350 S/B "Over Heating" UPDATE

On a previous post I asked your help for ideas on how to diagnose my 350 S/B "over heating" and VDO temperature gauge problems. Several of you gave me some good ideas on "obscure" things to check and he's my progress report.

Per your advice....I richened up the idle circuit on my Edelbrock #1406 carb with a metering needle and spring change.

Several of you suspected the thermostat was faulty....As a test, I replaced the 195 degree thermostat with a Moroso flow restricter three disc set. First, the large hole one and it worked "too good", no more over heating, but the gauge would not even move unless I disconnected the electric fan and left the engine idle for an extended period. Then I tried the middle size. I think I had several things going on at the same time but this one change made the largest improvement. I do not plan to use the flow restricter disc as a permenent fix, I will install another thermostat most likely an 165 degree with the "fail open" design, since I normally run a "smooth no vent, no louvers hood and sides" on this Roadster.

I've always used a quick test of grabbing the "alternator pulley fan" to determine if the fan belt is tight enough. If you can't turn the pulley fan, then the belt is tight enough. Well.......This car has a custom alternator mounting bracket that mounts the alternator above the left head to make the engine skinny enough to clear the 1932 Ford hood sides. The problem is that the alternator pulley has about 270 degrees of fan belt wrap but the water pump has only maybe 15-20 degrees of fan belt wrap. You could take a screw driver and put it on two of the water pump pulley bolts and turn the pulley with very little effort. Cure was to tighten the belt just a little.

I relocated my VDO Temperature sender to the right side of my Edelbrock manifold. The right side is drilled at a 45 degree angle and It looked like it would be less prone to allowing an "air pocket" to be around the sender bulb like could have happened the way it was originally vertically mounted on the left side. You also told me about how the adapter bushing could shield the sender's bulb. I drilled out the sender adapter and retaped it deeper with a 3/8" NPT tap. This allowed the sender bulb to be located deeper in the coolant flow and not in a "air pocket". I also removed all traces of teflon tape and sealer. Just a dab of antisieze and screwed it in. So far it's working perfect without any fluxuations in reading.

The engine runs so cool now that I have unplugged the fan relay and might go with just a dash switch to use the fan only when its needed in stopped traffic. I've never had it connected to a "temp sender" relay.

Does anyone know the brand of the thermostat the has the "fail safe" open position which someone mentioned. I think it's what I want to try next.

Thanks so much for your help.
John Palmer

I wouldn't run the cooler thermostat. The hotter you can run your engine, the less cylinder wear you will have.

the lowest thermostat you should run is a 185, although i run a 195 in all my cars. A 160 will never close and then the fluid in the radiator doesn't get a chance to cool so heat will keep on building.

Actually, the hotter you run your engine, the more efficiently it cools. The coolant coming out of the engine and into the radiator will be hotter which means there will be a greater temperature difference between the fluid and the outside air. The temperature difference is what pushes heat from the coolant to the outside. Putting a 160 degree thermostat in a car will not fix an overheating problem.