OHV Ford six question

what year did Ford switch from the flathead six to the OHV six? this is whats in my 53.

 

52 and possibly late 51 in a few trucks.

 

Junkyardjeff is correct concerning the first OHV sixes. Those early Ford OHV sixes were good runners. My brother had one in his '54 Ford Mainline. He used to beat '53 and '54 Ford V8's. This was in the late 50's.

 

And was 215 cid.