Original 427 Street roadster coil springs

[my427cobra]

Just curious. Does anyone know what the front and rear coil spring ratings were on the 427 Street roadsters.

And I would imagine the comp versions had higher spring ratings?

Cheers
Greg

[Cobra #3170]

Originally Posted by my427cobra

Just curious. Does anyone know what the front and rear coil spring ratings were on the 427 Street roadsters.

And I would imagine the comp versions had higher spring ratings?

Cheers
Greg

I have some in the garage but they are not marked, they were quite low as I recall something like 350 and 450 lb/in respectively. I am pretty sure Nic or somebody else will know. If nobody responds I can measure the wire diameter, spring OD and coil count to calculate the rate. Some time in the late 1970's I had Hypercoil wind some replacements for me that are slightly stiffer but have the same coil count and spring diameter, they were marked as are all Hypercoils for rate. I can check and see what they are so you would have a ball park number, They were really expensive at the time so I switched to 2.5 OD after that because it is a common size for race cars.

[my427cobra]

Thanks Cobra 3170. That would make sense. Road test articles of the time decribed the ride as firm but not harsh.

I currently have 8" 500lb/in front coilover springs in the front but for street/boulevard cruising, way too stiff. I got talked into that rate even though my calc's and judgement told me they were going to be stiff. I just didn't know how stiff. When I put my 200 lb weight on the front bumperetts of the car, the suspension barely moves.

I'm going to move down to 350 lb/in springs as a first step and if it's still too stiff, then 275lb/in springs.

My front would be a little lighter than an original car. I have aluminum heads, aluminum water pump, shorty headers (rather than the original cast iron exhaust manifolds), aluminum rad and the battery in the trunk.

Nice thing about coilovers - easy to swap out.

Cheers
Greg

[DanEC]

Greg - I think trying to compare spring rates from original cars to most reproduction cars is kind of an apples to oranges comparison. I'm not familiar with the NAF suspension but unless it is a virtual duplication of the original, there are probably some differences in the points of connection to the lower a-arms up front and the lower suspension arm in the rear. Plus there may be some difference in the overal arm lengths. And the cant or angle of the springs will cause them to have a different, effective vertical spring rate component.

[my427cobra]

Hi Dan. Yeah, you're right and I thought about some of those things. But the front of my car is just too stiff (jarring stiff when driving), so I need to go down in spring rate.

My front shocks are QA1 streetster coilovers (a streetrod shock for an independent front suspension of the matching weight), my a-arms are Mustang II tubular uppers and lowers, about 1" narrower than stock (Speedway street rod arms).

Always trying to collect as much info as possible, benchmarks to work from.

Now just a little work to swap out the springs and reset the ride height (and o yeah, might have to realign).

Into the garage I go.

Cheers
Greg

[DanEC]

I see. Good luck. I don't like overly stiff springs either. Too hard on the car and the driver.

[my427cobra]

Well I put in the 350 lb/in springs and now when I put my body weight on the front bumperettes, I han actually get the front suspension to move up and down.

I'll give it a run tommorrow.

Cheers
Greg

[mickmate]

You should be a lot closer now Greg. Bear in mind we're running pretty light cars with a good set back on the motor so only a little nose weight to hold up.

[my427cobra]

Well what a difference. Front end now absorbs bumps without the jarring in the steering wheel.

I'll stick with the 350 lb/in springs for a while and let the suspension settle in again.

Cheers
Greg