FFR PDG GTM 2026 Teardown and Rebuild

It has been awhile since we ran a race. (or posted an update thread here) About a year and a half actually.

The last event saw a front end impact that did not hurt the car too badly, but did disable it until I got a chance to tear it down and inspect everything.

I started that this weekend in preparation for a September event this year at Thunderhill Raceway Park. I am trying to get everything sorted to run the inaugural 12 Hours of Thunderhill. As some of you may know, we built this car specifically for the 25 Hours of Thunderhill, but after some behind the scenes maneuvering the rights to that race were apparently sold to another track back east a couple of years ago and so Thunderhill Raceway Park, under NASA sanction, no longer had a big endurance race...until 2026. The original powers that be are organizing and putting on this event in the hopes to make it more attractive to racers with a number of potentially positive features for the average racer. They are lowering the entry fees. They are running the race in September so it hopefully is not so cold. And they are running all 12 hours during daylight hours so tons of money does not need to be spent on high end lighting for every car. Lots of other things as well, but I think it can best be said that the organizers are going back to the drawing board and trying to make a new event that is easier and more fun to run, as far as the racers are concerned. A good move IMHO and we will do what we can to support this event, hopefully by attending, but there is a TON of work to do before September.

Some of the items so far that we will need to address are:

1) Leaky fuel system. Went to put the car in the shop and fuel is leaking out by the pump area. Definitely have to sort that.
2) Water is leaking out under the middle of the car. Probably a loose connection. I have been having issues with the silicone hoses not remaining tight. Definitely will need to track this down.
3) Nose box is bent and sheet metal is tore up. R&R needed.
4) Fiberglass tore up. Will need to put that back together and repaint the entire nose.

Some of the items I am working on for this event and improving the car are:

1) Going to put in the smaller engine that makes right at 500HP at the crank. It gets much better fuel mileage and can run on pump 91. Lots of details needed here as I attempt to get a two engine package put together. In other words I am at this same time also purchasing all the parts to get to where we have a complete spare engine setup sitting in the shop/trailer. There are a lot of expensive accessories that need to be standardized and bought to end up having two complete engines ready to go. This is expensive and time consuming, but I feel it is the right way to run an endurance race. No point in driving 2 days to a race and having an issue that can't be addressed with an engine or transaxle. As such I am also trying to do the same with the transaxle.
2) We have always had two Mendeola transaxles in the shop. One is usually being serviced while the other is being run in the car. I have recently gone out and have been looking to purchase a third gearbox in order to have a complete spare in the shop/trailer. Mendeola does not seem to have any available, so I am looking in the secondary(ebay) market. This has been complicated because Ian at Mendeola has informed me that there are a couple of wear parts in the differential that they purchase from other manufacturers that have not been available for awhile and as such they are trying to find a replacement part/manufacturer. I have proposed just going to an entirely different differential assembly, and we are trying to get something together to test right now. I don't really want to run a new setup in a long and expensive race like this 12 hour, but we will have to see how scheduling works out this year.
3) ABS. I have been working on a motorsports ABS unit from the guys at RHT. I have all the parts in the shop, but actually running individual lines and getting compatible ABS sensors on the hubs is proving to be a challenge. Work in progress for sure, but I am moving forward on this little by little.
4) New front sway bar setup. The one we have on the car takes up a lot of space and is a bit unpredictable in its adjustments. It is not a "conventional" setup and I want to go back to what I know works from past experience. Again, lots of time and money needed to do this, and as I have not really torn into the front of the car since acquiring it, as far as clean paper rework of function and components, this is the time. Between the sway bar and the ABS it will mean rerouting pretty much everything in the front of the car including the water lines.(Ugh. Not looking forward to that)

So lots of things happening here and I thought I would bring you all along for the ride.

The pictures are of the front nose box damage and the rear hood pin areas where the hood pins were ripped from the car during the incident. It was a crash into a tire barrier and it doesn't appear to be a whole lot of damage, but you never really know until you get it torn down and start measuring things. Fingers crossed that the repair list is small.

