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[BUILD] My Ultimate C7 Track Car - The C7 GS.R

 
Old 01-26-2019, 02:52 PM
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Poor-sha
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Default [BUILD] My Ultimate C7 Track Car - The C7 GS.R

Well I think it's time to get this thread started...

After I wrecked my C7 ZR1 I was left in a position where I wasn't sure what to do next. I've had a C7 Stingray, a 2015 Z06, a 2017 Z07, and a 2019 ZR1, all of which I tracked extensively and had built a lot of expertise around. Each car was faster than the one before it and the ZR1 was incredibly capable but I was starting to bump up against the limitations of trying to track a car that was also a good road car. I was intenionally limiting myself to only basic mods so that I could preserve the tags, warranty, and resale value. Certain things like the factory catalytic converters were becoming real reliability problems and I was also growing tired of the increasing consumable costs as each car got faster and heavier. Finally, I wanted to dip my toe in the time trial scene and that means a level of prep and safety equipment that wasn't there with a pure street car.

In this "do over" moment I decided to move forward with a new plan. I wanted to stay with the C7 platform I knew and liked. I wanted to maintain a level of performance roughly on par (or better) than the C7 ZR1 for roughly the same cost. However, I wanted to remove all the street car things that a track car didn't need - emissions equipment, A/C, interior, etc. In doing so I also wanted to bring the weight down as much as I could without getting to Scott Tucker build* cost levels.

That led me to a GS 1LT as a base because that would start with the lightest weight and I decided to name my track focused Grand Sport project the C7 GS.R. My first call was to Jason at Katech to discuss their 700 HP 427 LT1 as I figured if I could get the GS down to ~3480 lbs full of fuel and no driver that combo would put me squarely in ZR1 power to weight territory. If it's one thing Katech has more experience with than anyone it's building reliable road race motors so the choice was easy. I worked a lot with Katech back when I had a C6 Z06 and it was great to be back in the family.

As far as brakes go I knew that AP Racing and Essex Parts was the only way to go. I've had the opportunity to work with Jeff and Daniel at Essex since they first released the brake kit for the C7 Z06 and it's been awesome. The level of support I got from them was great and they even let me try out some prototype pads like the new DS 3.12 to provide feedback. Unfortunately, the endurance front (CP9668/372mm) and regular rear kit I had used on the last three cars was on the ZR1 when I totaled it so I called Daniel up to get a new set on the way - there was no reason to mess with what works. It helps that I still had a bunch of spare pads and rotors at home.

As far as suspension goes again I knew I wanted to work with the same company that had provided me such great support on the prior cars - DSC Sport/TPC Racing. I first spoke to Mike Levitas about four years ago when the C7 controller was under development and it's really difficult to capture how much I've learned from him and the help he's provided. It's not often you can tap a Rolex 24 winning driver and race engineer to help with your project but he clearly loves this stuff. Luckily I still had a v4 DSC Sport controller that hadn't made its way in to the ZR1 as well as a set of Tractive RTx shocks. From talking to Mike and my experience tracking both FE6 Z06 and FE7 Z07 cars I knew the FE6 springs were too soft so I bought a set of FE7 springs along with the matching sway bar bushings. Since I didn't have to worry about ride comfort on the street it was finally time to get those spherical control arm bearings I'd been wanting to try and since it was Black Friday I ordered a set fromt AMT Motorsport with a note to Mark that it might be a bit before I send in my control arms.

