Engine timing and temperature

So.. I have been having trouble with the motor running to hot in slow traffic, It will quickly climb up to 230 deg and ill start to get vapor lock. On the long strait away,s and high ways it will cool down to 190-200 deg. So i finally bought a 16in electric fan and a shroud from Champion, After installing them i ran it in the pole barn for 30 min or so and the temp never went over 170 deg, but when i ran it on the high way it now runs up to 230 deg and wont cool down.
I have seen some post that timing can cause a motor to run hot. My initial timing is set at 18 deg and my full mechanical timing 39 deg at 3000 rpm (18 deg initial and 21 mechanical). At high way speeds in running around 3300 rpm. My question is if i set my mechanical timing so it doesn't hit full mechanical advance till it hits 4000-4500 rpm, will that help it run cooler?

motor info
351w (360ci) approx 9.5 to 1 compression.
Blue-print engine aluminum heads
Weiand Stealth intake.
Holley 650 DP
Howards Cam
MSD Billet RTR Distributor

 

No reduction in timing from 39 degrees at cruise rpm should result in less heat production in the cooling system. On well tuned vehicles running vac advance pots or those having efi controlled timing maps.. the spark advance timing figures at light load(steady state highway cruise probably consumes all of about 45-50 horsepower worth of fuel) can be and are generally much higher(over 50° btdc) due to the much less densely packed mixture being burned in the combustion space. Optimum spark advance at lower rpm(lower piston speed)has to do with considerably slower combustion space mixture motion, less densely packed fuel molecules, and much lower combustion pressures. Those conditions need a larger head start for the spark to fully burn a larger quantity of the mixture. Higher manifold vacuum, idle and steady state cruise, denotes engine efficiency and more is always better except during WOT which would point towards an induction or carb size restriction.

If you want to quick check what a reduction in timing would do to your air/fuel table combo?.. just twist the base timing down at the distributor and go take a drive. If it cools down any bit at all then you are dealing with a lean condition and should be remedied rather than bandaiding the situation with retarded timing. Lighter cars with 5 speeds and shorter rear gearing accellerate more quickly and tolerate faster/higher spark advance.. whereas heavier cars with 3 speeds and highways gears need slower mechanical curves and sometimes less total advance. Some holleys will often need high speed air bleed tuning as ignition advance goes up. Smaller bleed size will enrichen the mixture and larger will lean the AFR out.

 

Agreed

Back off 4* on base timing, total will still be @ 35*.

 

There's also vacuum advance which will put the total around 50 at cruise. This would not cause overheating though.
You obviously need a new radiator. The thermostat may be sketchy as well.

 

the radiator is fairly new, its a American Eagle 339, 2 row with 1 In. tubes. and its clean as a whistle. However i do have a high flow thermostat in it, I'm going to put a stock one back in. It might be flowing two fast for the radiator to cool the coolant down.

 

Old wives tale. Higher flow rates always win so long as the pump doesn't cavitate. A high flow t-stat.. or no t-stat at all will run much cooler than the tiny opening of a cheap restrictive 205 degree t-stat.

Another way to look at it. If the coolant flows less and more slowly through the radiator.. doesn't it stay in the block and heads longer too? Hot spots around exhaust ports and combustion chambers can literally boil and severely hurt conductivity if flow isn't sufficient.

 

I agree with this 100%. The increased speed of coolant flow does not cause hotter temps. You do want to avoid aeration and cavitation though, which can sometimes be caused by no thermostat at all.

 

Would there be any advantage going from a high flow 160deg to a high flow 180deg?

 

Yeah, 160 is too cold.

 

I have a 160 degree in my 347....as recommended by my engine builder. Never overheats. Doesn't even get close.

 

the few things I could think of would be hotter combustion and induction temps followed by less allowable ignition timing culminating towards lower exhaust Nox production. Maybe slightly better crankcase moisture reduction/ quicker boil-off. Totally wrong way to go about tuning a performance engine IMHO.

Most people are amazed at how much idle/part throttle ignition advance an engine will tolerate while making more manifold vacuum and low speed torque. Besides being hard on starters(kickback) and often needing start retard.. locking out timing to roundabout number of 38 degrees and running an adjustable vac advance pot limited to about 10-12 degrees of full manifold vacuum assist will flat out blow most people's minds to what they've been missing out on. Tires quickly spin with barely any throttle input, mileage increases once you learn self control to avoid spinning them, coolant temps go down. And utizing lower temp t-stats helps reduce induction and combustion temp spikes to push the tuneup potential harder and fully realize all those gains. I'd never dream of using anything higher than 160 during the warm season.

 

I spoke with a teck from lead foot racing (aka Champion and American eagle radiators) he said the same thing 160 deg is what he recommended. He believes it is the low air low in the 4 corners of the shroud at high way speeds that is raising the temp. he is sending me some flaps that will open up at higher speeds and allow air to move thru the dead spots as he called them. he said I should see 15-20 deg reduction in temp.

Groberts. I wish I lived a couple hundred miles closer to you, Id love to spend a day tuning on this car with you. I can tell you have an engineering background. I understand most of the tips give but not confident on how to achieve the results.

 

The motor oil is supposed to run at a certain temp. Additionally, if you drive your car in winter, your heater won't work with a 160 thermostat. Just as bigger is not always better, cooler is not always better.

 

That's true but lowering water temps 20 degrees equates to maybe 6-8 degree cooler oil temps at most. Slightly cooler oil just gives more margin during WOT runs when bearing loads and oil shear has the greatest impact. And when you keep in mind that oil viscosity changes with temperature.. if dropping way down from a 205 t-stat to a 160 gives extra lattitude for reducing oil weight to end up with less parasitic losses(windage and pump drag) while still having sufficient shear strength. Switching to synthetic gives slightly more lattitude there as well. All the little changes make way for other little changes and they all add up to more power without scrificing longevity or durability.

 

A lean fuel mixture will also increase engine temperatures.