Oil pressure drop on hard braking

[cstreit]

Gang,

This weekend I noticed (as I had heard before) that under hard braking, my early 911 has SERIOUS oil pressure drop. I mean from 100 lbs down to less than 20.

I've heard from several sources that this is a common problem. I also understand that there are places that make baffle modifications to a stock tank to prevent this.

Does anyone know of a source?

Thanks!

[VincentVega]

No personal experience with this, but below is what smart racing offers for later cars. I would imagine they can do similar work to any car.

High Performance Factory Oil Tanks *
Any time you put a 74-'89 911 on track and run the car hard, you run a good chance of starving the engine (specifically the crankshaft) from oil. Why? Because the oil-out location is at the back of the tank, under very hard braking, the oil supply is intermittently interrupted (the proof...just watch your oil pressure gauge under hard braking or going through a series of "S" turns; if you see the pressure gauge bouncing or fluctuating, the oil supply is being interrupted...crankshafts cost $2,000.00 alone!). The factory tank is a very good one for street driving, but it's not up to the demands of on-track driving because it does not have any internal baffles to control oil surge. We cut the tanks apart and add crucial baffles and lengthen the tank 2" which increases the oil capacity by over two quarts. This is a very popular modification with our fastest customers...and really anybody who drives their cars aggressively. It is a completely bolt-in modification, you don't have to modify the car or the oil tank mounts at all. It is a 100% simple bolt-in modification. We can also weld a -16 or -20 male fitting at the oil-out location for those who want to run screw-on (AN) type hoses, please inquire about size and a modest additional cost. Please note the * note below.

High Performance Factory Oil Tank: part #154200 $399.00
* Note: Please specify if you are using a B&B exhaust system so we can modify the oil-out fitting to accommodate the exhaust system.

[cstreit]

That's what I was looking for... Thanks!

[Elombard]

Chris are you running the 3.6 oil line reducers? Just reading about the way they work I wonder if it would help? They cause more oil to be in the tank at any given time, less in the heads and in the case. Really a band aid for the problem but if you still have some pressure maybe an extra quart or two in the tank would keep it from sloshing forward far enough to uncover the out hole on the tank. I wonder why they dont mention the modded oil tank for earlier cars? Maybe the out put is on the front of the tank?

[cstreit]

Good question, I need to look at where my pickup is obviously, or maybe I have a lter tank and don't know it...

[304065]

Chris,

My oversize idiot light comes on (20psi) when I stand on the brakes before the left-hander at Lime Rock. Same situation as you experience.

I'll just have to stop braking there.

[Bill Verburg]

Some of the early cars used smaller non baffled tanks which can contribute to the problem. I'm trying to remember where the exact specs and years are. But in the mean time Smart Racing has a large baffled tank which would probably solve the problem.
Smart Racing Oil Tank

[Jdub]

Hold on: do you have the "bowler" style of anti-cavitation screen sump? Or is this specific to the SC line? What you describe is classic for the '78SCs.

John

[dad911]

Chris, My 71 had oil starvation problems with the stock tank. I swapped in a later model tank, it holds more oil, and I believe its is baffled. I had to cut away some body sheet metal at the top of the tank where the filter mounts. The later tanks also use a different 'S' hose.

[911pcars]

If it is oil starvation due to oil surging away from the pickup, I'd think one could make a series of well-placed "cuts" into the tank and braze in some sheet metal baffles. Cutting the tank apart affords you more accurate placement, but it's the same net effect.

Sherwood Lee
http://members.rennlist.org/911pcars

[Vintage911Racer]

Smart Racing tank works very well. I had the same problem with my 67S. No longer happens. It not only holds more oil but it is baffled as well. Give it a try.

[cstreit]

From what I read, I thought the Smart Racing setup required YOUR tank for modification, it was not a new tank...

QUOTE:
" * the price of $399.00 includes the price to modify the oil tank as described above only and applies only to tanks that are in good condition. If they are rusty or internally corroded, there may be an additional charge to repair them. It is our experience that if you have a questionable tank, replace it with a better one - as they are abundant and affordable. It is does not include cleaning the tank beyond rinsing it out with hot soapy water and then coating it with a very light oil to protect the internal raw steel after welding. We can have the tanks certified ultrasonically cleaned for you for an additional charge of $100.00 each plus freight."


So this would be $400 PLUS my oil tank?

DAD911, can you give me a model year so I can start searching... Just a tank with a pickup at the front I think would work well...

[MotoSook]

Chris, I may know someone locally who has a tank from a 77. I'll check.

Should be just like mine..as you say last weekend.