GT350 Build - Autocross Time is Great but Track Time is Better

[Flyhalf]

I had to visit the builder this week to drop off several parts and pieces, and had a look at the car. Resting comfortably mid operation, waiting for its new CPC heart.

We tossed around the idea of just deleting the HVAC. But with the next build already being prepared for, the plan is to keep HVAC until then. But it is tempting to rip all of it out now.

In the lull of waiting for the engine to be built, I have been digging through old videos. Forgot about this one. Thanks for the fun version of sparkles @Flyhalf!

Nice!
The italian sparks are fun
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[WItoTX]

Well, the car is back together. 5 months start to finish. Modifications include a Gen 3 block, GT500 crank, Mahle Pistons and rods, custom RPG cams, new timing chains and tensioners, OPGs, Spec mini twin clutch, stainless works headers and exhaust, braided clutch line, and new hardware and springs for valves. Add to that, a new 8600 redline, and finally topped off with a new PowerMaster starter, when the car refused to start while hot. The engine itself was built by RPG, and the car put together at Bumbera performance in Sealy Texas. I have nothing but positive to say about Bumberas, fantastic shop, flexible, and good guys and gals who all race in some form or fashion.

There is more, but I don't remember all the rest.

Ended up at 494 wheel, on 93.

Now, it's time for shakedowns at the local track. I'm most interested in temps. The car, on road, still runs around 210 oil temp, which isn't bad, but I was hoping for cooler.

If the car can't cool, the plan is, there is a coating out there for the headers that get sprayed inside and outside, that rejects heat really well, comparable to header wrap. If Bumberas has good luck with it's trial run, headers will be coated on mine as well.

One more add. They had this absolute peach sitting on the lift. What I would give to have it on my garage.

We are real close to having a car that only needs maintenance for 2026, and if that's the case, several tracks are on my list for 2026. 2025 has been a rough year, looking forward to a more positive 2026!

 

[WItoTX]

A little early candy.

 

[honeybadger]

so cool. you're going to love it! One of the best parts about going CPC on a tracked car is the availability of running after market parts. GT500 oil pan is no issue. Spec mini clutch that removes 35 lbs? no issue. etc. it really opens up what you can use!

 

[svttim]

So to follow up from my first post. After my January 2022 event, based on tire temps and tire wear, it was obvious the front needed more camber on the front, and most likely the rear. I knew the factory set up wouldn’t get my camber to -3 degrees on the front. I had heard guys could get to -2 on the rear, but I had two shops tell me my car had no adjustment left in the rear. If you are in Houston, PM me and I will let you know the shops so you can steer clear.

I had Vorshlag camber plates installed. Unfortunately, I did not take a photo of them before the install. And the install photo doesn’t show much other than they are already maxxed out, at roughly -3 degrees.

But the results of the camber plates are below. Without widening the top of the strut tower, I was able to get to just about -3 degrees on both sides.

I also had the shop put as much camber in the rear with the factory set up as they could, and unfortunately was told they could only get to basically -.09. I don’t think they even tried. The Vorshlag plates are very well made, and definitely a high-quality product. There is no clicking, grinding, or other odd noises coming from the front that I have experienced with cheaper products. I would highly recommend them to anyone looking to install camber plates.

Also, I did not install the Vorshlag plates myself, but took them to a shop here in Houston. This was because I do not have a spring press at home, and the janky ones from the auto parts stores just scare the hell out of me, even though I’ve used them before.



So back to the car. February 2022, I ran with SCCA. With the new camber plates, the grip from the front is astonishing. The GT350 is not a light car, but I am able to come into corners with much more of a point and shoot approach, as opposed to having to get the car set up just right to get it around the corner. In addition to the camber plates, I dropped weight. I pulled the subs in the rear seat, pulled the deep cycle battery, and pulled one of the amps. With the DSC tuner, I saw my rear ride height go up 5 mm in the rear. The subs, amp, and rear seat weigh in right at 70 lbs. The battery another 27 lbs. Nothing like 100 lb weight reduction with minimal effort.

