Hello, I’ve got a standard suspension base 289 Cougar with stock springs front and rear. The front control arms were dropped long ago via the Shelby mod.
I’ve been considering a nominal increase in the front spring rate since on good sized bumps, even with trimmed bump stops they do contact the chassis. It bugs me. The shocks seem OK (KYB gas-adjust but old).
I’ve seen on another forum that the stock spring rate for the 390 was 260 lb./in., with the GT package it was 320 lb./in. I can’t find the base model spring rate. I see confusion on some places that think there’s a 620 and 750 lb. rate.
Anyone know the base Cougar 289 spring rate? Other after-market spring rates you know of? Thanks in advance.
Not sure of the OEM spring rates but on my 68 I’ve got the common 1" drop 620 front springs, Shelby drop and KYB Excel-G shocks. On 225/60/15 tires I still rub on large bumps. I’m kind of tired of dealing with it and considering swapping to coilovers on the front.
Thru the years, I have used Moog spring #8356. They are rated around 400Lbs. More than a 67 289 cat needs, but great for big block & 69/70 w/ 351 & loaded (A/C). Not as harsh ride as the 620 rated springs sold everywhere( some were blue) .
I dont have rating for your application, should be easy enough to find. I strongly suggest NOT using the 600Lb+ rated springs… You won’t like the ride.
Thanks, Cougar_Bill - I was thinking EXACTLY as you. When I bought the car in the 70s, I had all sorts of vision for track events, etc. Now that I have owned many real handling cars, I realize that’s a pipe dream for this antiquated crappy suspension design. I’m happy with it cornering flatly as it does now with a comfortable ride. I evolved to realize the best handling street cars were the ones with larger, well balanced sway bars and that do NOT have monster springs that beat you to death over bumps.
Your reference is timely - I’m trying to find spring rates on a variety of products, but alas - no one has the technical information. As an engineer this is quite frustrating. 400#/in. sounds like something I can deal with in my desired driving sphere. Lacking other data (which appears where I’m headed) - that’s a good fallback option.
OD - 5". Wire dia 0.610 in. Resultant ID 5.78". 8 1/2 coils (approximation).
By my estimates, this comes up around 340 lb./In.
Not remembering if this was my original springs, or those of my bud who took his 390 GT and turned it into a drag car - I’m thinking now I have the 390 GT front springs in my car. My bud donated his disk brakes to me, so likely his coil springs as well. I would have likely swapped them when I did the Shelby mod. if he had donated those as well.
Having said that - 9 coils would work out right at 320 lb./in. rate so I’m highly confident this is what I have. Let me put in the missing bump stop. If that doesn’t take care of the issue, I’m thinking the 400 lb./in. might be a nice update.
As an FYI for all, WCCC has a 289 #/in rate and a 365#/in (I think) rate.
Like the video, Cougar_Bill. Do you have the details on your car somewhere?
The Cat is a 69 XR-7, originally a H code Windsor. It has a very strong full roller motor with alum heads,approx 550+ A worldclass T5 rebuilt with racing components.
Suspension is factory w/ Moog parts. Shelby drop & upper A arm modifications as per the Boss 302 chassis mod book, export & reinforced cross member. 8356 coils springs with 1 full coil cut. 1" block in rear leaf springs (66-311). Brakes are factory with Porterfield carbon brakes. Tires are Hoosier TD track tires on 15" wheels.
