AUTOXER - 2015 GT Autocross Build

[LightningGT350R]

After years of reading other members build threads and accomplishments in autocross I've decided to log this years progress, with the goal of my first Nats trophy. I've done OK locally here in the Colorado SCCA Region. I win my class occasionally, and some years even win local championships, but I've never been able to put together two days of decent driving in Lincoln. I coned away a trophy in 2021 (albeit 11th place) with a previous car (2017 GT350R). So my 2025 season starts and the journey to hopefully, finally, leave Lincoln in Sept with something other than crushed dreams.

My current car is a 2015 GT Premium with a 6 speed. Not the ideal starting point as the car was heavier than it needed to be - still is actually. I bought the car because I thought is was a solid, well maintained car. Not the case. Oh, and it had a Vortech V3 SC on it with long tubes. Bonus! Not so much - more on that later. The car had 70k miles. The previous owner (I'm the 2nd) was a Army mechanic. That should be a good thing. But it turns out most of the wrenches turned on the car was done by a local shop. Not the owner. I had a pre-purchase inspection done and we found a bad (really bad) rear wheel bearing, and some oil seepage - top and bottom. The top was due to some crappy breathers being used to vent the engine. The bottom looked like a valve cover leak. No biggie. The car was a blast on the street . Crazy power (650+ whp) and drove pretty well. I had a lot of aftermarket suspension stuff from my previous Shelby that went on the new car - Ohlins coilovers + Vorshlag plates, FP swaybars and a few other things. Time to take it to an autocross...

And it broke. After maybe 4 or 5 events the car developed a miss. The tuning was horrible for anything part throttle, and then the oil leak started at the rear of the motor. After replacing some parts to fix the misfire (plugs, coils, intake) to no avail, at an autocross pretty early in the 2023 season, it puked oil badly out of the back of the pan and I was done. Long story short, the thrust washer was destroyed which allowed the crank to move excessively which destroyed the rear main. That had been going on for awhile as the crank sensor was covered in oil and clutch dust and that was causing the misfire. When I pulled the motor (planning to just swap the rear main) I also found that two of the motor-to-trans tabs were missing and a third was still attached via the bolt, but someone had tried to JB Weld in back to the block! Ingenuity at it's best. I decided to start over and build a CAMC car close to the max the rules allow, but still semi-streetable.

Here's the build list:

Engine
Replacement Ford Gen3 shortblock - wanted a Gen2 but those weren't available
ARP head studs
MMR billet rear main
MMR head coolant crossover
Boundary billet crank and OP gears
MMR remote oil cooler and oil filter kit
Ford Performance GT350 cam gears, tensioners, solenoids and chains
Gen2 heads - lightly resurfaced
ATI super damper
UPR catch can
MSD coils
2018 home ported manifold
JLT CAI
e85 tune
MMR water pump pulley
Fluidyne Radiator
Pypes long tube headers
Custom 3" exhaust with GESI high flow cats + Flowmasters built by Black Tie Race Fab
A/C deleted

Transmission
Tremec Magnum XL - 2.97 1st gear
McLeod RST clutch and flywheel
Steeda HD clutch line
McLeod Bleed Valve

Front Suspension
Ford Performance PP2 front control arm kit - This was a GT Premium w/No performance options
Ford Performance front swaybar
Eibach end links
Ohlins R&T coilovers - tuned by Shaftworks
Steeda bumpsteer kit
Ford Mach 1 front spindle and hub kit
OP Mustang GT4 wheel stud kit
OP Mustang 35mm wheel spacers
BMR front subframe

Rear Suspension
Whiteline subframe bushings
Steeda high strength differential bolt kit
Steeda adjustable camber arms
Steeda subframe brace
Ohlins R&T custom valved shocks - 3DM Motorsports
BMR Delrin vertical links
Meier Racing adjustable rear spring mounts
Steeda rear diff bushing kit
J&M upper shock mounts
OP Mustang R Spec rear hub kit with ARP studs
3.73 Torsen rear diff