The results are exactly what I was looking for. 29th out of 159. Top 20%.

Here is a video of that run. As you can see, I left a lot of time out there. Even at that, I was impressed with the newfound responsiveness of the car (My video quality will improve, I promise)



Most of the February event was learning the car with the grip in the front, and weight loss in the rear. While the front gripped extremely well, the rear, at ~-1 degree camber, left a lot on the table. After the February event, I had a better feel for the car, and began researching what to do with the rear of the car. This meant sleuthing M6G again, as well as other forums, for the best options. In the mean time, I left the car alone, and focused on improving my driving. If anyone knows about Texas u turns, they are a good test of grip!

I get to the March event, feeling good about how the car reacts both on the throttle and let off, having found some open parking lots to “practice”. Well that is perfect because this course has a lot of shrinking radius corners that really exacerbated the let off oversteer. I also showed up with water to cool the tires this event, as last time they got pretty warm and I could feel the grip fading. The following video is my “two” best runs. I in the first run, I caught up to the car ahead of me (transmission issues, in a 2022 Caddy CT-5 V). I am certain the 1st run was faster, but I also thought I clipped a cone, so I stopped, for “safety”, and got a rerun.



Well that got me 17th place (of 187), top 9%!

Better yet, it got me closer to the competition in CAMC, where I was 2.76 seconds back in February, I was now 1.43 seconds back, and I ended up in third place in CAMC.

Eric and Chris who beat me, also share notes with me, so would be lying if I said their advice, tips, and tricks haven’t helped me immensely. Eric also drives a 911 that is an absolute monster, and has been co-driver in an NSX, GT350, GT500, and plenty others I can’t remember. Chris has pulled about 400 lbs out of his car and done a lot of work to the suspension. It’s something to watch it at the track, absolutely planted around corners.

Back to my car. I still had issues with rear grip. So I reached out to my suspension guru, who said my car SHOULD be able to get to -2 degrees rear camber in bone stock format. He also suggested AAD camber arms for the rear, and all my reading and research was leading me towards AAD anyways. So I ordered a set, and waited for their arrival.

In the meantime, I continued weight reduction. I pulled the remaining two amps, the welded brackets and everything that held the amps in place, the crossovers mounted in the rear dash and the controller, and most of the power cable. What I thought would take me two days to do ended up taking an entire week, from pulling panels, labeling wires, organizing wires for future use, and keeping everything from damage so I could sell later. All said and done, I pulled another 60 lbs out of the car. The car had 160+ lbs of audio equipment! The following photo is the result, looking from the drivers side door into the trunk.

That has got me caught up to about two weeks ago. Since then, I received my camber arms, and got them installed. I ended up with the AAD camber arms, as well as the vertical link and toe link. First to go on was the camber arms, since I’ve heard and read they are pretty rough to get on without dropping the rear cradle. The AAD system is pretty simple, and I wish I would have took more photos of the various bits. As I said in my first post, I am learning. Basically there is two lockout washers that are offset, so if you are drag racing you can get your camber more vertical, or if you are roadcourse/autox, you can flip them 180 degrees for more camber. These lockout washers go where the camber arm mounts to the subframe, and then you slide the camber arm right in the middle. Then there is a simple dish shaped washer (Sorry, don’t know the technical name) that bolts to the spindle. The camber is then adjusted by loosening the middle bolts, and installing a new shim plate (The silver piece in the following photo) which has the hole drilled in a slightly different spot, left or right depending on if you want to add or remove camber.

The set up is pretty slick. While it lacks the infinite adjustability of a threaded type camber adjustment, the arm also doesn’t have threads at point where the arm feels the most bending force. This is just my opinion, but it looks incredibly strong compared to the others I researched. And camber adjustments take maybe 20 minutes from when I start jacking the car until I am climbing in the drivers seat to go for a ride. And with shims, you know exactly where the car will be at before you even set it back down. Here is the arm compared to the factory arm. It is about 2.4 lbs, where as the factory arm was around 5 lbs.

