I've tried everything: an oversized 26-inch aluminum radiator, a Weiand high-flow water pump, numerous thermostats (high-flow, low-flow, 160, 180, 190), and three electric fans (the last being a Flex-a-lite 3,300-cfm). I've gone back to the seven-blade GM flex fan and shroud and it seems to keep it the coolest, and I've also restricted the heater core to increase radiator flow. I can't determine if it's airflow or coolant, as it definitely benefited from both of these.
The car has stock pulleys, and I was thinking about altering or restricting the water pump bypass or adding a pusher fan. I'm out of ideas. Please help!
Heidelberg, ON, Canada
We had similar problems with my dad's '55 Chevy with a 468 big-block. Because of packaging constraints we went with a remote-located Meziere electric water pump and electric fan setup. This finally took care of the slow-speed build of temps. We don't think you're there yet.
The Flex-a-lite 3,300-cfm fan arrangement should have taken care of the airflow requirements at idle. Is it possible that the air is recirculating back in front of the radiator, feeding hot air to the radiator over and over? Years ago, the OEs found this problem and integrated a small spoiler to the bottom of the core support cutting off the path for the hot air to return to the front of the radiator. Without making any other changes to your system, we would create a simple (cardboard) spoiler to attach (duct tape) to the core support. Since the overheating problem is while the car is in traffic, you should be able to do this test in your driveway.
Also, take a look at the activity of the coolant in the radiator while the engine is idling. Of course, do this on a cold startup so no one gets hurt. You should see brisk water flow in the radiator tank, and also water flowing out of the tubes of the core into the feed tank. You'll need to watch the tank and feel the upper radiator hose to know when the thermostat has opened. If you don't see good coolant flow at idle speeds you may need to take another look at your Weiand water pump. Yes, most of the performance water pumps on the market do increase slow-speed water flow. Sometimes parts can be built out of tolerances, and it may flow well at higher engine speeds but have low flow at idle.
You'll find a solution to your heating problem. We really like what you've already tried. Restricting the water bypass will help. You can completely block the bypass and drill a couple of 3/16-inch holes around the perimeter of the thermostat. This not only gives enough water flow for cold start, it also bleeds out all the air in the cooling system when filling. Find that problem soon so you can enjoy your Camaro.
Bleed Baby Bleed
I did the Hotchkis upper control arm upgrade on my '78 Chevy Malibu and have had a soft brake pedal ever since. Now my emergency brake light is on. I have the stock drums in the rear. Do I need to change my master cylinder? Or is there something else? Thanks for your help.
New Bern, NC
When you installed the Hotchkis upper control arms, did you remove the calipers, or did you just support them out of the way? It sounds like you had to remove them and didn't properly bleed the brakes (remove the air from the brake hydraulic system). When you have air in the system, you will have a soft or spongy brake pedal. Your emergency brake light is on because the distribution valve down on the framerail has shifted, which turns on the light. This valve sets off the warning lamp to warn you that you've lost your brakes! Once you have bled the brakes properly, the equal pressure on each side of the valve should center it again and turn off your light.