The last one! #538 is getting V12 and RHD

[DopeOfWelding]

I officially have the last GTM sold! Technically not the last produced though, mine is #538 of 539. Last one for the USA. I’ll try to not bore you all with the details so I’ll give the short version of it.

539 total were produced, but number 538 was an incomplete kit. As of February 2024, 539 was being finished up for a Canadian customer and 538 was just a left over, un-powder coated chassis. I called in late January ‘24 about buying a GTM and was told they were discontinued. I had some very unusual plans for a exotic build I had been wanting to do for the better part of 20 years and explained to the right person at F5 that I really only needed a body and glass for my unconventional build. Although I would entertain buying a chassis if they had one. I was told that the chassis jig had already been destroyed but they could get a body together for me. I got a call back a few weeks later that they had one chassis left in storage that they kept as a possible “final send off” build for the GTM by F5, that they would sell to me. Due to the plan I have for this build, it worked out great that it was an incomplete kit since the parts missing is the stuff I don’t need. I ended up with a damaged body they were going to end up destroying, which also works perfectly for my project. It seemed to me that they were happy the last one they had was going into the hands of someone that could do something with what was left.

Fast forward to the 2nd week of March ‘24 and the GTM was in my shop and on the chassis table ready for surgery.

The plan: Styling updates to bring what is now, a dated looking car into the 2020s. It’s s great looking car, but having been designed in the early 2000s, it shows. The tail light panel and front valance will receive the majority of the make over. I intend on building the car as JGTC car ( Japanese Grand Touring Championship/ GT500) The car will have heavy JDM influence, including RHD conversion which I’m nearly done with already. The body will receive a mild wide-body. Lexan window sliders, rear window will have a scoop. Large dual element, swan mount GT wing. I also have LED Ferrari F355 taillights I will be using.

The power: V12. I have seen many talk about it, but I haven’t seen it done. I have a Mercedes Benz M120 6.0L from a 1994 SL600. Yes, the same long block used in the original Pagani Zonda. It will have the famous titanium equal length headers, ITB, Link stand-alone ECU, 60-2 crank trigger. Backed by a Mendeola SDR5 with 3.88 LSD. Transaxle is done and ready to ship.

Suspension: I already have it in roller status on C5 Z06 arms, sprung by custom QA1 dual adjustable coilovers. I know further tuning will be needed, but a good starting point. Brakes are going to be slotted 355mm 6 piston Brembo.

Wheels: I have Advan Racing GT premium forged center locks for Porsche GT3RS. 19x12 rear, 19X9 front wrapped in Toyo R888R 345 rear and 265 for the front. I’m making cup style center locks to eliminate the goofy Porsche lock mech.

Interior: I have full carbon fiber Bride Zieg IV wide racing seats and complimenting Sparco components like FIA approved 6 point Hans harnesses and steering wheel with Works Bell quick release on a Mazda RX-7 FC column. Dash will custom full carbon as well with custom gauges.

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I hope to keep this thread updated with the build as it progresses. I’m aiming to have the car completed in 2ish years time. This is far from my first rodeo, but given my car is so incomplete, I will be making everything as I go. Certain things I would like to follow the way the car was intended to be built, so I may need to pick some of your brains to overcome some obstacles!

Thanks for looking!

[ohmygosuness]

Very exciting to see how this turns out. Curious to see what chassis modifications you will do to make the V12 fit.

Out of curiosity, when did you place the order for Mendeola? I have mine ordered nearly 3 years ago and I'm still on the waiting list.

[DopeOfWelding]

Very exciting to see how this turns out. Curious to see what chassis modifications you will do to make the V12 fit.

Out of curiosity, when did you place the order for Mendeola? I have mine ordered nearly 3 years ago and I'm still on the waiting list.

The M120 isn’t grossly larger than an LS. It’s the same width, a few inches longer. I will be using a dry sump oiling system so that will greatly reduce the height of the engine. I may have to get creative stealing space where I can by the firewall. I know I’m already going to be swapping from distributor to coil on plug and eliminating the VVTI. Gooichi Motors makes some compact water necks and filter relocation parts. The transaxle will likely be shifted back up to 2” which is fine since I don’t have a transaxle mount with mine. I’ll have to fabricate one.