So the car went up on jacks, beginning on the driver’s side, started unbolting, easy-peasy. In my head I thought what were all these guys complaining about? This came right out.

Well I spoke WAY too soon. Getting out was no big deal. 2 hours into trying to get that freaking bolt on with the new camber arm, covered in blood sweat, dirt and grease, with my hand jammed between the bolt and a gas line, the shock, spring, sway bar, ride height sensor, and various brackets removed, I finally got that stupid bolt in! Lesson learned, the drivers side is brutal. Here is the finished install.

The passenger side only took an hour, and that was mostly trying to get the top bolt in again. I didn’t have to remove the shock or anything else, and it really was significantly easier without that gas line in the way.

With that, I got the string lines out, and figured out how much I had jacked up the toe, and where I was at with camber.

The toe is massively off, at 7mm in both sides (I am looking for 2 mm toe in), the camber was at -2.9 (I wanted approx. -2). So new shim in, and I got it back to -1.8 degrees. Toe still not right. Close enough for now. Here is the final install, without fixing the toe. That will be done once I put the toe arms on. (Yes I could have done them at the same time, but due to time constraints, and my wife wanting her half of the garage back, they are on hold until next week).

It's difficult to tell in the photo, but the front is at -3 degrees, and the rear at -1.8. My next autox is April 24, so I have some time where I will install the rear seat delete, vertical links, and toe links.

Finally, I want to give credit to @AADPerformance for an awesome product. The arms and the bearings are tight, and the paint held up perfect even after the beating the drivers side took last night trying to get it in. Not to mention the red looks awesome. And Parker over there has been incredibly helpful with purchasing, and quick delivery. In fact, all their S550 parts are in stock (Except for blue camber arms, which was my first choice), which is rare these days.

I appreciate everyone reading. I will follow up at some point next week with the next bit of install. Many have reached out, and I promise I will respond. Just trying to keep my head above water at work right now.

Go ahead and cut those towers. Not at all hard to do

 

[WItoTX]

Go ahead and cut those towers. Not at all hard to do

Those were cut 2 years ago haha, ready to rock now.

 

[WItoTX]

TLDR: The car is fantastic, and apart from some minor items, the car is in a really good place.

I got the car on track yesterday for the first time, the local MSR track. There was some high level goals I wanted to work through yesterday, and see if I couldn't at least touch my PB. Conditions were not ideal. We had a cold front roll through bringing rain, and completely cleaning off the rubber from the week prior. Air temps were mid 60s, and sunny, but with 30 MPH sustained wind, gusting to 45 mph. The track surface has been repaved in critical spots, so feeling out the new surface, combined with zero grip, I had myself questioning whether or not I even wanted to track my car anymore. The surface was brutal, doing 120 around sweeper was just holding my breath that the car would stay stuck to the track.

Goals were:
1. Learn the new torque curve and how power application feels at speed
2. Feel out the new track surface
3. Shake out any mechanical problems from pulling and reinstalling an engine, clutch, and transmission
4. Measure temps at the headers to figure out if I need to coat it or header wrap.
5. Track temp changes on the heads, and see how much heat is being generated to the oil.

Without going into the weeds, each of the above items were exactly what I was expecting. Oil temps never went above 240, head temps briefly touched 203, and mechanically, it was clear the shop that I had do the work (Bumbera Performance, Sealy Texas) takes pride in it's work product, and I am completely happy with the results. Aside from one or two push clips in random spots, every piece was put back in as good as, or better, condition than when I dropped the car off. By way of example, the splitter I have ties into the back of the stock splitter. I removed the track splitter before I brought it in, but left all those screws out of the car when I dropped off. Bumbera ordered all new screws and properly secured the piece that they didn't have to do.