Thanks for the report! Repairs don't look too awful, fortunately.
Have you had ABS up to this point, or will that be a new feature?
How are classes broken down for the 12H race? Are you stuck in one class or do you have a couple of options?

The tear down continues.

Some very interesting things found yesterday.

Even though we are running VP101 race gas, there does appear to be some issues with the fuel system. The leak ended up being from some material being used in the fuel system that is obviously not compatible with this fuel. We run Canton Mecca fuel filters that use a cartridge insert. This makes them easy to inspect and easy to replace a filter when/if needed. The cartridges have end caps on them and I have about a dozen of these on the shelf as wear items for replacement. It turns out the fuel leak was because of swelling of a sealing material that the manufacturer put on the end caps of the particular cartridge that was in the car. This material swelled up so much that it lifted the top off the filter housing and caused a leak. Had you told me this could happen I would not have believed it. The cap on the filter housing is at least 1/4" thick aluminum. These are hefty units, and I accept the weight they bring because they are almost literally bullet proof. Anyway, the swelling of this sealing material caused this leak. Upon inspection of all the filter elements I have in stock, none of them have this sealer all the way around the caps like this one cartridge does. Just one or two little spots to keep the caps in place during assembly. I am guessing this is a known problem and the manufacturer changed how they build these. I guess I just got lucky to have a "bad" one and I got really lucky this did not cause an issue while the car was being raced.

Spoke with a friend of mine that has much more experience than I do with racing and he said that all the modern fuels can have issues with rubber o rings, sealants, hose materials, etc. After speaking with him and looking closely at the VP website, and especially since the new engine is going to be running on pump gas from California, I have decided to replace the 40 or so fuel lines that are in this car with PTFE lines. It will be quite an undertaking both in labor and expense, but the number one thing I worry about in a race car, or any car for that matter, is fire, so the replacement will be done.

Started the engine up before starting to pull the fuel system apart and the coolant leak is a seal on the water pump. We have never had this issue before and I am wondering if it has anything to do with the coolant we are running. I have been using Summit Racing non-glycol NHRA approved coolant as we need to do something to keep corrosion at bay while still following the rules that say we can not use standard glycol based coolants on the race track. I will have to look at this closer once the engine comes out. I have a half dozen of these water pumps and if there is an issue, that would be bad as once the engine is in the car, there is really no getting to this area for service or repair...as I am sure all GTM owners are aware.

The ABS is a new feature. This car has been very analog for its entire life up to this point. Manual shifting, no traction control, and no ABS. Along with the ABS our ECU allows for traction control, it just needs wheel speed sensor inputs. The ABS unit has a pass through sensor feature, so both TC and ABS will be made capable once the ABS unit is installed. I very much enjoy having a raw analog car to drive so all these "Nanny" features will be able to be turned off if the driver so chooses. We also have really not had any issues with traction control. Even with the 600+ horsepower engine we have been running, there hasn't been any issues with tire slippage. I am guessing that would change in the rain. So really the TC would be for a future monster HP build, or if we are racing in the rain. Otherwise I don't anticipate using the TC at this time. The 500 HP engine ECU will not even have the TC set up.

The classing is much different for this event. It will be "bracket" classing. I am not sure how they intend to keep people from sand bagging, but basically there will be qualifying laps where you will then be classed based upon your speed/lap times. I believe the thinking here is you can go mild to wild on your vehicle and because it is strictly based upon your lap times, it really does not matter. Cars will be put into about 6 different time brackets and maybe they will just adjust on the fly, I don't know, and I got the feeling the powers that be don't really know yet either. Interesting detail that I am intrigued to see how it works out.

Here is a picture of the fuel filter cartridge.

So just to document where I am getting parts for this rebuild...

I build sway bars to the car, whatever car I am working on, with components from here https://www.hrpworld.com/. These guys are the real deal. Not a cheap option, but the parts work.

