A Tale of a Race Winning Rx7 Chassis

During the past Pandemic Christmas holiday, I decided to retrofit a decades old slot car race track for the digital age. My young son had been absolutely captivated with it nearly two decades ago and one day there might be grand kids to continue the tradition. I had to convert each analog car to digital by soldering in a Bluetooth enabled circuit board so that each car could be controlled wirelessly and up to 6 cars could race at once on a pair of slotted tracks. Now with lane changing and pit stops and computer controlled pace cars to provide traffic.

I have the Le Mans winning Mazda 787B in slot car form. But not a first generation racing Rx7. They never made one in 1:32 scale. I would have to make my own and I got a head start buying a vintage radio controlled toy Rx7 that happened to be in 1:32 scale. But what race version of the Rx7 should I make it? In the 1980s the Rx7 was a highly successful race car and there are many versions to choose from.

With the announcement of the exciting new Rx7-SA model, the Mazda factory sent two race prepped Rx7s to the 1979 Daytona 24 Hours Race.   Car #7 would be driven by the Japanese team of Katayama, Terado, and Yorino and Car #77 by the American team of Walter Bohren, Jim Downing and Roger Mandeville.  Car # 7 finished 5^th overall and took the GTU class¹, while #77 came in 6^th overall.  Shocked at the Rx7’s performance, the IMSA officials immediately reclassified the peripheral port engine with a 458 lb weight penalty by changing the car weight allowance from 0.9 lb/cc displacement to 1.1 lb/cc.² The factory cars were sold to Mandeville and Downing. #79 Rx7 was built by Dave Kent of Creative Car Craft in Hawthorne, California for the Sports Limited Racing Team and driven primarily by Bob Bergstom.  The team had Mazda Motors of America financial support but retired after only 9 laps at Daytona due to driveshaft breakage for lack of a central support bearing.  As the 1979 season wore on, the weight penalty ruling was reversed but not before Don Davendorf’s Datsun 280ZX clinched the GTU Driver’s and Manufacturer’s Championship.  Although Bergstrom DNF at Daytona, he did score a 3^rd at Road Atlanta 75 Miles GTU, 4^th at Laguna Seca GTU,  2^nd at Sears Point GTU, 5^th at Portland GTU, 9^th at Road America (1^st in GTU), and 4^th at Winston GT Road Atlanta to secure the second place in the GTU championship as did Mazda as a manufacturer. 

Bergstrom did not fare as well in 1980 but Rx7s from many other teams did win all but three races in its GTU class and Mazda easily took the GTU Manufacturer’s Championship.  #79 was sold to the new Dave Kent Race Team for 1981 season to become #92 and repainted white while retaining her original name that Dave had given her in 1979, Lulu.   A sister car #98 was painted red and named Linda after Dave’s wife and driven primarily by Walter Bohren while #92 was driven by Lee Mueller³.  Kent Racing dominated 1981 and won 11 of 16 races.  #92 won at Laguna Seca, Bainerd, Portland, Mosport and Road America & came a close second to Bohren’s #98 at Road Atlanta GTU, Lime Rock, Mid Ohio, Road Atlanta, and Pocono.  This gave Mueller the GTU Driver’s Championship and Mazda once again the Manufacturer’s GTU Championship.

This is a short 8mm film transfer of the 1981 Pocono IMSA race showing #18 winner Porsche 935 of infamous⁴ father/son team John Paul Sr/John Paul Jr passing #92.   #98 won the GTU class with #92 just behind it.

1982 started well at Daytona-24 Hours with #98 placing 6^th overall but winning GTU, #92 placed 7^th overall.   #98 was driven by Kathy Rude, Lee Mueller and Alan Moffat.  Both Kathy and Alan were Canadians, with Kathy born and raised in Victoria, British Columbia. She became the first female driver to win an IMSA race and the first woman to win a major professional road race in the US.  Then Dave Kent received a far too enticing offer from Toyota to run their GTU team with a pair of Celicas.  Unfortunately the move away from Rx7s did not go well and Toyota terminated the relationship at the end of September.   #92 made one final appearance in the Daytona Finale at the end of the season and DNF.

