Can you change the hex shaft by removing the oil pump cover? Six screws roughly? Car is not here just now so I can't just look.
If you pull the cover, will the driven gear just pull out? will the drive hex then just pull out, or are there bits that may fall out of place?

Lang G

 

Very interesting thread. So can you change the hex shaft with the engine still in the car?

 

Yes, by removing the cover the gears will pull out and then the drive will pull out. On the 996/7 to access the cover you will need to lower the engine and remove cats and engine mounting plate, on 986/7 the engine will need to be lowered and the engine mount removed.

 

PorscheTech3
" I made my own drive shaft from an 8mm Mac Tools Allen wrench and tested it to failure 153ft/lbs !!! Almost 3 times as much. So I make all mine out of Mac 8mm Allen wrenches now.
Thank you for sharing this in Post 27 above. Since you have this mod in 3 cars ,it is a reasonable road test of the upgrade. This leaves the oil pump drive shaft upgrade deniers no (financial) excuse for not doing it.
One caution, I would be hesitant to use a "made in China" allen wrench for this. Unless the wrench has a clearly stated (reputable) country of origin . stick with SO, Mac .Proto and similar.
Thank you for sharing your upgrade with us.

 

Your Welcome !!

One caution, I would be hesitant to use a "made in China" allen wrench for this. Unless the wrench has a clearly stated (reputable) country of origin . stick with SO, Mac .Proto and similar.

Exactly !! I used the Mac Tools hex because it was the first one I had tested after the testing the factory hex drive, and was extremely please with the results. I have no idea who makes these Hex Keys for Mac or if they make them themselves, but I would not be surprized if all the top tools companys (Snap-On, Mac, Matco, Proto )do not use Bondus Hex Keys Protanium Steel http://www.bondhus.com/features/protanium/body-1.htm[url] . I will do a test on this steel to see if it the same.

FWIW.. A bit of information on the 997 pressure relief piston , it was designed as a cure for an unusual noise/screeching at cold idle on the early 9x7 cars. I was involved in this factory concern in late 2004. when we first discovered that the noise was coming from the relief piston we ground the chamfer on the then 996 valve to eliminate the noise. Then the 997 valve was designed and used in production and to supersede the 996 valve, the spring has not been superseded.

 

Just an update on the oil pump drive shaft hardness. I tested the factory drive shaft and it measured from 32-37 Rockwell C varying at different points. then tested the one I made from a Bondhus Protanium hex key , it tested 54 Rockwell C,. So the stock drive shaft not only is more brittle, and fails at 1/3 the torque, but also is less hard too !

 

Very interesting and informative thread. Good to see alternatives and their characteristics as opposed to the OEM drive shaft.

 

Awesome!!!! Well done!

 

FYI- Since 2008 LN Engineering has manufactured a billet oil pump drive key. This was a development that we carried out, after experiencing our first drive key failure on track.

EVERY engine I have built since that has included the billet drive key.

 

So what are the actual measurements of the oil pump drive hex key ? So far I've got 8mm what's the length ? It looks like it might be 2"/50mm ? Of course exact #'s are always welcome

 

It would be nice to know the length also.

 

I'll dig up mine and measure it.

 

Thank you IMO.
That would be great because then Forum Members could try the tool suggested by Porschetech3 - the depleted uranium (whatever he found?) 8mm hex wrench cut down to your length.

 

i've been wondering about the piston upgrade. i make a habit of checking the PET for upgraded part numbers and then trying to determine why the change (i AM a geek) - ie, AOS has 5 or so interations, so common sense says use the latest and hope that porsche has engineered-out the earlier failure modes in the later version. of course porsche wouldn't advertise that earlier versions are problematic, so caveat emptor and up to a diligent owner to figure these things out. ditto chain tensioners, chain pads, and a few other parts.

i did the piston upgrade (5 minute job at your next oil change - different story pump drive) and saw a reduction in start-up chain rattle which supports the high oil pressure at start-up due to cold oil and piston binding theory. what i am wondering is - this piston is also the oil bypass valve on the oil pump yes? ie, when the oil pump experiences high oil pressure the piston moves and oil oil bypasses back to the sump, correct? if so, one of the theories on the oil starvation issue is that the oil is pooling in the heads because of scavenge pump location in the heads - i am wondering if the pooling oil in the heads is causing a high pressure situation and the bypass valve is activating? perhaps a stonger spring would help with the problem?

 

Yes.And welcome to geekdom Mr. Radium!
In a normal engine there are plenty of drain holes to replenish oil in the sump.In this configuration we rely on those two English scavenge pumps. If they can't "keep up" as the Brits would say, the accumulating oil in the heads will cause oil smoke in the exhaust and maybe dangerously low oil level in the sump ?
Solution - a partial at least may be to have a deep sump and reduce revs when you see oil smoke ?