225 Slant Six Crank but Won't Start (Fuel but No Spark, Dist. Rotor turns)

OK, some engines are worse than others "at doing this" but it is possible on most? all? engines with harmonic balancers to slip, as they are a hub, a rubber material, and an outer ring. So if the outer ring slips, the timing marks are no longer correct

Secondly, "with these old girls," mixing of parts over the years is VERY possible. Depending (this is in general, Chevy included) when you get into trucks motorhomes, all the rest, and the early Mopar V8s up through 69, the timing mark and pointer tab were in different places, so you might not even HAVE a mark that could be correct. That is, EG, an early timing cover with a later engine / balancer on something like a 360 V8.

SO to make certain the marks are TRUE you need a PISTON STOP. This is a device, usually adjustable, which you put into the no1 plug hole. This is NOT to stop the piston at TDC, but rather "someplace" "on the way up." So you put this stop in place, and rotate the engine clockwise, and make a temporary mark under your TDC pointer, wherever it stops. You now rotate the engine backwards, until it again stops, and make a second mark.

Now you'll have two stops, and the true TDC will be halfway in between. If the original mark is accurate, that is where it will be.

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The other issue is as I explained earlier. The no1 piston comes to TDC every time the timing mark comes up, but it only fires on compression stroke

There are TWO WAYS to determine compression stroke, (actually three)

1....The method I explained above, stick your finger in and feel for compression

2....Pull the valve cover, and bring the engine up to TDC. Then look at the no1 valves. Both of them are shut at compression, both of them are "about equally" open on the exhaust stroke, and both valves will move if the engine is turned slightly

3....Not really a method, "you can guess." Bring the marks up and put the distributor in with the rotor pointing "by the book". If it runs, "fine." If it does not the distributor is "180 off" that is 1/2 turn off. The right way to fix is to pull the distributor and rotate 1/2 turn. The "quick" way is simply to rotate the plug wires half way around the cap

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On that note, "3" You can actually "throw" the distributor in anywhere. Then bring the engine up on no1 compression, timing marks on about 5-8 BTC and look where the rotor ended up. Get the points to "just open," put the no1 plug wire in whever the rotor points and then install the rest of the wires.

You can NOT do this on all engines in the world. GM V6 are an example. (Odd /even fire) If you look carefully at a GM V6 cap, the towers are "paired" that is, two close together and then a space. On these engines you cannot "just move" the plug wires ONE tower. It won't run correctly.