My 914-6 GT Tribute car will for sporting street use with a twin plug carbureted 3.2SS engine. I am not sure if I should be using 100 or 150 lb springs.

Any suggestions?

I have a 1974 914 3.2L conversion that is running 140# rear springs but will be going to Weltmeister 180# progressive rear springs. The 140s did help with the additional weight and are only slightly more harsh for street driving than the 100# springs on my 2.0L LE. I don't have a rear anti-sway bar so I think the higher rear spring weight will be beneficial for track days.

Tom, I went with 180lb for my 2.2S. Street and track use. Feel I would reduce it a little. Best, MarkClick to view attachment

I use stock on mine. My car rides perfect

I have 140 pound springs on my car with Elephant Racing rubber bushings and Bilstein Sport shocks all around. Running a 3.2, stock bodied with deep 6 wheels. I also have F&R stock 914 sway bars. Car rides great.

I had 165 progressive rate springs on my 3.6 car and loved them for the street.

I think I have a set of 165 progressives…. Let me know if you’re interested and I’ll look for them and post some pics, would be looking for $100 plus shipping and any fees.

I run 200lb rear springs on my 3.2 conversion car. Doesn't seem stiff at all with the 15" tires. I also used to some track and ax, so I liked being a little stiffer. I had a 2013 GTI for a while that car was much stiffer .

I ran 140’s in the rear with my 3.2 and 914 trans. Had to upgrade to 200 when I switched to the 915 trans and heavier 108mm cv’s.

During the years of Club Racing, I ran a variety of spring rates. At the end of my racing days I was at linear rate 450 front, 400 rear. Now as just a street toy, I am running progressive rate stacked springs with an effective rate in the droop/compression regime for my car of 150-270 front and 230-330 rear. Spring rate at the shock for the rear is 161-248. The higher effective rate is corrected for the motion ratio of the rear suspension which is about 1.3 for the 914.

If you stick with linear rate springs, they are inexpensive and really easy to change on the rear. I have two crates of linear rate springs that go anywhere from 250 to 700.

My car is sprung a little too stiff for the street, but I don't drive it enough to warrant a change plus I do like the way it handles.

140 rears, stock front torsion bars
Add an adjustable front anti sway bar to help tune the front stiffness.
I would suggest adjustable koni shocks all around

I have 180 rears, bilstiens all around
Car it too stiff.

I got talked into 180s when I did the swap. Dropped back down to 140s and it rides and turns better.

Front end is stock 911 Carrera.

Turns out the weight increase wasn't really that big.

teeth and lower back cost money to fix.

Hi,
I am building a 914-GT replica and I am confused with the spring rate recommendations for Street use.

Without getting into the specifics of my car (weight of a 993 engine and Boxster S trans) I often see people suggesting 140-160Lb/in springs, or 160 or 180 progressives.
I guess that is for using with Bilstein shocks without threaded adjustment (I guess those springs have a 4.1 to 4.25" Outer Diameter, and a Free Length of 15").

On the other hand, Patrick Motorsports sells threaded adjusters and for Street they recommend 175-225 Lbs springs (I would consider 225 Lbs due to my heavier engine and trans). They mention that these are 2.50” I.D. x 8.0” Length

It does not matter if a Spring is short or long, if it has a small or large diameter, nor its preload.
Once he suspension starts going down, for each Inch of stroke the spring applies an extra force in Lbs determined by its spring rate.
This means that Patrick Motorsports recommends stiffer springs, or am I missing something ?

Hi Miguel, I think you have a good understanding of springs. PMS is an excellent shop and I am know they have done many 993 engines in 914 projects. So they speak from experience.

Here’s what the factory thought:
Click to view attachment

I don’t know the actual source of this data, though.

Each to their own really depending on usage and local roads. I would not want anything less than 200lbs with 15's for what I use the car for. Mountain driving and occasional track.


Here is what Patrick Motorsports says for what that is worth-
"For street use setup we recommend (175-225 lbs spring set) – For full racecar setup we recommend (275- 325 lbs spring set). The system allows infinite ride height adjustability and corner weight balance setup. Part # SUS 914 RCKIT and PMP914."