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Front springs Empty Front springs

Post by SSTOOLMAN on Sat May 30, 2020 9:01 pm

Hi guys, it's been a while . I have 1 front spring on my 73 that seems partially collapsed. I have some spring spacers it it now to level it out. I want to replace the fronts but theres too many choices LOL! I am pretty sure  Back in the day there were 2 different springs in our cars they were labeled with air conditionig or without air. I had a friend that had a 454 in it  and he was told the 350's with air used the same spring as the 454, does that sound right? There is a slim chance I may drop a 454 in at some point so I want to be ready, but until then I dont want to sit too high. I like a little rake.
What would be a good front load rate? 2500 lbs?
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Post by Joe73 on Sun May 31, 2020 6:43 am

You are and your friend are correct. There are lots of choices and spring choices do overlap. I went through this when my 73 was my daily driver. I scoured the parts books cross referencing spring part numbers.

Basically, there are standard springs/heavy duty/ac springs/ac heavy duty. So four choices in small block and big block. Each gets a little stiffer. So a small block with ac and the small block heavy duty would be the same as putting in big block standard springs. And if you go small block, with ac and heavy duty, your getting the same spring as big block with ac heavy duty.

I tried the heavy dutys, with an without ac and my last set I ran were small block, with ac heavy duty. With those, the suspension was maxed out ALL AROUND. Meaning the shocks were almost at full extension, so I was not getting full shock travel for a normal ride. When I took my car apart, my rear shocks could only extend about two inches. So when going down the road and you hit some dips, the shocks would top out. Not so much on the front since the springs were big and stiff.

As for the rear springs, I recommend just going with a small block heavy duty. But the front, Id go with small block heavy duty to match or heavy duty with ac. Either way, the front end will sit up until you get some drive time on it. I found that out in every instance of spring changes. Looks a bit funny, but you need the drive time.

My current suspension is small block heavy duty all around. Front end is still up a bit but the car hasnet been on the road since install.

Good luck with your choice.
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Post by bigredlaguna on Sun May 31, 2020 6:25 pm

If you want to get really confused, I catalogued a lot of spring choices and the applications they were on using the NAPA information a few years ago. It is all in the suspension section of the tech forum on this site.

I personally used the springs with the highest factory spring rate, which is 500 lbs/in, used by Buick in 73 for a small block with air HD, and 74 for a big block without air HD. I also cut one coil off so the actual spring rate is more like 570-600 lbs/in. This brought the nose down about an inch and the ride quality is superb. This was done on my 76 Laguna with air, and I am considering using the same springs and cutting to height for my daughter's 74 small block.

If you want to get as close as possible on the first try, you will have to do some weighing first, and then some math to figure out what you need for your specific car.
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Post by SSTOOLMAN on Sun May 31, 2020 7:39 pm

That's a lot of good info!  I have been comparing the AC Delco springs on Rock Auto
they range from (small block) 2100 to 2700 lbs (load rate front),(big block) 2300 to 2900 lbs load rate front. I am  looking at the ACDELCO 45H0008,  2375 load (small block with air). it cross references to big block with out air. I have a air car so it would be the same as what I have now. My option to go a little bigger would be the MOOG
8000 at 2555 lbs.
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Post by 76 Malibu on Tue Jun 02, 2020 6:52 am

There were a ton of springs available from the factory.  Look at the GM Information kits if you want to see all the springs offered.  The aftermarket does not offer the same number of springs that GM offered when new. They try to consolidate multiple parts into one part number to save money.  

Here are the 1973 factory spring specs:

Front springs 1973_c10

Keep in mind spring load is just the load the spring is carrying at the compressed height.  So if a spring has a load rat of 1780 lbs and loaded height of 11.0", all that means is that this spring will be 11.0" in height when 1780 lbs is on it.  A spring with a 2410 lb load rate and a 11.0" loaded height, means it takes 2410 lbs for it to compress to 11.0".  That doesn't always mean the higher load rate spring is stiffer.  It could simply be taller to begin with.  If you note on the chart above, there are lots of springs with the same spring rate and loaded height but different load rates.  This means that the the higher load rates springs are taller when uncompressed (see the free height column).  Heavier cars have a higher load rate, simply because heavier cars put more weight on the springs. So a Big Block A/C car will have a much higher load rate than a non a/c small block.

