I just finished putting in a new stock radiator in my '77 280z. However, when I started it up to get the coolant running, it seemed as though the gas was not being regulated correctly - heavy smoke and a real stink comin out the back. My other thought is that it may also have to do with the intake, which sounded like it was sucking away harder than usual. Funny thing is, the radiator and coolant system seems to work just fine. Any help or ideas would be GREATLY appreciated.

What color was the smoke?

You perhaps knocked off a vacumn line somewhere?

The smoke was grey - I'm thinking I MUST have knocked off a vacuum line...

Or, maybe the connector to the AFM? Did that once changing the radiator in my Z.

Gray smoke usually means burning oil, however it can also mean water vapor.

Black smoke usually means you're running too rich.

Did it smoke before?

Check for water in your oil and check to see if the water in the radiator is milky.

If either of the se thing appear you could have a problem with the head or head gasket.

Did you replace the radiator because the car over heated?

If neither of these things appear, then start on the vacuum lines.

Good luck.

Thank you very much for help - I'll try a few things and see what I can do...

I was working on my '75 280Z many years ago, and when I tried to start it, it smoked, choked, and generally wouldn't run. Took me a while to find, but SOMEHOW (I never figured out how), I had sucked coolant into my air flow meter, and there was coolant pooled in the bottom passages. Cleaned that all up and it worked fine again.

Don't remember what I was actually working on at the time...

I have now checked just about every connection that we could have possibly messed with (vacuum lines, distributor wires...) and everything there seems to be connected just fine. My new diagnosis is that the timing is off. The exhaust stutters, the engine shakes (a lot), between about 500 and 1000 rpms the smoke coming out the exhaust is gray, up to 2000 (which is the highest I could rev it before it cuts out all together) there is a lot of black smoke. I think that's all the symptoms. I am going to check the timing later today and if that doesn't fix it....

You might also want to check to be sure that the spark plug wires and connected in the correct order. 1-5-3-6-2-4

The spark plug wires are fine - I double checked, just to be sure.

Can also give grey smoke at start up. Verify correct fuel pressure and go from there.