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.

[mrbubblehead]

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.

i think you miss read his instructions.... try 28 degrees total advance. hose on...then reset your idle to 800 rpm and reset your mixture screws.

[ChrisFoley]

I agree with Doug.

I've been using Brad Penn 10/30 in my DD since last year.
Its a 1911 running D-Jet, with the stock cooler remote mounted under the trunk and a 180 deg oil thermostat inline.
Oil temps don't go above 220 even driving at 90mph for 15 minutes straight in 90+ air temps.
Changing to 20/50- won't improve your temp issue.
However, if you find that oil pressure isn't sufficient when the oil is very hot, you should go to a higher viscosity.

[NJ914Guy]

Guys, here's John's timing settings, copyed and pasted right from the instructions email that comes with the SVDA distributor. Are you still saying these are incorrect?

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Now it's time to set the timing. Reconnect the negative side of the battery, and turn the key on, but don't crank the engine. With a test light grounded on the engine case, put the other end on the negative terminal on the coil. Very, very slowly, rotate the distributor counter-clockwise, until the test light lights up. The light will stay lit up for a few degrees of the rotation, so it is important to stop turning the distributor body as soon as the light turns on, when rotating counter-clockwise. After this, simply tighten down the distributor clamp, and your engine should start right up. If you have a timing light, get the car started up, aim for 7.5 BTDC at idle FOR NOW, the hose connected or not should not matter (if it does that's the wrong vacuum port). After you set that, reconnect the vacuum line. Depending on where your timing was at idle with your old distributor, you may need to re-set your carb. To verify the correct operation of the SVDA, the timing should be

A) 28-30 Total Advance (hose disconnected)@ 3500 RPM.
B) 38-45 Total Advance (hose connected)@ 3500 RPM.

Let it idle and re-check the timing, you can now use this timing setting to set the timing at idle, though we do recommend you check the full advance settings to make sure the SVDA is working properly at both idle and full advance.
-----------------------------------------------------------------------------------------------

Rather than take the car back to the shop, could someone walk me through how to properly adjust my own timing? Should I pick-up a special type of timing gun?

Thanks

[ChrisFoley]

I'd set the timing at 28 btdc, vac advance disconnected.
Then verify that the idle and vac connected settings are in range.

On the fan, 28 btdc is right about where the last fin is before the heavy rib. TDC is around 4 fins from the heavy rib.
Some fans have a mark at 27.

[ChrisFoley]

Should I pick-up a special type of timing gun?

Thanks

A fancy timing light allows you to preset the advance you want and time to the TDC mark at 3500rpm. With a plain jane timing light you set to a 28 deg. mark painted onto the fan.

[NJ914Guy]

Thank you, Chris!

[ape914]

check your mixture too. lean running by even a small amount can cause over heat. get an O2 meter on the tail pipe or read the spark plugs

[NJ914Guy]

What's a good range for O2 on a carbed 914?

[ape914]

What's a good range for O2 on a carbed 914?

depends on your engine, but in cruise a bit on the rich side is ok on an aircooled car, else they will run hotter. you might try around 12.5:1 and see if that effects your temps. you got carbs, so go one jet size bigger and see what happens. a spark plug reading can help you. if your carbs were set for the old gas, they will run too lean with todays oxygenated fuel.

old gas =gasoline

new gas = gasolean

[ChrisFoley]

but in cruise a bit on the rich side is ok on an aircooled car, else they will run hotter.

That's actually a common misconception.
The engine will run plenty cool and get better gas mileage during light throttle operation if the AFR is between 16-17:1.
For full load operation you need the mixture no leaner than 13.2:1, with 12.5-12.8:1 being used more often to create larger a safety margin.
Anything between 14-15:1 will make the heads run hotter.

[r_towle]

I would suggest you listen to Chris.

Chris has taken the time to develop a 4 channel EGT system, a CHT system, and an AFM system that he trusts.

Based upon those three levels of research and testing, its obvious to me that he really cares alot about heat and mixture on these motors...

He has done quite a bit of testing on both street cars and track cars to learn tons about how to manage heat.

He even has is own horizontal cooling fan setup that he makes.

With the level of his real world testing, I would trust his results quite a bit...

He may not have invented some of what he sells, but he has tested enough of them to trust what he sells as good technology....

My point would be, listen to Chris.

rich

[ChrisFoley]

And I talk with my dad a lot. (IMG:style_emoticons/default/smile.gif)
He's a PhD aerospace engineer and has more than 60 years experience flying small planes with aircooled engines. He tends to maintain a larger safety margin than I do. (IMG:style_emoticons/default/biggrin.gif)

[MikeM]

Sorry about the hi-jack...
Chris, you run Brad Penn 10/30? How does that work as far as oil pressure and leaks? Any difference between that and 20/50?
Will my engine run cooler with 10/30?
Thanks,
Mike

[ChrisFoley]

Sorry about the hi-jack...
Chris, you run Brad Penn 10/30? How does that work as far as oil pressure and leaks? Any difference between that and 20/50?
Will my engine run cooler with 10/30?
Thanks,
Mike

I was running Brad Penn 20/50 based on the recomendation of Jake Raby, but after some in-depth reading online, I decided to try 10/30. Now I'm convinced that, for most of us northerners at least, 10/30 or 10/40 may be better year round, than 20/50 ever.
Some people think the thicker oil bypasses the cooler more readily, so they use lower viscosity oils and claim their temps are cooler as a result.
20/50 seems to make the pressure too high until the oil is very hot. Well my engine doesn't get that hot except when I beat on it for long intervals, or let it idle for a long time.
10/30 only seems to get too thin above 220F in my engine. That's why I'm thinking 10/40 may be a little better.

[MikeM]

Thanks Chris...I'm going to try Valvoline VR1 10/40 if I can find it...
Mike

[TheCabinetmaker]

The valvoline no longer has zinc in it, IIRC

[MikeM]

Damn...not even the Vr1?

[SLITS]

Want oil .... The "new" Kendall Gt-1 oil with Liquid Titanium has the appropriate amount of Zn in it. I've been running it in the 2.7L

[MikeM]

Probably not available in my area...