GT40 Engine to Transaxle Help

Rod Dittmar

Supporter
My Kit is ordered: RCR GT40 MK1 Frt & Rr, Both Nostrils, 2" Flares, Quad Tail Lights. My Tires are ordered: Avon CR6ZZ Frt 215/60R15, Rr 295/50R15. My Engine is ordered: Craft Performance SBF 347/363 Dart Block, 500hp & 450ft/lb torque. And, RCR/Fran has found an NOS ZF Transaxle for me which is currently being checked out. I've tinkered with a lot of cars & motorcycles in my life, but I'm in unchartered waters when it comes to mid-engines & transaxles. I know RCR supplies the adapter, but what else will it take to ensure all this mates together properly? For example: Do I need a unique flywheel with proper balance & number of teeth? Starter Motor? Should I be concerned about the pilot bearing? Any clutch recommendations? Lots of questions here, but just trying to keep my head above water at this point before things start to arrive at my door and I dive into the actual build.
TIA, Rod
 

Ian Anderson

Lifetime Supporter
Supporter

Would be a start.

Welcome to the world of 40 inches

Ian
 
There are a number of options, SAFIR providing one of the most period correct packages. It is, however, one of the more expensive options. I honestly don't recall where exactly from I collected all of my parts, but it wouldn't be a bad idea to call Dennis Olthoff for other options.
 

Morten

Mortified GT Asylum
Supporter
Hi, my Southern GT bellhousing bolts directly to my SBF 351C (same as a 302 on the back), no adaptorplate.
It comes with an AP Racing clutch and small size flywheel, as well as release bearing and holder for the arm for my RBT ZF 5DS25-2
I hope this helps in your quest.
regs morten
 
Just so you know, I sourced my original flywheel (fidanza), clutch (BMW M1), and I'm pretty sure bellhousing and TO from Summit. It takes a little research, but parts are available, and they don't have to be particularly esoteric. I think Summit had to create a part number for me, but they were able to get the correct disc/PP (RBT to SBF)
 

Howard Jones

Supporter
I'm pretty sure a ZF should bolt directly to a SBF and be able to use most high performance clutches that will normally suit a SBF flywheel. I would be sure that my engine supplier had balanced my motor with the flywheel I am going to use so maybe you should source it from him.

Who would know? the Pantera guys and their related vendors. Google Pantera high performance parts suppliers. Be sure to mention if you are flipping the gearbox in the GT40 configuration.

Good luck
 

Ron McCall

Supporter
Kennedy Engineered Products offers a bellhousing that will fit your application. Pantera Performance Center offers an excellent clutch/flywheel setup as well as a very well made external clutch slave arrangement for the GT40 application..
 
Just so you know, I sourced my original flywheel (fidanza), clutch (BMW M1), and I'm pretty sure bellhousing and TO from Summit. It takes a little research, but parts are available, and they don't have to be particularly esoteric. I think Summit had to create a part number for me, but they were able to get the correct disc/PP (RBT to SBF)
Be aware that if you source a BMW M1 ZF the input shaft is longer than the normal Ford application and will bottom on the crank recess thus wiping out the crank thrust bearings in short order. Ask me how I know...........
 

Rod Dittmar

Supporter
OK, thanks guys. Lots of valuable info here, and all of this is what concerns me. I don't want to make a big $$$ mistake. I think I'll wait to hear from Fran and his transaxle guy to see what I'm actually getting. Then I can decide. But... is it safe to say that my engine builder should use a zero degree balanced flywheel? What else can go wrong here? What about # of teeth on the flywheel and/or a compatible starter motor? Maybe I'm worrying too much about nothing?
 

Howard Jones

Supporter
Rod, you are NOT overthinking this or being paranoid! You are correct on your concern and you are on the right track and asking the right questions! When I built my SLC I had similar concerns. How to get everything to work together ON THE FIRST GO? I didn't want to spend a lot of time and money figuring everything out. I was sure this was all known information...…...I just didn't know it! So I picked a transaxle rebuilder that would agree to supply everything from the pilot bearing to the output flanges, including the starter and everything in between and a custom geared and built transaxle (Porsche G50). I wanted the vendor to be responsible for it all and I was clear that I would insist on that.

IMHO have the gearbox rebuilder source the core box for you. Don't drop off a unknown quality worn box only to find out that it requires a ton of work just to repair unknown damage. Just tell him you want a gearbox with your choice of gear in it rebuilt and like new. Research limited slip types and include one in your box from the get go. I really like torque biasing types like Quaife myself.