Brakes
Ford Performance 2019 Bullet Brembo brake kit
Girodisc 2 piece front rotors (just installed April '25)
2017 PP2 brake booster and master cylinder
JLT brake cooling duct kit
Stock PP2 pads
Motul fluid

Interior
Sparco seats
GT350 steering wheel
Steeda pedal kit
Rear seat, rear plastic, headliner delete

Body
Trackspec hood vents
Scott Drake rear spoiler with custom extension and Gurney flap
Steeda upper and lower grill inserts
MMR fender vents
AJ Hartman carbon splitter and GT4 carbon canards

Wheels/Tires
Apex Forged 18" x 12" wheels with Yokohama AD052 315/30-18, or Nankang CR-S 335/30-18 tires
Apex SM10 19" x 11.5" wheels with Michelin PS4S 315/30-19 tires

The car weigh in at 3550-ish. Maybe with the new rotors I'll get closer to 3500.

More to come...

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[Turbeau]

Nice! Watching this thread.

 

[mavisky]

See this is the dilemma I find myself in with my car. I'd feel much more comfortable going to a full CAM-C build with a boosted GT vs the current GT350 and I've modded my way into owning a car that's a bit too serious for the street and a bit too fat for autocross.

Good luck with the build and look forward to seeing it's progress.

 

[LightningGT350R]

See this is the dilemma I find myself in with my car. I'd feel much more comfortable going to a full CAM-C build with a boosted GT vs the current GT350 and I've modded my way into owning a car that's a bit too serious for the street and a bit too fat for autocross.

Good luck with the build and look forward to seeing it's progress.

BTW, the rear spoiler is yours, but now extended to the max 10" the rules allow. And your reasoning is solid. My350R was beautiful, handled awesome, good power, and excellent gearing for auto-X. But the values kept climbing and the Gen1 voodoo's are not known for their durability so I decided to part ways with it. To be honest, I really miss it. It was without a doubt the nicest car I've ever owned, and probably ever will own. Think twice, maybe three time, before selling yours. It's beautiful.

 

[mavisky]

I thought that may have been it, but didn't dive through the private message log to see. Glad to see it's still out there putting in work.

I agree with the enjoyment of the car and that's the reason I haven't sold it yet. Something about the feel of this car in particular is just special and I feel like most people don't realize the extent of that change without driving one.

 

[NightmareMoon]

See I went the other way and put a Gen 1 voodoo in my GT.

What's your top of 2nd gear going to be with that transmission?

 

[LightningGT350R]

See I went the other way and put a Gen 1 voodoo in my GT.

What's your top of 2nd gear going to be with that transmission?

I used to have a 3.31 (85 mph) Torsen in the car but just swapped it to a 3.73 (75 mph). The 3.31 was great for the Supercharger, not so much without it.

 

[NightmareMoon]

but what's your top speed in 2nd? Is it 60? 70? If you know your transmission 2nd gear ratio, your final drive, your rpm limit, and your tire revs per mile you can calculate it.

 

[LightningGT350R]

See this is the dilemma I find myself in with my car. I'd feel much more comfortable going to a full CAM-C build with a boosted GT vs the current GT350 and I've modded my way into owning a car that's a bit too serious for the street and a bit too fat for autocross.

Good luck with the build and look forward to seeing it's progress.

I'll use your comments to start the next installment of the build. As I noted earlier, when I bought my car it had a Vortech V3 installed on it. I almost immediately had issues with it. The tuning was off and it leaked oil out the back of the head unit. I eventually sent it back to Vortech for a complete rebuild ($1700) which included all new bearings, gears (my head was a "Heritage" unit and was incredibly noisy) and seals. That work was well worth it though, and combined with a retune for e30, and a new Vortech BOV, the part throttle drivability was much improved but the car always struggled to put down power reliably (635 WHP). I ran this combo (Vortech 5.0 + Tremec Magnum w/2.97 1st gear + 3.31 rear gear) for a few local events with some success. Then I had an "incident" with the car. I'll leave it at that. The aftermath required some rebuilding of the car, primarily the RF suspension.

After completing those repairs I continued to compete with the supercharged motor. Again, I had some good local runs but the car was very difficult to drive at the limit under power. Last year I decided to attend the Oklahoma Pro Solo in Fredrick. I, and the car, absolutely sucked. I was 2nd to last and while I'm no hotshoe, I'm not used to performing that poorly. I decided during my long miserable drive back to Colorado the blower was coming off. Between the large reduction in HP (and torque) hopefully improving my ability to drive the car more aggressively, I would lose 90ish lbs. off the front of the car and hopefully improving the handling of the car.

I had to relearn how to drive the car again, but it did work. My local PAX performance improved throughout the 2024 season and even with a very slow start, I ended winning my local CAMC championship. It was clear how much acceleration I had given up (down 200 whp), especially with the 3.31 rear gear. A gear change would have to be made to improve the off corner acceleration. But that would happen after the 2024 season, as would some other improvements.

For the 2025 season I moved the car closer to the edge of the CAM rules. I stripped the car of the interior bits behind the B pillar, added the AJ Hartman front splitter and canards, a Verus Engineering rear diffuser and vortex generators, and modified your rear spoiler to take it to the max 10" height. Lastly, I just installed Girodisc front 2 piece rotors. The car is right at 3500 lbs now. Its never done of course. But the remaining list of mods are out of reach financially for at least a year or two (two-way dampers, carbon bits to lose some more weight).

I've done a couple local events and will get those results written up this week.

 

[LightningGT350R]

but what's your top speed in 2nd? Is it 60? 70? If you know your transmission 2nd gear ratio, your final drive, your rpm limit, and your tire revs per mile you can calculate it.

75 MPH with the 3.73 in 2nd - the current setup.

 

[LightningGT350R]

The first event of the 2025 season was a Rocky Mountain Solo Summer Event #1 at Pike Peak International Raceway. This was the 1st real event with all of the aero on it. I was running the 315 Yokes from last year with 60ish runs on them as well as some street miles. The day started out with rain and was cool in the 50's but as I was running 3rd heat I was lucky and got to run in the best conditions (mostly dry, 70ish degrees).

My friend Bob is the car/driver combo (2017 GT350) that finished 2nd in CAMC last season and is usually my closest competition. But on this day, another friend brought out a car that won the CAMC championship in 2023. Its a 2010 GT that is built very well as he is an excellent mechanic and owns his own shop. He also has a really sweet 1994 GT that he finished 2nd at Nats last year in CAMT. Bob and I knew Brandon was going to be the guy to beat.

The car felt good overall. The car had terminal understeer for most of the season last year as I had added the rear spoiler and diffuser early in the year. I had basically tuned around those components to mitigate the understeer. At least the understeer made me feel like the aero was working to some degree. Or at least that's what I told myself. Since I had added the AJ Hartman front splitter I had reversed one of the large changes I had made to reduce the understeer - setting the rear bar to full stiff. So it's now at full soft as is the front bar. Also, as per AJ's suggestion, I upped the front spring rate from 600 #'s to 700. The balance on this day was good, but it felt very slow to react in transitions. The shocks were set at my baseline of -4 front and -7 on the rear. I eventually went to -3 on the front and -5 in the rear to try to speed up the rate the car reacted to inputs. It really didn't have much impact. Like I said the car was overall very good but my abilities weren't anywhere close to Brandon's and I ended up in 2nd about 1 second back. That was also 7th overall and a 976 PAX score.

