Coil Spring Rate

Last year I purchased a 69 Mustang roller with an MII front suspension. The car doesnt have much front end travel and will porpoise at the track. I know that the front springs are way too stiff because the old set up had a huge blower and iron heads, now has aluminum heads and a Dommy. I want to stay with the same conventional MII spring set-up and not use the coil over shock deal.
The front end weighs 1500# and the rear weighs 1600#.
The current ride height is okay with the springs at 8.25" long.

I need a front coil spring rate recommendation or do I call Eaton and have them go at it?
A spring part number would be great.

Thanks,
Dave

The porpise problem could be caused by a few different things. Shock settings, front and rear, Does the car hook and stay hooked? Lot of time the porpise feel is the rear tires breaking loose.

The back half is a ladder with 130 rate springs. Single adjustable QA1 shocks at all corners. Front set at 2, rear set at 5. Tried many shock settings and 2-5 seems best. It spins on the release but not badly 3 times in first gear. 60 ft is at 1.38-1.40

Dave what engine combo are you running ? Heads and headers in particular.

Thanks

John Myrick wrote:Dave what engine combo are you running ? Heads and headers in particular.

Thanks

547 cu-in, SCJ heads ported, Diamond flat tops for 13.5 compression, .685 280 roller, 1050 Dommy, 2.25/4.00 headers. Running E85. The car is a tube chassis without inner fenderwells and 31x13's on the rear.
The car runs 9.65 at 140 but if it would leave better 9.20's are possible.

Was gonna ask what headers you are using but with the tube chassis they are custom probably.

Thanks for the info

richter69 wrote:how far are the front springs compressed? total front travel? Is this a ladderbar or 4 link?

From the ride height to full extension the springs only travel 1".
Its a ladderbar set-up.

Are your springs stock length ?

whitefield wrote:Are your springs stock length ?

Dont know, I bought the car as a roller. The lower control arm is almost level.
I may need to just take the springs out and have them measured then order taller springs with a lower rate.

richter69 wrote:

Dave De wrote:

richter69 wrote:how far are the front springs compressed? total front travel? Is this a ladderbar or 4 link?

From the ride height to full extension the springs only travel 1".
Its a ladderbar set-up.

from ride height how much does the front end compress?

for starters I'd get some good double adjustable shocks on the rear at least.

From ride ht. to compression probably 2.5 inches. The shocks are QA1 TS303's and they have 3.5 inches of travel.
I may need to lower the front and buy taller tires to get back some ground clearance.
Am I asking for too much that cant be done with single adjustables?

richter69 wrote:Is the bottom bar on the ladder bar even with the ground, uphill, downhill?

Which is the preferred set-up ?

Ladder bar is even with the ground.