MILLING A STOCK '72 360 HEAD

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   And like someone else said 'YOU GOTTA HAVE THICK SKIN TO OWN AN AMC' and I agree.

And part of the reason we need to have 'thick skin' is also part of the reason why an AMCer needs to work harder and be smarter than mainstream in order to stay competitive because we are truly outnumbered on the big playing field which is tilted in their favor (favoring the more popular higher numerically produced cars ...which in some cases is like one million of them to four thousand AMC vehicles made = AMCers are truly outnumbered)

HENCE, THIS LONG EXPLANATION IN RESPONSE TO YOUR QUESTION! ...Hee hee hee...
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You want to increase compression on an engine that is already built and in the vehicle?

...maybe to go along with what a cam maker recommends for a certain cam?

Then maybe there will be a few here who are surprised to hear what I have to say in this regard:

...a little known 'secret' is that cams are cut to make about 7 to 1 compression. (!)

This 7 to 1 will be an actual dynamic compression ratio based on intake valve closure timing on the compression stroke.

The reason cam grinders do that is because the engine will naturally increase it's volumetric efficiency as rpm goes up, where, when the engine is operating in it's designed rpm power band, airflow phenomena begins to occur, producing ram effect for increased cylinder filling capacity and dynamic compression increases up to around 9 to 1.

So, even on a cam where the cam grinder specifies 'use 10 to 1 compression', the intake valve closure timing will still be calculated to have about 7 to 1 dynamic compression.

On a cam as such, if one tried to run it in a lower static compression engine it'll only make about 5 to 1 dynamic and about 8 to 1 actual during peak volumetric efficiency range of the engine's design parameters. -so the engine would not even make as much power as it did before with it's stock cam.

so... this is one of the problems with buying ready made cams out of a catalog which are not tailor made to suit the specs on your particular engine.

And this is why if a person wants to have a custom cam cut for their own particular custom built engine is most wise to be 100% honest when giving the cam maker your specifications so they can cut the cam to open and close the valves in relation to the actual compression the engine is estimated to make when it's running in it's better volumetric efficiency range of rpm.

Now an easy-to-understand illustration of this is the 'RV type cam'. RV type cams are cut to simply close the intake valve a little sooner to make the engine 'think' it has a higher static compression ratio.

(but there is a trade off because the same cam is not cut to make more high rpm power -it simply shifts the volumetric efficiency level a tad towards the lower  spectrum of the engine's peak volumetric efficiency range) -this way, an RV cam 'works' on stock engines to make more power in the lower rpm ranges for towing, and they are made to work with the stock valve train to be a 'drop in' mod. (which adds to their appeal; no need for other substantial engine modifications, moreover the engine becomes 'overbuilt' for it's towing application)

Note: I'm not making this up 'out of my own head'. Rather I learned more minute detail on this matter when I corresponded with D. Elgin Racing Cams to have a custom cam cut for 443 XRV8 stroker engine as he processed my order.

In fact, the 443 is considered to be a 'new engine' and D. Elgin who is a member of SAE placed the specifications of my engine on file with SAE as such with the camshaft specs he cut for it. (estimating it's volumetric efficiency level by studying my intake manifold headers and port work on the heads along with it's verifiable 9.7 to 1 static compression ratio)

...this is why you'll see in the catalog cam information 'use with single plane intake 10 to 1 compression, headers and high stall converter' etc -the cam is cut to make it's best running dynamic compression with those mods. (cut to make about 7 to 1 by intake valve closure timing and make about 9 to 1 actual when running in it's peak volumetric efficiency range of rpm... as demanded by it's mechanical limitations and original design.

So... what I'm getting around to saying is, instead of milling the heads to make more static compression ratio, you can have a custom cam cut for your engine that will be custom designed to work specifically with your engine's components... in effect, they can cut a custom cam to make your engine 'think' it has a higher compression ratio that it actually does 'on paper'.

One of the reasons for this is that it is in truth it is an 'emission designed' engine & that means the engineers at AMC back then slightly reduced actual dynamic compression ratio in order to reduce toxic oxides of nitrogen exhaust content... the 'easy way' to do it was make the combustion chambers slightly larger and reduce the static compression ratio we see on paper... not the cam.

As far as I know, the current EPA laws prohibit removal or tampering any emission control device on cars made in 1974 & up so '73 & older are still legal to modify as the car builder see's fit -basically they can do whatever they want  to cars which are made in 73 or older.

The individual states have their own rules and ways to keep 'gross polluters' off the roads so it's good to check the local laws... the thing is, a cam is 'sneaky' and they can't see it from the outside of the engine... so the laws contain a certain amount of 'grace' and the vintage engine builders tend to naturally build 'clean running' engines anyway... not to foul the plugs with all sorts of overrichness and loose oil clearances etc... so the new laws factor that in.

(this is why the '65 443 engine is installed in a '73 model AMC car... the '65 engine can be retrofitted into a '65 if they change the law back to the first emission control device (the PCV system) in 1965... to keep me, myself and I legal!

So recapitulated, to the best of my knowledge, instead of milling the heads on a '72 360, the alternative is to have a custom cam cut to bring it's actual dynamic compression ratio up to around 9 to 1 (where is should be... not going any deeper into the debate on oxides of nitrogen exhaust content) and I believe this will be fully legal to keep you a legal eagle soaring high in your classic AMC vehicle for now...

Note: there are bills up for consideration now having purpose to outlaw any and all aftermarket parts for use on emission control type engines on public roadways... -going beyond the old laws which state saying the repair shop or the individual cannot tamper or change the devices. 

...not sure if SEMA was able to get enough signatures on their petitions to thwart the bill...

If I did not mention the legal ramifications, this could kill my own interest in making aftermarket hop up parts for my favorite AMC vehicles and I would be advising people to commit crimes against US Federal Law... which would definitely not be in wise for me or for the greater good of our AMC community as we move into the future ...plausibly surrounded by electric cars.

Moreover, this is what XRV8 Race Parts is attempting to persuade; that we need to consider the pre-'73 and pre-'65 vehicles with more interest for their lower entanglement with US Federal emission control laws... whereas there is potential by the 'do gooders' to outlaw the cars also that are modified next... considering how the laws proceed to incriminate.
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Now, if you were intending to build a race engine, I would be more interested and have much more to say! 