Submitted for your approval, the case of one Mike Pickett, who against all odds solved a mysterious overheating problem in his little plastic clown car, perhaps saving you from the agony of extended trial and error in the future.
Our story begins a few weeks ago, shortly after Mr. Pickett installed the shiny new Panchito heads on his 1776cc, dual ported, fully flowed, type 1 engine with the external oil filter, external oil cooler with thermostatically controlled flow and fan, full engine tin, dual Kadron carbs, electronic ignition, HVX mods, 1.5” exhaust, oil temperature sensors in the oil relief (for dash gauge) and in the sump cover (for Speeduino ECU electronic logging). Everything seemed really peachy for a week or so. Mr. Pickett suspected that he could run leaner main jets based on the early A/F readings he logged after installing the new heads. 130, 125, and dare we, 120 main jets were tested while swapping 55, 50 and 45 idle jets to find the elusive Kadron sweet spot of A/F mixtures on cruise and a relatively hesitation free transition (turns out at sea level it is 130 mains and 50 idles).
Alas, as the summer solstice approached, Mr. Pickett noted a significant uptick in the dashboard oil temperature gauge. Just the change of seasons, he reasoned. To his dismay, the oil temps continued to climb each and every time he drove the car, be it during the afternoon tropical sun, or in the cool breezes of early morn. Curses, he thought, there's a problem. It wasn't that Mr. Pickett didn't enjoy solving problems, it was simply that he seemed to have been involved with that activity for quite a long time and would rather have a short respite.
Nevertheless, as needs must, Mr. Pickett went back through the changes he'd made in the last 6 months and undertook a program of tests and data logging to remedy the overheating issue.
He thought, "what are the symptoms:"
Engine runs hot reaching up to 235F. It normally rose to 180F and no further prior to a recent rebuild. The engine comes up to running temperature within 10 minutes and then keeps rising. Driving slow or fast doesn’t make a difference. This began to show up shortly after completing HVX mods and installing Panchito heads. Hot air exits both the internal as well as the external oil coolers. Oil temperatures verified using a cooking thermometer in the dipstick tube. Dashboard temperature gauge (oil relief) reads steady, but the oil sump sensor reading jumps from 180F to 300F depending on engine speed and temperature. Oil sump sensor reading is steady and matches the dipstick temperature when the engine is turned off.
"Well," he said, "I guess I'll try:"
- Adjusting air:fuel ratio - nope
- Adjusting air flow - engine tin, pulley size (aluminum tape, 7" crank pulley)
- Adjusting oil level - overfilled the dipstick mark by 1/2 quart
- Changing oil filters
- Changing oil viscosities (10-30, 0-40, 0-50 synthetic)
- Cleaning out oil relief passage, piston & spring - no binding, but some debris found!!! Perhaps left over from the HVX mods? Perhaps there's more?
- Cleaning out oil control passage, piston & spring
- Increasing oil pressure - ran through several pressure levels up to 60 psi cold idle
- Improving air flow through external oil cooler - created longer standoffs so more air could get behind the cooler
- nope, nope, nope...
While a small amount of improvement was measured, it was clear that the main problem was not solved. So, in a spate of online ordering, replacement oil relief/control springs and pistons, deep oil sump, replacement internal cooler and lots of cans of brake cleaner were delivered. Mr. Pickett guessed that while he had properly pressure cleaned the block's oil galleys and the oil coolers, some debris must be floating around the system and mucking up the works.
- Drop the engine
- Replace internal oil cooler
- Remove the threaded plugs and flush out the oil galleys
- Flush the external oil lines and cooler and try eliminating the external thermostat
- Add additional oil capacity with deep sump - perhaps HVX mods put more oil in circulation (inside heads mostly) and the oil pickup runs dry
- Call up Pat Downs, place an order and build a new engine
Still with me? So what happened? This morning, I disconnected everything from the engine and removed the alternator and fan in preparation for dropping the engine. Imagine my delight when I found two paper towels lining the inside circumference of the cooling fan. Aaargh, I could have just stuck my hand back there and run my finger around to have checked it earlier....
We live in the tropics and get 20-30 mph trade winds almost every afternoon. I'm sure the paper towels were part of one of my fuel jet changing adventures. They must have got loose and blown behind the doghouse tin. Too much analysis and not enough luck.
I share this brief tale of foot-shooting hilarity to encourage you to keep loose paper towels on your list of suspects should your car ever suddenly begin to overheat.
What's next? Stay tuned to this bat channel for adventures installing IDF style throttle bodies and fuel injection...