is the shocks unless it is crashing into the bumps as you drive.

 

I dont feel it hitting bump stops, its just stiff and bounces you out of the seat sometimes. After dearching, the rear springs are nearly flat when loaded. I have a set of stock springs and was considering swapping leafs to dial in a rear rear height thaat I like and hopefully and lose the blocks. I'll look at the Napa springs. Not going back to stock height and as high as these cars were stock I have plenty of middle room to add more spring back to the ride and still enjoy a moderately lowered stance.

 

I'm not familiar with GR3's and having had success with KYB's on GM products......I hate their ride on Mustangs.
1. Check bump stop clearance
2. Maybe mark them and take a drive to ensure your not hitting them
3. Do you run any additional bars on rear, like "shelby bars"? pivot points bind
4. Make sure dearched spring isn't running out of shackle travel
5. May consider a different shock if none of the above is an issue.
6. How much poly do you have in suspension? Poly strut rod bushings are bad.
7. Spring perch health and thoughts on roller perches
8. Sway bars binding or hitting?
9. Ball joints fully articulating/binding?
10. Can you determine which end of the car is most annoying?

If you aren't running out of travel, hitting bump stops, or hitting the tarmac, then the lowered stance in theory shouldn't be the issue. If you are doing either of these, then obviously like a mini truck you'll ride rough. Assuming you aren't hitting stops, then your really only talking the spring rate change of cutting a 1.5 coils. Yes, this will stiffen, but you'd still be far from what many of us have ran. Any chance shocks are bottoming out in travel? Or what I found was that the KYB's are just generically valved and weren't compatible with my setup. And I ran the car like this for many years before going to a more expensive shock. Wow, handles and rides better now.

I'm just playing devil's advocate since the ride height without bottoming out shouldn't change ride whether its down slightly, stock or up. Its spring rate and shock...not where relation to earth that dictates.

BTW, it looks killer in current stance

 

Before you rule out tubular control arms, my whole front suspension on my 66 is tubular with all rod ends. No rubber or poly anyplace. The car actually rides very soft and smooth. It just seems to glide over bumps. My cars stock replacement GT spec uncut coils. I realize it's not a 70 but simply my results.

 

NAPA spring referenced is equivalent to a Moog 8304. Didn't run the
numbers but it would probably be 500#/in or so at 1.5" down from
factory ride height. I'm guessing you would chop it down to around
a 14.5" free length. (total guess)
The fact the car wants to launch you out of the seat is probably
shock valving. I can't see the job getting done well with KYB-
anything. Just my personal opinion....

ex-Global West GM
1991-1995

 

You about nailed it ,takes just a little spring compressor to install. Mine are at 13.5 and I just twist them in.

 

Thanks for the feedback. I was mistaken, these are the silver KYB GR2's I am running. Maybe this is a shock thing? I'd still like to bring it up an inch. I have heard nothing but good things about Bilsteins. Maybe a better set of shocks and replace my front springs with new Napa or Moog with a more conservative cut.

 

KYB = Garbage

 

The Bilsteins are a great shock. The sport valve works best with a stiffer than stock coil spring.


Bilstein shocks - Opentracker Racing Products

 

We're really lucky to have inexpensive Bilstein shocks available for our cars. Bilstein shocks can get expensive in other applications. I don't know why anyone would not go Bilstein for a stock replacement style shock. If you're not getting Bilstein you may as well get Monroe, or whatever is the cheapest shock you can find, because that shock will be better than KYB.

Konis are another shock that work as intended but they are more expensive than Bilsteins for our cars.

 

KYB = Garbage

I have been doing some reading and looks like others would agree. I really thought the rough ride was from the springs. I am sold on Bilsteins now and am shopping around for a street set. Also plan to replace the front springs. Is there any DIY kits for roller perches?

 

Is there any DIY kits for roller perches?

Yes

DazeCars, For Sale Page

 

I understand the reluctance to go with a good front end suspension replacement.....it is a big pill to swallow.

S or T's Bilstein coilovers will make your problem disappear, however.
Not only is the ride height easily adjustable, but the springs are easily replaceable. Shaun's "street" setup works just fine.

I'm a bit short of butt time but can report that the ride of the front end is as good as I hoped it would be......the rear still sucks. Fixing that is beyond my willingness from the TM&E standpoint.

 

As I said previous, I can appreciate the tubed coil over solutions but cant justify $2500 for them. My cars ride isnt that bad. I went ahead and bought the Bilsteins and will try them out. I think I'd still like to raise it up an inch and will need new front springs to do that. So if I were to go with a lighter spring like the Moog 8304, a 500lb spring, I gather it will allow me to cut less to get to my desired ride height and help retain closer to original spring rate?

 

Raise the rear as you planned. Then install the front spring of choice,you know my opinion.
Then make sure the CAMBER is 0 , role car back and forth and adjust if necessary. Positive camber raises the front.
I like to do a center to center measurement on the springs just from one coil to the next. Bottom of one coil to bottom of next with FULL weight on wheels. If you cut ONE coil the front will drop pretty much what ever that measurement is. IIRC my favorite spring measures pretty close to 1 1/4" coil to coil so One coil lowers car 1 1/4". Sometime new springs have the last coil ,bottom as installed,bent a little flat so your first cut will lower the car less than 1 1/4" so measure coil to coil after each cut , and reset camber also. I think you will end up cutting 1 1/2 coils to just under 2.