I get my AN plumbing fittings from https://www.anplumbing.com/pre-made-hoses.html. I find their website FAR superior to buying fittings from Summit or Jegs as the prices are very close to each other but the search function is great at AN Plumbing. That link is specifically for the PTFE hoses I am switching to, but they have all the other fittings too.

The ABS stuff is from https://www.rhtmotorsport.com/. I sourced some expensive Bosch Motorsports sensors, but am also going to try some GM sensors since we run the GM ZL1 Camaro hubs on this car.

Got the GM sensors here https://www.gmpartscenter.net/search...nsor&ptid=1912.

Running an Auto Verde 3 stage dry sump pump that I had in the shop from a previous project but it needs a pan and scavenge lines. https://www.drysump.com/index.php/oi...ra-shallow-pan
https://www.pegasusautoracing.com/pr...p?Product=3481 If you use this pan, just know that it comes standard with two -12 fittings and one -10 fitting. My pump required three -12 fittings and they provided the swap out on the fitting. This is a good pan, but it does not have a provision to get oil back into the engine block. On my first and second setups with this pan I welded a block under where the stock oil filter would be so I could drill and tap a -12 oil pressure line into that, but this time I am using an oil galley adapter from Katech that has a part number of 9001. This is a -10 adapter, so I got a -10 to -12 adapter from AN Plumbing so I didn't have to change the entire hose. -10 is more than enough volume for engine oil supply lines, but my cooler has a -12 so I just continued that since I could make the adapter at the block with the old setup whatever I wanted. I can't find it on their website or I would provide a link for the Katech adapter, but here's their general link. https://katechengines.com/ I also use Katech for engine builds that are not crate engines.

Dry sump pump drive components https://www.jonesracingproducts.com/

I am building the dry sump pump mount and lines here in the shop.

Canton doesn't offer the exact fuel filter housing I am using, but here is the equivalent that they show on their site. https://www.cantonracingproducts.com...ing-ports.html That uses the same cartridges as the ones I have in the shop use. Just hopefully not the ones with the extra goo! To be clear, I am using an older style housing from this same manufacturer that is no longer available.

All the electrical components like plugs, wire, heat shrink, etc. come from here. https://www.prowireusa.com/

Items from Summit Racing or Jegs:

https://www.summitracing.com/parts/ati-918855

https://www.summitracing.com/parts/ARP-330-2802


I'll try and continue the links here so people can see exactly what I am using on this rebuild.

you should fuel leaks are not fun...that car already had fuel fire due to a bad fitting good luck

Shane added the BMW MK60 ABS to a customer car, he probably has some good insight as well.

Yes and no. Everything I read about that system we used seemed to be positive. But I'm not really in a position to push these cars....since they are customer cars. About all I was able to do is attempt to lock up the brakes and verified that the ABS did indeed engage and did prevent the brakes from locking up. How that system performs under cornering and race conditions, I have no way to know or test.....but like I said, there were plenty of people using that system for racing with great results.

Quote:

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Originally Posted by acmikee

you should fuel leaks are not fun...that car already had fuel fire due to a bad fitting good luck

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I know. I was there. I helped rebuild the car overnight so we could finish that race. No one was willing to get in the car after the fire so I did.

As soon as I got the car from Richard I completely redid the fuel system, and everything rear of the fire wall. I wanted to be sure there were no lingering issues.

With the exception of one vehicle, which I believe had a very old fuel line, and your mentioned PDG fire, I have never had any issues with fuel lines that were neoprene rubber. I changed them every few years just to be safe, but now I have multiple sources telling me that these will deteriorate over time where the PTFE ones will not.

Retrofitting all the fuel lines in this car is not something I want to do, nor will it be a cheap endeavor, but if there is even a .0001% chance these fuel lines could cause an issue they need to be replaced.

Quote:

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Originally Posted by beeman

Shane added the BMW MK60 ABS to a customer car, he probably has some good insight as well.

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Yes, it is the MK60 unit.

