[HC5120]

Installed the HHP springs today. I am not going tp list every step and the torque specs as those are easily found.
HHP said no realignment is necessary. I may do that in the future, but the difference in ride height is the difference of having 1, 2, 3 people in the car, or a full tank of gas versus almost empty, etc., so we'll wait and see. Car drives really good, though.

American Muscle has a good install video on it: video

And on the BMR site they have directions for installing their springs, but it's all the same. Go to this link and then click on "installation" down a little ways on the page. BMR installation instructions

There are a couple of ways to do the rear springs. In the AM video, they remove the inside A-Arm bolt and drop the A arm from there. If you do it this way, you have to drop the exhaust some to get one of the bolts out. That's pretty much how the BMR directions are, but they have you remove the caliper and also remove the bolt for the lower trailing arm.

In all it took about 3.5 hours with two of us (though my assistant helped about 70% of that time), and the total time just depends on how stubborn the suspension parts want to be coming apart and especially going back together. If doing it again, I am sure we could do the whole job in 2 hours if we were both completely focused on it, and after having done it once. Some of the rear suspension bolts were a bear to reinstall. That's typical with suspension stuff.

Here is the difference in ride height with the HHP springs for all four corners compared to the stock springs.

Front left: plus 13/16; Front right: 0
Rear left: minus 1/8; Rear right: minus 7/16

Here is a pic of the stock front springs compared with the HHP spring

Installed:

Rear springs side by side:

Rear springs installed

We used this Eastwood strut spring compressor. Worked awesome. I researched tool options quite a bit, and this seemed to be the best made. The directions say not to use an impact on it, but reading reviews online, etc., lots of people do. It worked flawlessly. Seemed very safe. $165.00 from Eastwood.

All and all, it wasn't too bad of an install. The rear springs actually took longer because it was tough to get the bolts back in the arms and the lower shock.

The biggest worry with this install is probably compressing the springs for the front struts. I felt the Eastwood tool was very safe and solidly built and dependable.

The car drives good. I can't tell much of a difference, but I don't drive it that much just cruising around town. We will see what difference it makes at the track.

As I stated in the drag racing 101 thread I made, this isn't a necessity for 10 second cars or even high 9 second cars if they race on an excellent track with excellent prep. But it's one more thing to (hopefully) add consistency for bracket racing for me, and help me on my home track which is challenging (we'll see). I have run a 1.53 and 1.54, but my 1/8 mile 6.80 at 4400 DA in my sig was a 1.58. I think I can do quite a bit better, but we'll see in a couple of weeks. My goal is to hit high 6.60s in the fall when the good air comes back and I have fresh tires. That would be solid for a 2.85 pulley and 93 fuel at 4500 DA. I would like to go back to a 305-17 tire, too, so this might get me closer to being able to do that.

If I have something messed up that you see in the pics, thanks in advance for the heads up.

 

[baabootoo]

Good info. I think that I would still pay the $100 and get a 4-wheel alignment.

 

[HC5120]

I have the AAD rear suspension and got some more tabs from them, so we can dial in the rear camber a little more, and I might do the alignment at some point, though I just have it done with the street tire setup, not the race tires. The alignment is going to change going from the street performance tire on the front to a skinny, and to the wider rear with a different backspacing and wider tire. It would be interesting to see how much that would change the alignment. And also how much the springs changed it. I always set it up for the street. There is a decent margin in the specs as far as alignment goes. Right now the car is within specs, though it was set up with racing in mind, in terms of the rear camber.

IDK, I'm no alignment expert.

 

[Trizzle]

Could be a placebo but stomping on it felt like the front end came up a bit more. Install was pretty easy like you said. Rear drivers side was the only spring that fought a bit to go in. Just waiting on my DS and tires and its off to the races! (Literally)

 

[SickToo]

Strut is what determines how far suspension can drop before tire leaves the ground

Rebound dampening is what determines the rate it drops at

All you changed is the spring

 

[HC5120]

Could be a placebo but stomping on it felt like the front end came up a bit more. Install was pretty easy like you said. Rear drivers side was the only spring that fought a bit to go in. Just waiting on my DS and tires and its off to the races! (Literally)

We spend an hour on two bolts on the rear suspension. Sometimes that happens, and it's tough to get things lined up.

 

[HC5120]

Strut is what determines how far suspension can drop before tire leaves the ground

Rebound dampening is what determines the rate it drops at

All you changed is the spring

You are correct: all I changed was the springs. Your razor sharp analysis is, as always, much appreciated, SickToo.

It will be fairly straightforward in seeing what difference it makes since this is the only thing I've changed, and I know that the car most of the time will run a 1.58 60' and now and then a 1.54. I have logged 100 passes or more, so I know what the car runs, and I know how (in)consistent it is. Pretty easy to test this.

I paid like $150.00 for the springs and did all of the install myself, so it's worth giving it a shot.

 

[SickToo]

We spend an hour on two bolts on the rear suspension. Sometimes that happens, and it's tough to get things lined up.

Yes, the lower shock bolts do not have to come out so ya coulda saved time there. The inner control arm bolts are fun ha. Getting those back in it’s all about jack position and good set of tapered bars. If you take the outer bolts out for the control arm and change the ride ht they are a ***** to get back in

 

[SickToo]

You are correct: all I changed was the springs. Your razor sharp analysis is, as always, much appreciated, SickToo.

