ORIGINAL: earlwb
You need to either find a prop driver/thrust washer and collet to fit the crankshaft, or make one up on a lathe.
Then you may need to make a special prop nut and washer to fit the threaded part on the crankshaft. it depends on how thick the propeller is. Usually you make a spinner nut with a long shank on it to fit the threads and then you ream out the prop to fit the shank on the spinner nut.
The prop driver washer may allow enough clearance to work with the car carb, but you may have to flip the carb around and angle it. Otherwise you have to use a different carb.
You can see how it was done on this Toki or Fuji .05 engine. They made a more thick thrust washer to clear the carb and then the spinner nut was made longer with a threaded shank on it to extend the prop out farther. You need to ream out the prop more for this method.
http://i248.photobucket.com/albums/g..._engine_01.jpg
Man I wish I had a lathe even more now than ever....
ORIGINAL: ThumbSkull
APC and other manufacturers limit their props for safety reasons to 190,000/diameter. They can explode at RPM's over that.
That means an 8'' prop is limited in capability to under 24,000.
The extra airflow from the prop over the large car heatsink means the engine will never reach operating temperature so your break-in won't be proper.
I have cylinder heads I can modify (cut most of the fins off) to use as a break-in head OR if I get an oddball, I'd just cover part of the head with foil or ziptie a piece of tube sock to the head. This is what we normally do to break-in a car engine in the car in colder weather.
I would think a custom prop would be the ticket to handling the higher rpm of a car engine.
I personally dont think car engines ever break-in to run at their peak the way they are outlined by the engine OEM to be broke in. As I understand it, ABC, AAC, and ABN engines should be run at or slightly faster than the RPM they're expected to run at during normal use during break-in, though slightly rich. Running 1" smaller dia. prop and setting carb rich enough to run at that rpm is how Jett recommends breaking their engines in. I ran my TT .46 in this way and its still getting better every run and its at about 1.25-1.5 gallons now.