I am new to Datsun, I always wanted a Z and stumbled into a 1972 240z about a week ago. The car ran when I bought it, run being a overstatement. Now it will not start, it sputters, nothing more. I have gone through the round tops and adjusted the floats, that seemed to help it run and start a little better when it still ran. I set the timing to 5 below like the haynes said, that helped it start better when it did, and finally I put a little marvel oil down the cylinders to even out some compression numbers that I had. these are cold numbers at 6000 above sea level;

1.) 120

2.)120

3.)95

4.)100

5.)120

6.)105

After sitting for a day my new numbers are;

1.)125

2.)120

3.)45

4.)60

5.)120

6.)95

Now the car will not start like I said, just sputters. When the car ran before it hesitated during throttle application and idled like it had a large cam. Any advice?? Please help.

The comprssion is not great but is not likely the reason it won't start. Check to make sure you have spark. Maybe the points need to be cleaned and adjusted.

the compression levels look to me like a classic example of head gasket failure... I know from experience; your description of how the car ran before failure also sounds familiar.

Are you using a screw-in gauge or one of those ones with the rubber plug you hold in the spark plug hole? It's odd that you would lose 50 and 40 psi on 3 and 4 just from sitting for a day. The measurement results doesn't look right. They should be consistent, if you're not starting the engine between measurements. You said the first was cold, so I assume that you measured cold, waited a day and measured cold again. No reason for the head gasket to blow, just sitting.