It will be fairly straightforward in seeing what difference it makes since this is the only thing I've changed, and I know that the car most of the time will run a 1.58 60' and now and then a 1.54. I have logged 100 passes or more, so I know what the car runs, and I know how (in)consistent it is. Pretty easy to test this.

I paid like $150.00 for the springs and did all of the install myself, so it's worth giving it a shot.

Would love to see someone have a baseline like you have, install the rears and log the difference, and THEN install the fronts and do the same

 

[HC5120]

Yes, the lower shock bolts do not have to come out so ya coulda saved time there. The inner control arm bolts are fun ha. Getting those back in it’s all about jack position and good set of tapered bars. If you take the outer bolts out for the control arm and change the ride ht they are a * to get back in

I'm not sure I could have gotten the spring out without taking the lower shock bolt out. But next time I will give it a shot. We were using a lift, but sometimes with this sort of thing it can be easier to use a couple of floor jacks just because it can be handier in terms of jacking here or there on the control arms, suspension components. Yes, we use tapered bars, etc., and know all of the tricks. This stuff just sometimes fight you all the way.

 

[SickToo]

Would love to see someone have a baseline like you have, install the rears and log the difference, and THEN install the fronts and do the same

 

[HC5120]

Yes, that would be interesting. These springs have worked for others, from what I've read on various forums. Sometimes they don't, but I think so much depends on the track. We see fairly often people with hellcats with just a tire run good times and solid 60', but that's because of the particular track. I also wonder about how consistent people are on a wide range of prep and runs. I've run a 1.53 once and a 1.54 a few times, but the other 50 times it was 1.58 or higher. I want to be consistent and run nearly the same every run). I hope to get in the 1.4x eventually, which I think would be good for the power I have and the track I run on. It will take some work, I am sure, but that's the fun of it.

 

[PSL]

Having mine installed tomorrow, switching to these from Eibach pro-kit springs. The stance won't look as good I'm sure but hoping for a softer ride and better weight transfer, less scraping as well.

 

[SickToo]

17 or 18 inch Mickey will do wonders to how it rides : )

 

[Trizzle]

Having mine installed tomorrow, switching to these from Eibach pro-kit springs. The stance won't look as good I'm sure but hoping for a softer ride and better weight transfer, less scraping as well.

They are a bit squishier. My testing consists of the train tracks i drive over everyday.

 

[SickToo]

More coils/smaller wire

Can see in the pic that they are softer than stock

 

[HC5120]

Springs are made differently and they do make a diffe

Having mine installed tomorrow, switching to these from Eibach pro-kit springs. The stance won't look as good I'm sure but hoping for a softer ride and better weight transfer, less scraping as well.

Most lowering springs are designed for handling/corner carving and they have higher spring rate, are stiffer. This is bad for drag racing. If you want to see what a stiffer suspension does on these cars, just put suspension in track mode at the drag strip and enjoy the burnout you do for a 1/4 mile. That's for a stock hellcat. The whole design of most pro touring type springs is to stiffen the suspension all around. I've only seen one person on this site whose hellcat runs better with the suspension on track and I think they have some other modifications???

Then you have to have the right shock to match the springs and your intended use. Of course, for 95% if us on this site, we are making compromises because we drive the car on the street, too.

For all out drag racing, the shock and spring have to be matched. With other cars, I've had stock springs on the front with single adj, and the shocks made virtually no difference, especially with a "pro touring" spring. Likewise, if you have a tall, light spring in the front that dumps the front end for lots of front end separation/travel but a stock shock, you don't get the full benefit of the spring either since you can't control the rebound or compression, you're just stuck at whatever the valving is on that particular street shock.

Normally, you just throw on a single adj on the rear and for a street car that and a good race tire will work pretty good for a mid 10 second car. With the electronic/adjustable suspension on the hellcat, you can't do that. We are always having to make sacrifices with a dual purpose vehicle.

The HHP springs ride real nice on the street, and the car sits very close to stock. I will take some pics with the stock wheels and tires and then the race wheels and tires next week and post them.

 

[HC5120]

More coils/smaller wire

Can see in the pic they are softer than stock

That's correct. I was kind of surprised that the rear springs were like that.

So what effect would that have compared to a spring that has larger coils but fewer of them?

 

[SickToo]

In reference to the rear It should make it so that once the weight of the car is on the spring and it’s at its static height it will take less weight to compress it X amount compared to a spring with fewer coils

Ever cut one coil off a stock spring?

There is more to consider tho. I don’t know how close to 50/50 your shock is valved. My shocks are not adjustable

 

[HC5120]

That's really interesting. These cars have such a low first gear and so much torque, that maybe the rear spring compressing more easily might actually reduce the violence of the initial hit which would help with traction perhaps.

Does that make sense?

I wonder if there is info anywhere on what the valving is on the hellcat shocks in street/sport/track.

Side note, back in the late 50s my uncle took my grandma's Plymouth and heated the springs up to lower it. Road just terrible. She wasn't too happy about that. Early days of hot rodding they did all kinds of wild stuff.