I got REALLY lucky with my Mendeola. I gave up on using one and was sourcing an alternative as I was told by Mendeola it’s 6 months when I spoke to them in February. Only to find out that many people like yourself wait 1-1/2 to 3 years. I was looking at Ricardo M7003 6 speed. Pricey, but not by a ton more than a new Mendeola. The Mendeola is around $13- $14k now. I happened to be on Facebook marketplace one day and one popped up, brand new in the crate. Struck a fair deal and sent a deposit. It was a blessing since I’m trying to complete this car in 2 years, and it’s greatly hinging on fitting the v12 in it as soon as possible.

[JimStone]

Wow, that's a heck of a plan. Clearly you know what you're doing. Respect to you GTM guys.

[ohmygosuness]

Maybe I should've just done that instead of waiting. It's making me want to cancel the order and get a Porsche trans. I've been itching to make it AWD. But it would need a ton of work.

What ECU are you planning on using?

[DopeOfWelding]

Maybe I should've just done that instead of waiting. It's making me want to cancel the order and get a Porsche trans. I've been itching to make it AWD. But it would need a ton of work.

What ECU are you planning on using?

Finding a Mendeola for sale isn’t too common. I have seen the Ricardo’s come up for sale in the $15-$20k price range. Problem with the G-50s is they are a fortune ($10k for a junk yard core, $20-$25k for a ready to run box) and not as strong as a Ricardo. The M7003 from the Ford GT is really the only other option IMO since they can eat 800hp and ask for more and are the same length as a Mendeola. I believe about 50lbs heavier. Other Ricardo’s such as the one from the Panera are not as strong and don’t take kindly to hard launches.

As for the ECU, right now the plan is to run a Link and add a 60-2 trigger to the harmonic balancer. I know the M120 V12 has support from Halltech, but that maybe a little out of my budget unless I can pick up some sponsors. I just about have my life savings dumped into this car already. Oops

[ohmygosuness]

Damn. G50s really going for that much? I guess a rebuild would put it in the same price range as Ricardo/Mendeola. But at least the Mendeola would come new out of the box.

What made you go for the M120 as opposed to the beloved LS motors?


I just about have my life savings dumped into this car already. Oops
Same here! The things we do to build our dreams...

[VRaptor SpeedWorks, LLC]

Looks like a very ambitious project! Welcome to the madness here.

[Tooth]

Can't wait to see this come to life.

[DopeOfWelding]

I can’t say I have searched every corner of the web for G-50s but that seemed to be the average I have seen over the last 6 months.

As for the M120. An exotic looking car should sound exotic no? At least that was my reasoning. I didn’t want to sit in the car and feel like I was sitting in anything remotely like a corvette. The M120 has a great track record for reliability, puts out a modest 400hp in stock form, forged internals, can be made to scream like a 70s formula 1 car, used in the Pagani Zonda… and I only paid $3,300 for one with low miles!
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[Jim1855]

I like the odd, unique and unusual if it makes sense. This does and should be seriously cool. V-12 has a nice "ring" to it.

A local builder stretched a GTM, installed a LS something motor and a traditional RWD automatic. That didn't make sense to me, but I suppose the trans was cheaper. He did run events like the Silver State.

Jim

[DopeOfWelding]

My Mendeola SDR5 arrived this week! Did a little clean up on the V12 as well as sourced out some go-fast goods that will make it singggg. Also set the car up on the table at “ride height” so I can start making up all new tabs for my QA-1 coilovers. I also bought a small powder coating set up so as I make mounting tabs and such, I’ll just powder them and bake them.

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[beeman]

Are you using the OEM c5 front UCAs? They will make it a challenge to gain camber without losing caster. Less caster means more squirrelly at highway+ speeds. I used the OEM front UCAs but moved the upper mounts towards the rear for more caster and maybe 1/4 inch inboard to help with camber. I now have 8+ available caster and more available camber than I need, I think I set it for like 1.8 to start. I also added anti squat while I was at it to better match the C5 corvette, I added half the angle of the corvette UCA to be conservative.

