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.

[tradisrad]

Dave, You are right about comparing the Honda to the VW engine; they are two different fruits. Some Hondas are designed to run lean utilizing the v-tech technology and the wide-band O2. But as far as I know, which may not be much, the VW engine is not designed to run lean.

My main confusion with this thread is that now I am reading that it is ok to run lean to reduce oil temps when every other thread tells us to run our 914s on the rich side to reduce oil and head temps. With out the proper monitoring equipment an arbitrary lean mixture is just asking for trouble.

Is it possible for the OP to set his carbs to run lean while cruising on the freeway and rich in other driving conditions so he has power? Or does he need to drop hundreds of dollars into monitoring equipment to achieve this? From the OP he is monitoring his oil temp with a dip-stick temp gauge. Not very high tech no expensive.

Many guys have added a second oil cooler to help reduce oil temps. Some have even gone as far as changing the entire air cooling system (to the horizontal fan set up) to reduce temps.

[mrbubblehead]

Is it possible for the OP to set his carbs to run lean while cruising on the freeway and rich in other driving conditions so he has power? Or does he need to drop hundreds of dollars into monitoring equipment to achieve this? From the OP he is monitoring his oil temp with a dip-stick temp gauge. Not very high tech no expensive.

Many guys have added a second oil cooler to help reduce oil temps. Some have even gone as far as changing the entire air cooling system (to the horizontal fan set up) to reduce temps.

yes, that is the best thing about weber idf's. they are very well thought out and engineered. your idle jets, which deliver fuel to the progressive circuit, can be real lean. especially when complimented with the svda. the svda will advance up 42 degrees. idle/progressive circuit will be used for part throttle and cruise situations. this is where you get your killer m.p.g. and lower cylinder head and exhaust gas temps.

then, when you jet your mains rich, (12.75-13.25) you dont run the risk of being lean at WOT. the svda will run out of vacuum and retard back to 28 degrees. so when your giving your 250 lbs buddy i ride (high load), or cranking it up thru the twisties, you wont run the risk of running lean because you will be on the mains anyways. this time you will be on the other side of the curve (rich of peek) running cooler.

stoich (14.7) is the death zone. this is where your cylinder head temps and exhaust gas temps are highest. and should be avoided at all times.

NOW, i dont have actual proof of this. this is 80 year old information. these tests where done years ago. the aircraft guys are masters of this. aircooled or watercooled. it dosent matter. it is what it is. the aircraft guys have alot more riding on this information. higher fuel costs, higher engine overhaul costs, but most important, they cant look for the nearest off ramp if there motor blows chunks. literally.

and no, he dosnt need to invest in a bunch of hidollar instrumentation. i think ac.net rents a portable wideband instrument. just install it, do your jetting, then send it back. only the real anal guys (myself included) invest in the instrumentation. so we can see what the effects are from the changes we make.

[tradisrad]

yes, that is the best thing about weber idf's. they are very well thought out and engineered. your idle jets, which deliver fuel to the progressive circuit, can be real lean. especially when complimented with the svda. the svda will advance up 42 degrees. idle/progressive circuit will be used for part throttle and cruise situations. this is where you get your killer m.p.g. and lower cylinder head and exhaust gas temps.

then, when you jet your mains rich, (12.75-13.25) you dont run the risk of being lean at WOT. the svda will run out of vacuum and retard back to 28 degrees. so when your giving your 250 lbs buddy i ride (high load), or cranking it up thru the twisties, you wont run the risk of running lean because you will be on the mains anyways. this time you will be on the other side of the curve (rich of peek) running cooler.

So, it is really the combination of the special dizzy and the idf carbs. thanks for clearing this up for me.
My 914 (just got back from driving it (IMG:style_emoticons/default/smile.gif) ) is still d-jet and I've never been much of a carb guy. However, I must say that this set up sounds interesting allowing both economy and power.
Maybe I'll look into it for a future mod. Can more HP be gained by this over d-jet? Is a special cam needed; Raby's 9550?