Also forget the roller perch kit, just buy them from Opentracker or Street and Track ready to go.

 

I have some thoughts on this too if it's ok? I have spent a lot of time getting the basic system to work due to class rules in SCCA. I know your not racing but a lot crosses over to make a great riding / handling little cruzer. I started years ago slamming my cars also because it looked sweet. Later on I did the same thing and wanted something a little more refined. I also wanted to go faster too. I started with plotting out the geometry and realized it was better a little higher up. Then I also realized like the previous gentleman said I was pounding the bump stops. I wont bore you with all the details but the end result was a version of what my dad use to use way back.
600 lb coil with about a 7.25" ride height measured from the bottom of the pinch weld behind the front tire.
The Bilstien Street valve is a great shock. RCD and myself developed that shock years ago. you can't go wrong for the dollar.
1.1/8" sway bar with the correct length end links.
Moog strut rod bushings (Rubber)
Rear ride height should be about 8" from the pinch weld to the ground just in front of the rear tire.
Bilstien streets rear too.

I know this is more than you asked for but this has been a great base line for me. I also like realigning the ball joint with a 1" shelby drop. I am not a big roller perch guy. Yea they are nice but Id'e rather put the money into a piggy bank for some good tires or making sure every thing is tight before I get into bells an whistles. The boring basics have always made my customers cars feel the best.

Oh.. FYI what ever you cut off the free length of a coil will lower the cat about double that distance. So if the spring is a 13" tall coil and you cut it to 12" the car will lower about 2". I have had a ton of guys over the years buy another set of coils because they used the 1 coil or two coil method. Good luck.

 

I have some thoughts on this too if it's ok? I have spent a lot of time getting the basic system to work due to class rules in SCCA. I know your not racing but a lot crosses over to make a great riding / handling little cruzer. I started years ago slamming my cars also because it looked sweet. Later on I did the same thing and wanted something a little more refined. I also wanted to go faster too. I started with plotting out the geometry and realized it was better a little higher up. Then I also realized like the previous gentleman said I was pounding the bump stops. I wont bore you with all the details but the end result was a version of what my dad use to use way back.
600 lb coil with about a 7.25" ride height measured from the bottom of the pinch weld behind the front tire.
Find a garbage can for the bump stop shroud or deep dark ravine.
The Bilstien Street valve is a great shock. RCD and myself developed that shock years ago. You can't go wrong for the dollar.
1.1/8" sway bar with the correct length end links.
Moog strut rod bushings (Rubber)
Rear ride height should be about 8" from the pinch weld to the ground just in front of the rear tire.
Bilstien streets rear too.

I know this is more than you asked for but this has been a great base line for me. I also like realigning the ball joint with a 1" shelby drop. I am not a big roller perch guy. Yea they are nice but Id'e rather put the money into a piggy bank for some good tires or making sure every thing is tight before I get into bells an whistles. The boring basics have always made my customers cars feel the best.

Oh.. FYI what ever you cut off the free length of a coil will lower the car about double that distance. So if the spring is a 13" tall coil and you cut it to 12" the car will lower about 2". I have had a ton of guys over the years buy another set of coils because they used the 1 coil or two coil method. Good luck.

 

Thanks for all the great info. I agree, at my current height it just feels too low getting in and out of the car. I dont think I am hitting bump stops but I can mark them or put putty on them and confirm. Raising it up an inch will give me more suspension travel and with new springs trimmed to a taller height maybe a little lighter spring rate up front. My Bilstein's arrived yesterday but am still waiting on springs.

 

Thanks Grabber! Have you used the Daze kit? I'd like to retrofit my set and go roller perches. Will have to check to see if they have metric shaft. I did get my Bilsteins and springs this week so hopefully will get them in this weekend.

 

Mike, yes i got my kit from him several years ago. It had everything that was needed to build a set of them.

 

If this all doesn't get you what your looking for, I'd also consider one of the "upgraded" strut bars as a future purchase. I doubt a roller lower arm is necessary for your desires, but again a easy upgrade as things progress to help suspension to move as engineers designed the geometry.

 

Ok, I have both perches and roller kit in transit to me. Looking forward to this project

Back to the spring discussion, I went ahead and bought the Moog 8304, (the NAPA equivalent) and noticed that the new springs are .625" dia cross section where my originals were .675". Are they doing something different with metal treat where they can use smaller dia section width? Or maybe the ones that I came in my car aren't originals?

 

According to the Moog spring specification chart, the 8304 have a .609" diameter.

http://www.moogproblemsolver.com/moog/wp-content/uploads/2012/08/MOOG_Coil_Springs_Spec.pdf

Here is more info on these springs: http://forums.vintage-mustang.com/vintage-mustang-forum/643572-68-6-cyl-coil-springs.html

 

Thanks to everyone for all the advice. I did finally get the front done as I thought it would be easier to dial in the rear to match the front once I got the front height set. All that said the ride difference in the front is remarkably improved. It does have more of a smoother "floating" affect but in turning and handling is firm and feels more like a modern vehicle. The changes to the front include Bilstein street shocks, roller perches (DIY) and new Moog springs.

I did use the lighter 6cyl springs and the finish cut was one complete coil to achieve the new height I was after. Very pleased so far with the improved ride quality. I look forward to completing the rear changes this weekend and making the car level again.