Topic: Cylinder head thickness?

[evopgt]

Hi all, I’m working on my 77 cb750A. I can’t seem to tell if the cylinder head has been previously milled at all. All Ive got is measurements with a micrometer from valve cover mating surface to head gasket mating surface. My numbers are consistent at 2.84” thick on the sides and in the middle of the head, Is this consistent with a factory head thickness? Or has it been milled down?? Thanks for any input.

[Medyo Bastos]

2.850 is oem


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[HondaMan]

Measure the distance from the head gasket surface to the intake valve's edge. If it is less than 1.85 mm then you will need to have the valve seats cut back in a little bit to keep the valves and pistons from getting too close. Or, you can also slightly mill pockets into the tops of the pistons, either way works. In the "A" engine these tolerances were not as close as in the other engines. The F2/3 are the closest of all at 1mm minimum clearance during overlap, although the typically-stretched cam chain has the intake opening after TDC anyway..

The "A" engine has wide clearances and a very late-opening intake valve (it opens 5 to 8 degrees ATDC), so it would take 0.040" of milling before the "A" head would have any issues...

[evopgt]

Thanks guys. Good info.. It seems it has had .01 taken off then at some point. I’ll probably just roll without milling. It seems pretty flat with a straight edge. I’m going to do some more measuring too as Hondaman suggested and decide whether to mill or not. I guess if Hondamans info is right about being able to mill the A’s .040” without problems, I could just get a shop to mill another .01 off and still be good if I had too.     

[scottly]

On a '77 K head I measured 2.844" with calipers.

[MRieck]

 I've taken .060 off heads, .006 to .010 etc isn't going to make a real difference on late model heads.

[evopgt]

Well hondaman, the measurement from edge of intake valve to head gasket surface came out to 2 mm so, There shouldn’t be a prob there. Every time I straight edge it I seem to get different results. I take my .10 feeler gauge and it may barely sneak through some places. Then Ill do it again and it won’t sneak through the next time. Frustrating. I may just drop the jugs and head off to the machinist and tell him to check the decks and correct as needed. Seems like There’s enough material left to mess with.

[scottly]

If you can fit a .10" feeler gauge, your head is beyond hope!

[evopgt]

.1 mm I mean. Lol