The RPG engine rips. Power drop off above 7500 is a bit more significant, but the engine is in the power so much earlier than the Voodoo ever was, making it a massively wider range or useable RPMs, especially on a fairly tight track like MSR.



I got a good flyby pass too:

 

[5.2 liters of democracy]

First off, I love your attention to detail in this thread. I love reading a good long update, especially when it pays off in the end like it seems it has!

I'm now in sort of the same boat as you. I've officially signed myself up to a CPC conversion. Outside of re-pinning the harness, was there anything else needed for the conversion? Any unknowns I may not be accounting for?

Thanks ahead of time!

 

[WItoTX]

First off, I love your attention to detail in this thread. I love reading a good long update, especially when it pays off in the end like it seems it has!

I'm now in sort of the same boat as you. I've officially signed myself up to a CPC conversion. Outside of re-pinning the harness, was there anything else needed for the conversion? Any unknowns I may not be accounting for?

Thanks ahead of time!

The re-pinning the harness was the least of the concerns surprisingly. The shop was well versed in it, having converted a bunch of F-150's to the Coyote firing order.

It's all the ancillary stuff that gets you. While you are in there, why not replace the clutch? If you are doing that, then the clutch line, throwout bearing and master cylinder. Then the motor is out, so why not do headers? And then those need to get coated (I didn't, but because there is a new coating, used by SpaceX for heat rejection, that I am waiting on someone who is testing it out before I go that route. If not, I will wrap headers).

Then, why not do other stuff since you are in there? So timing chains, VCT, OPGs, oil pan, etc...it's all stuff that isn't top of mind, but with the engine out, why not just bite the bullet.

The only regret I have, and it's not a huge one, is I wish I would have done an intake right away, because even though the engine can rev to 9000, it really drops off at 7500. Which is good for temps, but it's definitely a spot to dig into in the future. And, if you still have active exhaust, I would get the simulators right away, or just completely remove them, so you don't have to worry about a valve not working at an event. That happened to me two weekends ago, and just a PITA. So valves are gone now. I'd also consider the oil balancing/coolant lines at the back of the heads, but after doing a lot of digging, I am not convinced they really do anything. I guess it would have been cheap insurance. FP does run them, but oil isn't flowing back there. So I am not sure they are any benefit.

Now if I could get the same cooling system that HB is running, I would probably not concern myself with heat anymore. But one thing at a time.

 

[5.2 liters of democracy]

Boy am I familiar with that. When I got my first replacement engine it was exactly that. I've been waiting so long for the builder to address the issues that I've given up and decided to go just buy a new engine and do the conversion now.

So you've found the GT350 intake is limiting then? I've been toying with the idea of trying to wedge the Cobra Jet under there since I'll be running the Watson mounts that lower the engine a fair bit. I'll likely reach out to Tim at MPR to see what he recommends since I'll also be spinning to 9k.

 

[WItoTX]

Boy am I familiar with that. When I got my first replacement engine it was exactly that. I've been waiting so long for the builder to address the issues that I've given up and decided to go just buy a new engine and do the conversion now.

So you've found the GT350 intake is limiting then? I've been toying with the idea of trying to wedge the Cobra Jet under there since I'll be running the Watson mounts that lower the engine a fair bit. I'll likely reach out to Tim at MPR to see what he recommends since I'll also be spinning to 9k.

I would definitely reach out to him. He was a valuable source of information, and helped with a ton of questions. I think the 350 intake is limiting, but I am up 30 HP over stock too, with so much more power down low, that I think the new engine makes the power let off more noticeable at the top end.

My original block is going to go back to him. Planning 2027, and build that motor exactly how I want. Dry sump, new components, and sleeved. Then figure out how to make cooling work, something like HB did. Then make the swap back in with the new motor.

I'd really like an electric oil pump too. But I don't know if that is even possible.