One of the guys on the race team ran this unit on his street car and it seemed to work just fine. Used the rather expensive ZR1 wheel hubs with bult in sensors for that build, and we just don't want to run those since they are over $400 per hub, while the ZL1 hubs are about $100.

Quote:

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Originally Posted by crash

One of the guys on the race team ran this unit on his street car and it seemed to work just fine. Used the rather expensive ZR1 wheel hubs with bult in sensors for that build, and we just don't want to run those since they are over $400 per hub, while the ZL1 hubs are about $100.

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I have the ZR1 hubs for ABS on my build... Is there a write up on the ZL1 hubs? C5 fitment wheels will not fit the ZL1 hub, correct?

What we have were listed and sold as ZL1 hubs from a dealer. They have an SKF marking on them and are a direct fit replacement to the SKF and standard C5 hubs that we used previously. EDIT: Except for the spline count. The ZL1 runs the larger spline count, which IIRC is 33 splines. The bolt flange is larger diameter, it is also thicker. The hubs have an issue with some brake top hats, but not others because of the increased flange dimensions. Other than that there have been no issues. The ZL1 hubs use an external ABS sensor, and I am going to have to drill some holes and probably do some machine work to the C5/C6 uprights to get them to work. The ZL1 hubs I have do not have a GM type number on them which I was not expecting. Pretty much every GM part has a GM specific part number on them. I do find that a bit odd.

All bolt patterns are the same. Offsets I believe are either identical or very close to each other. I did not measure, but no interference issue when we swapped C5 for ZL1.

From my notes, these are the hubs we used on that car....which were $76 each at the time. Those are rear hubs, but we used them on all 4 corners.

https://www.rockauto.com/en/moreinfo...t=1636&jsn=949

Thanks for that link Shane.

I think I posted a thread previously...a long time ago, on a thread far far away...where I discussed the differences between the hubs you could get from, essentially, China, and the SKF hubs. The difference appeared to be in the cage construction within the hubs themselves. We quickly found out that the "no name" hubs failed very quickly and would not last us an entire 25 hour race. This also included the GM factory standard C5 hubs. Then we got the "race SKF hubs" that had the black finish on them. IIRC these were sometimes referred to as the "X Hub". Those got expensive and harder to find, so I called SKF directly to see if there were any alternatives. The ZR1 hubs have a larger spline count and an "active" ABS sensor but the same internals, according to SKF, as the "race hubs". We used these ZR1 hubs for a race season or two and they worked fine, but, as I said, they are over $400 a piece so we went looking for something cheaper. As we did not use the ABS sensor at the time, the fact that the sensor was separate on the ZL1 Camaro hubs did not really matter to us. These used the same larger spline count as the ZR1 hubs but were a quarter the price and were a direct fitment match. So that is what we have been using for a few years now with no issues. They do need to be swapped out after about 40 hours of race use. Now that we want to put ABS on the car we are back to either paying up for the ZR1 hubs, or trying to retrofit the Camaro sensors onto the C5 uprights. Or moving away from that and trying to fit the Bosch sensors. I did get some tone rings to try to fit the Bosch sensors but haven't gotten very far on that yet. Definitely a "work in progress".

ahh....that all make sense!

For the rear axles, don't discount the possibility of adding tone rings to the inner CVs with sensors, fronts are easy because spline count doesn't matter.

Quote:

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Originally Posted by beeman

For the rear axles, don't discount the possibility of adding tone rings to the inner CVs with sensors, fronts are easy because spline count doesn't matter.

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Yes I have been looking for tone rings that fit the outside diameter of a 930 CV. I haven't found them yet, but that would be a good solution.

Do you know of a source for this item?

As far as running them inner or outer, I have thought about that and believe I want to run the tone rings and sensors out at the wheels. Just in case there is an issue with a CV or axle.

I would figure out how many teeth you need for one rotation to match the front tone rings, draw it up in CAD, and have send-cut-send make you a tone ring out of sheet metal. I think that Shane might have this capability to cut this for you as well, maybe even draw it up for you.
I think that the metal would have to be ferrous to interact with the sensors.