Here's the pile of parts I've accumulated so far, I'm doing my part to support the forum vendors :

  • DSC Sport v4 controller
  • Tractive RTx shocks (not shown)
  • FE7 springs
  • FE7 sway bar bushings
  • AMT Motorsport spherical bearings (not shown)
  • WeaponX rear toe links
  • AP Racing Radi-Cal front endurance kit with 372mm rotors and matching rear kit
  • ZL1 AddOns front and rear titanium tow hooks
  • GM "track only" additional brake ducts from the 2017+ Z07 cars
  • Shorai lithium battery (I've had this on hand and never put it in the car)
  • Also not shown are the Forgeline GA1R 18" wheels that I bought from CW4L and fortunately weren't on the ZR1 when I wrecked
I initially started shopping used Grand Sports but being a hardcore PDR data junkie I wanted at least a 2018 to get the additional sensor data and I also knew the 2019s had a number of updates for track use from the ZR1 program. Frankly there wasn't a ton to save on buying a lightly used 2018 anyway so I placed a call to same person that sold me the last four C7s - Mike Furman at Criswell Chevy. I asked for a 2019 GS 1LT M7 trans with PDR, Elkhart Lake Blue with full length silver stripes. He gave me the price and we placed the order.

While I waited for the car to arrive I started this other thread asking you all what your ultimate C7 track car would be and it netted a lot of great ideas. Thanks!
https://www.corvetteforum.com/forums...car-build.html
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Old 01-26-2019, 02:53 PM
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Last Monday morning Mike Furman called me and the future GS.R had just come in. I really wanted to get this project started and take advantage of the break in the weather to get it home so I asked if I could pick it up the same day. Mike rushed to get the car unloaded and prepped for delivery that afternoon. Here she is in the garage, unmolested with less than 50 miles on her.




The first thing I wanted to do was establish a baseline. I filled up the tank a few miles from home so I could measure everything with a full tank. I then added 200 lbs of ballast to the driver seat to measure camber, rear caster, and ride heights. I was too lazy to string the car up to measure toe or get the slip plates out to measure from caster. Here are the results.

Camber:
RF: 1.15 deg
LF: 1.00 deg
RR: 1.55 deg
LR: 1.30 deg

The rear caster was really not good with the RR at 0 deg and the LR at 1.0 leaned forward (!). That LR was the opposite from the way you want the car for consistent handling and I'm pretty sure that was even outside of GMs spec. It was probably just barely in spec without the ballast.

I measured the ride height three different ways, this too was done with 200 lbs of ballast. The first is from the ground to the bottom of the fender opening. In the front I used where the spat meets the painted fender and in the rear I used where the fender turns inward. The second measurement was using the GM tool to measure the Z height from the lower control arm bolt height to the lower ball joint height. The final was the height to the jacking points where I used a straight edge to simulate as though there were no opening.

Ride Height
RF: 27 3/4, 37mm, 140mm
LF: 27 7/8, 38mm, 135mm
RR: 28 3/8, 40mm, 145mm
LR: 28 1/4, 37mm, 141mm

Finally, I removed the ballast and put the car on the scales. At 3463 with a full tank I'll admit that I was hoping for lighter. However, that's 96 lbs less than my 2015 3LZ Z06 (3559 lbs) and 184 lbs lighter than my 3ZR ZR1 (3647 lbs). Below is a screen show that also shows the corner weights.




I've spent my evenings this past week pulling the control arms so I could send them off to AMT. The good news is that I had to remove the brakes anyway to do that and removing the shocks and rear toe links made that easier. Now the springs are easily accessible as well. So while I wait for the control arms to come back I'm going to swap out the springs, sway bar bushings, install the tow hooks, and I've already installed the DSC Sport controller.

Summit Point has events the last 3 weekends in February so I'm hoping to make it to one of them to shake down the suspension before I ship the car off to Katech for the motor and trans work. More on that to come...

