[vertigto]

I've been told that isolators are not typically used in front A-arm applications. I asked because I didn't want to mar my pretty/new BMR A-arms or have metal on metal noise. In the end I couldn't decide on spring length/stance and bit the bullet to get Viking coilovers, so that I could adjust it to my particular taste. Got them from OPGI/CPP and they weren't as ridiculous as some kits or a whole lot more than quality springs/upgraded shocks, relatively speaking of course.

[JLMounce]

Originally Posted by grivera

Thanks- shopping for spacers is overwhelming. I’m looking for a 1 inch spacer to put in spring cup in case the 2” drop is too much. BMR said I could use a coil spring isolator to get a little height but they don’t sell them. How do these look?

https://www.amazon.com/Energy-Suspen.../dp/B000CNB56S

Also, do the tubular control arms typically need these isolators or are they optional?

Makes me wonder if I have to add them top and bottom it will affect height significantly.

Spring isolators come in many different flavors. In a 1969 firebird that has coil cups in both the lower arm and the upper perch, you can't use isolators like what you are looking at. Those are designed for a flat spring perch like what you see on a 67-72 A-Body.

They were never used from the factory. In fact you didn't really start seeing a lot of use of isolators on springs until the mid 80's and even then only on nicer cars to try and dampen out as much noise and vibration as possible.

If you decide you want this and to tame a 2" drop slightly, you want to look for the isolators that are rubber tubes and which slide over the pigtails. You're never going to gain a ton of height back with those however. Maybe 1/4" total and that would be on the high side and assume you did both upper and lower isolators.

Although I don't typically recommend them, doing a hybrid coil-over may be more up your alley. That will allow you to set your ride height from factory down about 2" or in between.

If you decide to go that route, I do not recommend the lower budget hybrid coil-overs like the single adjustable QA1's. The threaded sleeves on the lower budget entries are only pressed on and they have a tendency loosen and fail, especially if the car is driven on rough roads or put in high load situations like spirited driving. You want versions that have the sleeved portion of the shock body either welded in place, or preferably manufactured with an integral helix for the lower spring perch.

If you decide to go that route, diligently inspect the shock mounting surfaces in the lower control arms. The factory arms were never designed to hold anything more than a shock load and you'll be asking them to carry about a 1/4 of the weight of the entire car. If you suspect any softening of the metal, or there is visible rot, replace the lower control arms or otherwise reinforce the lower shock mounts.

I don't like spending people's money...and these are spendy, but it's my personal opinion that this bolt in coil-over conversion is the best out there, before going to the labor and expense of a true coil-over.

http://www.cachassisworks.com/Attach...XXX_DS_WEB.pdf

These are more of a true coil-over because they no longer use a cone type spring that is a hybrid between a coil-over spring and a traditional coil spring. It's captured upper mount allows the system to articulate like a coil spring does without introducing side loading on the shock body that you see with a hybrid coil-over setup. It's motion ratio is better as a result which typically means you can also run less spring rate.

It's one draw back is that instead of utilizing the spring pocket for the spring, it uses the upper shock mount, which again runs into the same issue discussed above with placing a load on a part not really designed to take it. They use a captured washer system to do it, which should help spread the load, but it's still not entirely ideal.

But my recommendation is still to use a traditional coil spring. I would look at the SPC line of springs because they aren't the larger drop springs like you see from BMR, Hotchkis etc. They come in just over an inch lowering. If you stick them in and want to go lower, you can trim a coil to get you where you need.

It's a bit more work, but you're not messing around with re-engineered or compromise parts. Once you get it setup, you'll never have to worry about it again and you can drive in confidence knowing you haven't made major modifications to how the engineers originally designed everything up there to work. It's also quite a bit cheaper

[grivera]

Thanks Jason- lots to digest. I’m not interested in the coil overs at this point. So measuring my car at the rocker panel, rear is about 6” to ground and front about 7.25”. When using lowering springs is the end result usually as advertised? I’d’ like it level or just a little lower than back.

[JLMounce]

Originally Posted by grivera

Thanks Jason- lots to digest. I’m not interested in the coil overs at this point. So measuring my car at the rocker panel, rear is about 6” to ground and front about 7.25”. When using lowering springs is the end result usually as advertised? I’d’ like it level or just a little lower than back.

Sadly, not on a 50+ year old car. If this was a 2015 mustang we were talking about, yes absolutely.

The advertised drop in the springs is based on the “stock” ride height from the factory manuals.

As previously mentioned, over time cars will sag and wear out. They will have new parts installed or possibly installed incorrectly. It’s become common for factory replacement parts to be homogenized across makes and trim levels. It’s not unheard of for a “factory restoration” car to actually sit higher than as it was delivered because of repop parts being designed to accommodate multiple different part numbers.

The end result is that you could have a situation where a 1.25” advertised drop turns into a 2.5” drop actual. Or a 2” advertised drop winds up sitting half an inch higher.

Your car looks like it’s had a set of front springs put in it at some point and it sits high in the front. Or conversely the rear leafs are sagging quite a bit. That isn’t unheard of. When I swapped mine out, the factory leafs fell apart in two pieces as soon as I released the clamping pressure from the u bolts.

