New Info-
I recently rebuilt a stock 3.0 with Comptech cams, adjustable cam gears for degreed and changed centerlines, 3.2 head gaskets, headers, Intake manifold mod, and an AEM for tuning. It’s no super hot turbo car, but it does have 10.7:1 compression with the gaskets and makes about 300-rear wheel. This dyno run had the coolest water temps of any I have ever encountered, including stock rebuilds. The car has a larger radiator (Not quite Ron Davis size), but in the past I have seen little temperature reduction with larger radiators at a dyno. Not enough air flow.
Changes that may have contributed to the good temps-
Mugen low temp thermostat.
The heater core water routing is now plugged at the engine and the front hose, rather then using a bypass hose to jump from the inlet hose over to the outlet hose by the battery. The heater core has a valve to stop flow when interior heat isn’t needed.
When installing a Comptech oil filter adaptor for an oil cooler or an Accusump, we usually plugged the OE oil cooler lines… But, I was thinking that the OE flow path might be needed so I ran hose for the original path, only bypassing the OE cooler.
All of the above are low cost modifications and seem plausible for temp reduction… but!
My gut says that the most likely solution was my new vacuum coolant tool. This tool is one I read about that helps the widespread import problem of getting all the air out of your coolant system, especially rear engines. I first used it on this car and now I will use it on every coolant system fill.
Coolant tool-
It’s a simple gun with a rubber cone, a gauge, a trigger, a valve, and a long clear hose. You plug your compressor line into it, and run the clear hose to a clean 5-gallon bucket with mixed antifreeze. The cars coolant system needs to be drained first. Then place the universal rubber cone over the coolant filler opening (The one your radiator cap was on).
The first thing it does is draw a vacuum in your coolant system, keep the trigger pulled for a minute or so until the gauge reads it’s highest vacuum. (The trigger has a latch so you don’t have to hold it). The vacuum actually collapses many of your hoses… this is normal. Release the trigger and the air line, then let it sit for 2 minutes to see if you have any system leaks… sure enough I did, on one of the large radiator hoses in the front and one small hose that runs from the engine to the filler bottle. I replaced the clamps with high quality stainless steel clamps (The ones with serration gears are stronger then the ones with open cut gears). If you have the time and budget, it’s not a bad idea to replace all of the OE clamps, as they defiantly don’t clamp as strong. Now that the system holds pressure and wont likely leak or introduce air. Reconnect the air line and draw vacuum again, then slightly open the valve to draw some coolant up the clear hose to purge any air in that hose. Close the valve, draw max vacuum, disconnect the air line, and open the valve. The vacuum in your coolant system draws the antifreeze into it, eliminating any chance of introducing air or having air trapped somewhere obscure like the water pump. I add 10% more coolant to the 5 gallon bucket so I have no chance of sucking air.
Even if you were to purge all of the OE bleeders, it would be difficult to get all of the air out, especially in aftermarket radiators that don’t have bleeders at the highest point. Any air that made it to the water pump would cause cavitation and would reduce your water flow.
Soon I can test these methods on a much higher performance engine, and I have a few more ideas just in case.
