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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. 

He would:

  • 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...





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  • shootfoot
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When I used to mess with Corvair engines this was a big issue, the engine has a horizontal fan on top and many an owner had a grease rag left on top of the engine get sucked down onto the heads and cylinders to create an over heating issue that would drive a novice crazy. We were always telling guys to look in the turkey baster for loose rags. The fan shroud looks like a Turkey baster. Thanks for sharing you story. It happens more than we would like on our aircooled beauties.

A friend of mine recently told a story about a flat track racer who, like many people, would keep debris out of the multiple velocity stacks by stuffing them with shop rags.  To make a very long, and entertaining, story short; more than one rag got sucked into the engine when they fired it up.  

In the end it was all for naught...after hours of picking out rags in the pits the driver promptly turned right instead of left in the first turn.

You can’t win for losing.

These instances are one of the reasons I spend far too much time trying to find a single washer, bolt, or nut that I drop but never seem to hear hit the garage floor while working under the hood.

@edsnova posted:

Glad you found it Mike and sorry it took so long. Question. You wrote "Dashboard temperature gauge (oil relief) reads steady, but the oil sump sensor reading jumps from 180F to 300F depending on engine speed and temperature."

Why would the dash gauge not give you the correct oil temp reading in this instance?


Thanks, Ed. Actually, I think both are "right," but they are two different sensor locations and two different methods of measurement. The dash gauge (914 multi gauge) is just a magnet-wire needle like most of our gauges. I would bet that there's a lot of inertia to the movement and it gives the average reading over a second or so. The oil sump sensor is read by a Speeduino ECU at a fast sample rate (e.g. 180ms between discrete readings). I think the Hoover Mods push a lot of oil into the heads and external cooler circuit. That makes it easy for a hot spash of oil squirting out of the oil returns to raise the sump sensor for a short time.  

That's my theory. I will double check it when I get the deep sump installed and will also try switching around the wires on the sensors. It's always possible that the Speeduino sensor has a wiring flaw that adds the jiggle. Since the dash gauge matches well with my dipstick temperature measurements, and since the Speeduino matches the dipstick when I turn off the engine, I'm pretty sure I'm correct on the oil temp. Figuring out the Speeduino jumpiness will happen, but doesn't worry me a lot. You can actually set the sensitivity of the Speeduino gauges. I'm interested enough to study it a little more before I resort to that.


"Adventures in Speedster Ownership Volume 2", where our intrepid owner learns to ban all paper towels and shop rags from his shop. 

Good find, Mike.  Hope they've got some great craft beer there to celebrate with!

Absolutely correct! They actually do have a fantastic brewery a couple of miles down the road from us. They've always got a lot of interesting short-runs to try, but my go-to favorite is Big Swell IPA. Marianne prefers Bikini Blonde :-)

Wow, Mike your story reminds my own car chasing a lean mixture for two full seasons and another one on my house reno where the electrician pulled his hair out for 2 days tying to find why pot lights were not functioning with his new wiring on the reno. He left and promised to send me someone else who was better at trouble shooting.  

A night later,  I went to bed fell asleep then suddenly I woke up and it was 3 am, I must have been dreaming, and I had one thought ringing in my head, "GO DOWN AND SCREW IN ALL THE BULBS"  I don't dream much so I obeyed the thought.

I got up went down stairs turned all the bulbs on, hit the switch and Jesus take the Wheel, they all worked.    I was so shocked but very thankful. 


FYI, I never heard back from the electrician.


I once had to replace the fuel filter on 351 Cleveland on my '73 Mustang Convertible.   It was a pain...  I didn't want to remove the power steering pump, and the fuel pump was on the outside of the engine block, right inside the PS pump.   I could barely get a 1/2" wrench in between to turn the nut about 1/16th of a turn.... flip the wrench and make another 1/16th turn... repeat for 30 minutes while your hand cramps up.  Only to repeat the process in reverse to tighten the nut on the new fuel pump.

But the new pump worked, so I guess it was worth it.  A week later, the same symptoms appeared, and I thought, "Great... I got a bad fuel pump from China."   So I ordered another fuel pump.    But then waited a few months to swap it because I didn't want to go through the whole 1/16th of a turn routine again.