[VRaptor SpeedWorks, LLC]

Since he has a Gen II, the front UCA mounts are already moved back an inch compared to the Gen I.....

[DopeOfWelding]

The V12 has found its way into the car! Also finished up the pedal box and steering column swap to right hand drive. I still need to address the steering rack but that is actually to simple part. I had to redesign the column mount to raise the column up at least 2” from the stock style mounting location which means it HAD to go right through the dash bar. That spot received some significant reinforcements. I’m happy with the use of the RX-7 tilt column. Did I mention that I’m 6’6” tall?? Between the V12 taking up additional cabin space, the fixed carbon fiber Bride seats, my height and the car having a 39” overall height… I like challenges.

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As for the M120 V12, I knew I would have to make some compromises to make it fit like moving the firewall forward some. I know I was going to have to convert it from distributors to coil on plug. I also removed the water pump and will be using a remote electric pump, that freed up a lot of space. But the most expensive problem that I knew could have been an issue… I have to convert to 5 stage dry sump oiling. I need to get the engine lower. I can lower it 1-1/2” as is now, but dry sump will lower it around 6” significantly improving clearance for the independent throttle bodies (which made the engine taller, but let’s be honest- totally necessary.) the dry sump system in total about $6,500- $7,000. Ouch. Had the cut out the X-brace above the transaxle to fit the engine, but I have a plan for that as well to have a removable brace there.

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[DopeOfWelding]

A few additional photos

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[cob427sc]

WOW! I love this kind of a project, just a little (heh, Heh) out of my retirement budget capabilities. I wish you good luck! I have built various maybe called odd ball or at least different cars along with numerous restores over the years including 7 FFR cars. Just finishing a V8 engine/Bugeye Sprite transformation. Looking forward to your progress.

[VRaptor SpeedWorks, LLC]

Very nice work! Love to see the progress on such a huge project!

[Shoeless]

Hell yea man, keep up the great work and sharing updates. I love seeing stuff like this!!!

[DopeOfWelding]

Some progress updates. Made a transaxle mount as well as a new removable X-brace. Been spending some time doing CAD work to prototype some much needed parts. The center lock wheels require custom adapters so I had to design and 3D print the prototype. A few revisions later I have them dialed in. I also and about to print a 1/10 scale model of the car so I can start designing the new front, new rear, as well as the wide body that I will do the old school way with auto modeling clay.

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[DopeOfWelding]

Some pre-widebody renderings I am working on. It’s been a useful tool to work out the color palette for the project. I will 3D print it, sculpt the new nose and tail from clay, then 3D scan it. It may be worth having the CNC cut from foam.

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The color is based off of Nissan Millennium Jade

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[fauxbra5.0]

Some pre-widebody renderings I am working on. It’s been a useful tool to work out the color palette for the project. I will 3D print it, sculpt the new nose and tail from clay, then 3D scan it. It may be worth having the CNC cut from foam.

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The color is based off of Nissan Millennium Jade

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Thats absolutely stunning! What program are you using for your renders?

[beeman]

Looking great. I was actually earlier today pondering the pros/cons of fabbing up a removable X-brace...
How much wider are you Front/Rear?

[DopeOfWelding]

Thank you! The GTM was a CGI obj. file I purchased online, converted it to an STL file in Blender, then imported it into a CAD app I use on my iPad called Shapr3D. In there I import my center locks I made, modified a Advan GT file I got online from 5 lug to center lock, made the window sliders, my own badges, as well as other parts I made.

The app has great visualization tools so you can apply finishes, textures, paint to any 3D file and see how it will look. Also has an augmented reality tool so you can place parts you designed on your car using the iPad camera in real time. Crazy technology!!

