Overheating on a 170 in a 1961

[redfalken]

There should definitely be a notch in the edge of the harmonic balancer for timing. It may have been painted over or dirty. I usually put a dab of white paint on it once found so it's easier to see under the timing light.

Or, if it's running well enough for a drive, find a steep hill and mash the throttle going up. If you hear pinging let off the gas and pull over to retard the timing a bit. Do the same test until the pinging almost goes away. It may barely ping when you really hit the gas but won't ping during normal driving.

That is usually the best way to find the timing your particular engine and the gas you are using runs best at. The manual has the timing way too retarded in my opinion but they did it for gas economy and having it a little more advanced gets more power and performance.

I've always been told that having the timing too advance can cause overheating problems too so make sure that is dialed in.

[Luva65wagon]

The thermostat may be opening, but too slowly or not completely. If uncertain - change it.

Also, many thermostat are completely closed when cold. I always drill about a 1/8" hole near the edge of it and place this at 12 oclock when I place the thermostat in the housing. This allows you to fill the radiator and have the coolant flow everywhere without hitting a wall and form an air pocket.

If you Google "Drilling hole in thermostat" you will see many pages on this. I've never read anything on-line about this (just did it now to see if there was anything out there I could point you to) and it seems there is a lot of debate about this. I learned this long before there was this thing called Internet. I'm only advocating one hole, placed near the top, to allow air to escape the block when filling. Any run-time advantage, as mentioned on threads of the Google search, are superfluous to this discussion as I feel a good thermostat, radiator, etc., etc., negate any other mods to a thermostat people may be doing. Many think no thermostat will help cooling, but it doesn't. You need some resistance to flow to allow coolant time in the radiator a allow the radiator to act as it is designed for - a heat exchanger. Too fast and it doesn't get that chance, and too slow the engine can heat the coolant more than the system can cool it.

Agree with Kenny too about the timing. Making the changes based upon driving it is ideal, though you can begin all of this at the factory setting to get you in the ballpark.