Running Hot on the Highway Options

[NJ914Guy]

My car is a 1973 914 2.0 running dual Weber 40 carbs, an Aircooled.net SVDA vac advance distributor (vac port connected to dual carbs) and a Pertronix electronic ignition module.

Here in NJ, on a 80-90 degree day, the car runs great on the back roads ranging from 30-45 MPH. Using the dip stick temp gauge, she runs around 180-195 for oil temp. If I take her up ont the highway and run the car at 65-80 MPH for 10-20 minutes, the temp will run up to 220-240, based on the outside air temps, which seems too hot.

I assume that since I am fine on the back roads, my flaps and fan are clear and working fine? I do have 100% of the factory tins in place, and from 180-240 degrees, the car runs strong at all temps.

I am thinking that I have a problem and would like to rule out some things. Here's my list of things to try. Please feel free to comment or make additional suggestions.

1. Change oil. I am running 10W-30 now. Have some fresh Brad Penn 20W-50 on hand. Could an oil change help?
2. Drop the oil screen and check for any sludge or blockage which may be impacting oil flow.
3. Check timing on the SVDA dizzy. I am wondering if it's advancing a little too much on the highway? Per John's instruction, when we installed the dizzy we set timing to: 38-45 Total Advance (hose connected) @ 3500 RPM.
4. Pull spark plugs and check for lean conditions.
5. Check carbs and idle jets. Not sure what's in there, but I hear that I want idle jets of 50.

[ape914]

from what i know about lean burning and aero engine is that Charles Lindberg (First man to solo fly Atlantic Ocean) taught the lean burn technique to the US military in WWII in P-38 fighters,. He extended their range in the Pacific fighting. (Lindberg actually shot down some jap planes, although he was officaily banned from combat, (the President determined it would be bad Press if a hero such as Lindberg was lost in combat or worse, captured). Lindberg often made excuses to go on "test runs" with the rest of the planes into combat. He got into the thick of it several times. Lindberg got a lot more milage out of the engine by going leaner than the crews thought they could. however that was a big fat water cooled inline motor, super charged, running 120-140 Octane.

Lean burn to run right needs to have other modification to be done, timing is often advanced, as the lean mixture has a slower flame front speed. High compressions can also be used to compensate for the loss of power lean burn gives.

makes me think .....If one would wire in two MPS one for rich sporty driving, one for lean cruising, and one could take advantage of some adjustable spark advance, one could maybe make a "sport/ecomony" switch on the dash.

Still interested in hearing how racer chris gets his lean burn to run best?



I suggested first to go richer because I have found more often than not cars will be lean rather than rich when they have these kinds of problems, Even a stock factory set up car will be running too lean on todays fuel, so my first reaction is to try to richen it, if richer makes the car run hotter, then you know your on the other side of the curve and you can try the leaner route. what ever works for your engine and driving needs.

Like tradisrad thinks....Twisty roads, rolling hills, cars to pass, and you will probably prefer richer, if your steady on the interstate, leaner might be nicer if it can save some gas.
deviate a lot from factory specs in mixture and you have to start changing other things to maintain drivability. all a trade off.