Back in the day before the turn of the last century we didn’t have the internet like it is today with its vast array of information. We were lucky to have a dial up modem to log onto our AOL account!
So we couldn’t just click a year and model car and click “Service Bulletins”. We had a little reference book for the year that listed all the titles and a bunch of big books that listed the complete service bulletins in detail. Each year when the book came out you sat down and read it cover to cover. One of these bulletins discussed the problem with hot low oil pressure and oil foaming. Lets take a closer look.
The bulletin discussed the existence of an updated cam oil line fitting for the cam housing on pre- 3.6L 911 engines that restricts oil flow to the camshafts by nearly 50%. I thought the Bulletin was quite interesting, but I still had some questions that it didn’t answer, so I did a little R&D on my own making special upper valve covers with windows so I could see the oil flow inside without taking a shower in hot 911 engine oil while running the engine. Let’s discuss my findings.
911 engines after late 1966 and all the way up to the last 1989 3.2L Carreras and 1990 3.3L Turbos all use the same adapter piece connecting the cam oil line to the camshaft housing. (Part #901.105.361.00)
Starting with the 1991 911 Turbo this adapter was replaced with a new updated adapter with a reduced center orifice. (Unfortunately, Porsche did not give a great deal information as to the reason for the update, other than to reduce oil foaming.) The new adapter (Part # 901.105.361.01) has a groove around the center to differentiate it from the older adapter when installed on an engine. (See Figure #2)
(Original adapter with 6mm orifice and updated adapter with 2.5mm orifice)
Oil foaming is caused when there is too much oil in the crankcase and it gets “whipped up” by the rapidly rotating internal parts. You might be wondering, much like I did, if such a large reduction in orifice size would still deliver enough oil to the cam housings. To find out, I installed these adapters on several cars with greatly varied oiling needs and scenarios with my custom see through valve covers.
One of weakest oiling systems I installed the adapters on was a 1975 911S. This was a high mileage car that had no front oil cooler, a small early style oil pump, was still running the original 5-blade cooling fan and the thermal reactors were still in place. As you can imagine it did not take long to see 220-230 degrees of oil temperature and no idle oil pressure in this car. I figured that if the updated fitting worked in this car, it would work in anything.
After installing the adapters, I pulled the top valve covers and had someone start the engine. Oil vigorously sprayed from all of the holes in the camshaft spray bar, which told me there was no need to worry about low oil volume to the cam housing. The surprise bonus was that the car now showed about 10 psi on the oil pressure gauge instead of a bright red warning light. All this for two $27 fittings!
The next test was on my 914-6 racecar, which has an interesting camshaft/cam housing setup. The cam housings are later ‘74 cam housings with a central oil spray bar. The camshafts however, are ’66-911 cams with internal oiling (oil pressure from the cam journal exits holes at the heel of the cam). Porsche used one or the other, but never both types of oiling in the same engine due to the inevitable loss of oil pressure at idle. I installed the updated fittings and ran the same valve cover test.
This time I was amazed to witness what could only be described as a very messy geyser of oil coming from the right side cam housing. With 210-degree oil temperature, the oil pressure was almost 30psi due to the engine’s turbo oil pump. Pressure with the old fittings was closer to 10 psi.
After all our tests, I came up with the following conclusions:
-The fittings decrease oil to the cam housings and decrease oil foaming.
-The decreased foaming allows the scavenge oil pump to transfer oil out of the case and into the storage tank much faster. This in turn keeps the oil tank level more consistent and causes the oil level gauge to react quicker.
-Less oil foaming will lead to less consumption of oil through the engine breather system.
-The smaller orifice creates higher oil pressure at the main and rod bearings as well as at the piston squirters. The increase we noticed varied from 10-20 psi.
All in all, these fittings seem to be a great addition to any early 911 engine. With an extremely low cost and huge lubrication benefit, I am sure that even the most frugal 911 owner will be eager to spend a little and gain a lot in performing this update.