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[DopeOfWelding]

beerman

In my case with the V12, it’s 100% pros. Removal or installation if the engine would be just about impossible with the factory brace in place. The brace is really only there to stiffen up the upper control arm mounts from flexing inward. The .120 1” DOM is overkill compared to OEM tubes there. Just aired on the side of caution since mine have bends for additional exhaust room and style points. The bends technically made it weaker so .120 should be more than enough

In the rear I am at 1-1/2” wider each side at the top of the tire with 3° of negative camber, but I will dial that back to about -1° to -1.5°, so it may be closer to 1-3/4” or 3-1/2” overall. The front is pretty mild. 3/4” of tire sticking out right now. Seeing how I’m redesigning the front and rear of the car, the wide body will be subtle, but should add a little more aggressive look to the car.

[Shoeless]

Love the updates!!

Random question. With all the modeling work you have done, would you happen to have an stl of just the GTM logo? I've been itching to send something like that out for a quote to get printed out of Ti 6-4 just for the hell of it because who else has their car badging printed out of titanium :cool:

[crash]

Just be aware that as you widen the track it is appropriate to consider also lengthening the wheelbase in order to keep the length to width ratio in the correct window. Not doing so can lead to handling issues "down the road" so to speak.

The race only GTM I am building has been widened 2" on each side and has a corresponding length increase of roughly 6".

Just something to be aware of.

[crash]

Just to maybe save you or others that are looking for the center lock thing some $$...https://www.trigowheels.com/

[DopeOfWelding]

Love the updates!!

Random question. With all the modeling work you have done, would you happen to have an stl of just the GTM logo? I've been itching to send something like that out for a quote to get printed out of Ti 6-4 just for the hell of it because who else has their car badging printed out of titanium :cool:

Yes I do! I can isolate it and send it to you

[DopeOfWelding]

Just be aware that as you widen the track it is appropriate to consider also lengthening the wheelbase in order to keep the length to width ratio in the correct window. Not doing so can lead to handling issues "down the road" so to speak.

The race only GTM I am building has been widened 2" on each side and has a corresponding length increase of roughly 6".

Just something to be aware of.

It is something I have considered. I have done some considerably more wild cars in the past. Given this is more of a show car with race capabilities, I don’t think I will push the car to the point of feeling adverse effects of the extra 3ish total inches in the rear and 1-1/2” total in the front which today is pretty conservative. I also look at it from the standpoint of the 1000s of stock wheelbase cars that are wide bodied for racing (ie JGTC, British GT, World Time Attack and so on) In my experience width changes that small, any changes in feel or handling are negligible. There still remains the chance the rear wheels may have to be moved back to make the CV axles happy if the transaxle is too far back to accommodate the V12. I’ll have a better idea once the dry sump pan is installed and I can get the engine in its final location.

The GTMs oddly enough have a pretty long wheelbase comparatively to other mid-rear engine space framed cars. F-40 wheelbase comes in 5” shorter and about the same width I will be.

[DopeOfWelding]

Just to maybe save you or others that are looking for the center lock thing some $$...https://www.trigowheels.com/

I wish I could run those!! What a steal of a price!

My Advans are specific to the Porsche 991/992 GT3 RS. If you’re familiar with their center locks, they are horrible to put it kindly. A conversion for 991/992 wheels to a 5x120 doesn’t exist without making custom. And all 4 have to be different none the less too. The front wheels and rear wheels have differing bore depths. One side of the car will be reversed thread making all 4 center locks different from one another. I’m anticipating a $4K price tag for the hubs ��

[Shoeless]

Yes I do! I can isolate it and send it to you

Hell yea man, thanks!!! I'll PM you my email address. No rush whatsoever.

[frankenford]

how long did it take you to get your mendeola?

[DopeOfWelding]

It's been a few months, sadly had to take a short hiatus. But during the unwanted break from my GTM120 project, I managed to pick up some new tools to help with the project! Which meant learning how to use said tools. I bought a MASSIVE 3D printer and a good 3D scanner. They have been an incredible addition to the project and have paid for themselves with just the first few prints. I am back to consistently working on the car again. These are the latest updates.

