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HHP springs intall

5852 Views 61 Replies 8 Participants Last post by  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
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Rear springs side by side:
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Rear springs installed

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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.
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Automotive tire Tire Black Motor vehicle Rectangle

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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.
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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.
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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.
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.
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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.
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.
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.
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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?
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.
Suspension setup is so particular to a given combo, and very complex, like you said above.

It's just such a crazy low first gear in these cars.
Can you post before and after pics. I might go this route.
Hey, the difference is hardly noticeable. And I can't tell a difference driving it on the street, but I take it pretty easy with the car unless I'm at the track.

The difference from stock in height for all 4 corners was the following:

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

Here are the initial heights at all 4 corners with the street tires on with the before and then the after in parentheses:

FL-29 1/16 (29 7/8); FR-28 7/8 (28 7/8)
RL-30 1/16 (29 11/16); RR-29 7/8 (29 7/16)

I think I have pics of before and after with the stock wheels. I will also get pic of the car with the race wheel setup and post that as well.
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Both of these pics are with the HHP springs. Fronts tires are 28" and rear tires are 29.4", 315-50-17.

Wheel Tire Car Sky Vehicle

Tire Wheel Car Vehicle Sky
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Made a handful of runs with the new springs. Races and test and tune got cancelled on Saturday, so didn't have a lot of for testing and used bracket racing Sunday for that while still trying to be marginally competitive.

Prior to the HHP springs I had been running lower tire pressure because of struggling to be consistent off the line. I do have a diablosport suspension controller, too, which I also ran last year. I ran suspension on street for four runs, and made one run on track. Still need to experiment with that.

First run tires 16 psi cold (what I ran last year with stock springs), 1200 launch (just where drivetrain is loaded): the car almost bounced off the line, and then did that again on the 1-2 shift. 1.59 60'.

The next few runs I had 18-18.5 cold. 60' was bad. 1.65, 1.63, 1.62. I asked my buddy to video the run. The car was literally rolling off the line with launching at the rpm I was at. That is how dead hooking the tires were, lol. They were asking me, "Hey, maybe you should try launching the car?"

Last run, I was like, I'm gonna give it the beans and launch at 1800. Well, pushed through the lights; I think I was closer to 2,000. I need to see what the max rpm I can get out of the converter is.

No question the car plants far better, and I think I just need to add rpm for my launch and play with tire pressure.

Too bad I blew that last run. I'd run 104.65 mph the previous run (4200 DA), and if I could have gotten a good launch, I know I'd have gone 6.70s. Probably won't see that air again until September or October.

Like is always the case, whenever you change something, takes some work figuring things out. In two weeks when we race again, I will get a bunch of runs in because it will be three days, and include test and tune in the morning.

I do think the springs are going to work, it's just that the car is planting so hard that the lower rpm launch can't overcome that inertia. We'll see.
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Yes it was basically from the side. I was like, omg, it literally looked like I hardly even hit the throttle. I did mash it on the run where I rolled through after the other car took off, and it hooked pretty good, but I didn't get a time because I'd already pushed through the beams.

There's really nothing to see from the video, except that it's the laziest launch ever, lol. Pretty funny really once I saw the video. Kind of surprised it was still a 1.62. It's just completely different with these springs. I was running like 15 psi cold sometimes trying to get the car to hook. I wouldn't be surprised if I am able to run 20psi or more now.
Mine works better closer to 20 than it does to 15

How wide is the wheel?
You know, those skinny little 10" wide wheels. I'm still waiting for you to find me some 17x12 wheels that will fit on a 16 hellcat NB and are under a grand. Then I'd squeeze the 305R-17s on them.

I ended up at 15 psi cold because that's what it sometimes took to get the car reasonably consistent on my track. It's lower than pretty much everyone on this forum. I have usually run them at 16.5-17 cold, but sometimes needed to go lower. Will try 18-19 psi cold next time out and work up from there. Probably 1500 rpm launch and see what happens. The next race weekend we have I should get about 15 runs in, so I should be able to get things headed in the right direction.
It's a huge difference with these springs. Just need some rpm at the launch. I'll get there.
Did you guys read what I wrote? I didn't even launch the car. The tires hooked so hard that it practically lugged the motor. I never got a proper launch in. I used to have to run 15 psi to hook and so started lower and the usual rpm I launch with didn't work, and I didn't figure that out until looking at the video, the laziest start you've ever seen, like someone was standing behind the car pushing it. I am leaving everything the same but going to work on tire pressure, though I have to raise launch to 1500. Next time out, it will be 1500 launch the whole day and adjust tire pressure.

Take a minute and read what I wrote, jeez

You guys can suck eggs, especially sick2 with his fat old wheels, ha ha
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I know, just having some fun. It's like this when you make a change. I was really kicking myself cause the DA was so good, and then I blew my run pushing through the beams trying to get the stall up.

I have 2.62. I would ideally like to switch back to the 305-17 on a wider wheel with no beadlock and come up with a different way to keep the tire from spinning on the wheel. That would be faster IF it hooks. I have a set of 305-18s on some bravados that I can do an AB test with, too, so I will throw those on once I figure a few other things out.

I ended up with a too big of a tire because of trying to get it to hook up more consistently, but I hope the springs will make it possible to go back to the smaller tire.
The right size tire is the one you can get to work. That being said, a smaller tire is lighter and faster IF you can get it to hook.

2.62 x 4.71=12.34; that's like a TH400 with a 5.00 differential. Would a 29.5" tire on a car with a TH400 and 5.00 rear gear be too much tire? With the 3.09 it would be like running a 5.87 rear gear with a TH400.

The 305-17 is also only 28" tall, so that's like effectively lowering the final/effective gear ratio, which might be better for the 1/8 mile, again all dependent on the tire actually dead hooking.

Just my two cents.
I finally got some runs in. These were all about 5000 DA. Ran anywhere from 6.83 to 7.08, depending on traction/60 foot.

For test and tune, no prep at all, I managed a 1.62. They prepped the track some for the bracket qualifying rounds, and I ran a 1.55, 157, 159. In the last two years, I have never run two 1.5x 60' in a weekend (I've only run a few 1.5x's in the last couple years), and I ran these three all in a row, and the track was sketchy. Apparently VHT is hard to get, and so we are trying to make what we have last until the end of the season. So they only prep before qualifying, and that's it for the day. Usually they'd prep again after qualifying.

If you race on a well-prepped track, then the stock springs are probably good, imho. We see a lot of people on this site throwing on a tire and hooking up pretty darn well. Just depends on the track, and how important consistency is to you.

I do have a suspension controller installed, and I will swap that back out for the stock one some time while at the track and do a back to back test, eventually.

I got third place out of about 25 or so cars in the pro class Saturday, and made it several rounds today, Sunday. Two weekends of bracket racing left.

Overall, I am happy with the HHP springs. The car rides just the same as it did before, and it's more consistent at the track, though testing has been tough due to minimal prep.

Ran 15 psi cold all weekend. Still ran 104.67 MPH on a run, so the low tire pressure didn't impact that.
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