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Good day all. I removed the head on the 740 and noticed some circular marks on the underside corresponding to where the valves rise. Most are quite faint and no indentation could be felt; however, one does have a barely palpable indentation. The valves all look fine and operate as they should. Is it possible that the lifters have been adjusted so the valves are rising too high? Hopefully, the head hasn't been over-planed at some point, although I do have a spare. Any diagnostic advice will be most welcome. The marks can be seen above cylinder 4 in the attached photo.

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The more likely culprit is that the head was milled which made it too thin. If the valves are indeed hitting no matter how lightly, you made need to find a copper gasket which is usually thicker or can be ordered that way. Not sure but I believe Olson's Gaskets in Washington State has or can make solid gaskets in special oversize thicknesses and may even have some in stock.

You could first set the valve clearances to spec and then do the rather standard test, described here many times in the past. Put some modeling clay or putty on the heads of the valves, put the head on with the used gasket but DO NOT bolt the head down. Rotate the engine through several cycles; if the head rocks up and down you will want to hold it down with hand pressure, then remove the head and inspect the thickness of the clay remaining on the top of the valves. Any valves which are actually touching the head will be clearly apparent.

Alternatively but not quite so definitive would be to just lay the head in place with a used gasket and watch for any movement of the head while you slowly rotate the engine.

If you are out of clearance because the head was milled excessively, you probably won't be successful in finding a thicker-than-stock head gasket - so time to check out your spare head. Many folks over the years have tried doubling up on head gaskets but this is never successful for more than a very short time, it at all. Others have had extra thick gaskets made from solid copper sheet, quite expensive to have made and I've never seen it succeed either.

Roger on the putty test. Willco. Thanks much.

Clay / putty test is a good way to check the clearance. Looking closer at the head the circular area appears to be more visible closer to the center of the combustion chamber.

Since the chamber is higher in the center I would think any contact with a valve should be seen closer to the edge of the chamber.

I've also place a head on the block without a gasket and no head bolts. Slowly turned the engine over by hand, looking for movement of the head.

Or just borrow the kids Play-dough and place some on top of a valve.

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Yes, 32, that occurred to me as well. All the marks are more pronounced toward the center. Can't think of how that pattern would occur.

Serious question: What would the down side be to taking a dremel tool and relieving some of the dome where the valve appears to have struck? Since the center of the dome is higher than the outside of the dome a valve strike on the high side and not the low side doesn't make sense.....to me anyway. The clay test should test these results.

What would the down side be to taking a dremel tool and relieving some of the dome where the valve appears to have struck?

Taken far enough, altering the flame propagation and probably more importantly, weakening the structure. To just grind away a couple of thousandths, probably nothing significant.

Tried the Dremel job some years back on a '54 Cavalier head that had been resurfaced unnecessarily. In those engines the valves are not perpendicular to the deck so what hits first is a crescent-shape from a segment of valve head. Lots of grinding but in the end we hadn't yet gone deep enough but were afraid to go any deeper. We then tried the extra thick solid copper custom-made head gasket and it gave enough relief but leaked profusely. Finally, scrapped the head.

Might be mistaken, but notice in the last photo that the spark plug appears to be one of a projected core type. It is incorrect and may cause problems with the valve hitting it. JWL

Thanks, J.W. Hadn't yet checked the type of plug in there as the engine has not come close to running since in my possession. I've ordered the correct wiring, nuts and plugs for installation prior to trying to start.