Took 3D scans of the engine and transaxle so that instead of using an adapter plate to mate the M120 to the SDR5, I will instead make a full custom billet bell housing.
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I use the scans to get accurate representation of parts so that I can design around them.
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Then send the designed parts to the huge printer so they can be made in a single piece for maximum strength. Then they can be test fitted to the components. Here is the bell housing prototype printing.
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I scanned the sides of the engine as well so that I can start designing engine mounts. The real question is now... Steel welded engine mounts that I will have laser cut? Or should we go with anodized billet aluminum!?
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[DopeOfWelding]

Bell housing prototype with the Tilton hydraulic TO bearing
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Test fitted to the engine
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Then they became one!
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Gooichi Motors who have been super helpful with everything I am doing with the engine, were cool enough to let me print a mock up of their 5 stage dry sump oil pan. They will be doing another production run soon but in the meantime I will bolt this on and put the engine back in tomorrow and it should now sit much lower where I need it to be. I can finally do the engine mounting!
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[beeman]

The nice thing about welded sheet steel engine mounts is that they can either be designed with cardboard or CAD software, but I like that I can get the engine and gearbox in the car exactly where I want them, then tack the mounts together in the car so they are perfect.

[DopeOfWelding]

The nice thing about welded sheet steel engine mounts is that they can either be designed with cardboard or CAD software, but I like that I can get the engine and gearbox in the car exactly where I want them, then tack the mounts together in the car so they are perfect.

I have done it that way for the better part of 20 years. Tried and true. But now with this technology, it is so crazy accurate. I scan it and model the parts, it has been accurate to the .001" Now I can just draw them and test print, if it looks to be what I want, then off to CNC or laser it goes. But of course, plans can change or parts can still be modified all the same.

The real beauty is, I have very little time to physically work on the car currently. Now I "work" on the car from the comfort of my tablet while I lay in bed at night. Then have a CNC service make the part or have SendCutSend cut the pieces out, they arrive a few days later. So when I get to put in actual wrench time on Fridays or Saturdays, I am no longer losing 2-3 hours cardboard templating and cutting from steel before the first tack weld goes down. I walk in, fire up the welder and get right to it!

That is... Until I can afford and have the space for my own CNC mill. Don't be surprised if by halfway through this project that a CNC is added haha

[Shoeless]

What printer did you end up going with? And yes, that is rather large.

[crash]

If it were me, I would combine the techniques. Do a sheet metal prototype, then use that to scan and machine a nice aluminum part with the holes accurate to the install because you perfectly fit them via welding in place with the sheet metal prototype. Best of both worlds. And yes, anodize the aluminum. It seems most people here building GTMs do not do anodizing of parts, but it has always been my preference. Looks great, lasts forever, relatively cheap-especially if you do bulk parts.

[DopeOfWelding]

What printer did you end up going with? And yes, that is rather large.

I bought a Elegoo Orangestorm Giga, then modified it. It is now enclosed with recirculating HEPA filtration and hardened nozzle so I can print ASA-CF. I also put a 1 piece PEI sheet on it and a few filament driers. This is my first FDM printer, I guess I don't know the meaning of "dip your toe in." Lol

[J R Jones]

On V12 fitment: Two weeks ago I reviewed a RCR Ferrari P4 at the Road America vintage event. That chassis was designed for a SBC and my buddy's LS7 fits OK.
The Ferrari V12 intrudes into the cockpit and the axles angle aft from the rear uprights to the transaxle. Ten pounds of Ferrari in a five pound RCR bag.
jim

[DopeOfWelding]

On V12 fitment: Two weeks ago I reviewed a RCR Ferrari P4 at the Road America vintage event. That chassis was designed for a SBC and my buddy's LS7 fits OK.
The Ferrari V12 intrudes into the cockpit and the axles angle aft from the rear uprights to the transaxle. Ten pounds of Ferrari in a five pound RCR bag.
jim

I bet that Ferrari V12 RCR is incredible! if you have links, I would love to see it!

