Have you tried replacing the water pump? The blades may have corroded. With the thermostat removed, there is less back pressure… but your car will run cold during non-summer months. In addition, you might consider a new radiator with additional cores.
You have more engine to cool, especially if your originally came w/ the low HP model. If it’s built, the cooling load can be greater. Instead of a stock WP, you probably want a high flow model…
So at this point we’re clearly throwing spaghetti at the wall, but I have heard of different engine applications requiring different waterpump applications. Meaning, a 350 waterpump in one application might not be the same as others. Or belt routing could be screwed up. What I’m saying, waterpump could be turning in the wrong direction. Major reach.
For what its worth, I feel like youre on the right track, but he did mention that he put a new waterpump in.
Do you have any idea what device is being used to trigger the electric fan? Is it an adjustable thermostat? If you get extra desperate you could throw a 185 thermostat in and jump the fan to the battery. If it doesnt overheat then you know its a fan issue. The issue is coming into play when you have reduced water flow and less air (stop and go traffic). So this would make you think its either a flow or air problem.
When the engine is cold, remove the radiator cap.
Make sure the radiator is full.
Start the engine. And as the engine idles watch the coolant in the radiator.
If bubbles begin forming in the coolant as the engine idles, that’s an indication of a blown head gasket.
Tester
Yep, there are cheap aftermarket pumps, good for the stock engine. Then there are racing equipment types (around $100) that really push the water. He said he put in a 427 radiator, so I assume it’s maybe from an old car. I don’t follow these, but my brother claims the new aftermarket radiators have twice the cooling capacity. He’s installed some REALLY big Big Block engines in old Vettes and Camaros and it’s the only way to keep them reasonably cool in a TN summer.
I assume the engine doesn’t have reducer pulleys installed, he’s tested that the electric fan is coming on, and it’s blowing thru the radiator (not sucking air forward). I thought of this last because he mentions the flex fan install so the fan could be in front of the radiator. The flex fan, hopefully, is inside a fan housing. I’m also assuming the engine doesn’t have a blown head gasket or similar problems. I’m told wrapping the headers (if installed) can reduce engine compartment temps and improve performance.
For the electric fan, I know people sometimes have the “stock” temp sensor to turn them on. For traffic situations, they install a parallel switch on the dash to manually turn them on. They’ll also turn off AC (if equipped) when stuck in traffic. He also mentions boiling over, so I hope he always runs coolant in the engine.
The flex fan had me wondering also, never considered an electric pusher fan/flex fan combo. Shroud would be nice…pictures of 327 vette engine compartments show them.
Flex fan = kill-me-fan.
Tester
Just some very wild guesses here but what about…
What kind of belt system on the engine? Any chance the water pump is rotating backwards? This can happen with small block Fords regarding V-belt pumps and serpentine belt pumps.
Are the cylinder heads original to the engine block? I (very vaguely) seem to remember a difference in the cooling passages. My memory is very murky on this so I’m just throwing it out there as a what-if.
lol Yes, but they were the fan of choice, back in the 60’s and were a quick fix for many overheating problems, as the factory systems started having problems. With more blades and bigger surfaces, they pulled 30% more air, w/o cutting running power significantly. They were a predecessor of the clutch pulley, which was replaced by the electric fan.
Is this a newer style 350 that came with a serpentine belt and you retro-fitted it with the older style V-belts ? or vise-versa
Your water pump may be turning backwards.
And if the water pump was/is turning backwards so was the fan.