For the 1983 season, Kent Racing no longer had Mazda factory backing so they found a new sponsor with Firestone Tires and ran their cheap S-rated $36 eight inch street tires for racing along with new red livery!! #92 redeemed herself at 1983 Daytona -24 Hrs with a 12^th overall place (1^st in GTU). Mueller recalls holding his breath during each lap of the circuit’s signature high speed banking for fear that the street tires would implode under the stresses. They benefited from a deluge of rain during the 18th hour when a tire change was scheduled and they were able to run fresh tread in wet conditions giving them an unexpected adhesion advantage. Better yet, they beat the Kent built Celicas that Toyota had turned over to the Dan Gurney’s All American Racers team. The last time #92 was seen with Kent Racing was at Riverside in April with a 28^th place finish.  

It is believed that the Lulu chassis made a final appearance under the Kent Racing banner in the 1984 Daytona 24 Hours and Sebring 12 Hours once again running on Firestone street tires but racing as #82 since #92 had been reallocated to another team.  #82 is traditionally the Trinity Racing Team number with Western Airlines as a major sponsor in 1983 but their car is white so it is unlikely the team would go to the expense of repainting it for just two races.  Likely, Lulu was temporarily given a new number with some new graphics to acknowledge Western Airlines on the hood and Trinity Racing on the rear spoiler.   The car finished 4th in GTU and 20th overall at Daytona and 10th in GTU at Sebring and was again the star of more Firestone advertising.  Lulu was apparently sold to Dick Greer Racing and she reappeared later as #92 later in 1984 and amazingly soldiered on until early 1989 (and had her number changed to #82 in 1985) but without victories.

#92 was reacquired in 2017 by IMSA driver Kelly Marsh who drove #98 rebadged as #93 and repainted teal for the Mid O Race Team.  #92 was thoroughly restored and painted in her 1983 Firestone Red livery and was awarded the most historically significant IMSA car at the 2020 Amelia Island Concours.    The first generation Rx7 won 8 straight GTU driver’s and manufacturer’s championships from 1980-1988 and won over 100 class race victories and is regarded as the most winning car model in professional racing history. 

1. _{GTU – Grand Touring cars under 2.5 L. 13B engined cars contested in the GTO category. GTX was the top class.}
2. _{For the 12A engine, each rotor has a combustion chamber displacement of 573 cc. To convert rotary displacement to a conventional 4 stroke piston engine we see that a complete combustion cycle takes 720^o of crankshaft rotation in a 4 stroke. In the rotary, 720^o exposes only 4 of the 6 rotor surfaces to combustion so 573 cc x 4 = 2.292L engine. At a 0.2 lb/cc weight penalty = 2292×0.2 = 458 lbs The politics of racing being what they have and will always be, at the same time allowed the Datsun 280ZXs to run short stroke engine setups so they would qualify for the under 2.5L class !!!!!}
3. _{There is some confusion as to whether the Bergstrom #79 chassis ended up being #92 or #98. Despite the conflicting sources, I’d like to think that #79 became #92 became #82 and then was saved, restored and honored in 2020.}
4. _{John Paul Sr had a near psychopathic level of rage and was charged with marijuana smuggling and then later with attempted murder as he shot a federal witness in the case. He fled the US and was recaptured, served 11 years of a 20 year sentence and then disappeared after a woman he was dating was found dead. Without a real sponsor for his expensive Porsche 935 Turbo, he had to finance his race career with alternative methods.}

If you want to see how the finished car turned out, you can check out my Instructables entry here:

https://www.instructables.com/Making-a-132-Scale-Mazda-Rx7-Slot-Car/

AND for a final unexpected chapter on this story see:

Unexpected vintage racing Rx7 metal models.

And to see some truly exotic Mazda cars photographed like never before:

Advanced Forced Perspective Motorsports Projects