Upgrade oil pump in 3.0 SC?

[scott_rogers]

So my 1981 911sc is getting the engine rebuilt. Met with the mechanic last night to discuss options. He said the current stock oil pump looks good after he took it apart to check and replace seals. He said it is unlikely this pump would fail in the future (pump has 160k miles on it) but it would be much harder to replace later if it did.

Trying to decide if its worth the approximately $900 to upgrade to a Carrera pump now or just stick with stock. Car is getting a few upgrades during the rebuild, but nothing crazy for a car used for DE, Autocross and street.

Would it be better to spend my $900 on other go fast parts, or should I just bite the bullet and upgrade the pump as a precaution? Also the idea of having to take out 8 or so bolts to change the oil seems painful.

Your thoughts would be appreciated! Thanks

[Henry Schmidt]

The SC pump will not fail unless it swallows something. Under those conditions, no pump will survive.
The SC pump can be modified to flow additional oil volume with no reliability issues for considerably less than the cost of a new pump.
If you choose to use a Carrera pump, Aaron Burnham, rennwerks@hotmail.com
makes a very cool sump cover that allows for oil changes without removing the plate.

I think our host offers them.

[KTL]

One upside I can see to the later pump is the integrated screen. Reason I say that is because I recently had a SC strainer come apart on my engine.

How often do you open up your sump plate?

When it comes apart, the stainless screen bits can get into the oil system. However i'm shocked I didn't find any in my engine. Although I still haven't cut open the filter yet.

When the screen comes apart, the dish portion that slides over the pump venturi/suction tube is allowed to move freely and starts to wear into the tube. I was lucky that I change the oil alot (race car) and discovered the screen problem right away. Otherwise I suspect the tube would be worn thru like this one

Oil Sump Tube - How Much Of A Problem Is This?

I'm not saying this screen problem is a problem for each and every pump. Just pointing out that these cars are getting old and the screen may be an occasional problem people run into. The screen comes free from the base flange where its tacked on with what looks like brass brazing. The tacks don't come loose. It appears that the suction of oil thru the screen for countless hours eventually fatigues the screen at its anchor point and breaks? Mine broke so cleanly it looked like it was cut.

Note that my screen is an original Porsche part that failed. Not some cheap URO aftermarket stuff, that I know there's been some problems with (e.g. the oil tank S-hoses that are falling apart shortly after installing).

[lindy 911]

Henry,

Does Supertec do the SC pump mod? What is involved? I'm going to be pulling mine apart again for the through bolt / #8 bearing oil drips and would like to get this done. Do you recommend cross-drilling the crank with this mod. What about other mods like the case?

[Henry Schmidt]

Supertec does in deed perform the oil pump modification. Along with this mod we always run cam feed line restricters.
For the last 2 years we have been doing the cross drill modification on every engine we build.
It involves cross drilling the crank, grooving the #4 main bearing as well as enlarging the oil feed hole to the #4 main bearing.

[Walt Fricke]

Henry - what are the pros and cons of grooving the #4 main bearing versus grooving the the crank bearing? For those who don't have a lathe to groove a bearing, avoiding doing that every time bearings are replaced seems like a plus. And a bit less hassle getting bearings coated.

[Henry Schmidt]

Originally Posted by Walt Fricke

Henry - what are the pros and cons of grooving the #4 main bearing versus grooving the the crank bearing? For those who don't have a lathe to groove a bearing, avoiding doing that every time bearings are replaced seems like a plus. And a bit less hassle getting bearings coated.

The easy answer is that grooving the crank weakens the crank but when properly done, it's just fine.
The way to deal with grooved bearings in a constantly freshened race engine might be to just buy an extra set of main bearings to groove for future builds.
With one set of mains you can groove 6 pairs of mains for backup.

When we built the SuperCranks the design team went with grooved journals and cross drilling every main.

[Flieger]

Grooving the crank should move the critical speed for the torsional vibration in the flat-6 crankshaft down a few rpm, too.

[scott_rogers]

Thanks for the insights everyone. I hope that this thread proves useful to others in the future as well. I'll post more info on the rebuild as it nears completion.

Happy Holidays

[911 tweaks]

scott & anyone...any more info to add to this great thread...??

[Eagledriver]

For a car used for DE, Autocross, and street, I wouldn't do any of these mods. Your engine will go another 160k miles and then you can ask these same questions. I assume you've been driving your SC in the above manner for a number of years. Your mechanic will be inspecting the engine when he takes it apart. It will show almost no wear to anything but the valve guides, intermediate shaft bearings, and possibly the rings, and aluminum intermediate shaft gear. If he can tell you that anything about your engine shows it needed higher oil pressure or better lubrication of the rod bearings, then you should consider these mods. Otherwise save your money for some "R" compound tires.

-Andy

[Eagledriver]

By the way, I've been racing a Spec911 for 13 years now with a stock SC pump and non-crossdrilled crank. My rev limit is set to 7300 and I try to shift at 7200 on every shift. My engine has 230HP on the chassis dyno. The engine has been apart 3 times for piston/ring changes and valve job. I do about 8 race weekends per year plus some street driving and DE's. Bottom end has not been apart since I built this engine.

-Andy

[KTL]

The only reliability benefit I can see going from a SC pump to a Carrera pump is the built in strainer & venturi plate. Having the built in screen avoids the problems I pointed out in the links in post #3

Otherwise you gain nothing from the swap since they both have the same size scavenge and pressure pump sections. Even though the Carrera pump is new, you aren't going to find much indication of wear on the SC pump. These oil pumps are VERY good pumps. Very precisely machined and well built.

However, there are just a few areas where the flow can be improved by massaging some sharp edges created by the casting & machining process. Certainly not a must-do, as they perform fantastic "out of the box" so to speak.