restoring a factory 90's imsa gtu racecar
 

I thought I would share my 4 year journey of restoring a 1990 imsa gtu mx-6 tube frame racecar.

First some history of this chassis . It was original one of 4 chassis commissioned by Mazda affiliated race teams to contest the 1990 imsa gtu championship. John finger had one of the well known cars that is now owned by Mazda and has made appearances at sevenstock and other special events. These cars were built by renowned engineer /race builder Bob Cuneo of Chassis Dynamics, a leading builder of IMSA racecars. What made these cars special is there was little regard to cost when creating them. Some things that stand out are : the uprights were specially cast out of magnesium, the hubs were custom machined from high grade aluminum and utilized single lug nuts, the transmission was a rear mounted transaxle supplied by Hewland , suspension geometry utilized long control arms for minimal deflection, brakes were huge 4 piston Alcons, the fuel cell was located in front of the rear wheels, a carbon fiber driveshaft was used, slide valve injection, aircraft grade fasteners everywhere, 13b pp motors with factory race parts, etc , etc. It was campaigned by Mazda specialist Al Bacon and after about 5 years bought by a racing dentist.
The car was then sold to and was converted by Mandeville Auto Tech to an imsa fd rx7 body in 1996 to run the 1997 Professional Sports Car Series in the gts-3 class . It was run by RAE motorsports and competed in the Sebring 12 hour and Daytona 24 hour races. One of the drivers was lead singer of the rock band AC DC. I purchased the car in 2012 after the new owner crashed the car at the 2011 Mitty historical race. We hope to have the car ready for the 2017 race season here on the west coast .

https://cimg8.ibsrv.net/gimg/www.rx7...612684022b.jpg

This is how the car looked in 1997 . Note the 18 inch bbs 3 piece wheels

https://cimg4.ibsrv.net/gimg/www.rx7...fdb92580e1.jpg

This how the car looked in 2011 just before it was crashed.

https://tse1.mm.bing.net/th?&id=OIP....9&rs=0&p=0&r=0

This is the way it would have looked in 1990 as an mx6.

I had been looking for a tubeframe car for years and found out a lot of the ex imsa cars ended up in South and Central America. A few looked pretty beat up on running on some pretty rough tracks. And the good ones were not for sale.

One night I came across a youtube video of a racecar idling in the pits. I could make out the team name on the transporter and contacted the team owner to see if it was for sale. It turned out it had just crashed and was in fact for sale. So I flew down to New Hampshire and looked at the car. It was dismantled and there was a lot of work to do. I left without buying the car and as soon as I got home I felt I should have bought it. So I arranged some friends to fly down, rent a Penske truck and take the long drive back to Seattle .

Here is the video .

completely awesome. So are you going back to the Mx-6 body or the FD body?

https://cimg8.ibsrv.net/gimg/www.rx7...6c26af724.jpeg
https://cimg9.ibsrv.net/gimg/www.rx7...63a566e57.jpegFront clip needed full replacement
We only have the rx7 body and will stay with that.

This is what showed up on day 1.

https://cimg0.ibsrv.net/gimg/www.rx7...ed3d6e0c6.jpeg
https://cimg1.ibsrv.net/gimg/www.rx7...36c57006d.jpegMotec with slide valve injection

https://cimg9.ibsrv.net/gimg/www.rx7...0c2355eb7.jpegFront crash boxes and bell housing
https://cimg1.ibsrv.net/gimg/www.rx7...20b037e43.jpegFuel pumps

https://cimg5.ibsrv.net/gimg/www.rx7...194f6eac1.jpeg
https://cimg6.ibsrv.net/gimg/www.rx7...70630317f.jpegHewland dgb . These were used in f1 in the 70s and can am /gtp cars .
https://cimg7.ibsrv.net/gimg/www.rx7...23ed76c39.jpeg

https://cimg3.ibsrv.net/gimg/www.rx7...5963d5667.jpegThe first step was to put the puzzle back together and assess the damage
https://cimg4.ibsrv.net/gimg/www.rx7...da228f6dd.jpegThe floor was beaten up pretty bad .
https://cimg5.ibsrv.net/gimg/www.rx7...b3f319f9b.jpeg

https://cimg9.ibsrv.net/gimg/www.rx7...43809906b.jpeg
https://cimg0.ibsrv.net/gimg/www.rx7...2c3d162ee.jpegThe machine work on the hubs was top notch.
https://cimg1.ibsrv.net/gimg/www.rx7...0af38992f.jpeg

This is a really cool thread. Thanks for posting the history and photos, I look forward to seeing the rest.

