I still have my '79 FXEF (80") and I was wondering if I had an oddball. (9.4:1 comp)
Good for you! That was one of my favorites. That compression ratio is higher than stock, but there is nothing wrong with it, they tend to run great on decent gasoline, especially with high-overlap cams.
I thought about calculating the actual compression ratio on this one but I did not take the time to cc the heads. Maybe next time I have it apart. I'm expecting that it's right up there. I have never checked for shearing... but do you guys fight oil temps?
I don't worry about it, as soon as the mechanical sound of the motor changes at highway speeds in the three digit temps I change the oil. With some oils it was about a thousand miles,so I quit using them, some would go twice that. In cold weather I will let the oil go quite a while, in hot weather I change it often. I don't know who makes RevTech oil but I'm seeing good results with it, it holds up to heat even better than Delo SAE50 HDEO.
Back in the mid 1980s HD published some guidance on oil and temperature, if I recall correctly, every 20 degree increase over 200 degrees meant a dramatic decrease in oil life, and temps in the 230 degree range were really hard on the oil, and consequently the motor. I tried various oil coolers over the years and never really saw that much difference under extreme temp/severe service conditions. What I concluded was if the oil temp was routinely exceeding 220, just change it more often.
Conversely, my 1988 Evo 80" Softail never gets above 200 on a hot day.
That matches my experience as well. The Evos run cooler and last longer. I'm thinking about an Evo, I think they have been out long enough that I can finally trust them.