Whilst trying to find a cylinder head to replace the one with crack between valve seats that lost its insert, I noticed that the diameter of no 9 and no 10 bolt holes were different to the others. I can only think this was to make assembly easier or was it a drawing error that had to be corrected? The correct is diameter is 10mm but these two were over 12 mm on 8 heads I looked at, but the diameter was not consistent or down the whole bore.
More investigation required.
Head bolt holes
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Keith Clements
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Head bolt holes
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PJGD
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Re: Head bolt holes
Keith,
Take a look at the Jowett blueprint of the cylinder head (that I think that you photographed and placed in the drawings file on this site), and you will see that those diagonally opposite stud holes are like that on purpose. The upper one is Ø.438/.437" x ⅝" deep, and the lower one is Ø.5005/.4995" x ⅝" deep. They are jig location features so that the head can only go on the fixture one way for all the remaining machining operations
Having said that, I have one head here where the spacing between the valve guides is different! How did that happen!
Philip
Take a look at the Jowett blueprint of the cylinder head (that I think that you photographed and placed in the drawings file on this site), and you will see that those diagonally opposite stud holes are like that on purpose. The upper one is Ø.438/.437" x ⅝" deep, and the lower one is Ø.5005/.4995" x ⅝" deep. They are jig location features so that the head can only go on the fixture one way for all the remaining machining operations
Having said that, I have one head here where the spacing between the valve guides is different! How did that happen!
Philip
Philip Dingle
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Mike Allfrey
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Re: Head bolt holes
The same with the engine I am currently involved with. That is the stud which I extended through the coolant inlet. Having to drill a completely new tapping size drilling with a long series drill, it was all new weld material, so I had to start from scratch.
I decided to get a sliding fit sleeve to fit into the oversize cylinder head drilling. Its inside diameter is tapping size for 3/8" BSF. Worked a treat.
I can only presume the larger drilling was for tooling/jigging purposes,
The crack you mention, another place for me to have a good look at. Have not seen such a crack since petrol tractor days.
Cheers,
Mike A.
I decided to get a sliding fit sleeve to fit into the oversize cylinder head drilling. Its inside diameter is tapping size for 3/8" BSF. Worked a treat.
I can only presume the larger drilling was for tooling/jigging purposes,
The crack you mention, another place for me to have a good look at. Have not seen such a crack since petrol tractor days.
Cheers,
Mike A.
E0 SA 42R; Rover 75