Our F did the same, the chevy gas was a nice running unit. We pounded 500 acres a yr through it. Traded for a 6620, it had more capacity was a difficult to work on. Our F had a black 438 corn head, which was also easy to repair. Traded at 2800 hours, should have kept the F and got a second machine ot a M. I do miss the smell of the burnt corn, but now have the engine noise to keep me happy (lOl)