All that to say this will always be a trial and error deal, especially if your mixing stock parts with aftermarket.

If that isn’t what you’re after I would encourage you to purchase a complete “kit” from one of the reputable shops. Hotchkis, BMR, Ridetech, Detroit Speed all have basic “stage 1” kits that would work. They will typically have photos of the product installed so you can see how the cars sit. That’s about the only time you can really get that “as advertised” product.

I still think those 1.25” drop SPC springs will get you about where you want. Installed correctly clocked in the spring perch I think you’ll get more like 1.5” drop which will get the car fairly level. But full disclosure, it’s an educated guess based on my own experience, nothing more.

[grivera]

Thanks for the candid talk. My leaf springs were replaced in 2005 but don’t have many miles. I’m not opposed to replacing them though.

Are these the SPC springs you’re referring to?
https://www.jegs.com/i/SPC/827/94393/10002/-1

[JLMounce]

Yup those are the ones.

[grivera]

What is too much spring rate when it comes to a car that will not be auto-crossed?

[JLMounce]

Most of the aftermarket coil springs you find are going to be around 500 lb rate in the front and the leafs will be between 150-175 lb. This is pretty typical and more in line with what the car should have for a combination of street driving and performance driving. It's not harsh, but it doesn't float and wallow like a car with factory springs.

On performance oriented first gen's that see mostly track time, you'll see people running spring rates in the front up to or even above 800 lb rate and closer to 500 in the rear. ride quality would be pretty harsh though.

[grivera]

Thanks- the BMR coils are 620#/inch

[JLMounce]

That's probably a bit heavier than I'd want to go for a car that is only street driven. I have the hotchkis springs on mine and they rode quite nice when installed in the factory arms with a .5" tall ball joint. When I went to the SPC upper and lower arms, I dropped the front end an additional half an inch to put the jounce bumper in constant contact with frame. This has the effect of removing about an inch to inch and a quarter of bump travel and the jounce bumper progressively adds rate as it's squished. It's probably closer to 600-650lb total wheel rate without the addition of the sway bar right now. Handles great, but ride has definitely suffered.

It's not jarring, but it's quite firm. Like late 80's corvette C4 firm.

[grivera]

So with the factory a-arms and hotchkis springs were you at a 2” drop? At the BB Chevy spec?

[grivera]

Jason- do you have any pics of your bird when you had the 2” drop coils/leafs and factory a-arms?

[JLMounce]

Originally Posted by grivera

So with the factory a-arms and hotchkis springs were you at a 2” drop? At the BB Chevy spec?

Yes, pretty darn close. I had redone the factory arms with PST bushings and a steering rebuild prior, so it was sitting pretty accurate to how it would have sat from the factory.

Originally Posted by grivera

Jason- do you have any pics of your bird when you had the 2” drop coils/leafs and factory a-arms?

Yes, here's a photo of the car with the factory arms, 2" hotchkis drop springs in the front and 3" Hatchkis leafs in the rear.



Here's how the car sits now. The SPC lower control arms have height adjustment shims available to help tailor ride height and corner weights. I removed 1 shim pack, dropping the car a further .5" in the front.

[grivera]

Thanks - the car looks great!

Interestingly the rear of mine appears to sit lower than yours and the springs on mine are reportedly stock springs. They were extra parts...

[JLMounce]

According to your measurements, your rear end is a full inch lower than mine, depending on where you're measuring from. I picked the lowest point further aft on the rocker and same for the front. My car is about 7" both front and back as measured from the rockers.

There's stuff on the cars that can effect that height that doesn't much anything to do with the springs though. body bushing condition, type of shackles on the leaf springs, lowering blocks etc. It's probably not a good apples to apples comparison.

[grivera]

Mine has stock shackles and no lowering blocks from what I can tell. Also, the body bushings were replaced in 2009 with factory style rubber.

I took measurements from rocker areas closest to rear of front tires and front of rear tires.

[indymanjoe]

Stunning car Jason! BTT

[JLMounce]

Originally Posted by grivera

Mine has stock shackles and no lowering blocks from what I can tell. Also, the body bushings were replaced in 2009 with factory style rubber.

I took measurements from rocker areas closest to rear of front tires and front of rear tires.

I measured at roughly the same locations. Interesting finding indeed.

Originally Posted by indymanjoe

Stunning car Jason! BTT

Thanks!

[grivera]

Originally Posted by JLMounce

According to your measurements, your rear end is a full inch lower than mine, depending on where you're measuring from. I picked the lowest point further aft on the rocker and same for the front. My car is about 7" both front and back as measured from the rockers.

There's stuff on the cars that can effect that height that doesn't much anything to do with the springs though. body bushing condition, type of shackles on the leaf springs, lowering blocks etc. It's probably not a good apples to apples comparison.

What size wheels and tires do you have in rear? Mine are 245 15 60 (26.5 inches)

[JLMounce]

Will, it's a 275/40/17 on a 17x9.5 wheel. It's 25.7" total height.