It's spring rate you want to look at for how stiff a spring is.  Wire diameter generally and the number of coils plays the biggest role in spring stiffness, since the diameter of the springs is pretty well the same for all G3 springs.  The bigger the wire and less the number of coils, the stiffer the spring.  That's also why cutting a spring stiffens it, since your are reducing the number of coils.

FWIW, I am running Global West springs on my Malibu. They are somewhere in the 550 in/lb area.  I have Bilstein shocks with them.  Compared to the stock wallowing springs, these are far better but still ride softly.  In fact, if I were to do it again, I'd probably go stiffer as I find these a bit soft for my tastes.  My car is just a cruiser, so it's good enough for now and at least it handles fairly well.

If someone wants a stiff spring, Moog 80090 might be a good choice.  They are about 700 in/lbs and are short.  They might require a little trimming to get the stance right though.
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Post by Joe73 on Tue Jun 02, 2020 7:06 am

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Post by bigredlaguna on Tue Jun 02, 2020 9:31 am

76 Malibu wrote: Keep in mind spring load is just the load the spring is carrying at the compressed height.  So if a spring has a load rat of 1780 lbs and loaded height of 11.0", all that means is that this spring will be 11.0" in height when 1780 lbs is on it.  A spring with a 2410 lb load rate and a 11.0" loaded height, means it takes 2410 lbs for it to compress to 11.0".  That doesn't always mean the higher load rate spring is stiffer.  It could simply be taller to begin with.  If you note on the chart above, there are lots of springs with the same spring rate and loaded height but different load rates.  This means that the the higher load rates springs are taller when uncompressed (see the free height column).  Heavier cars have a higher load rate, simply because heavier cars put more weight on the springs. So a Big Block A/C car will have a much higher load rate than a non a/c small block.

It's spring rate you want to look at for how stiff a spring is.  Wire diameter generally and the number of coils plays the biggest role in spring stiffness, since the diameter of the springs is pretty well the same for all G3 springs.  The bigger the wire and less the number of coils, the stiffer the spring.  That's also why cutting a spring stiffens it, since your are reducing the number of coils.

FWIW, I am running Global West springs on my Malibu. They are somewhere in the 550 in/lb area.  I have Bilstein shocks with them.  Compared to the stock wallowing springs, these are far better but still ride softly.  In fact, if I were to do it again, I'd probably go stiffer as I find these a bit soft for my tastes.  My car is just a cruiser, so it's good enough for now and at least it handles fairly well.

If someone wants a stiff spring, Moog 80090 might be a good choice.  They are about 700 in/lbs and are short.  They might require a little trimming to get the stance right though.

This is why after doing all that research, I decided to figure out via math what I need to use for what I wanted. The spring rate is the most important figure to start with in my opinion, because most guys want to firm up the ride a bit along with a drop. The most difficult part is figuring out where to start, or what rate to end up with if you haven't done this already. 600 lb/in vs 800 lb/in doesn't mean anything unless you have ridden in or driven a vehicle like the one you are going to modify that already has the tougher springs in it.

Again my opinion, but if you like the "floating on a cloud" ride quality with just a bit more control, then the 500 lbs/in springs would be the lowest rate springs to start with. With one coil cut, that puts the spring into the same rate range as most aftermarket lowering springs. I am satisfied with the choice I made because I like the seventies ride quality. New cars ( with some exception) while having a smooth ride, are still jarring to me over small imperfections like a residential intersection that has a 2" drop-off due to a new overlay on one of the roads. The Laguna just soaks that up.

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Post by Joe73 on Tue Jun 02, 2020 11:23 am

In my current build I used Moog 5415 and 8002. They are for small block, no a/c, Heavy Duty. Im very happy with the stance. Front is a bit high since they are new springs, but it will settle if I start driving it.
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