Posted on: February 7, 2016

from the March 2001 Rootes Review:

The cooling article in the last Rootes Review garnered lots of comments and questions. The following letter from Bill Holden is typical of many letters and comments received. Bill’s comments and questions are printed below along with Chuck King’s and Tiger Tom’s responses in italics. Be sure to check the other tech tips in this section of the  TEAE site for additional information and plots not printed in the Rootes Review.

As an old & moldy mech engineer who took electives in internal combustion engine design along with the requisite thermodynamics, etc., courses, I greatly appreciate the extraordinary volunteer effort done by you and the Kings with the assistance of others mentioned for the disciplined and definitive Tiger engine cooling study and report. Superb effort!

I’ve run a totally stock (with perhaps a notable cooling exception) 260 MK1 A Tiger for six summers now in Virginia heat & humidity conditions that’s never puked but has had “interesting” temperature excursions at various traffic & movement conditions.  The first time I saw this happening, it alarmed me (vs. past experiences with many other cars). But after making careful examination of components (checking 160 degree thermostat; fully opens at 170 degrees which I see exactly on my gauge) and careful observations, I quickly determined that 200F will be the average running temp of this car while underway around 65mph/2500 rpm. 70mph/3000+ rpms will have me pegged at the 100 C mark. You just defined acceptable operation for a Tiger. It could be cooler but the best part is that you haven’t “overheated”.

Questions/comments

a. I totally agree that air flow thru the radiator is the #1 ingredient for engine coolant temp control.

Now you know why the article was titled” Tiger and Alpine Cooling Tales are All Hot Air”.

b. I did a before & after with Redline wetter and agree with your findings; could find no noticeable change (used RAYTECH infrared temp gun) ‘shooting’ the outlet housing over a timed period for idle conditions. I used the dash gauge for underway observations. I included reduced antifreeze mix to 20-25% with wetter per Red line’s comment about better results with less glycol.

c. I’m unfamiliar with FX or CX terms, and how these compare with the stock configuration; perhaps you can explain this in the next chapter of this effort.

Modern fin design and attachment to tubes are far superior to the OEM radiator. FX and CX are core styles that should be recognized by radiator shops. One manufacturer is Universal Auto Radiator Manufacturing Co.

d. Did you think of running tests with/without the thermostat to dispel old myths I’ve heard that “no thermostat causes the coolant to flow too fast and therefore hasn’t time to heat exchange and leads to overheating”.

Yes and we decided to test only with a thermostat because good driveability and engine durability requires use of a thermostat. If time permits, we may be able to test this summer.

e. “My cooling exception”. My car came from the West coast where a 1988 restoration occurred and the previous owner had installed new heater core. But not needing heat there and not wanting stagnant coolant in the core, latent heat, etc, the heater core not connected, he had placed a short hose looping the supply to return coolant outlets. I think this bypassed coolant to the block so I blocked/capped both these. I think I saw cooling improvement afterwards and this is the way I am set up. It seems this condition would be the same as the heater (temp) OFF position. Maybe a small point to ponder.

Chuck tested a variety of water flow configurations at idle. None improved cooling. Some made it worse. All tests were done with heater core water flow turned “OFF”. An idle on interstate test was done with the heater core water flow “ON” and the blower on high. The temperature was reduced one degree at 200 degrees during idle.

f. What preps were done for the stock conditions; How old were the components in King’s car and was system (radiator, block) specially cleaned for the testing?

Chuck and Andy’s test mule (Tiger) was a freshly rebuilt 260CI engine with 500 miles on the engine at the start of the test. The “stock” radiator was a mechanically solid radiator that was cleaned and “rodded out” by a local radiator shop. All other radiators were new except the CX core that had approximately 30K miles of use.

g. Again, great job, and thanks much.

It’s been our honor ….. TT, Chuck & Andy

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