914-6 original overheating issues above 85 mph?, 914-6 Options

[unpolire]

An aerospace engineer friend of mine was over and we were discussing 6-cylinder powerplants in the 914. A friend of his bought a 914-6 new and used to complain that he could not drive over 85 mph, after skiing in Reno, on his return, due to detrimental air pressure over the engine cover area as a result of the body's aerodynamics. Has anyone experienced this?

[0396]

Please advise your buddy's friend that I can resolve his concern....he can sell it to me.
Please Pm me the info-(IMG:style_emoticons/default/smile.gif)

Thanks

[JoeSharp]

I never had a problem with mine.

[einic]

I never had a problem with mine.

On my 914-4 there are two plastic vanes under the floor in front of the engine creating a low pressure. It should be on the 6 as well?

[damesandhotrods]

I can’t imagine Porsche selling a car with cooling problems above 85 mph that was going to see the Autobahn. Skiing in Reno is a winter sport, so summer heat wouldn’t have been a possible issue. I’d suspect something wrong with the car…

[bulitt]

Engine running too lean, Too much, or too little timing advance, broken fan impellers, air flaps as mentioned, wrong spark plugs, mouse nests in tins, too high compression ? Thats why I don't ski.

[JoeSharp]

Mine had the flaps but I don't think that is the answer.

[ArtechnikA]

Engine running too lean, Too much, or too little timing advance, broken fan impellers, air flaps as mentioned, wrong spark plugs, mouse nests in tins, too high compression ?

Too lean is hard to manage at 6000'+ unless you work at it.
Hard to imagine broken fan bits in the 911 fan which runs at about 1.7x crankshaft speed.
Spark plugs don't really affect oil temp.
Flaps came in 1973, no original 6's had them.
Same with compression - if it's too high, it's not original ;-) It also falls at altitude.

Debris covering the cylinder and head tops and the oil cooler is a BIG factor.

I've had two factory /6's and never had cooling issues at "energetic highway" speeds or on the track.

It's a PITA to pull the fan shroud and clean out the detritus but other than intake gaskets and such, the materials cost is low, and the benefits high. The air is colder at altitude but it's less dense and doesn't cool as well, in addition to lowering available power.

[Eric_Shea]

I never had a problem with mine.

On my 914-4 there are two plastic vanes under the floor in front of the engine creating a low pressure. It should be on the 6 as well?

Nope. Those came later on the 4's (72-73??). I kept them on my current tub because it's a damn good idea.

Also, -6 have a ZA 5th to spin the motor a little faster to help keep them cooler.

That said, I never had overheating issues with the oil but, on my -6 the fuel pump got it bad on the way to the Steamboat Parade going about 100+ on an open stretch of Desert past Vernal. The passengers side flapper exits right on to the pump. Vapor lock. Maybe that's what he was talking about. (IMG:style_emoticons/default/confused24.gif)

[sixnotfour]

excuse not to drive fast .............. its the cars fault

[ConeDodger]

There is really only one place to ski in Reno. Mt. Rose. It sits along Mt. Rose Highway between Incline Village and Reno, virtually halfway in between. I'm assuming your friend was going up and not down. Reno on the valley floor sits at about 4500' while the pass going to Incline Village is at 8900'. If your friend was going up, and winding it out pretty good, I can see things getting hot. It could also have been a timing issue. Advance it enough, and you can see some pretty impressive temperature...

[sixnotfour]

He was also reminiscing , about when I........ 1970- 40 yrs ago.


more than likely he was low on oil, common problem with -6 owners

[ConeDodger]

He was also reminiscing , about when I........ 1970- 40 yrs ago.


more than likely he was low on oil, common problem with -6 owners

I wondered about that too Jeff. Wouldn't the oil tank keep the engine full? I guess I don't really know how that wet sump works. Better learn if I'm going to put a 6 in... (IMG:style_emoticons/default/blink.gif)

[xsurfer]

Today's fuel requires larger main jets I've been told. Memory is vague but I seem to remember a min. of 125 mains. I had temp problems crossing the country in my stock six. I'd check the jetting then, as I am, checking the cooling system for debris. Lastly I'm having the stock oil cooler cleaned at an aircraft oil cooling company.

He was also reminiscing , about when I........ 1970- 40 yrs ago.


more than likely he was low on oil, common problem with -6 owners

[ArtechnikA]

I wondered about that too Jeff. Wouldn't the oil tank keep the engine full? I guess I don't really know how that wet sump works. Better learn if I'm going to put a 6 in...

6's have dry sumps.
Yes, the tank keeps the engine supplied.
But it also acts as a thermal flywheel.
And oil in the tank radiates a significant amount of heat to the airstream even through the fender as you quickly discover if you touch the area after a long run or track session.

In this regard, it's like being low on oil in a /4. Oil that sits in the tank is radiating heat and not making another trip through the engine heating up. The less there is, the more often it is recirculated.

85 mph with stock-ish tire diameter is a little shy of 4000 rpm, which should be plenty of airflow to keep the engine cool.

But stock /6's also had points, and when the rubbing block wears, the timing gets retarded. Too far off spec in either direction makes heat.

[maxwelj]

I bought my -6 in Europe and it's first 20000 miles were mostly autobahn at speeds often closer to 100 than 85. Never had an overheating problem. The oil pressure light would flicker a bit at idle after a long run sometimes, but that wasn't deemed a problem by the mechanic. As I recall, I was running straight 30 wt at the time.

[sixnotfour]

It says right in the owner manual when warm the light may flicker at idle.

Rich I forgot about the points, my tach would always jump around when dwell was long.

[xsurfer]

Today's fuel requires larger main jets I've been told. Memory is vague but I seem to remember a min. of 125 mains. I had temp problems crossing the country in my stock six. I'd check the jetting then, as I am, checking the cooling system for debris. Lastly I'm having the stock oil cooler cleaned at an aircraft oil cooling company.

He was also reminiscing , about when I........ 1970- 40 yrs ago.


more than likely he was low on oil, common problem with -6 owners

[Cairo94507]

Though the underbody flaps did not come out until the '73 model year, I have a set that will be installed on my Six because it is a good idea and simple to do.