 

[LightningGT350R]

My 2nd event of the 2025 season was a Rocky Mountain BMW autocross event at the Colorado Air and Space Port. I really like these events as they split the day up into a TnT in the morning with 3 or 4 practice runs on the course, then a lunch break, and then 3, 4 or 5 competition runs on the same course in the afternoon that are scored.

The weather was perfect. Cool in the morning but mid-70's in the afternoon for the competition runs. The only change to the car was the addition of the Girodisc front rotors. They netted a 19 pound loss from the front of the car - and rotational mass at that. The course designer is a friend who also runs CAMC in his 2018 Camaro. He was running the new Vitour P1's - 345 square!. In the end while the car felt great overall, I still wish it had a quicker response in transitions and during the lunch break I tried to make a front swaybar change but the bolts on my new adjustable links wouldn't allow it as they would have rubbed the strut. Something to fix later. Dave ended up taking the class win (open class - Non-BMW) by about a second.

The next RMsolo event is in a week at the same venue. I'm travelling this week so no time to work on the car. I'd like to swap to my new Yokes but I don't think I can get that done before the event.

 

[CobaltFilly]

After years of reading other members build threads and accomplishments in autocross I've decided to log this years progress, with the goal of my first Nats trophy. I've done OK locally here in the Colorado SCCA Region. I win my class occasionally, and some years even win local championships, but I've never been able to put together two days of decent driving in Lincoln. I coned away a trophy in 2021 (albeit 11th place) with a previous car (2017 GT350R). So my 2025 season starts and the journey to hopefully, finally, leave Lincoln in Sept with something other than crushed dreams.

My current car is a 2015 GT Premium with a 6 speed. Not the ideal starting point as the car was heavier than it needed to be - still is actually. I bought the car because I thought is was a solid, well maintained car. Not the case. Oh, and it had a Vortech V3 SC on it with long tubes. Bonus! Not so much - more on that later. The car had 70k miles. The previous owner (I'm the 2nd) was a Army mechanic. That should be a good thing. But it turns out most of the wrenches turned on the car was done by a local shop. Not the owner. I had a pre-purchase inspection done and we found a bad (really bad) rear wheel bearing, and some oil seepage - top and bottom. The top was due to some crappy breathers being used to vent the engine. The bottom looked like a valve cover leak. No biggie. The car was a blast on the street . Crazy power (650+ whp) and drove pretty well. I had a lot of aftermarket suspension stuff from my previous Shelby that went on the new car - Ohlins coilovers + Vorshlag plates, FP swaybars and a few other things. Time to take it to an autocross...

And it broke. After maybe 4 or 5 events the car developed a miss. The tuning was horrible for anything part throttle, and then the oil leak started at the rear of the motor. After replacing some parts to fix the misfire (plugs, coils, intake) to no avail, at an autocross pretty early in the 2023 season, it puked oil badly out of the back of the pan and I was done. Long story short, the thrust washer was destroyed which allowed the crank to move excessively which destroyed the rear main. That had been going on for awhile as the crank sensor was covered in oil and clutch dust and that was causing the misfire. When I pulled the motor (planning to just swap the rear main) I also found that two of the motor-to-trans tabs were missing and a third was still attached via the bolt, but someone had tried to JB Weld in back to the block! Ingenuity at it's best. I decided to start over and build a CAMC car close to the max the rules allow, but still semi-streetable.

Here's the build list:

Engine
Replacement Ford Gen3 shortblock - wanted a Gen2 but those weren't available
ARP head studs
MMR billet rear main
MMR head coolant crossover
Boundary billet crank and OP gears
MMR remote oil cooler and oil filter kit
Ford Performance GT350 cam gears, tensioners, solenoids and chains
Gen2 heads - lightly resurfaced
ATI super damper
UPR catch can
MSD coils
2018 home ported manifold
JLT CAI
e85 tune
MMR water pump pulley
Fluidyne Radiator
Pypes long tube headers
Custom 3" exhaust with GESI high flow cats + Flowmasters built by Black Tie Race Fab
A/C deleted

