29-07-2018, 08:58 PM
I found the snug fit dummy valve the best check of absolute concentricity.
I have dismantled several high mileage Minx heads and found porous castings with extensive pits in exh seats yet seemed OK. Obviously must occupy little width. If just due rust probably not deep.
For the BMC A guide clearance is given as .0015 and .002 min, and as modern valves are all one dia reaming might not be necessary esp for inlets.
I find new fixed reamers cut aggressively; one source suggested lubricating and this moderated the cut and gave very high finish.
I wonder what seats are like when the head is tightened and engine flat out hot!
I have dismantled several high mileage Minx heads and found porous castings with extensive pits in exh seats yet seemed OK. Obviously must occupy little width. If just due rust probably not deep.
For the BMC A guide clearance is given as .0015 and .002 min, and as modern valves are all one dia reaming might not be necessary esp for inlets.
I find new fixed reamers cut aggressively; one source suggested lubricating and this moderated the cut and gave very high finish.
I wonder what seats are like when the head is tightened and engine flat out hot!