With a stock suspension I would not go stiffer then the factory GT coil which I believe is 480 pounds per inch. I would stick to the factory 110 pound per inch GT in the rear and I wouldn’t go more then the 4.5 leaf 138 pound per inch in the rear. Keep the shocks on the softer settings.


You have to allow the suspension to do it’s job. Making it too stiff and the tires will loose contact with the road surface. I would also focus on making the body of the car stiffer too.

Last edited by Huskinhano (1/31/2018 7:49 AM)

My car will be more street driven and some funny mountain road  but far away from race.
With old springs and new shocks i think is only half job .
Does anyone have find noticeable differences between progressive and linear rate , if using ?
My arms are not stock . Upper and perches with roller , lower renforced  .

Huskinhano wrote:

With a stock suspension I would not go stiffer then the factory GT coil which I believe is 480 pounds per inch. I would stick to the factory 110 pound per inch GT in the rear and I wouldn’t go more then the 4.5 leaf 138 pound per inch in the rear. Keep the shocks on the softer settings.


You have to allow the suspension to do it’s job. Making it too stiff and the tires will loose contact with the road surface. I would also focus on making the body of the car stiffer too.

​X2 - That is what I have. 

My front GT's have an included 1" drop and the 4 leaf rears are reverse eyed.  You can see the car to the left.  I love the roller perches.  Shocks are GR2's that I got for free.  Not my favorite.  A-arms are Total Control.  I got rid of the TCP strut rods as they made the ride too harsh for me.  I also have Traction Masters in the rear.

​Keep the Koni's they are the best you can get.  Just adjust them to the stiffness you desire.
 

red351 wrote:

One thing I have notice over the years collecting coil springs is ford or somebody didn't install the by the book front springs. So I just keep then all.... Reason is, going by the book specs (wire size/coil count and free standing unloaded height) they are still in perfect health. Its just  way did someone put this (by the book) set of 67 S code 390 coil springs in this 67  C code 289 coupe. My simple thinking says  coils don't weaken as much as we are always told too think. Now a car that been in a barn fire (yes) or its been sitting in a swamp for years and have rusted or rotted the wire size down (yes) or its been sitting in a junk yard again for years with 5 cars on top (yes). Leaf springs are like a different animal....A good Cleveland can wrap them up so tight, they will never be the same again....

Long live wheel hop and spring wrap!!!!!!!!!!

Global West is one of the best vendors around, so you should have no problems with  your springs.  I believe that 540's will be sufficient.  640's, while several of us have them, are more of a racing spring.

​You should do the Arning drop.  It gives a much better camber curve for better handling on those winding Italian roads.

lowercasesteve wrote:

Global West is one of the best vendors around, so you should have no problems with  your springs.  I believe that 540's will be sufficient.  640's, while several of us have them, are more of a racing spring.

​You should do the Arning drop.  It gives a much better camber curve for better handling on those winding Italian roads.

 
Well , i dont wanna do the same mistake twice .
When i placed the arning drop and roll the car , tire  was sitting too much inside fender .
These are yet lower so first i will do like original  .next time i can try dropping it.

I used the search bar to find an old topic!!

1966 Mustang Coupe, 1988 5.0 HO, T5z, EFI, MAF

It seems front springs are all about the weight vs the spring rate in regards to getting the desired ride height.  With the 5.0 swap and T5z, is there significant additional weight relative to stock V8?  The 640 lb springs would be really stiff for a stock car but I'm thinking the additional weight might make sense to go w/ the stiffer springs.  I wish there was a chart for this.

TremendousWand wrote:

I used the search bar to find an old topic!!

1966 Mustang Coupe, 1988 5.0 HO, T5z, EFI, MAF

It seems front springs are all about the weight vs the spring rate in regards to getting the desired ride height.  With the 5.0 swap and T5z, is there significant additional weight relative to stock V8?  The 640 lb springs would be really stiff for a stock car but I'm thinking the additional weight might make sense to go w/ the stiffer springs.  I wish there was a chart for this.

I think a 5.0 with T-5 should be lighter than a stock 289 with 4-speed, except the weight of the 5.0 accessories may add up to negate any weight savings.  In any case I don't think it's any heavier.  I know from personal experience that the T-5 is significantly lighter than a 4-speed.