What is the bolt pattern used on the ross and tracey gear box. I dont have actual drawings and I am coming up with 12 bolts on 5.875 inches diameter. That seems a bit small and it doesn't seem to work out very well. I am working on a cast housing and l would like to make it the same

Paul Shamlian

That is about right for the Tracy box but the Ross is different. Most Ross's came with a cast
bell housing.

The bolt pattern for the Mazda bell is this.

We built a few sand cast bells and they were much heavier than the milled
1/2 inch thick adapter plate with spacers mostly used with the Tracy box.

The best thing to do, if your building your own gear box,  is use the Mazda
high pressure die cast bell house. Now you have to have a bracket to mount
the engine. We called that a Schertz beam. After Bill Schertz the inventor.

Bill used a Tracy box and adapter plate. That was before we incorporated
the motor mounts into the adapter plate to save more weight.

Paul Lamar


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