Just yesterday I managed to pull the factory oil pan and chain driven oil pump and install a mock up dry sump pan. I dropped the V12 back in and found its final position. The harmonic balancer is sitting just about where the intended LS one would be. The engine does creep into the cockpit a little but not a ton. Just the front of the valve covers. That's only because it is DOHC. So some tweaks will be made to accommodate that. With the seats in place, I still fit somewhat comfortably. I do need to make some chassis mods under the engine and transaxle, but I have the plan figured out for those already.

Dry Sump mock up pan installed. Much more compact
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The engine is now MUCH lower than previously. Before it was sitting so high, the velocity stacks were hitting the rear hoop of the roll bar. I couldn't even slide the intake forward to bolt it on. It was in the roof. But now we are sitting nice. The rear two stacks will still be contacting the rear window, but that is okay since the rear window will likely have a air scoop.
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Some under side photos.
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[beeman]

Love the velocity stack intake. Do you have photos of the engine position with the gearbox attached?

[crash]

That is an extremely shallow pan. With the pickups on the drivers side and the crank rotating in the clockwise direction from the front of the engine perspective this may add to issues with windage and oil frothing. If I were you I think I would look at, at least, putting the scavenge pickups on the passenger side of the pan. Or make the pan deeper and use a windage tray between the pan and crank. Best case is you are giving up performance with this shallow pan, and worst case it could lead to premature engine failure. You may want to talk to the people at Dailey Dry Sump about design and maybe building you a custom pump and pan combo. Their stuff is very compact and relatively reasonably priced.

[VRaptor SpeedWorks, LLC]

Looks like the entire oil pan is above the chassis tube? So you have 1.5" to work with to make that part of the pan deeper where the chassis isn't in the way?

[DopeOfWelding]

Love the velocity stack intake. Do you have photos of the engine position with the gearbox attached?

Not as of yet, I will on Friday. The “X” brace that sits behind / below the engine needs to be cut out and removed. I already added the brace that will replace it and be apart of the new engine cradle, so it is safe to chop out. The new bellhousing will interfere with it. Once I chop that out, I will put the transaxle back up in place!

[DopeOfWelding]

That is an extremely shallow pan. With the pickups on the drivers side and the crank rotating in the clockwise direction from the front of the engine perspective this may add to issues with windage and oil frothing. If I were you I think I would look at, at least, putting the scavenge pickups on the passenger side of the pan. Or make the pan deeper and use a windage tray between the pan and crank. Best case is you are giving up performance with this shallow pan, and worst case it could lead to premature engine failure. You may want to talk to the people at Dailey Dry Sump about design and maybe building you a custom pump and pan combo. Their stuff is very compact and relatively reasonably priced.

The guys that designed the dry sump pan deal in exclusively big horsepower M120 V12s. 1000hp NA ITBs, 1400+hp pro charged, as well as they have their hands in some Pagani Zonda race engines. I have full trust in the stuff they have put together, especially since I will not be pushing this thing nearly as hard as they do! I'll be happy with my little 450-500hp! I regularly talk to the owner of the company, I can express the concerns as he is not by any means a close-minded guy.

I also think the depth of the pan is very deceiving since the skirt of the block comes down very low. The main caps are 4 bolt plus 2 through the exterior of the block tying them in like a girdle.

The factory windage tray is a pretty compact, well designed part that sits tight in there. almost tight enough to call it a crank scraper! This was before I pulled the pump out.
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[DopeOfWelding]

Looks like the entire oil pan is above the chassis tube? So you have 1.5" to work with to make that part of the pan deeper where the chassis isn't in the way?

It's roughly 1/2" above the chassis tubing now. The pan I printed is the file supplied to me from the company that makes the actual part, they were cool enough to send me the file to let me print the mock up pan. I don't have any plans on changing it or designing my own. They exclusively do M120s , R&D and tested it. So I'm running it as is. It also looks deceiving because the crank centerline is probably a good 3" up in the block, making the pan appear much more shallow than it really is.

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[Straversi]

Impressive. Love how technology is advancing hot rodding.
-Steve