1965 gt350 & K code front coil spring specs?

[SeanSide]

Hi everyone,

I am gathering information for my project and discovered from someone's forum post, claiming he is reading this info from a 1960-1968 ford parts catalog in his possession, that the "GT special handling package" had different front coil spring specs depending on what options the car was equipped with. I imagine this slight difference was lost in time, just like the Koni shock valving got stiffer for heavier engine cars, i guess the available springs must be stiffer for the heaviest cars out there to avoid customer comebacks and/or accidents. My intention is to get the closest to the balance and ride quality the 1965 gt350's originally had.

My question is this:
- What are the exact specs & dimensions of the front coil springs for a 1965 gt350?
(So i can get Eaton to make custom front springs that matches the specs of a 1965 mustang fastback / 289 / manual 4 speed / no A/C / no power steering)

Here is the post i found on stangnet.com by user "Realmongo":
-  The Coupes and fastbacks used the same front springs and there were 2 versions for '65 that were used in the Special Handling Package which was included with GTs and K Codes. It also could be ordered separately on all V8 models. The C5ZZ-
5310-E spring was rated at 1491 pounds and was identified by a brown stripe. These were used with power steering and W/ and W/O A/C or manual transmission with A/C. The C5ZZ-5310-F spring was rated at 1413 pounds with a red stripe and were used with manual steering and no A/C.
There were 2 sets of rear leaf springs used. The coupes used 1 style, while the fastbacks and convertibles used the other as they were heavier in the rear than coupes. The fast back and convertible used C5ZZ-5560-E rated at 650 pounds load rate, while the coupes used C5ZZ-5560-F rated at 610 pounds load rate.

Link: https://stangnet.com/mustang-forums/threads/1965-mustang-front-and-rear-sprin-rates.910350/

According to that information, i should be looking at the:
- C5ZZ-5310-F front spring
- with a red stripe
- rated at 1413lbs

Another piece of information i found on shelbyforums.com by user "Texas swede".
(But I'm not sure if he was describing the spring i am looking for):
- Springs were Ford HiPo (K-code).
Fronts are 8 1/4 coils with a free standing height of 13 7/8". Coil diameter is 0.60"

Link: http://www.shelbyforums.com/threads/what-springs-came-on-the-66-shelby.8418/

Thank you in advance!

Shawn.

[TA Coupe]

The pound ratings above are absolutely comical. The fronts are approximately triple and the rears are a little more than triple. Realmongo needs to stick his head in a toilet.

      Roy

[Bob Gaines]

I don't want to discourage you but I ordered a set of springs from Eaton and got them last week for a 66 GT350 . They were meant to replace a missing pair for my car. Of course I ordered them for a 66 hipo Fastback.I have had them in and out of the car 3 times now to cut the springs so as to get the ride height within factory specifications. The strange thing is that they started out on my shop floor matched up to a set of springs that came out of a 65 GT350 I have. The wire was the same thickness and the free height was the same as the old used coils that came out of the 65 GT350. The car sat about 3 inches too high. The Eaton guy didn't know what to say.I finally got mine cut properly so that the ride height is within the factory height range for a hipo/Shelby car. I expect a stiff ride after I get it on the road.

[68blk500c]

Providing factual information.  Assuming resized scans post, absorb C5ZZ-A,B,C,D,E,F on pages 22, 23, and 24; Then cross-reference on page 4.  From some Ford book.

[SeanSide]

Bob, thanks a lot for the info. I'm happy to hear my suspicions we're justified and sorry to hear you had that much trouble. I will know what to expect when i get to that step.

68blk500c, absolutely amazing! Judging by the description in the other forum, that seems to be exactly the document "Realmongo" was reading off of. I will read into it.

Huge thanks to everyone!

[J_Speegle]

Please remember and consider that the MPC (the document shown and referred to) is a collection of parts that were available at the time that book/pages were publish so they don't always represent what was original, sometimes just what would work that they carried at the time. The original ride height is from factory documents at the time of production but unfortunately they are not available for the GT350 but instead a K code and you have to figure the slight difference due to variables. Depending if its a 65 or 66 you have tire size, wheel size (possibly) and if the car has the lowered/modified upper a arm location

[TA Coupe]

The charts above show the weight that the Springs can handle, not the spring rate. 69/70 Trans Am cars would generally use something between 850/1200lbs spring rate. I started with 850's and cut 1 1/4 coils so it's supposed to be somewhere between 950 to 1000. Car is lowered about 2.5 inches.

     Roy

[Helmantel]

The pound ratings above are absolutely comical. The fronts are approximately triple and the rears are a little more than triple. Realmongo needs to stick his head in a toilet.

      Roy

They are load ratings (like you said in your later post). For the coils it was the load it requires to compress them to a certain height representative for ride height (9 inch for a 65-66 IIRC, taller for the different 67+ shock towers). The leaf spring load rating is the load it takes to flatten them.

The large difference between front and rear is that for the front, the leverage of the suspension needs to be taken into account (the spring does not sit on the ball joint but somewhere halfway down the A arm). 

For the front: 1413 x 0.6 = 848 x 2 = 1696 pounds
For the front:                      650 x 2 = 1300 pounds
Total:                                                   2996 pounds 

The spring rate (stiffness) is the extra load it takes to compress the springs another inch.