 

[honeybadger]

Boy am I familiar with that. When I got my first replacement engine it was exactly that. I've been waiting so long for the builder to address the issues that I've given up and decided to go just buy a new engine and do the conversion now.

So you've found the GT350 intake is limiting then? I've been toying with the idea of trying to wedge the Cobra Jet under there since I'll be running the Watson mounts that lower the engine a fair bit. I'll likely reach out to Tim at MPR to see what he recommends since I'll also be spinning to 9k.

I really need to make something. I wonder if we could 3d print the runners and then make a plenum out of carbon fiber?

 

[WItoTX]

EDIT: I forgot I already put the cams and stock OPGs in my shed. I am only down an oil pan.

After the holidays, I had some time to pull apart the rest of the the stock Voodoo shortblock. As a reminder to why I am pulling apart the stock motor, in April 2025, this was what my oil looked like following a track event. Purdy, isn't it???

RPG sent the stock block back with everything EXCEPT the oil pan.

First thing I looked at were cylinder walls. All the cylinder walls had a bit of markings on them. I wouldn't call it scoring as I couldn't feel them. Not something I found super concerning, but definitely something I'd keep my eyes on had I saw this with a bore scope.

Everything spun freely, and there was no play noticed. With that, flipped the motor, and snapped some photos for reference when this motor goes back together.

One thing really cool about these motors (Apart from the fact that the rod is an inferior cast piece instead of forged) is that the rods are cast as 1 piece, then effectively broken to get them to fit perfectly on the crank. The red circle below is that fracture line after loosening the bolts.

I got them all pulled, and a couple shots of the crank. These two are about the worst of the wear on the crank.

I'm hoping those marks can be worked off. I'd love to reuse some of these parts on a street only build. I pulled the mains after this.

Since this is already pic heavy, I will skip the image of the mains in the block.

Here are the rod bearings. All of them look "used". You can see some pitting, some groves, some questionable wear, on at least 3 of the 8 bearings.

And here are the mains. You can see scoring, enough to catch a fingernail, and odd pitting.

Rod Bearings:

On this one, the like you see that has a bend in it, that is etched into the bearing itself.

In the end, I may have pulled the engine a little earlier than necessary, but I'd rather not have a failure at 140 mph that dumps oil for everyone else on track.

Keep in mind, this engine has seen 4.5 years of AutoX, 15-20 track days, in temps from upper 40s to above 100. It's seen the entire rev range get used in it's 14,000 miles. I'd argue I was no where near as hard on it as many others are. I constantly changed the oil (Usually every 500 miles max), fresh air filters, FL-2087 filters only, and the stock 91 tune. Zero changes to NVH on the engine. It still let go.

EDIT: I THINK I AM WRONG HERE, WILL BE CHECKING THE SHED TONIGHT FOR CAMS AND OPGS....Again, the big variable I mentioned in the first paragraph, I wish I could have seen OPG's. I am requesting them from RPG, but I'm not holding out much hope. They also failed to ship a few other items, which were worth some money, a little disappointed there.

 

[5.2 liters of democracy]

I think you 100% made the right call to pull the motor when you did. Those bearings look as bad or worse than mine after it had let go, minus the set of bearings where the catastrophic failure happened. Seems like you did the right thing and got ahead of it.

As far as RPG is concerned, it's unfortunate they're operating the way they are. I'm concerned I won't get my motor stand back. I had put some wheels on the Ford stand to make transportation easy. I'm hoping it isn't lost when I finally hear back from them. I'm hoping RPG can get those items over to you and we can see how things were looking in there.

 

[honeybadger]

Definitely the right decision to pull that motor. you can even see a little bit of heat build up on the rod ends.

Sucks about the missing stuff with RPG. When I shipped my long block to Tim last time, I built my own wood crate and it arrived back to me in the exact same box with all my parts a couple months later. I was quite impressed to see the same box used ha

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