Dropped a new 290 h.p. chevy crate into the 84 Z. Had overheating troubles with the 350 going out. Have a 2 row aluminum radiator, air dam, correct thermostat. So, it's 90 degrees out there and I'm rolling at 65-70 mph for about an hour and temps bounce good at 185-195. It's when I stop and idle that the needle starts to climb. No way I could roll down Woodward with all those other monster machines .Why don't they over heat? Tried a single fan on the last 350 in that car with no improvement. Guess I well have to change my driving habits and stay off the freeway. Just bounce around town. Damn.

 

What temp are you reaching and what fan switch do you have in. When you are stopped the car will heat to the switch point eventually and then stay put when the fan comes on.

 

Tx for reply but car does not have electric fan. had a single Black Magic on previous 350 in this that did not seem to help. One thread suggested a double fan eased his overheating. But heck already have 5000 into this swap AND they neglected to add trans fluid so there's another $2000. Well double check the fan clutch.

 

Verify you're ACTUALLY overheating. I had a similar problem where the temp on the dash would climb, but it turned out that the gauge was just reporting incorrectly since it was getting heat soak from the ambient air above the exhaust manifolds when I had it in the head. When I moved it to the intake manifold it got better. Still influenced but the ambient air, but it was better. The Holley ECM was reporting the actual, consistent temp.

Also make sure your fan is spinning the correct direction

 

Id look into an electric double fan setup.

 

Or any electric fan for that matter. The mechanical fan only spins as fast as the water pump, so when you're basically parked, and you need it the most, it's barely spinning. Alternatively you could try and overdrive your water pump.

 

Do you have a shroud around that fan? Makes a big difference. So you can drive at speed with no problems but you overheat at idle. That sounds like it could be low coolant or air trapped in the system or even a sticky tstat if not the fan.

 

Scooter is right the stock gauge sucks with a factory fan switch 235F my gauge would be way in the red while my after market gauge and IR temp gun would show 235 when it came on

 

hey thanks for the replies. Yeh fans rotating right direction, have shroud, have dam, have $16 thermostat, have heater core delete ,fan clutch good. using Evans high boil coolant in 2 row aluminum radiator flushed and pressure checked. 290 h.p. crate with performance intake and shorty headers. Temps are good while cruzing but at the first stop light the needle climbs to 230 and she stalls out won't start again till it cools down. ??? A heat soak condition I hear about. and would you recommend a dual fan that well adapt to existing radiator.22 year owner of this 84ZZZ TX again.

 

That's a head scratcher you have there. I have seen this happen before with head gasket failures but the overheating wouldn't be the only symptom you would see. So, from what you have said that doesn't sound likely. It shouldn't be difficult to cool that engine. Your fan/shroud are factory pieces? You sure you have full coolant and the system is bled completely? Just shooting in the dark now but how about the water pump? Is it a CW or CCW rotating backwards maybe?

 

I will assume the radiator is in good shape/flushed/fins in good condition.
After verifying the temps like Scooter says...

Is the fan diameter sized correctly to the shroud and at least partly 'in' the shroud?
What carb and how is it set up?
What is your timing set at?
Are you running a vacuum advance?

 

Do you mean the Waterless coolant?

 

Are you only using the factory gauge? Under 200F my factory gauge seems to work decent but after that it seems about 20F above my aftermarket one / IR temp gun. Take some pictures of your setup maybe we can notice something. Other than that all I can think of is maybe reverse water pump.

 

I'm going to point out a few possibly easier, less thought off things to check as i've seen them before, but don't take it as me calling anyone stupid. If you have AC, have you checked between the radiator and condensor for crap being built up, as that will cause the radiator to not cool as well. The other easy thing to check is coolant flow. If you pull your radiator cap off (be super careful and do it super slowly if the engine is hot and it's not really recommended) and start the engine and make sure that you can see the coolant move pretty good. If there's no movement, your water pump is probably shot. It will be more evident with the thermostat open and the engine at operating temp. That's the easiest way i've found to check how well the water pump is working. Also, what temp thermostat did you put in it?? Stock? 180? 160? When was the last time you checked/replaced your radiator cap? If the spring in it is weak, it won't put as much pressure on your system and that will drop the boiling temp of the coolant. Also, old radiator hoses won't keep as much pressure on the coolant and do the same thing.