70 Cutlass 350 cid overheating

I wonder if you know of an overheating problem on a 1970 Cutlass 'S' 350 cid 2bbl (no a/c) that simply does following. The water temp just rises and rises when at idle or for example, at a fast food drive thru line. VERY apparent in summer and indeed at all times but most noticeable when weather is about above 40 deg.far. Now I've had 2 rebuilt head manifolds, water pumps, a 4 core rad etc... I've done all this stuff and am sure of no gasket leaks etc... On 455cids and certain 350's there is a TVS switch which channels or adds intake vacuum to the regular carb vacuum to advance ignition which (as the GM shop manual says 'reduces engine coolant temps'

I don't have this but I don't think such small intervention as to touch-up the rmp (as I think this TVS does) would stop such a major cooling problem, what do you think?

Finally, this TVS is on 350's with Y-72. Do you know what this Y-72 option is?

Thanks, any help appreciated.

-Doug

I think you are barking up the wrong tree, personally, But the order of troubleshooting preferences would be. cooling system, i.e.; rad, water pump, slipping belts, slipping clutch fan, thermostat sticking or improper heat range, wrong pressure cap?

then I would check timing, and ignition dwell. Things to ponder, is this an old block that might have scale inside restricting flow? Is there an exhaust restriction, muffler, tailpipe, heat riser valve, blocked heater bypass valve, blown head gasket? pinched intake gasket? too lean/rich a carb. Many ponderances, Good Luck Danno

Sounds like the fan isn't working. The fan's job is to increase the flow of air through the radiator when the car isn't moving; if it doesn't work, the car overheats when stopped.

I'm not familiar with that particular car, but some fans have clutches. If yours does, that's what I would check first. Whether it does or not, see if the fan is the correct one for that car. If you've got the correct fan and it's working properly, you might look into adding an electric auxiliary fan.

Check for restricted exhaust system, had a Pontiac that drove me nuts. Just drop the exhaust pipe and run it . Worth a shot. superbee

Y-72 Heavy Duty Engine Cooling & Generator (1970, 71)