Things like projected engine power and torque must be known by the gearbox builder! How else can he build you a suitable gearbox? Now is the time to discuss gear ratios! Other things will also require this information...……...clutch and even the starter motor. How much compression and valve spring pressure as well as engine size will the starter need to crank over? Important stuff if you want to do this only one time. Everything must be selected to work together and this should be done at the outset.

So California Motorsports was selected after I went and met with them in person and the plan worked perfectly. The whole thing went together without a hitch on the first try.

So, see if you can duplicate this approach. Talk to the suppliers (mainly transaxle) and ask them to source all this stuff and stand behind the parts selections. You may pay a bit for the service but at least you will not end up with expensive pieces that don't work or fit. It will be a big check! But only one and once......

No matter what anybody says. The flywheel should be included along with the crank damper and clutch pressure plate when the rotating assembly is balanced. ALL serious crank (engine) balancing shops do it this way. They do it so that tolerance stacking error doesn't ruin what would otherwise have been a accurate balance job.
 
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Bill Kearley

Supporter
One would have to expect that Craft Performance would have balanced your engine thus the correct flywheel ect. If I ever redo mine I'll be using the McLeod twin disc.
 

Neil

Supporter
Howard
Rod, you are NOT overthinking this or being paranoid! You are correct on your concern and you are on the right track and asking the right questions! When I built my SLC I had similar concerns. How to get everything to work together ON THE FIRST GO? I didn't want to spend a lot of time and money figuring everything out. I was sure this was all known information...…...I just didn't know it! So I picked a transaxle rebuilder that would agree to supply everything from the pilot bearing to the output flanges, including the starter and everything in between and a custom geared and built transaxle (Porsche G50). I wanted the vendor to be responsible for it all and I was clear that I would insist on that.

IMHO have the gearbox rebuilder source the core box for you. Don't drop off a unknown quality worn box only to find out that it requires a ton of work just to repair unknown damage. Just tell him you want a gearbox with your choice of gear in it rebuilt and like new. Research limited slip types and include one in your box from the get go. I really like torque biasing types like Quaife myself.

Things like projected engine power and torque must be known by the gearbox builder! How else can he build you a suitable gearbox? Now is the time to discuss gear ratios! Other things will also require this information...……...clutch and even the starter motor. How much compression and valve spring pressure as well as engine size will the starter need to crank over? Important stuff if you want to do this only one time. Everything must be selected to work together and this should be done at the outset.

So California Motorsports was selected after I went and met with them in person and the plan worked perfectly. The whole thing went together without a hitch on the first try.

So, see if you can duplicate this approach. Talk to the suppliers (mainly transaxle) and ask them to source all this stuff and stand behind the parts selections. You may pay a bit for the service but at least you will not end up with expensive pieces that don't work or fit. It will be a big check! But only one and once......

No matter what anybody says. The flywheel should be included along with the crank damper and clutch pressure plate when the rotating assembly is balanced. ALL serious crank (engine) balancing shops do it this way. They do it so that tolerance stacking error doesn't ruin what would otherwise have been a accurate balance job.
Howard, I agree that California Motorsports is a good source for transaxles and for transaxle work. I visited them in Lake Havasu City, Arizona some time ago and talked to them about doing some work on my G50. Many other shops subcontract their transaxle work to California Motorsports.
 

Howard Jones

Supporter
There is some difference of opinion when it comes to adding the clutch pressure plate to the balance stack. Some engine builders say to not do this because a replacement clutch would not necessarily balance out the same. Others say the pressure plate isn't replaced all that often, it's usually just the friction disk so they add it to the mix. I think if you know that you have selected the forever clutch type and know you will not change to a different vendor later then why not balance it with the engine parts. After all the clutch will be on the motor for years. Why not be sure its balanced.

The engine guy I know well in California balances the clutch separately and to 0 error. Then a new replacement clutch can be similarly balanced and installed without taking the motor apart. I think maybe this can be a personal choice but not the rest of the rotating assembly. That's a must do. Even a new crate motor isn't really balanced. They do it by part selection weight not a full on dynamic balance.

Neil that's who did mine. Completely satisfied and I highly recommend them. At least for Porsche gearboxes. I am sure there are ZF shops out there of the same caliber.
 
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