Patrick what temperature are you trying to achieve. 180 is a good running
temperature, even 200 on a hot day like you have is fine. Run Mobil 1 and
forget about it. If you're running high compression than a higher Octane is
needed. Also what's your timing set at? More advanced the hotter it will
run, also are you running too lean... just my 2c
Good Luck,
Wayne
> This whole process was taken on because of the difficulty that I have
> experienced in getting my 1.6L, 67.5 Roadster to run in the temperature
> range in which I had expected. Understand that I live in central Texas,
> where it is not unusual for the air temperature to run over 100 deg. in
> the summer.
>
> First, a bit of "how the cooling system is supposed to work" theory.
> The water in the engine pulls combustion heat out of the cylinders and
> head. The thermostat controls the water flow rate through the system
> to allow the engine to get up to operating temperature more quickly
> and then control the temperature of the engine once operating temperature
> is reached. The radiator gets rid of some of the engine heat as the
> water flows through it. If an engine produces more heat than the radiator
> can get rid of, the engine temperature will rise. The amount of heat
> that the radiator can get rid of is generally more than the engine can
> produce, thus allowing the thermostat to control the engine temperature,
> rather than the radiators dissipation controlling engine temperature.
> The heat in the radiator is gotten rid of by airflow through the fins
> on the radiator. When the vehicle is stopped, or traveling less than
> about 20MPH a fan is required to move the air. This fan may be either
> electric, or engine driven. On most vehicles the ram effect of air
> entering through the grill produces enough air flow to get rid of the heat
> without a fan. This ram effect is not enough on our roadsters to cool
> the radiator!
>
> I have experienced over temperature conditions on my roadster since I
> bought it. I have cleaned the radiator, replaced the thermostat, and
> hoses. The factory scoop is in place at the bottom of the radiator.
> None of these changes produced acceptable temperatures.
>
> I tried replacing the engine driven fan with an electric fan, but it
> didn't
> help, on fact, the temperature rose a bit. (No fan shroud). I tried
> both pusher and puller mounting, but the 14" fan just couldn't keep up
> with the cooling requirements. The electric fan was on a thermostat that
> was set to turn on when the radiator inlet temperature reached 190. On
> the road the temperature would still run about 190, with it dropping
> slowly
> at stoplights. I finally bypassed the fan thermostat and that allowed
> the fan to get a bit more control over the heat, but it still didn't
> supply
> enough cooling.
>
> When I turn on the heater (fan on high) the engine temperature drops about
> 10 degrees. This seems to say that the radiator is not dissipating enough
> heat for whatever reason. It may be that the radiator is crudded up, not
> enough heat transfer area, or the air flow through the radiator may not be
> high enough. I removed the 3 row radiator that was in the car when I
> bought
> it and replaced it with a high efficiency , 2 row radiator. This change
> brought the temperature down a few degrees, but still not enough.
>
> I tried adding an air dam between the radiator and the cross member to
> cause
> more air to flow through the radiator, rather than around it to increase
> the
> ram effect, but it didn't help.
>
> Next I replaced the water pump. The original one was from Auto Zone. I
> installed a Datsun pump and the temperature dropped another few degrees.
> (Generally, I wouldn't have done this because I figured that the problem
> was external to the engine because of the temperature drop when the heater
>
> was turned on, but the rear pump cover gasket started leaking so it had to
>
> come off any way.)
>
> I removed the electric fan and re-installed the engine driven 7 blade fan
> with fan shrowd and the temperature came down to about 180!
>
> The temperature would stay at 180 solidly in all driving conditions except
>
> when the temperature was above about 104, a bottle of water wetter took
> care of that!
>
> Water is a better heat conductor than antifreeze, so the lower
> concentration of
> antifreeze the better the heat conduction. Redline recommends an
> antifreeze
> concentration as low as 15%, so I set mine to protect to +20 degrees -
> remember, I live in Texas and we don't see really low temperatures here in
>
> the winter!
>
> The only thing that I don't like about this configuration is the amount of
>
> noise the fan makes. It shounds like the 240Z I used to own! I really
> liked
> the lower noise lever of the electric fan! I may try replacing the 7
> blade
> fan with a 4 blade fan to see if it still provides enough air movement
> while
> reducing the noise.
>
> Today it was 112 and the engine temperature sat steady at 180, whether I
> was
> running 65 down the road, or sitting at a stop light. Things are now MUCH
>
> cooler in Texas!
>
> Other things that may be causing excess heat:
> I don't know how much crud is built up in the block. I bought this car
> a year ago and have no idea how much time is on the engine.
>
> The head has been milled past the limit. The compression ratio is very
>
> high. This could cause higher combustion chamber temperatures than
> normal.
> I have another head to put on the engine, but haven't gotten to it yet.
> Maybe next week I 'll get to it.
>
>
> --
> - Support Habitat for Humanity, A "hand up", not a "hand out" -
> Pat Horne, Network Manager, Shop Supervisor, Future planner
> CS Dept, University of Texas, Austin, Tx. 78712 USA
> voice (512)471-9517, fax (512)471-8885
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