I actually spoke to Ian at Mendeola awhile back about this and he said they have a very simple setup where they use cut sheet metal and just bend the tabs 90 degrees to make the signal flags. This I believe uses the CV 6 bolt bolt pattern for mounting to the CV.

Very simple, but I am looking for a bit more of a substantial tone ring.

Going forward I will simply cut a tone ring into the My Race Shop 930 CV to Vette stub axles, but I have quite a few of those in stock and am not going to do a run of those any time soon, so some sort of add on is currently needed.

There are (surprisingly) quite a few tone rings available on the internet and also on Amazon. The problem is that most do not show actual dimensions, but simply list by vehicle application. Some of them are cheap like the ones I just bought for $10 a piece, and some are hundreds of dollars for one ring. I'm probably going to just randomly order some more of the cheap ones for different applications and see if I can get lucky.

Attachment 228298

I have these that I just removed last week. I'm assuming they're way too small for you (Miata axles), but you're welcome to them if you think you could make them work. ID is about 2.758". ID of the step is about 3.1"

Thanks Shane.

Yes I believe I would need something in the 4" range.

I have some smaller ones I could get creative with, but I really want to keep this simple.

I will continue the search.

Sometimes things evolve in a race car over time. Such was the case of the brake system on this car.

While trying to make the stock C5 calipers work in extreme racing conditions, as I understand it, one of the things that Richard and crew did before I was part of the team, was to use a brake fluid recirculator system to deal with boiling fluid problems. This meant a lot more plumbing than a non-recirculator system. Pretty much as soon as I started with the team they had already moved away from the recirculator system and then very shortly there after we moved to use the big StopTech calipers and associated quality racing pads and fluid. This got rid of the fluid boiling issues. However, all those earlier lines were still on the car, which you can see here.

That aluminum box that is attached to the brake system is a rather ingenious prototype unit by Jim Hausler that measures the brake pressure for both front and rear circuits and then, with the flip of a switch, turns an Auto Meter tach into a brake bias meter. Very cool item, and we have used it continuously over the last 15 years or so, but with the introduction of the ABS system I believe we are no longer going to be able to run this.

As mentioned previously, I am replacing all the fuel lines with PTFE lines for safeties sake. Here's a picture of the short fuel lines that are now replaced. The actual number is half what you see there as the picture shows the original red/blue, and sometimes black, reusable AN hose end lines next to the new PTFE swedged lines. Even though this is showing double the number of lines, it still illustrates how complicated the fuel system is in this car. There are roughly 8 more long lines that I don't have a picture of yet as they are still being made.

For those of you that do not know, because this car was built for endurance racing, and for redundancy as well as fuel capacity, there are two completely separate fuel systems in this car. Each holds just under 22 gallons for a total of 44 gallons of fuel in this vehicle when fully loaded. Those two systems have to combine in order to go to the engine, then be separated again for the pressure regulated return lines to the separate tanks. Also, in order to make sure we get all the fuel out of the tanks, this car uses dual lift/surge tanks and has both lift pumps and pressure pumps. As I said, and as this picture shows, it is a complicated system.

We also have both an automatic and manual electronic/electric system to try and drain the tanks in a balanced fashion over a non-stop 3 hour track session, which is roughly one full fuel load.

I have been having issues with the AiM MXL2 dash that is on the car currently. Summit is offering an AiM Power Distribution Module at a small discount to some of the other listings I have seen, and the PDM basically comes with a free dash, so I am replacing the MXL2 data logger dash with what is essentially an AiM MXP data logger dash and a PDM 32 unit. Not going to jump into the wiring rework before this race, but it will leave that option open for the future on this car. The wiring is pretty complicated and, again, something that has "developed over time" and therefore not quite as efficient as I would like it to be. Another project for another time, but since the dash needed replacing anyway...

I will say that it appears that the PDM must be in use with the included dash, so if you don't want a PDM for some reason, this isn't the setup for you.

Here is the exact part number I have...https://www.summitracing.com/parts/AAG-S0276