Mini rod slant 6 pulling tractor

Looking for photos and/or info on a slant 6 Mopar powered mini-rod pulling tractor built and owned by Jim Pospisil of Dynamic Balancing in Cedar Rapids, Iowa. I saw it compete at the Great Jones county fair in Monticello, Iowa in the late '70s. It had 3 foot chrome zoomies and I believe Hilborn injection, and was supposedly balanced to 12k rpm. It sounded like an Indy car revving. Any help would be greatly appreciated. Thanks

 

If you have ever lifted a slant 6 crank and pictured it spinning that fast, I'd suggest doing a piston speed ****ysis. Lots of calculators online. The 225 stroke is 3.91 inches.

More reading here
https://www.jalopyjournal.com/forum/threads/how-to-determine-safe-piston-speed.764534/

 

Not really helpful to my inquiry, as I posted it was "supposedly " balanced to 12k rpm. I heard it run once, and never heard anything rev like it did this side of an Indy racecar. Other than it being a slant 6 built by a very successful balancing shop, I have no information on the engine specs. It could have had any size bore/stroke or home made custom internals. Thanks

 

I'd love to see what they did. 12,000 rpm on four mains and with the airflow limitations of that head..... It would be amazing.

 

The information I received was secondhand, maybe it was only 10,000 RPMs but apparently you've never heard of the 225 hyper pack (look it up) which was raced on NASCAR tracks at 7,500 RPMs and finished in 1st 2nd 3rd 4th 5th 6th and 7th place on its debut race. And the application I'm referring to only had to run for less than a minute.

 

Actually the NASCAR Hyper pack was 170 cubic inches, I remember reading about them in 1960

 

According to my research the hyper pack was a parts package applicable to either 170 or 225 c.i. engines

 

Like all things NASCAR at that time frame, if an auto factory didn't produce a certain number of the vehicles on the street, they couldn't use it in a NASCAR race.

There were street Valants and Darts produced by Mopar with aluminum slant 6 motors with a hyper pack head, intake, exhaust, and cam package specifically to qualify for the NASCAR cl***. The aluminum block production was very limited and was gone after the NASCAR cl*** was terminated. It was originally designed for the smaller 170 CI block (I believe there was a CI limit in the NASCAR cl***), then offered later as an option on the 225 CI block for a couple of years.
The limited run of the hyper pack head did not have the flow restrictions of the production heads, a few of those heads are still out there.