I change from a 305TBI in my 91RS and put in a 350 now it heats whenever the car is under a load (heavy acceleration, climbing up a hill, driving around down in hot weather with A/C on, it also heats up quickly when sitting at a stoplight. When the fan turns on it does cool down except when it is 90*or more outside and the A/C is on the temp slowly rises up to say 230-240.
I have check EVERY aspect of the cooling system and everything is FINE. I replaced the radiator with a BE COOL and no change. Yes, my fan turns on even tried dual perma-cools no beter than the single stock fan, airdam is new, waterpump is new 180* stat, no colapsing hoses, no air flow restrictions just a few bent fins on the A/C condenser, timing is 8*BTDC, used a block tester and no probs there. I have double and triple checked EVERYTHING!
The only conclusion I can come up with is that there is something wrong internally with the motor, but I don't know what. When we originaly put the 350 in I used a different intake manifold which was craked and water went into all of the cylinders and we bent a bunch of push rods upon initial startup. Maybe something else happend with the cylinder heads? We also adjusted the TBI idle speed, could this create a lean or rich condition and cause it to run hot?
I am completely lost and don't know what to do. I am about ready to rebuild the 305 and put that back in and HOPE it cures my problem!!!

 

Where is your timming set? And did you unplug the brown wire when you set your timming? Also, chekc the bottom rad hose when hot, & top. See if they are both hot. That will tell you if you have flow. If not, simple thermostat. Thats' all i can think of for now.

 

first off if your depending on your dash gauge for the temp readings you may be chasing your tail 230 to 240 doesn't sound that far out of spec., my bird with a 305 usually runs about 220 or so without the air on, those things are nortoriously wrong. if not, then let me ask you, what kind of belt set-up are you running (I.E. serpantine or V-belt), if your running serpantine and you bought a regular water pump then it may be running backwards or vice-versa if you are running a V-belt system.

 

I know that Camaros run hot but I mean that this thing will rise in temp about 30* in under two minutes, when the fan kicks on this takes about 5-10 minutes to cool it down. That can't be "normal". The temp guage is accurate within 5* I have verified that. As for the waterpump (I have sepentine belt) it is the right one because the pulley mounting holes on the waterpump hub is a different size between serp and V-belts, thier not interchangable.
When it is say 90* outside and I have the A/C on and I get on the freeway the temp will climb up from 180 to 220 and it will not come back down even at driving 80 mph. If everything is working normal the temp should start to drop right away at freeway speed not stay around 220*?

 

MAYBE AN OIL COOLER WOULD HELP A BIT. i KNOW IT WOULD NOT HURT. YOU MAY ALSO WANNA PUT ANOTHER FAN SWITCH IN THERE SO YOUR SECONDARY FAN COMES ON EARLYER IT MIGHT HELP ASWELL. BUT IT SHOULD FOR SURE COOL DOWN WHEN YOUR ON THE FREEWAY i WOULD GET UNDERNEATH THERE AND MAKES SURE YOU DONT HAVE AN OVERBEARING AMOUND OF BUGS STUCK IN THE FINNS. OTHER THAN THAT I HAVE NO IDEA WHAT IT COULD BE. BUT I REALLY DOUBT ITS INTERNAL CAUSE IF IT WAS INTERNAL YOU WOULD BE HAVIN ALOT MORE PROBLEMS THAN THAT.