Anyone here running 750 lb/in front coils?

[Hack]

I just recently swapped 620s into my '70 vert and they don't seem that stiff at all to me. I still have the 6 cylinder in it, but I plan on going to a 351C (this summer if everything goes well, next summer might be more realistic).

I have stock shocks in the car (just replaced last year). I don't think the shocks will matter much in ride stiffness, but I might go to something better in the future. Will this make a big difference in ride harshness if I go to different shocks?

I'm considering 750s. Anyone here run them? How do you like them? My car will be driven on the street probably exclusively. I may try some autox or some such at a later time, but I've got a lot of other things to do on the car first. I'm just looking for a fun street performance ride; I like to turn corners hard.

Also, right now I'm running 195 70 14 tires, but I will be going to 245-45-17 in the future. I expect that will make the car seem a little stiffer.

 

[mustang70]

I had the 720's and KYB's in my 70. It never seemed to harsh to me. You might want to put some better shocks and the tires you want before swapping the springs. They will make a difference in the ride.

 

[12sec67]

i have 720's and kyb's with my 17's and it was really stiff! i had to put some summit adjustables and on 70/30's its a lot softer than before and still handle great along with the shelby A-Arm drop!

 

[bnickel]

i have the 750's and i think they are just right for a front heavy 69/70 with a 351 or bigger, especially with ac and ps.

 

[streetgrande69]

i can't speak for how a nything except for stock and 620's are. i think my set up is good for daily driving(not saying whats good for me is good for you.)

I want to add that your sway bar also effects the stiffness of your front suspension. the larger the diameter, the more it will add to the stiffness. do you have a stock or aftermarket sway bar?

 

[HistoricMustang]

i can't speak for how a nything except for stock and 620's are. i think my set up is good for daily driving(not saying whats good for me is good for you.)

I want to add that your sway bar also effects the stiffness of your front suspension. the larger the diameter, the more it will add to the stiffness. do you have a stock or aftermarket sway bar?

75% of the time a run a 750#. Other 25% a 620#.

HistoricMustang
www.historicmustang.com

 

[Hack]

i can't speak for how a nything except for stock and 620's are. i think my set up is good for daily driving(not saying whats good for me is good for you.)

I want to add that your sway bar also effects the stiffness of your front suspension. the larger the diameter, the more it will add to the stiffness. do you have a stock or aftermarket sway bar?

I have the stock sway bar. Thanks for the info. I should probably swap out the sway bar, tires and pick some shocks before I buy the springs.

I also want to rollerize the bushings in the front end, so I should probably also do that.

 

[Hack]

i have the 750's and i think they are just right for a front heavy 69/70 with a 351 or bigger, especially with ac and ps.

Thanks! Frankly I was really surprised at how soft the 620s seemed, especially with an I6 and no options. Other than the car being a convertible, it's currently as light as a '70 Mustang came from the factory.

I also considered that my weak rusty chassis could be making the suspension feel softer, but I have subframe connectors. I wonder whether people in the 70s just expected a "living room couch" kind of ride in their cars. Even in the cars intended to be sporty. My Nissan Sentra is more stiffly sprung, and my '85 GT is a lot stiffer.

 

[Edbert]

I'll attest that ragtops flex a lot more than hardtops, but I feel the 620s are plenty stiff. Are you running 75 series (stock) tires? High sidewall tires will take a lot of stiffness out, try putting the 245/45/17s on there and see if it is still too soft before you go to the hassle and expense of new springs.

if the roads you drive on are very smooth the 750s might work out, but rough pavement will actually cause you to see poor handling with the ultra stiff springs. Try getting some high pressure gas shocks in there and use those other wheel/tires first.

 

[grego37]

I've got 620's and adjustable Koni's (set mid way) in a 68 mustang street car. Plenty stiff for me. And I love the ability to adjust the stiffness of the shocks.

Good idea to change your shocks before you do anything else.