Help setting valves on a 225

Sorry to disagree Dan, but my in my experience, adjusting the valves with the engine off is far easier. An engine running adjustment is no more accurate than one done on a properly warmed up engine that is shut down. Working on a running engine also has the disadvantage of being potentially quite messy. With a simple understanding of crank spacing and running mates, it is possible to have all valves adjusted in two complete revolutions of the crankshaft (720 degrees) in as little as ten minutes. The amount of metal contraction due to cooling in even 30 minutes of engine off time will not have an appreciable impact on the accuracy of the valve adjustment. This is especially true if you are using feeler blades to do the adjustment, since they lack the accuracy that a dial indicator can provide.

Dartncharger - if you follow the advice of adjusting a valve when "the opposing valve starts to depress" you will have some severe difficulties. I think the person giving the advice was likely referring to using the running mate as a guide to when to adjust. If I may explain a little...

On a 6 cylinder engine, there is one piston coming to the top of its compression stroke every 120 degrees (or 1/3 of a turn) of crank rotation (720 degrees divided by 6). When one piston is at the top on its compression stroke, there is another piston (called its running mate) at TDC also, but it is on the exhaust stroke.

Since at the top of the exhaust stroke, both valves are in motion (during valve overlap) this makes it easy to identify where to adjust the valves on the running mate (the other piston at TDC).

To find running mates, simply write the numbers of the first three cylinders in the firing order (1 - 5 - 3) then draw a line and write the next three in the firing order beneath the first three (6 - 2 - 4). Thus, 1 & 6, 5 & 2, 3 & 4 are running mates. Starting anywhere the engine happened to stop, rotate the engine until you see which exhaust valve is closing. Keep turning until you see the intake valve on the same cylinder start to open. Both valves are now in motion as this is the overlap phase of the camshaft. Call this the rock position. Stop turning the engine over and adjust the valves on the running mate to the one whose valves were both moving. Since these pistons are now at (or close to) TDC, the lifters of the running mate are on the base circle of the cam lobe. Do not worry that you may not be EXACTLY at TDC - a few degrees of crank rotation one way or the other will make absolutely NO difference, as the base circle of the cam lobe covers well over 90 degrees of crank rotation. Once you have adjusted the valves on this cylinder, simply rotate the crank 1/3 of a turn (120 degrees) and adjust the valves on the next cylinder in the firing order.

How do you know you have turned 1/3 turn? The same way as before - watch which exhaust valve is closing and turn the engine over until the intake valve begins to open (rock position) - now adjust the running mate. You will find that you are adjusting the valves on the cylinders following the firing order of the engine, while the valves you are using to guide you are 1/2 rotation behind, but also following the firing order.

Thus you will adjust as follows (assuming cylinder #3 is on the exhaust stroke):
Valves on #3 in the rock position - adjust #4
Turn 1/3 until-
Valves on #6 in the rock position - adjust #1
Turn 1/3 until-
Valves on #2 in the rock position - adjust #5
Turn 1/3 until-
Valves on #4 in the rock position - adjust #3
Turn 1/3 until-
Valves on #1 in the rock position - adjust #6
Turn 1/3 until-
Valves on #5 in the rock position - adjust #2

Finished!

Be as consistent as you can on the amount of feeler blade drag you set the valves with. One thou (0.001") of clearance changes valve timing by almost 4 degrees of crank rotation. Too tight and your valves are opening early and closing late - too loose and the valves open late and close early. This can affect idle quality, power, fuel consumption and emissions. If you set them so tight as to remove all lash altogether, the exhaust valves will overheat (and likely burn) - if the car runs at all. My 1966 Chrysler manual calls for 0.020" on exhaust and 0.010" for intakes - but check a manual for your year to be sure.

If you want true precision, mount a dial indicator such that its plunger is aligned parallel with the valve on the tip of the rocker. This is a little more time consuming and really quite unnecessary however, as you should be able to be as accurate as you need to be using feeler blades. If you can find them, a set of go-no go feeler blades work very nicely. These are a stepped feeler blade with 0.002" difference in the "step" of the blade.