Hot Running SC - Not all the time though....

I know this sounds like the start of a very common issue among 911s, but my case seems diff to me,I think...
The car - 78 SC, very healthy, smooth clean idle, has had all the typical updates (clutch, tensioners, airbox), has a Turbotrol aux oil cooler, 108K miles, and I think it runs rich if anything other than perfect.
The situation - Under normal commuting conditions here in SE Michigan, the temp NEVER goes over 180. However my problem is that I had a bad overheating condition while partaking in my first Drivers Ed last weekend at Waterford Hills. I didn't notice until the end of the session but the temp had exceeded 250 by quite a bit! ****! Came in, checked everything out, and everything seemed OK. Full of oil (only about 1000 miles on it, Castrol 20W-50), fan belt tight, aux cooler oil lines hot. I could not figure out what was wrong. I let it cool for a session and then tried again, and damned if it didn't rocket up there to 250+ within 3 laps.
Mind you, Waterford Hills is no long high speed track that is hard on motors, rather it is a short 1.something very technical track that is quite fun, but not exactly high speed. It is mostly 3rd gear with a 2nd gear corner thrown in there.
Anyway, my point is that I wouldn't expect to have issues here. The PO had done DE at tracks where I would expect a heat issue and he claims it never got over 220 or so. He's a buddy so, I believe him.
The cooler is clean, the heads and cylinders are clean, it doesn't have any birdsnests, I'm stumped!
So I packed it in, not wanted to blow it up, and I'll be damned if it didn't run 180 all the way home (50 miles)...

Help, please.

Chris
Black 78 SC
Check out my car at photopoint http://albums.photopoint.com/j/AlbumIndex?u=682043&a=4973012

I recall seeing an article in either vol 7 or vol 8 of Up Fixin Der Porsche (old Panorama Tech articles) in which Bruce Anderson identifies a rare oil pick-up (from the sump) proble that I believe was specific to '78 SCs. I don't quite recall all the details, but apparently the car would run fine in ordinary conditions, but on a track the oils s=would slosh away from the scavenger pump nozzle and result in overheating. The fix was fairly simple. Perhaps I'll look for it. Interested?

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'83 SC

Oh most definitely!!
What volumes of Upfixin should I get, i.e. which ones pertain to the SC's?

Thanks a bunch.

CB

only thing I can think of other than the solution previously mentioned is that the hard oil lines running under the pass side of the car to the front cooler have been crushed. Seems to be a common problem when shops lift them with body hoists.

I saw the article again, and I believe it was in Volume 8. Volume 7 contains articles published around the time SCs were produced, and Volume 8 contains articlews compiled in the following few years. They are wildly fascinating. Most are written by Bruce Anderson.

The one in question said that on some '78s and '79s, the pick-up nozzle was unable to gather the proper volume of oil. So, oil accumulated in the sump, and (potentially) the tank runs dry. Causes overheating. The fix is a redesigned nozzle, installed just inside the round sump cover plate at the motor's bottom center. This is all my interpretation. If you can't find the article, let me know.

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'83 SC

Actually, thanks to the PO, I have a huge library of PANOs to review and research problems like this. What I've found in the past couple of days is this:
The original sump screen looked like an upside down strainer you'd find in your moms kitchen, you know the kind with the handle and the two little hooks around the edge?
Anyway, this screen would do nothing to keep the oil in the general vicinity of the sump pickup during high-G activity. They revised the sump screen in '80 (I believe) to a new design that was quite a bit different. The new one only had screen around the circumference and a steel bowl in the center that created a venturi effect which I guess helped keep oil around the sump pick up. One thing they mentioned, which I definitely experienced, was a loss of power. I attributed it to getting the engine so hot, but it in fact is caused by the crankcase literally filling up with oil because its not getting sucked up by the sump pump. That would explain the inefficasy of my oil cooler. It all makes sense now.
They also messed around with the pressure relief pistons and springs at the same time. I don't think the reasons for the changes are related, but the springs and stuff are cheap enough, I'll do it any way.
Going to order some parts tonight, should hopefully be able to try it out on the 18th at the next DE. I'll let you all know how it worked.

Thanks for the leads.

PS Its all spelled out in the Dec 1999 PANO, pg 12.

CB

The article I saw is dated 5/89, so I assume it's in that issue of PANO. Yes, it's the same condition you described. I'll be interested in whether this upgrade solves the problem.

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'83 SC

Well I finally had the opportunity to try out the fix outlined in the PANO article (the revised sump screen) last weekend. I must say that it helped enormously! Driving around town, you won't notice a thing, but once on the track it kept the temps down to 230 or so by the end of the 25 min session.
I was exceeding 250 in about 15 minutes before. I haven't done the relief valve piston upgrade yet, partly because I'm sure the sump screen was the major issue, but if it was importantenough for them to write a Tech bulletin, and the parts are cheap enough....

Summary, if you have a 78 SC that over heats onthe track only, check your sump screen and update it if you have the original, non venturi style. You'll be quite pleased. I spent about $90 or so,all included, buying the parts from Stoddard

that's "cool." (I couldn't resist) Good night.

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'83 SC