I'm not sure. My guess would be to fight detonation, as they expected these engines to get very hot on a regular basis. Maybe the low compression would be easier on the bearings? I'm just guessing here, of course. Interestingly, the old 318 Poly's made for heavy truck and industrial use were also 7.0:1 compression. When I was a teenager, they closed a local cement plant. My friend breathlessly dragged me up there so we could buy some of the old hemi's they had there that were used to power giant, stone conveyer belts and other large equipment--many outdoors, no less. The hemis all turned out to be 318 Polys, and I called him an idiot because I passed up a date with a cute girl to go get one of the things! This was about 1981, and those old Polys had run seven days a week from the 1950's and 1960's, and didn't give any trouble. They were all caked with cement dust, too. That's saying something. And I am still shocked at the incredible size of the machinery a single Poly engine can run. roger@xxxxxxxxxxxxxxxxx wrote: > > Why such low compression. Very interesting. Just for cheap pump gas > cause the motor home did 6 mile to the gal? ---- Please address private mail -- mail of interest to only one person -- directly to that person. I.e., send parts/car transactions and negotiations as well as other personal messages only to the intended recipient, not to the Clubhouse public address. This practice will protect your privacy, reduce the total volume of mail and fine tune the content signal to Mopar topic. Thanks! '62 to '65 Mopar Clubhouse Discussion Guidelines: http://www.1962to1965mopar.ornocar.org/mletiq.html.