*Listen to the Dinner with Racers podcast episode on the Level 5 / Scott Tucker DSR build. It's over the top. http://www.dinnerwithracers.com/epis...vel-5-special/

Last edited by Poor-sha; 01-26-2019 at 02:57 PM.
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Old 01-26-2019, 02:53 PM
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Placeholder for motor build

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Old 01-26-2019, 02:53 PM
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Placeholder for aero build

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Old 01-26-2019, 02:54 PM
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Placeholder for cage

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Old 01-26-2019, 03:01 PM
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Old 01-26-2019, 03:21 PM
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This is going to be fun to follow. Sub'd.
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Old 01-26-2019, 03:27 PM
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Can't wait to see it on the track!
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Old 01-26-2019, 03:29 PM
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Yeaaaaaaaa! Glad to see you back Sean! Going to be fun to watch
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Old 01-26-2019, 03:34 PM
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That's awesome Sean.

I'd say you were pretty close to the limits for what a non-pro (and I don't mean that in a derogatory sense) driver could do with a streetable platform.

Are you going to do a full cage/race seats/gut the interior?

I'd be surprised if you didn't have a full cage installed at the pace you run...

*edit* I scrolled down & saw you had a placeholder for a cage.

Your garage is sick, BTW.

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Old 01-26-2019, 04:05 PM
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Sub'd!!
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Old 01-26-2019, 05:25 PM
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I don't frequent the forum much, but always try to catch up with poorsha's posts and youtube vids as they are always worthwhile. Well today is the first I learned of your accident, and I am thrilled you walked away from it. Holy smokes... I saw the post of the Zr1 in the insurance yard, and then saw it was in VA, and thought of you, but was like naaaa.... until I read on. Sorry for the loss of the car, but so happy you were not killed man. I am not a race car mechanic, but I have a shop 15 min down the road from SP, if you ever need anything or tools, you are more than welcome. Looking forward to a cool build... will come check you out in the spring at SP. :-)
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Old 01-26-2019, 06:16 PM
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Originally Posted by nch209 View Post
I don't frequent the forum much, but always try to catch up with poorsha's posts and youtube vids as they are always worthwhile. Well today is the first I learned of your accident, and I am thrilled you walked away from it. Holy smokes... I saw the post of the Zr1 in the insurance yard, and then saw it was in VA, and thought of you, but was like naaaa.... until I read on. Sorry for the loss of the car, but so happy you were not killed man. I am not a race car mechanic, but I have a shop 15 min down the road from SP, if you ever need anything or tools, you are more than welcome. Looking forward to a cool build... will come check you out in the spring at SP. :-)
Thank you very much for the kind words and the offer. I hope to see you at SP this year.
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Old 01-26-2019, 06:31 PM
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Congratulations, love the Blue!!!
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Old 01-26-2019, 06:34 PM
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Pretty damn excited for this thread.

Read my thread on swapping the leaf springs if you're doing it yourself. Had never seen another DIY on here about it. All others just remove them

https://www.corvetteforum.com/forums...post1598603925

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Old 01-26-2019, 06:44 PM
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Old 01-26-2019, 06:45 PM
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Originally Posted by BrunoTheMellow View Post
Pretty damn excited for this thread.

Read my thread on swapping the leaf springs if you're doing it yourself. Had never seen another DIY on here about it. All others just remove them

https://www.corvetteforum.com/forums...post1598603925
Thanks. I did read your thread and in fact that's why I decided to pull the control arms and do the suspension myself. I actually bought the GM spring compressor tool on ebay but it's much easier once both control arms are out. The worst part of that job was popping the lower ball joints out. Lots of beating, heating, and cursing. Here's what it looks like at the moment.


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Old 01-26-2019, 07:10 PM
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Thank you for posting this - going to be great watching the progress!

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Old 01-26-2019, 07:25 PM
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Originally Posted by Poor-sha View Post
Thanks. I did read your thread and in fact that's why I decided to pull the control arms and do the suspension myself. I actually bought the GM spring compressor tool on ebay but it's much easier once both control arms are out. The worst part of that job was popping the lower ball joints out. Lots of beating, heating, and cursing. Here's what it looks like at the moment.

Oh you had to drop both control arms anyway for the bearings. That's right
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Old 01-26-2019, 08:56 PM
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Any particular reason you are not going with a full coilover setup?
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