Building a Dirt Track Modified

Building a Dirt Track Modified
By
noderel: 

Building a Dirt Track Modified
 By Dave Brackett, with Larry McCulloch 

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Dave

In 1978, I had a neighbor Harry Hardy, and a good friend Glenn McCulloch. We lived in the Sierra foothills near Sacramento. Glenn and I had been involved in drag racing for years, I was a chassis man and Glenn a great motor man. We wanted to get back to racing, and neighbor Harry was interested as well. We decided to build a Modified to race at the local dirt circle track in Grass Valley, Ca. I would build the the chassis, Glenn would do the motor, and Harry would help and supply most of the money. 
 

The good racers of the day had powerful small block Chevys, and raced in the typical dirt track fashion, up high with lots of momentum, and hoped they stuck. Frankly, we could not afford to go that route, so we talked a lot and came up with a different idea. We would build a lightweight car, use a light motor and place it beside the driver on the inside. With this offset center of gravity, we thought we could run the bottom of the track and be competitive. 

I ordered some rectangular tubing to build the base of the chassis, while Glenn decided on a small aluminum Olds V8 engine. He brought me a block, and we talked about a rear end. Glenn and I both favored light vehicles, so we decided to use a VW transaxle. We got one and I started mocking up the car. I set the motor between the front and back left side wheels, the driver would sit to the right of the motor. I would build a coupling arrangement to attach the motor to the transaxle with chain.

Harry brought wheels, tires, seat and steering box. After fashioning the base of the frame from 2 X 3 inch tubing (see photo), I built the roll cage, from 1 1/2 " tubing . I then built a tubular front axle with spring over shock suspension, attaching it with tubular wishbones and a panhard bar. The rear end was mounted with VW transaxle minus the motor, using the VW torsion rear suspension. The trans was flipped over with the input shaft facing forward.

Now on it's own wheels, I mounted the motor (see photo) and built an adapter to bolt to the rear of the crankshaft with a sprocket for double #50 chain. Next was the coupling end on the transaxle.

2

Built an adapter to bolt to the rear of the crankshaft with a sprocket for double #50 chain.

 

 

2a

After fashioning the base of the frame from 2 X 3 inch tubing, I built the roll cage, from 1 1/2 " tubing.

3a

Now on it's own wheels, I mounted the motor.

In modified racing, it is important to change gears at the races. I had to design some way to do that on the transaxle side of the connection. I took an old broken quick change rear end, cut off the back part that held the ratio gears. I modified it to fit on a plate mounted across the VW transaxle bellhousing. I welded a VW clutch hub to one side of the quickchange to fit over the input shaft of the transaxle, and a double row #50 chain sprocket to the other (see photo).  A window was cut in the bellhousing to allow the chain to pass through. This car was very light, so this setup worked great, with the addition of a drip oiler to keep the chain lubricated during races. I then mounted the steering box with cross drag link to the left front spindle. 

It was time for a body. Aluminum panels were formed around the drivers compartment, seat mounted with belts, fuel tank placed, battery and electronics installed, and ready for the motor. I also built headers for the Olds motor.

Glenn had built a 215 cubic inch Olds all aluminum V8, to 265 cubic inches. He added a hotter cam and better valve train, did some porting and polishing, and installed a Holley four barrel carb. The car was run on alcohol and had no clutch or starter to save weight, so it was push started.

It was time for nerf bars, always a problem for Modifieds, since they were constantly bumping each other. I decided to build rather stout bumpers from rectangular tubing, and mount them with telescoping springs. When the car was hit front or rear, the bumpers moved and absorbed the impact. The car survived relatively well, except for often replacing front wishbones and panhard bar. 

The car was raced the first year at Grass Valley Fairgrounds circle dirt track, with some success. I don't think it ever won, but always finished well. With the light, well balanced car, it was able to drive under the the other cars, and that bothered our competitors. When the racing organization meeting was held for the next year, the rules were changed and motors had to be in line with the drivers. 

Sadly the car was retired and disassembled and I have no photo of the finished car. I last saw the bare frame hanging from the ceiling in a friends shop. I have always wondered how well the car would have run, if they let it continue racing. Maybe we scared the competition, "I hope so!"