Transmission
Tremec Magnum XL - 2.97 1st gear
McLeod RST clutch and flywheel
Steeda HD clutch line
McLeod Bleed Valve

Front Suspension
Ford Performance PP2 front control arm kit - This was a GT Premium w/No performance options
Ford Performance front swaybar
Eibach end links
Ohlins R&T coilovers - tuned by Shaftworks
Steeda bumpsteer kit
Ford Mach 1 front spindle and hub kit
OP Mustang GT4 wheel stud kit
OP Mustang 35mm wheel spacers
BMR front subframe

Rear Suspension
Whiteline subframe bushings
Steeda high strength differential bolt kit
Steeda adjustable camber arms
Steeda subframe brace
Ohlins R&T custom valved shocks - 3DM Motorsports
BMR Delrin vertical links
Meier Racing adjustable rear spring mounts
Steeda rear diff bushing kit
J&M upper shock mounts
OP Mustang R Spec rear hub kit with ARP studs
3.73 Torsen rear diff

Brakes
Ford Performance 2019 Bullet Brembo brake kit
Girodisc 2 piece front rotors (just installed April '25)
2017 PP2 brake booster and master cylinder
JLT brake cooling duct kit
Stock PP2 pads
Motul fluid

Interior
Sparco seats
GT350 steering wheel
Steeda pedal kit
Rear seat, rear plastic, headliner delete

Body
Trackspec hood vents
Scott Drake rear spoiler with custom extension and Gurney flap
Steeda upper and lower grill inserts
MMR fender vents
AJ Hartman carbon splitter and GT4 carbon canards

Wheels/Tires
Apex Forged 18" x 12" wheels with Yokohama AD052 315/30-18, or Nankang CR-S 335/30-18 tires
Apex SM10 19" x 11.5" wheels with Michelin PS4S 315/30-19 tires

The car weigh in at 3550-ish. Maybe with the new rotors I'll get closer to 3500.

More to come...

My friend, what sparco seats are you using, and no cage with stock seatbelts? 5' 10" 200lb male here, 36" waist. I daily.

 

[LightningGT350R]

My friend, what sparco seats are you using, and no cage with stock seatbelts? 5' 10" 200lb male here, 36" waist. I daily.

Sparco QRT Evo's. I have a standard size for the driver's seat. And a Evo L (large) for the passenger. I'm a 34" waist and the standard fits fine. The Large would probably fit you perfectly, but I'm not sure they are in production anymore but I think there are newer versions of the Evo's available. Maybe the QRT-X?

 

[LightningGT350R]

The 2nd Rocky Mountain Solo summer event of the season was last weekend. I had taken a family trip the week prior so nothing was done to the car. I really wanted to swap tires to a fresh set of AO52's prior to the event but there just wasn't time. My frenemy (he really is a friend, but is beating up on me on course so....) in the Camaro was running in X class in a different heat so time might not be completely comparable, but the trend continued. This event he was running a brand new set of Bridgestone RE71RS's on an also new set of 18" x 12" Apex rims. I think he's made of money.

Anyway he again set a time I couldn't come close to. I was .8 off. I was in the 2nd heat and the temps were well into the 80's which wasn't a helper for my old Yokes. I tried running higher pressures at this event with mixed results. I also tried a couple runs with softer shock settings (just rebound as my shocks are singles) and while it helped deal with the very bumpy north end of the course, it didn't help on the stopwatch. This video is of my last (5th) run. I had just sprayed the heck out of the tires before this run. I also used 1st gear a bit more mid-course and just before the finish. Those LS motors have a ton more torque than the Coyote and the digs out of the slow turns really emphasize that. I did win the CAMC class and 16th overall. A 964 PAX made for a poor points day.

The new Yokes went on this week in preparation for Spring Nats in Lincoln in a little over a week. On a positive note, another friend got some great pics of my car, and my new external mic for my GoPro worked awesome.

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