I finally got enough gumption, and crawled underneath to disconnect the fuel line that leads to the pump (gravity fed).  I had a broken off golf tee ready to shove into the fuel line to cap it while I worked on the pump.   I was surprised when no gas came out.

Turns out I had just run out of gas this time 

The car sat in my garage for 3 months and it was just out of gas.

Last edited by Jethro

So I just spent about two months chasing a fuel starvation problem in Bridget, my Subaru-powered TD replica. I'd back out of the driveway, put her in gear to move out and she'd fall on her face, then stall and not want to re-start. More than once I had to use the INI starter to pull the car back up the driveway into the garage.

Now, when this all started, it was the new spring season, and I had a good idea what the problem was: Late last October when me and the boys hit our annual PCA Air & Auto Classic in VA Beach, the rubber gasket under my fuel cap was breaking up. So I peeled it off. One of our number, Dale Schumacher, helpfully offered up a spare gasket. I put that on and forgot about it for two days until I gassed up for the 250 mile drive back to Joppa and found IT HAD DISAPPEARED.


Pins and needles all the way home, waiting for that thing to screw me up on the highway.

It never happened. I got home, parked the car, put the battery tender on it. But I did not forget.

Part of me thought the thing might have disintegrated. But when I had trouble in April I thought, "A-HA!" I dragged the tank with a bent coat hanger and turned up nothing.

Later I emptied the tank, put the fuel in other vehicles, inspected inside with a small light, shook the tank, cleaned it with brake Kleen, again raked it with a coat hanger and probed with another little hook device. And re-set the fuel hose nipple on the bottom of the tank.

Nothing in there. So, having eliminated as a possibility the obvious culprit, I replaced the fuel filter. Then I tested the fuel pump and got 30 lbs which seemed a little low. Easy fix; got another one. Installed it.

It was DOA.

Took that back, ordered another. Also again replaced the filter just before the pump, and the Subi high-pressure filter the goes in line after it.

Drove the car 2 miles to the gas station and back and that worked fine.

Next time I went to take her out it was the stall-at-the-bottom-of-the-driveway scene again.

I re-tested the fuel pressure. 32 this time. I went up the line and started eying the fuel pressure regulator. Unplugged the vacuum hose to that and the pressure went up and the engine surged, as it's supposed to. 

I cleared the lines. I blew air back up into the tank. I took the car out and sometimes it ran fine around the block. Sometimes not. I noticed the fuel filter before the pump had air bubbles in it. One time it looked like it had collapsed. So I replaced it.

Thought about the return line, maybe blowing bubbles in the gas tank like a fish tank aerator. It had never caused an issue in the 6-7 years I've used it, but I fashioned a bit of hard line to carry the fuel down to the bottom of the tank, just in case.

I took the car the long way around the neighborhood and it stalled about half a mile from the house. I pulled into a neighbor's driveway. Looked at my empty fuel filter. Scratched my head. Called AAA. You can't ride with them due to COVID so I called my wife too.

I pondered.

Finally while waiting for the flatbed I unplugged the hose under the filter and gas filled it up. So I plugged it back in and the car started and ran. Drove home. Called AAA to cancel the tow. Pondered some more.

Neighbor suggested a pinhole leak above that first filter, allowing the pump to suck air, but not enough to leak gas. I pulled the tank again and changed that section of fuel line.

Test drove. Still saw air in the filter. Saw the fuel level in the filter drop.

Maybe there was just like air trapped in the fuel line above the pump?

Screw it. Ordered the fuel pressure regulator ($120) and installed.

I test drove again to the gas station. She stalled on the way home. I fixed it again the same way as before, un-plug, re-plug the hose.

Now the wheels started to turn. 

Every element of the fuel system had been changed. Nothing improved the condition, which was intermittent. After it stalls there's no fuel in the filter. Given time, or an unplug-replug of the fuel line, the filter fills back up with fuel and you can go for a bit.

I pulled the fuel sender again and shined a light down in the tank.

There, at the bottom, was that opaque gasket that disappeared in October. It was poised to again block the fuel outlet. I fished it out.

You'll be unsurprised to learn that the car has run fine ever since.


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  • mceclip0
Last edited by edsnova

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