Our vision for this car was to rebuild it to a standard similar to when it raced in 1997 but update some things to make it ultra competitive. We will add electronic power steering, abs, and more aero downforce. In the future we may add more power through a turbo or a 4 rotor. Or maybe 3 rotor turbo. https://cimg4.ibsrv.net/gimg/www.rx7...793391ce6.jpegWe also made the rims wider using wider inner barrels .
https://cimg8.ibsrv.net/gimg/www.rx7...0c8782d40.jpeg
https://cimg0.ibsrv.net/gimg/www.rx7...8e0e8da5e.jpegFactory bbs gold . Width are now 18x 12 and 18x13.5.
One of the first things we did was refurbish the beautiful 3 piece bbs racing wheels.

With the crashbox on we measured out the underbody splitter. We used carbon fiber and Kevlar for strength as it holds up the nose. We also made some simple moulds for the carbon brake ducts and canards.
https://cimg4.ibsrv.net/gimg/www.rx7...efb59959d8.png

https://cimg7.ibsrv.net/gimg/www.rx7...d05a85636.jpegThe crash box is made of aluminum and attached with pull out pip pins. Top duct is for engine
https://cimg3.ibsrv.net/gimg/www.rx7...97c55e12e.jpeg
https://cimg0.ibsrv.net/gimg/www.rx7...b5a8a4a71.jpeg
https://cimg4.ibsrv.net/gimg/www.rx7...770795131.jpeg

While I had the carbon fibre out I thought I'd build a duct for the rear transmission cooler and a diffuser. The vents were bought from hrp world. They have an amazing amount of specialty road race supplies. https://cimg1.ibsrv.net/gimg/www.rx7...fc9da261d.jpeghttps://cimg4.ibsrv.net/gimg/www.rx7...c22245e61.jpeg
https://cimg6.ibsrv.net/gimg/www.rx7...851c7b5a8.jpegJab rock wood on the bottom to protect the carbon fibre

https://cimg4.ibsrv.net/gimg/www.rx7...484cc0289.jpegI believe we built this at a 13 degree angle which was supposed to be most efficient for a diffuser of this length. The whole car is flat bottomed and with the fuel tank in front of the rear wheels this should add a lot of down force
https://cimg1.ibsrv.net/gimg/www.rx7...014577144.jpeg
https://cimg1.ibsrv.net/gimg/www.rx7...63db572e7.jpeg

https://cimg1.ibsrv.net/gimg/www.rx7...56c03e569.jpeg
https://cimg9.ibsrv.net/gimg/www.rx7...f666fac8e.jpegCut away all gone bent chassis bars to fit hood
https://cimg3.ibsrv.net/gimg/www.rx7...e8197ca4c.jpegWe left enough room for a monster nascar radiator if we ever need more cooling for a 4 rotor .

https://cimg7.ibsrv.net/gimg/www.rx7...68c4ca8658.png

13 x 1.25 rotors with massive 4 piston calipers on a car weighing around 2000 pounds or less should work well.

https://cimg6.ibsrv.net/gimg/www.rx7...4762198344.png

Cannon sized exhaust ! We filled it with scrubble, a bunch of stainless steel filings. It should cut down the noise but it is quite heavy .We decided to build a second exhaust in thin wall 321ss with a rebuildable coast fab racing muffler

https://cimg1.ibsrv.net/gimg/www.rx7...63dcc0ae20.png

exhaust is 4 inch diameter.

Amazing work !!

Luckily a fellow racer in my area had moulds made from the Mazda imsa panels. We made the door out of carbon fibre . https://cimg5.ibsrv.net/gimg/www.rx7...ef69dbbf2.jpeg