running hot on freeway

356 Porsche-related discussions and questions.
Message
Author
User avatar
Ron LaDow
356 Fan
Posts: 8092
Joined: Wed Mar 26, 2008 11:45 am
Location: San Francisco

Re: running hot on freeway

#16 Post by Ron LaDow »

Apologies if this is too elementary for the folks here:
Engine coolant (water/oil) heat is the waste of the HP made, not the HP possible from a given engine; an engine capable of 110HP will not cause excess coolant temp if it does not make more than what is required to push the car down the road at X speed.
Assuming the engine fueling/timing/CR are in line, it's worth looking for anything which is requireing higher HP at X speed: Tire pressures, tire widths, brakes dragging, alignment, etc.
I remember R&T used to cite "Tapply Data" (sp?) in the road tests; it was more or less a coasting test to correct for such cofounders.
Back when this was a list-serve "List", I did a survey, and while it was a long way from what anyone would claim to be "scientific", it showed a very strong bias to 'overheating' in single-grille cars, even though the grille size is not the 'throttle' on the cooling air entering the engine bay.
Ron LaDow
www.precisionmatters.biz

User avatar
Martin Benade
356 Fan
Posts: 12189
Joined: Wed Nov 23, 2011 10:52 am
Location: Cleveland, Ohio

Re: running hot on freeway

#17 Post by Martin Benade »

Was a single grille a problem, or just perceived to be a problem?
Cleveland Ohio
62 Cabriolet
56 VW
02 IS 300
04 Sienna

User avatar
Jules Dielen
356 Fan
Posts: 3166
Joined: Fri Mar 28, 2008 3:25 pm
Location: Arizona

Re: running hot on freeway

#18 Post by Jules Dielen »

I have a few sigle grill cars, only this one runs hot. I had 2 different engines in this car before this one went in, the other 2 did not run hot either. I am 99% sure it is an engine related problem.
Jules

Water pumps are for windshield washers only.

User avatar
Ron LaDow
356 Fan
Posts: 8092
Joined: Wed Mar 26, 2008 11:45 am
Location: San Francisco

Re: running hot on freeway

#19 Post by Ron LaDow »

Martin Benade wrote:Was a single grille a problem, or just perceived to be a problem?
Dunno.
When I did the survey, I asked things like tire size, carbs, exhaust, lowering, etc.
What was very clear (like a big difference) among those who reported elevated temps were those driving single-grille cars.
Sorry I didn't save the results, even though the sample size and randomization were far from optimal, but that result was loud and clear.
Ron LaDow
www.precisionmatters.biz

User avatar
Ron LaDow
356 Fan
Posts: 8092
Joined: Wed Mar 26, 2008 11:45 am
Location: San Francisco

Re: running hot on freeway

#20 Post by Ron LaDow »

Jules Dielen wrote:I have a few sigle grill cars, only this one runs hot. I had 2 different engines in this car before this one went in, the other 2 did not run hot either. I am 99% sure it is an engine related problem.
I'm not about to disagree. Do you have a dyno available to fiddle with the tune? If it is an engine problem, and not related to CR, you can find it there.
Ron LaDow
www.precisionmatters.biz

User avatar
Greg Bryan
356 Fan
Posts: 3692
Joined: Sat Oct 04, 2008 1:05 pm
Location: San Pedro, CA 90732; Fallen Leaf, CA 96150
Contact:

Re: running hot on freeway

#21 Post by Greg Bryan »

How about fuel ratio too lean, either from carb setup or fuel delivery?
Greg Bryan

User avatar
Vic Skirmants
Registry Hall of Fame
Posts: 9279
Joined: Tue Oct 27, 2009 5:02 pm
Location: SE Michigan
Contact:

Re: running hot on freeway

#22 Post by Vic Skirmants »

OK; I'll mention it again; small oil pump versus large.

User avatar
C J Murray
356 Fan
Posts: 9161
Joined: Fri Oct 23, 2009 7:24 pm
Location: 30MI WEST OF PHILA
Contact:

Re: running hot on freeway

#23 Post by C J Murray »

As far as early vs later engines...when Porsche went from 75hp to 90hp they increased the size of the oil pump, added the velocity stack to the fan shroud, removed the wire screen, and changed to the 28 vain fan. In other words they needed more cooling to get to 90hp. Then they went to the twin grills. We race single grill cars but we also remove the rain treys which makes a giant difference as well as placing oil coolers where they get 120mph fresh air.

