Keeping Your Cool

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While performing the partial rebuild of my Triumph GT6

I experienced a number of problems to figure out. One

such issue was an overheating problem I encountered.

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When I first took possession of the car, it ran rough but

did not overheat. My long list of 'fix and repair' items included the removal and cleaning of the radiator and flushing of the engine block water jackets. While the radiator and coolant all looked good, replacing all fluids was a basic part of my strategy. So, with a clean radiator and fresh coolant, why was my car suddenly overheating?

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It was painful to hear a nasty gurgling sound when I turned off the engine. I lifted the bonnet to witness boiling water filling the overflow bottle to overflowing. Yea, boiling water means a hot running engine and engine oil breakdown. Not good!

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It must be due to something I did. I tend to dismiss coincidences such as the thermostat or water pump suddenly malfunctioning. This overheating problem materialized after having performed so much work. This included removing the engine block, rebuilding the dual carbs, upgrading to an electronic ignition system, adjusting the timing, and rebuilding the mechanical fuel pump. Arg! What could it be. Still, I can't dismiss something suddenly failing like the thermostat or water pump. 

Research led to the usual suspects (thermostat, water pump, radiator cap) including one expert indicating a carb running too lean could cause overheating. Kinda runs against what you'd think. My first troubleshooting was to remove the radiator cap, start the engine, and see when and if the thermostat opened-up allowing water to flow into the engine block. All seemed to work properly. Hmmm...

I next adjusted the carbs to a richer setting. Not only did the engine run rough and idle poorly, it still overheated. So, I pulled out my wallet and purchased a new water pump, thermostat and radiator cap. I replaced the thermostat and inspected the old one. It looked to be in very good conditon. Alas, the engine still overheated. Not frustrated yet, but I was getting anxious.

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And then it hit me like a brick. The timing. I set the timing according to what the owner's maual called for- 13-degrees BTDC (before top-dead center). I sorta have photographic memory and remembered seeing 100 octane. To advance the timing that much called for fuel with an octane rating that was common in the 1960s, but no longer. Not unless you want to pay $10/gallon for race fuel. Even then, you will only get 98 octane from your local gas station that sells race fuel.

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I have a smart friend, Chuck, who explained engine timing to me. That understanding allowed me to figure out the source of my overheating problem. Timing that is too far advanced can enter pre-ignition or detonation. When this happens your engine will start to overheat. Detonation contributes to overheating. So, I reset the timing to about 6-degrees BTDC. Not only did it improve the cold start-up and warm idle, it solved the overheating problem.

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It was both a relief and quite satisfying to solve this thorny problem. So many people lay out hundreds of dollars on hi-flow radiators, oil cooling systems, auxiliary electric fans and other parts and still experience a overheating problem. That's gotta be frustrating. While I did spend a few dollars on a water pump I did not need, at least I have that spare part on hand when my 50-year-old water pump finally does fail. 

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Overheating problem? Be sure to verify your timing is set right.

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