I have a 216 with a floor shift 3 speed Trans in my late 1947 Chevy truck and since having it in the truck whenever I shift from 1st to 2nd it grinds. I get going up to speed when leaving the stop and push in the clutch the engine is at idle with the clutch in before I attempt to go into 2nd and instantly grinds. I tried adjusting the clutch but no good results. Tonight a guy told me to double clutch when going from first to second. It seems to be helping a lot. My question is why does this work and is there any type of adjustment I overlooked that I can go back and do to resolve having to double clutch all the time? Going into 3rd is no problem.