1972 911S Oil Starvation Question

[JB]

Does anyone have any knowledge or experience in road racing a 1972 911, specifically in regards to possible oil starvation of the engine. I have heard rumors that with the oil tank being smaller and in a different location (forward of the rear wheel well), in some dynamic situations oil flow to the engine can be interrupted. Can any one substantiate this?

Thanks,

JB

[Grady Clay]

JB,

My personal opinion is that the oil tank should be as a GT-3RSR Cup car. Basically in place of the engine oil cooler. The reason is that allows the most direct oil feed to the pressure pump intake.

You can research some of my prior posts where I describe being able to turn on the low oil pressure light under extreme braking situations in a 935K3.

Best,
Grady

[LakeCleElum]

JB - I think the '72 tank lacks the baffles that would prevent oil starvation during high speed cornering. I read a thread here recently of someone that modifies the '72 tank to add the baffles and makes it a little larger also....I'm someone will come up this in the next few hrs...Good luck...Bob S.

[cstreit]

ALL early 911 racecars running good rubber have this problem.

Specifically under heavy braking and left turns. The oil pump feed line is on the left rear of the oil tank. Since the tank doesn't hold as much oil while the engine is running at high RPM's, under those conditions the feed input from the tank can run dry or suck up air causing cavitation.

Your solutions range from a front mounted/remote tank or modifying the existing oil tank by adding a baffle or two to help keep the oil near the pickup.

I did this modification for myself and have done it for several people since then with good results.

Smart Racing also sells the front tank or takes the modification of the existing tank a step further by increasing it's capacity as well. (Of course they charge a lot more than me. )

Look at this thread for my method:

Oil pressure drop on hard braking. My answer with Pics


There is some speculation, though no emprical proof that the updated cam oil line fittings with the smaller orifice also help by reducing foaming and keeping a more constant level.

http://www.dietersmotorsports.com/tech/2002/3-2002.htm

[David W]

I wanted to share my insight on the oil starvation problem. I have owned two 72’s, a 72E RS Replica I vintage raced back in the early/mid 90’s and my present 72S. While I never experienced a problem with the E, I was only running 225 60 15’s (in HSR) so my lateral G’s were not that high. I noticed the oil gauge “bumping” at turn 7 at Road Atlanta. At Mid Ohio I came across a real 72 2.5 race car, I can’t recall the original series the owner ran in. Anyway he related how they had problems blowing engines in the early days and had to modify the oil tanks. I looked under his car and there was a deep sump added to the bottom of the 72 tank. I sold the E (regretfully) and moved on to a wide body GTU car. I believe Smart Racing does the extensions on the 73 on tanks, I don’t know about the 72’s.

I am now completing the restoration of my 72 S RS look with a 3.2. With 8x16 and 245’s it should l have some stick. I will not race it by plan on doing some DE’s. I did not want to experiment with my (rare) 72 tank so I decided to install an oil accumulator on the high pressure oil side. I have removed the oil pressure idiot light (and base) and installed a -10 line to a Moroso 1.5 quart accumulator. I have an inline electric switch. I installed it on the original AC compressor mount. I should have it running this week (finally!) and will share some photos.

My next project is a 73 track car; I plan to use a 3 quart accumulator with it.

Bottom line, in my opinion, it is cheap insurance to either install an accumulator or the extended oil tanks for track use.

Regards, David

[Jack Olsen]

On my car, TRE Motorsports belt-cut the tank, added an inch and a half or so of metal, and welded it back up. The idea was to increase capacity for the 3.6-liter motor. I run 315 tires in the back, but I've never noticed oil pressure problems under load. (Of course, I might just not be seeing it.)

[Plavan]

I sent my oil tank to Smart racing for the upgrade. It was a Sportomatic oil tank so there was some other holes i needed welded up. I would see the red light all the time in braking and left turns. Now I do not. Although the stupid mechanic when replacing the oil tank twisted one of my oil lines....needless to say thats why I'm building a 2.5L shorty race motor now. The old (new) motor failed because of this Yahoo. I would of installed it myself but I was in a process of a move and did not have time.
I would never recommend www.alteredspeed.com shop for anything (Jay Jarvis). He also charged me for work not performed. No integrity at that shop. STAY AWAY.

[Bill Verburg]

Chris, Jack and Chad all did the right thing. Increased capacity and baffles are the ticket for all the earlier cars w/ modern rubber on track.

[Grady Clay]

All,

Not to hijack this thread but how about looking at the larger picture.

This is an issue with all 911s that have good grip and are used close to the limit cornering and braking. Also every street only 911 could benefit.

I’ll challenge all the pros and skilled amateurs to design a new dry-sump system that is similar to the GT3-RSR where it replaces the engine oil cooler. I’ll pay US$1.00 each for the best 100 designs.

As a first draft, it should:
Fit in the normal oil cooler location and up into the engine compartment.
Fit in all early (’65-’89) 911s, 914-6s, and possibly more later dry sump 911s and Boxters.
Not interfere with any existing chassis, intakes, etc.
Be a bolt-on replacement.
Be reliable to high Porsche standards.
Incorporate a full-flow filter in the pressure circuit.
Have a serviceable screen in the pressure pump pick-up.
Have a remote oil cooler with thermostat in the pressure circuit similar to the existing cooler (possibly use the existing cooler with an adaptor and air ducting.)
Accommodate all existing Factory front cooler systems and plumbing.
Be easy to install, service, replace, and change oil.
Have spare parts available.
Be reasonably priced considering everything Porsche.

Other things to consider might be a centrifugal oil-air separator and better oil-air management in the crankcase.

Some extensions might be to convert wet-sump to dry-sump.


The first stage is to better define the criteria I outlined above. Chime in everyone.


Best,
Grady

[Wil Ferch]

Someone else on this board simply baffled his OEM tank...without adding capacity...and it went well.

Can't recall the thread, tho.....

Wil

EDIT:
Here it is...
Oil pressure drop on hard braking. My answer with Pics

[Wil Ferch]

Something else...
In that thread, Chuck Mooreland asks the question I had rolling around in my head too....if the hose connection is moved to the front of the tank...won't that help? Braking forces are more substantial than accelerative forces....

Wil

[Bill Verburg]

For those not familiar w/ the set up Grady is talking about, this is a GT3


This could be done in a 911/964 or 993 w/ mods to the firewall/seat area.

[Grady Clay]

Bill,

Thank you for the illustration.

Come on all, invent something similar.

The first order is to revise/improve my list of criteria.

Best,
Grady