Front spring rates

[65comet]

Does anyone know if Ford used different front spring rates on the 67-72 F100 for big block, small block or 6 ? I'm driving a 71 F100 that was a 390 truck from the factory. I've got an aluminum headed 302 and lighter manual trans than stock. Not enough give in the springs, the whole truck moves with the dips and bumps in stead of suspension moving. I'd like to get a lighter spring but can't find info on spring rates. Would a progressive spring be softer than a stock spring and did Ford use a lighter spring for the small block ? Thanks for any info.

[basketcase0302]

"65comet"Does anyone know if Ford used different front spring rates on the 67-72 F100 for big block, small block or 6 ? I'm driving a 71 F100 that was a 390 truck from the factory. I've got an aluminum headed 302 and lighter manual trans than stock. Not enough give in the springs, the whole truck moves with the dips and bumps in stead of suspension moving. I'd like to get a lighter spring but can't find info on spring rates. Would a progressive spring be softer than a stock spring and did Ford use a lighter spring for the small block ? Thanks for any info.

I know they did for the Stang' of the same era so am pretty sure they did for our trucks too.
Have you tried submitting the different parameters into part searches for a few different vendors?
That should confirm it.

[two-bit]

Did a quick search on Rockauto.
Shows a Moog 8226 for 6cyl trucks.
and a Moog 8228 for v-8 trucks.

So i would guess they did. Not sure what the difference is between the two.

Two-bit

[JoshT]

Wow, there really isn't any info on those is there. I even looked up a Moog spring chart. It lists both part numbers, gives a diameter, and absolutely no other information.

Sorry can't answer your question about the springs used on the small block trucks. It wouldn't surprise me if they did, but the aftermarket has consolidated it down to just the two springs. That kind of thing happens a fair bit.

This will be rather crude explanation of the progressive rate springs, but is about how I understand it.

The stock springs would have been a constant rate spring. That means that the first two inches would have taken the same amount of force to compress as the last two inches. If your spring had 6" of compression and rate was 100lbs/in then it would take 100lbs to compress it the first inch, and with 600lbs it would be compressed the full 6 inches.

With a progressive rate spring the spring rate changes as it compresses. The spring might have the same overall capacity, but the spring rate varies. The first two inches might compress at 50lb/in, the next two at 100lb/in, and the last two at 150lb/in. That first two inches at 50lb/in would equal a softer ride, the second two inches of compression would be about the same as stock, and last two would be harsher than stock. Ride starts out softer, but the harder you work the suspension the stiffer the ride becomes. Most of your normal driving will likely stay in that first two to three inches of compression, so you get a better ride, but don't sacrifice capacity because it retains the same 600lb capacity.

I went with the progressive rate springs on my 4x4, but haven't really driven it much since I did.

[65comet]

Thanks for the input. I actually found stock front spring rates here on Fordification. Lot's of good info here - http://fordification.com/partnos/springs-front.htm

Looks like most spring manufacturers have cut it down to making 2 constant rate springs and 1 progressive rate spring for these trucks. I'll be calling the manufacturers on this.