P15 with a 350 Chevy - Cooling System Questions

[kbuhagiar]

Hello Folks,

I am in the process of tweaking the cooling system on my 47 Plymouth (with a 350 Chevy engine). The first thing I would like to do is verify the accuracy of the water temperature gauge, which is the stock factory mechanical unit. The engine side of the gauge is threaded into the driver's side cylinder head.

I will be using a hand-held infrared thermometer.

Question - should I check the temperature right at the head, where the gauge is connected? Or should I check it at some other location?

Also, I would love to hear from anyone else who has a 350 Chevy installed in a P15; I'm curious to hear about your cooling system configuration & modifications, and what you consider a 'normal' operating temperature (mine will idle, with both fans going, at around 205-210, according to the gauge).

Thanks in advance!

[hkestes41]

The Coolest System would be to replace the 350 with a real engine like a 340 or 360.

Other than that, I would remove the radiator cap and measure the temp of the coolant in the radiator tank. That should give you a good indication of the accuracy of the gauge. The temp of the coolant in the head would be a little higher just due to the fact that it is nearest the heat source, but there should not be a significant difference.

[BobT-47P15]

If you can pull the bulb out of the engine, and have room to get to it

with a container of boiling water, you could stick the bulb into the

water and see if the gauge is accurate at that temp.

Boiling Points for Water at Standard Pressure

100 degrees Celsius (or Centigrade)

373.15 K (kelvin)

212 degrees Fahrenheit

[homebrewer]

Mine has air conditioning and at freeway speed would run right around 200 on the stock gauge with the air off. Got up around 210 or so with air on. I used a slightly modified P 15 radiator with a 3 lb cap and a recovery bottle made from a windshield washer reservoir. This was on days in the 90's with an electric fan set to come on around 180. I added an aux. temp gauge and the temps were just about the same. I did a lot of research on cooling, proper running temps etc. I got as many different opinions as I got answers. I bought a Walker radiator with built in AC coil and changed the electric fan to one with higher output. put on a 7 lb. cap. I noticed about a !0 degree difference. I personally do not think it was worth the extra money. In my opinion, these chevy's should be able to run 210 - 220 with no problems as long as you are not boiling the coolant out of them. I have to state that I haven't done any mtn. driving or climbing, so I don 't have a clue as to what this would do to the temps. BTW, I run 70% water 30% antifreeze and 16oz of water wetter in mine. Hope this helps, Good Luck, Geoge

[Don Coatney]

I will be using a hand-held infrared thermometer.

Question - should I check the temperature right at the head, where the gauge is connected? Or should I check it at some other location?

Is this hand held infrared thermometer a one time use device or can you check the temperature at more than one location? If it were me I would check the temperature at several locations to see if there is a hot spot.

Edited November 16, 2010 by Don Coatney

[chopt50wgn]

Sending unit temp gauge in the head will likely give you a higher temp on the gauge. If you are using an infrared temp gun, take temps in the radiator, head,and block.

Remember the sending unit ,if it's in the manifold at the front near the radiator outlet, you are also gauging coolant at its highest temps as it is leaving the motor.

[Plymouthy Adams]

set the tank on fire first to calibrate the temp gauge..got to have a valid reference point

[blucarsdn]

I have a '39 Plym conv cpe with a Chevy 350 CID 330 hp Vortec, 700R4 trans. GM 10 bolt diff w/323 gears.The car has AC. The radiator is a Davis Racing 3 row aluminum cross flow that we stood up. The fan is an electric unit that has it's own shroud.

I know, I should have used a Mopar 318/360 HP, I wish I had, however, at the time we were planning the power train I could not find any info about Mopar engines other than guys that thought, if it does not have an early Hemi V8, it ain't worth running.

I am running a 195 thermostat and 16 lb's pressure cap and a verticle alum puck tank.

My engine sits at a constant 200, winter/summer.. On a steep grade the temp will rise to 210, this is not a problem because with a 50/50 mixture of coolant and 16 lb's of pressure the boiling point is above 280 degrees.

A modern V8 engine, anything after about 1979, is designed to run at 200 degrees, running them at colder temps creates engines that run rich, cause emissions and sludge in the oil.... Bill

[Rodney Bullock]

I was told that if you us the infrared first point the beam at the thermostat housing. Then take the reading then poit it at the lower radiator hose, note the reading then point it at the radiator head. The numbers will fluxuate. the numbers should be lower at the lower radiator hose. this is the water returning to the motor. The radiator head should be second coolest. Just for good measure I would test the water pump as well. I would never put the beam on the sending unit as that is screwed into the head. The cly head is going to be hot no matter what.

[kbuhagiar]

I was told that if you us the infrared first point the beam at the thermostat housing. Then take the reading then poit it at the lower radiator hose, note the reading then point it at the radiator head. The numbers will fluxuate. the numbers should be lower at the lower radiator hose. this is the water returning to the motor. The radiator head should be second coolest. Just for good measure I would test the water pump as well. I would never put the beam on the sending unit as that is screwed into the head. The cly head is going to be hot no matter what.

Thanks for the input!

[53_Suburban]

set the tank on fire first to calibrate the temp gauge..got to have a valid reference point

It takes a Mopar to burn a Mopar

[Don Coatney]

I would never put the beam on the sending unit as that is screwed into the head.

Why??? Is it not important to know that temperature? Afraid you will break it? I shoot everything on my engine after I have calibrated my unit not necessarly using Tim's meathod. All 6 spark plugs top and bottom, coil, ballast resistor, distributor cap and all wire connections, oil filter top, middle, and bottom, freeze plug on the head and side of the block, radiator hoses top and bottom, thermostat housing, water pump, radiator top and bottom, base of both carburetors, top of both carburetors, fuel line before and after the fuel pump, both the intake and exhaust manifold, water hoses going to and from the heater, wheel bearings, brake rotors, etc.

A hand held temperature probe is one of the best diagnostic tools one can own. Works on human body parts just dont probe your eye:rolleyes: