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How do I measure how much can be milled off 1951 288 head? I'd like to do this before paying to have it milled and then using clay. I'd use clay to verify. How much do the valves rise above the block? I'm going to try to measure and will post. Will also try to measure depth of cylinder cavities in head and post. I have 2 dial indicators but need a mount.

I would NOT mill more than .030" off the head. you will loose breathability in the crossover area. Are you milling because of pitting, flatness, or because you think you're going to get a significant increase in comp. ratio? If the latter, there will barely be a discernable difference. If you've got performance experience you might notice a difference/ Most will not. It was a good running engine as designed and with the fuel that was available. The flathead design has it's limitations.

Old heads have unknown section thicknesses due to rust, casting variations, and the possibility that the head has already been milled, and perhaps the block decked. I would only mill it as necessary to correct minor pitting or distortion. Packard designed the head to achieve minimum chamber area and volume consistent with good overall performance. They also machined the combustion chambers to achieve consistent chamber volume and maximum flow characteristics while minimizing carbon deposition.

I guess I didn't describe my situation properly. I don't know if the head has been milled before. I don't know if it needs milling, I will have the machine shop measure the warp, if any. Hopefully the shop can tell me how much, if any, needs to be milled. I'd like to know if that much can be milled. I'd think that would be based on measurements of how deep the cylinder cavities (combustion chambers) are. In other words, are the cylinder cavities deep enough to clear the protrusion of the valves above the block.

How much warpage is tolerable for a 1951 288?

I've read that flatheads are more accommodating of warpage than overhead valve heads because the flatheads will flex. Also, copper head gaskets are further accommodating.

IMO, The comments Ross posted about 10 years ago on head thickness and milling that are posted and then re-linked by HPH in response to one of your other questions are probably the best you will find as far as recommendations.

The clay test as described in one of your different posts has also been performed by others who had questions about milling limits. It is not a precise test but does help to answer whether too much has already been milled from a head.

It’s never been clear to me that warpage is such a problem in these heads as, with all the studs and nuts and being relatively thin, they should pull down. Corrosion, gouges or dips in the surface is another matter that would require milling.

That said, you have two choices. Take a chance and have it milled or do the clay test first and decide from there. There are no known measurements that will tell you in advance if it can be milled or not.

It's VERY important to get the gasket surface on the block completely clean. Avoid scraping at it so hard you remove metal. It's important to get all deposits off the block surface, including material around the base of the head studs, which can be tedious in some cases.