I’m replacing the 30year old front springs on the 67 , 442.The original springs had a free height of17 1/2 “. The Detroit steel springs that were ordered for that car are 2” shorter and thickness of coil was 1/8 “ thicker. They assured me those springs are correct for that vehicle to achieve its proper ride height. Has anyone else done this swap out on the coil springs?They also said that the spring rate is different on their springs , so that’s why there is a difference in length.Thanks for any advice or knowledge on this, Brian

 

In general, a thicker wire diameter means a stiffer spring. To get the correct ride height, it will therefore have a shorter free length. 64-7 A body Oldsmobiles will take tangential ends. The top end will be flat on 68-72 cars. Additionally, the ends will be close to aligned on 64-7 springs so both ends will index in the frame and A arm pockets.

 

While Run to Rund has laid out the correct technical specifications, correct "ride height" is (or should be) in the FSM. I do know there have been MULTIPLE threads here about it. I suppose between the factory books and OCA judging, there's an acceptable ride height. Otherwise, it's subjective. Some like them high like a 4x4, while others like them low like the springs are blown out.
Springs sag once compressed and will settle to their final height. I wouldn't trust any manufacturers for a final ride height. You can make a reasonable guess based on the compressed height measurement, but it may settle below or above the desired result. Bottom line: it's trial and error; no one can predict your final result.

 

https://www.springsnthings.com/

 

This is the spring package I used on my 66 442. It measured 1/2" from factory specs. I'm not sure if they are still available or not.
AC Delco 45H2004 Rear & NAPA 277-1837 Front. If I remember I had to cut 1/4 coil off the rears to get the correct height

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Thanks 6 for the info. I’m replacing the front springs mainly because of the bottoming out problems that have started to occur when driving over roads with swales on them.Our roads are not the best here in northern Illinois.

 

Thanks T for the spring info , I actually did call them yesterday and got a quote and the specs and they seem to fall in place with the originals.Now it’s decision time Go with springs and things or go with the Detroit springs that are 2” shorter and thicker with a different spring rate. The Detroit springs were delivered but I can always return.

 

The original front springs were quite stiff, 425 lb/inch.