Will a car running rich 10:1 @ 3500 according to dyno sheet cause a engine to run hot at highway speeds. Car is set up fpr 180 degree operatong temps but run's 215*. The motor is 383 running TPI with Map set up. Im have a C3 trans plant car.

 

Generally, lean mixtures and retarded timing cause an engine to run hot. Possibly the cooling system won't reject heat fast enough to keep the temps down. If you never see anything over 215* (or even more), you really have nothing to worry about.

RACE ON!!!

 

Brand new Dewitt radiator, spal fans,new GM aluminum high flow pump,all new hoses. Talk to DeWitt and they state the system should be good for 800hp. I'm lucky to be making 350hp. I cant find a TPI tuner in Chicago and am at a loss. All signs show lean but dyno show rich and timing is set a 8* advanced with ecm showinh 45* at high way speeds.???????? Not a airflow issue because I rev the engine standing still to 3500rpm and car will shot right up to 215*.Anybody...

 

Rich mixtures cause a reduction in combustion temperatures. Make sure that your radiator is not clogged with debris. I don't know what spal fans are, but the electric fan used in C4's moves adequite air in my 87 at stoplights in 90 degree weather to maintain 200 F which falls to the 195 stat temp when I get underway. I have a Stewart high volume water pump. My OEM water pump allowed 220 F under the same conditions. 3500 rpm at stoplights is too high in my opinion and shouldn't be necessary and may even contribute to increased coolant temps. My idle speed is 700 rpm and I can maintain 200 F with my stock electric fan forced on with a manual switch.
If you really do have a lean condition, then your engine will make more heat which will result in higher coolant temperatures but should also cause knocking/pinging which should be obvious when your engine is under load. Offhand I would say you don't have enough airflow through the radiator. Many C4 owners with Dewitt radiators have posted that their coolant temps are lower than their stock radiator.
Make sure you have your air dam in place. The air dam is aerodynamic
and above 35 mph causes a lower air pressure behind the radiator which increases the air flow. Fans are really only for under 35 mph to ensure enough airflow to keep the engine cool. C3's had a mechanical fan with a clutch. My 69 and my 74 vettes ran cool even at stoplights in the summer!

 

I went down this road last year. So this may help but can't hurt. We installed new hoses after the rebuild to a 383 on a 79 vette. The hoses were just a little longer than stock as we would find out later. The car continued to heat up to 220. Long story////. Short story. The upper hose was arching to high up in relation to the rest of the cooling system. This allowed the hose to trap air and caused the water pump to simple cavitate. Meaning it pumped no water out of the motor and into the rad. We noticed more than once the rad was cooler than the motor and yet the temps remained up. When we tried simply pushing the upper hose down one day by hand the hose became instantly warmer and the temps fell. By cutting the hose shorter and eliminating the place were air could trap the problem went away. Hope this helps.

 

You realy need a data loger. The Dyno is great but most operators are only looking at WOT and the fuel tables are locked for WOT so you could have a lean condition every where else and WOT and still show rich on the dyno.

 

I have a X ray scanner and am not sure what to look for as to o2, map voltage, knock sensor counts, retard ect....

JFB, I am not running 3500 at stop light, I meant that I could simmulate the condition when standing still in the drive. Rev the engine and temps will shot up. I can drive all day around town with a 180* thermostst and engine temps will stay at 185*. Only at high engine speed do I have a problem.

What type of fuel pressure should I be running at 3500rpm cruising. That is going to be the next test.

I don't hear any knocking under accerlaction or any time else for that matter.

Thanks