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HD front springs
Posted by: Wrencher ()
Date: July 29, 2020 11:52AM

Curious if anyone has experience with the HD front springs from Clark's.
The catalog lists a 1/2" drop installed, which is fine, but I was wondering about the spring rate?
Real world experience would be nice. I do some track events with this car (140 with Crower cam, port work, headers, late transmission, disc brakes, larger front and rear sway bars and so on) and curious about these springs.
I'm currently building a replacement front subframe with all new stuff.

Hans

The Larry Shinoda Collection: '65 Corvair Monza 140, '69 L-68 Corvette Roadster, '70 BOSS 302

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Re: HD front springs
Posted by: PGVair ()
Date: July 29, 2020 04:39PM

I presume this is for a late model? If so and if Clark's springs are the same as factory HD springs they should be ok. I have factory HD spring on two LM's which are good street springs. I have one LM with one coil cut off the front springs. It rides good as well and seems to handle better than the factory HD springs. If you are going to do track events you might want something different. Seth should be able to advise.

Wade

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Re: HD front springs
Posted by: Wrencher ()
Date: July 29, 2020 09:17PM

Sorry, yep, a '65. It tracks OK now, I'm not real aggressive, I'm still running T/A's on it, so that should give you an idea. The next step would be sticky tires, a roll bar setup, good seats, 5 point belts, etc..., and that's a big step. I raced a full on 88 Trans Am, so I know the commitment in time, preparation and money to go serious racing. The Corvair is primarily a street car. Glad to hear the HD springs worked for you, good to know.

Hans

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Re: HD front springs
Posted by: JimBrandberg ()
Date: July 30, 2020 05:59AM

When experimenting with springs for my road racing car I had access to a spring rate tester but found Corvair people don't really talk in the same language as spring people.

Corvair people will talk in terms like HD, convertible, etc.

Spring people will talk in terms of wire diameter, number of turns, free length, spring rate, etc.

I was surprised that Rock Auto actually had some spring information.

I bought some Clarks rear HD convertible springs for a Corsa a few years ago. The physical measurement were different than the ones I took out but the ride height was exactly the same.

I wish I had time to compile my random information into some sort of a table, it's written down but scattered.

Someone like Bob Coffin or Ken Hand might be more organized.

If you have Monza springs now and go to HD springs it will be an improvement for what you're doing.

Jim Brandberg
Isanti, MN
CorvairRepair.com



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Re: HD front springs
Posted by: jamesolefjensen ()
Date: July 30, 2020 08:28AM

I installed Clark's front and rear HD springs along with the factory front sway bar, Konis, 16" rims and tires (205/55 on 7", 225/50 on 8"), and rubber bushings everywhere.

The overall setup does very well. The ride is comparable to the 86 Corvette I had except it rolls a little more in the turns. For the street, it is tolerable on all but the very worst roads here in CA.

With a spare tires and a tool bag in the trunk, the front lower arms are slightly lower than parallel to the ground to (eyeballing an imaginary line between the inner pivot and ball joint, if that makes any sense).

Hear, hear on the seats. My Recaros are light years ahead of the bar stools originally installed.

James
65 Corsa
SF Bay Area

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Re: HD front springs
Posted by: jamesolefjensen ()
Date: July 30, 2020 08:32AM

Slight typo; I only have one spare tire in my trunk.

James
65 Corsa
SF Bay Area

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Re: HD front springs
Posted by: MonzaDave ()
Date: July 30, 2020 09:14AM

I have the Clarks HD springs front and rear on my '65. They're supposed to duplicate the springs in the F41 HD package. I don't know how close they come, but I'm totally satisfied. I also have urethane bushings and Koni shocks set at about 50%. The ride is good on our frequent road trips and handling is excellent. Here's a picture showing how it sits.

Dave Keillor
Rochester, MN

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Re: HD front springs
Posted by: doug6423 ()
Date: July 30, 2020 09:30AM

That looks good!
Where did you get the front air dam from?

Doug
65 Monza
Cincy, OH

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Re: HD front springs
Posted by: MonzaDave ()
Date: July 30, 2020 09:53AM

That was the old Corsa Enterprizes spoiler. I believe that David Herrin III has them (The Source). A better one is the one designed by Mel Francis (he also designed the Corsa Enterprizes spoiler) and I believe that John Miller sells them. If you need more information on either of them, PM me. Here's a picture of the new Mel Francis spoiler -- it's the one to get.

Dave Keillor
Rochester, MN

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Re: HD front springs
Posted by: martyscarr ()
Date: July 30, 2020 05:47PM

I contacted Clark's to see if they had the spring rate for their HD springs, but they say they don't have that info. They did provide the following:

1285 pound capacity
13.5 inches tall
6 7/8 coils
.550 wire diameter

This is for their HD springs for 65-69 coupes/4 doors, part #C762CP, they say they are equivalent to the GM 3875088

Has anyone measured the spring rate of these HD springs?

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Re: HD front springs
Posted by: jamesolefjensen ()
Date: July 31, 2020 08:21AM

Personally, I have not measured the rate but it can be calculated. The info above is almost everything needed for accepted design equations. The only thing missing is the outside diameter of the spring. The formulas are out there on the innerweb.

If a quick and dirty answer is wanted, we could assume (ass+u+me) that 1285# collapses the spring to the solid height and 13.5" is the free length. In this case, the spring rate would be 1285/(13.5-(.550*6.875))=132 lbs/in.

As a licensed mechanical engineer, I am very confident that my calculation could be wrong.

James
65 Corsa
SF Bay Area

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Re: HD front springs
Posted by: martyscarr ()
Date: July 31, 2020 02:41PM

Okay, I called Coil Spring Specialties to see what the spring rate of the HD spring for late coupes and 4 doors. They were very helpful and looked up the original GM spec for spring 3875088 and said it is 210 pounds per inch.

HTH

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Re: HD front springs
Posted by: martyscarr ()
Date: August 01, 2020 08:49AM

found a little more data, this info from the 1965 heritage package



Edited 1 time(s). Last edit at 08/01/2020 08:49AM by martyscarr.

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Re: HD front springs
Posted by: andyman260 ()
Date: August 01, 2020 07:17PM

I’ve been running the Clark’s HD springs for ice a decade and love them. This is in comparison to the cars without that I’ve driven. Combine them with bigger wheels and tires and you have a nice setup. I run 15x7 205/45R15 which is now apparently only made of unobtainium.

Andy Allen

Oak Park, IL

1966 Corsa w/air

708.921.8937 cell

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