Higher compression in combination with shorter duration cams, very lean mixtures, and too little advance are to be avoided if you want to run cool.

So, in 1958, what did Porsche say about oil temperature? Here...
http://www.willhoitautorestoration.com/oiltemp.php
'57 Speedster
'59 Sunroof
'60 Devin D Porsche Race Car
'63 Cabriolet "Norm"
'67 911 S Original Owner
'03 Ferrari 575M
'09 Smart Passion

User avatar
Doug McDonnell
356 Fan
Posts: 6061
Joined: Sat Apr 05, 2008 8:21 am
Location: Augusta,Michigan

Re: running hot on freeway

#24 Post by Doug McDonnell »

CJ Add double flapper boxes to changes for cooler running. Jules try a run with the engine lid popped to open and see if it makes a difference.
1965 356C 2000 BMW 740i Sport 1967 Honda CL77 There is never enough time to do it right, but always enough time to do it over.

User avatar
Wes Bender
356 Fan
Posts: 4861
Joined: Wed Aug 27, 2008 10:54 am
Location: Somewhere in the Gadsden Purchase, USA

Re: running hot on freeway

#25 Post by Wes Bender »

I agree with Vic that the small oil pump has some effect. Is it possible that you have a partial blockage in the new oil cooler? The switch from a stock cooler to the more modern aluminum ones usually results in a significant drop in oil temps.

Re. the oil, I would probably still be running a straight 30 wt non-detergent at the 1500 mile point in the break-in, but that's just my opinion. Others use different break-in regimens.
Some days it's just not worth chewing through the restraints.....

User avatar
Craig Richter
356 Fan
Posts: 1305
Joined: Thu Dec 15, 2011 9:01 pm
Location: San Miguel de Allende/Traunkirchen

Re: running hot on freeway

#26 Post by Craig Richter »

Vic makes the point (twice for emphasis) that the early small-geared oil pumps aren't going to run as cool as big-geared later pumps. This must be directly related to pressure, because higher pressure will force a larger volume of oil thru the motor in a given time, and this faster "cycling" pulls more heat into the oil to be expelled by all the features you guys mention above. Jules, it's good your oil pressure light doesn't go on at idle, but have you actually checked the pressure at running speeds?
 

User avatar
Pascal Giai
356 Fan
Posts: 165
Joined: Thu Jul 03, 2008 7:25 pm
Location: California

Re: running hot on freeway

#27 Post by Pascal Giai »

Jules

Make sure to check your air/fuel ratio with the correct equipment.
You may fry your new pistons if the engine is running too lean.
It doesn't take long to destroy them, don't ask me how I know...
I never had any issue with small oil pumps, yet !

Pascal

User avatar
Thomas Sottile
356 Fan
Posts: 1530
Joined: Wed Mar 26, 2008 3:02 pm
Location: Stamford CT
Contact:

Re: running hot on freeway

#28 Post by Thomas Sottile »

I have a friend with the same problem for 1 year until he looked and saw his heat boxes were screwed closed.!!

User avatar
Craig Richter
356 Fan
Posts: 1305
Joined: Thu Dec 15, 2011 9:01 pm
Location: San Miguel de Allende/Traunkirchen

Re: running hot on freeway

#29 Post by Craig Richter »

Isn't it amazing all the screwed-up turkey s....tuffing found after all these years!
 

User avatar
Jules Dielen
356 Fan
Posts: 3166
Joined: Fri Mar 28, 2008 3:25 pm
Location: Arizona

Re: running hot on freeway

#30 Post by Jules Dielen »

I'll check air/fuel mixture again and change the oil. The partially blocked (new) cooler is of course a thought.

as to the big vs small oil pump and single grill talk... I had a different (small oil pump) stock 1600 engine in this car before i installed the rebuilt engine. I drove it back from Monterey, CA to Phoenix in 105F clear across the desert for a day on the freeway and did not have any problems. It also made the trek from Phoenix to Park City and back and I attended a NMS event without any issues. I put 12k miles on it with the old engine and the oil temp never even got close to 200F, although that one did have low oil pressure at idle/ operating temp running Brad Penn 20W50. No propped hoods needed with that engine, why should it with this new one?
Last edited by Jules Dielen on Fri Apr 20, 2018 12:34 pm, edited 1 time in total.
Jules

Water pumps are for windshield washers only.

Post Reply