The port dia is 5/16 like the print calls for. Its the angle that was off, some ports where drilled better as the angle was closer to what it should have been. I agree the ports are drilled too big & the guy that drew up the prints should have designed the ports a tad smaller. My opinion is, a low speed engine does not need as big of port runners. I did talk with a guy on another forum that his Holt engine had the same problem, with the head bolt hole & the ports open to each other. The heads came already done so I got to make them work somehow. Best Regards, John :wall:
