I could use a little advice here. I have a Rocket 350 in my '72 Cutlass and it runs very well but on the hottest days it tends to run a little on the warm side. It does not overheat but it will cause a difficult hot-starting. I upgraded to a larger radiator and that helped a lot but it still is not good about idling for an extended period in hot weather. Here are my thoughts:
1. I put the hood insulation back on in an effort to maintain originality. Was this a mistake?
2. I do not drive it in winter as a rule. Is opening up the thermostat a good option?
Let me know what you think please. Thank you in advance.

Paul

 

Hood insulation should have nothing to do with it. It's there as a sound-deadener.

How do you define "warm.?" (Give us a temperature.) Hot starting problems are not caused by an engine that ran hot when it was running. Any engine, when turned off, heats up a bit before cooling down because the engine is still hot, but the coolant has stopped circulating. Hot starting problems are often caused by poor electrical connections or vapor lock.

 

^^^THIS. Is your "hot starting" problem a non-crank problem or a fuel percolation problem? The fixes are obviously very different.

 

I do not have a quantitative value for it as the gauge is more qualitative. I will need to use a pyrometer to be more exact. I just know where the gauge is typically and it has been above that point when idling for extended periods.

 

Fuel percolation. I have insulated the carb from the intake manifold and that helped considerably. When the coolant stops flowing the fuel in the line expands from the mass of hot engine.

 

Does this car have fuel return or not?

 

Not being used at the moment...

 

You might want to rethink that...

 

Hood insulation should have little if any affect on operating temperature.
I'm not sure what "opening up the thermostat" means.

 

What fan are you using? Do you have a shroud? Also what temp thermostat? I had a considerable drop in temperature just going from a regular 195 to a Robert Shaw 180 high flow thermostat. Get a lazer pointer temp gun, see what it is really running. Consider reconnecting the return line, the factory put it there for a reason. With the return line on my 88 Cutlass, I only had fuel boiling issues at 230+.

 

Not sure what you mean by that.

• If you mean changing the thermostat to one with lower opening temperature...
  • if the thermostat is opening completely (and yours probably is because the temperature creeps above your usual temp), a cooler-rated thermostat will do nothing to change the ultimate temperature. It will only delay the onset of the higher temperature.
• If you mean removing the thermostat...
  • often this causes higher temperatures because the water pump cavitates (loses efficiency) and the temp rises above that with a thermostat.
  • with that in mind you can experiment to see if that can do any good.
    • some get results by removing thermostat blade or drilling holes in the thermostat blade
  • do not lower the operating temperature below about 170 for any weather.

This work should be near the end on your list of possible solutions. You may not have a coolant temperature problem at all--pyrometer will tell.

 

To be honest, without an actual operating temperature at idle and cruise one cannot suggest a direction. Engine temp will rise considerably with extended idling combined with summer temps. There are many reasons an engine can run warm outside of idling. Carb lean condition, timing, fan clutch, low coolant, head gasket, timing chain, etc...

 

I did mean drill out the opening but I doubt that will help much judging by your reply. Thank you!

 

I will reconnect. Thank you so much!

 

If your engine temp climbs when the vehicle is sitting still like in traffic or parked, but will go back down when moving, you likely have an airflow or coolant flow problem. Do you have a fan shroud? You can aid the airflow by using weatherstrip foam thick enough to fill all the gaps around the radiator so the fan only pulls air through the radiator and not around it. Make sure your fan clutch is working properly, they do go bad. Play with it and get a good feel for the tension in the clutch when the engine is cold, then let it heat up, shut the engine off and let it heat soak a minute or two and feel for increased tension in the fan clutch. You may also hear the fan noise increase when the engine heats up and then reduce noise as the engine cools. If not, they are not expensive or difficult to replace. A high flow thermostat will increase cooling capability by letting more coolant flow through the radiator. A lower temp thermostat just opens sooner without increasing the cooling capacity.