IIRC the 68-71. 340 had 10. 5 to 1 compression ratio. So if those are
8 to 1 then you would be leaving at least
25 hp on the table, which translates to .25 second in the 1/4. If your going to race it and you are gotta get another tenth of a secind less racer, go for it. If its a street , occasionally strip
car, save your money, go with what you have.
I have a buddy that is always after the elusive tenth of a second. I stopped by his place one day and he was under his car with a small propane torch using it to heat the undercoating to scrape it off.
