A heads up about Engine Quest heads

On my first motor, I knurled the valve guides, but replaced one exhaust valve guide that was still too loose. The first day on the road the car died going about 40 MPH with an accompanying puff of white "smoke" billowing behind on the highway. Found a dropped exhaust valve, hole in piston, bent connecting rod, and split cylinder bore. Guess I didn't ream the new guide to provide enough valve stem clearance?