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yes it cools down when you revv it in N,

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The fact that it cools down when you rev it makes testing for the problem quite a bit easier.

The mixture and timing issues you are looking at are a possibility, but other things are much more likely.

To zero in on the problem:

Take the temp of the radiator at the inlet and at the outlet (buy/borrow an infrared gun). You should have somewhere in the 25 to 30 degree temp drop from inlet to outlet.

If you have less than 20 degrees temp drop, you are probably looking at low airflow. Not enough air to cool the water going through the radiator.

If you have more than 30 degrees temp drop, you are probably looking at low water flow. Not enough water to carry the heat out of the engine.

If you have the right temp drop, and the engine still heats up, then you are looking at being low on both water and airflow, or perhaps the mixture and timing issues.

Also try running it with the hood open. If it stays cool with the hood open, you have another thing that says airflow shortage.

If you have an airflow issue try the following tests.

With engine idling and the hood closed, reach in through the grill area and feel for airflow at the radiator. All the airflow should be INTO the radiator. Many times you will feel air coming back out of the radiator, especially at the corners. All this does is recycle already hot air and makes a huge difference in cooling. If you find air coming back out, it is very likely it is because the fan is too far into the shrould. Especially on tapered shrouds, the air will get pushed back out. Remember that a very large part of the air comes out the ends of the blades and if it hits the taper of the shroud it will be directed back towards the radiator. As I said earlier, having only .375 of an inch of fan in the shroud worked the best for me. Also check to see if hot air is finding its way back to the front of the radiator out around any openings by the radiator, or bouncing off something and coming back along the ground.

If the fan in the shroud doesn't do it, and you are still low on flow, try another fan. When I tested them, the 7 and 5 blade (on clutches) fans moved about the same amount of air, and stalled the clutch at the same rpm. I like the 5 because it is quieter, lighter and easier to install.

I that still doesn't do it, you will need to look at spinning it faster with different pulleys.

If the testing shows a water flow issue, that is easy to fix with a bigger pump and high flow thermostat, or by speeding up the pump with pulley changes.

Be methodical and collect your data carefully, and I think you will be able to track it down.

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