I just thought of something that may or may not have anything to do with this.
I'm putting a G3 Hemi in my 68 and last fall I sold my 318 and 904 kind of suddenly. That left me with a gas tank 3/4 full of 93 octane. I siphoned it out and quickly filled a 5 gallon gas can. I put some in the Jeep Comanche, some in the Subaru and some in my John Deere lawnmower.
I started cutting the grass and within a few passes the OHV Kawasaki engine in the mower started sputtering, smoking and lost fire. I drained the gas, cleaned the plug and filled the tank with my usual alcohol-free gas. Fixed! It was the damnedest thing. That low compression banger just did not like high octane. Maybe a low compression slanty is similar. I run 87 octane in my rebuilt 225 and never have a problem.
