Which Oil Cooler to Use

[Dave Wildrick]

There are two types of oil cooler for the 912. The early style mounts conventionally, does not have the top tab, and is retrofittable easily to any earlier engine. These fit '65-'68 912s.

Are you saying that the 912 oil cooler without the top tab will easily retrofit to a C engine?

Stoddard currently lists the "tabless" 912 cooler (616-107-041-01) as in stock and priced at $134.82.
Does anyone know if that is a direct bolt-on to my 65 C engine, or do I have to enlarge holes with a drill and jerry-rig spacers and weird seals, etc.?

[Mervyn Hyde]

I appear to have the same oil cooler VR 04102. Seems to be aluminium, but I need to check further, and it is clean on the outside at least. Six vertical rows with a Honeycomb lattice. The car seems to run in the right temp zones. No leaks at all from the cooler, but I will clean and pressure test afterwards. There are no 912-type mounting points on the top.

I have no idea how efficient these are?

[Vic Skirmants]

That is the late STEEL cooler.

[Al Zim]

Porsche (the factory) redesigned the 356 case at the end of 1963 production (356B) Sometime before production ended these cases were installed because they ran out of earlier cases. In your B supplement parts book a list of these cases is in the front of the book. In the case of the Super and S-90 the case is distinguishable with a 7 digit serial number beginning with a P0XXXXXX. The ease is easily recognizable since it does not have the triangle in front of the shroud between the shroud and the flywheel (the flywheel is at the front of the engine). The metal was thinner under the oil cooler stand and would seep or crack. The solution is to heli-arc the area between the base of the oil cooler and the case. We do this to all our engines. WHAT KIND OF OIL COOLER TO USE? For normal and super we use the VW metal cooler. It is new! If the customer insists we will use the aluminum cooler. On the S90, SC and 912 we use the aluminum cooler. In my opinion unless you are driving like crazy the VW cooler is more than adequate. REGARDING SLUDGE IN THE OIL COOLER: If you have sludge in the cooler your engine has already blown up! Since there is no full flow filter on the engine, any particle in the oil are caught in the main and rod bearings are now serve to grind the crank. Excessive metal partials ((read fuzz) on the magnet indicate that the crank grinding has already started! Engines that have been resting for years will generate metal crank grinding particles as soon as the rings scrape the rust from the cylinders. al zim

[Mervyn Hyde]

Thanks gentlemen. I only pulled the motor out yesterday afternoon. Had just started the cleaning process. The oil cooler looked quite clean and leak free but I am thinking I should replace it. From what you say it is probably original?

The car is an early 63 sold T6B N (610544).

So steel or aluminium is the question at this stage I guess. Should I get an NOS steel cooler, leave this one in place, or buy an ally one?

[Al Zim]

It is VITAL that you check the piece that screws into the case and supports the oil line to the filter and the oil temperature and pressure switch. If this piece has 4 holes in it make sure the holes are round. If they are not throw the piece away because it was tightened too tight and stretched. This will break and cause immediate destruction of your engine. The replacement part has a hole (one) in it that is about the 3 mm in diameter this will not break and explains how ineffectual the oil filter is. If you decide to remove th oil filter, you will have to make a line from the oil filter pick up to where it goes back into the case or the oil temperature will not work properly. al zim

[Mervyn Hyde]

Thanks Al. I pulled the oil junction block off and cleaned it out. There is one large bolt through the fitting to the case with the sender terminal and that is all, other than the oil filter vertical line. The bolt that goes through the oil junction block is held in place by the standpipe that screws into the case. I checked for 4 holes but my part seems to have the one hole that you describe. There is no sign of stretching.

Still not sure about this original oil cooler. It is now squeaky clean and could do perhaps with a dusting of silver paint but I am loath to pull it off or throw it away as it works fine and there are no leaks or cracks.

(photo is not mine)

[David Jones]

When it comes to oil coolers it is in my opinion a waste of time and money to put in a more efficient oil cooler if the original is cooling the oil as much as it is needed to do. Overcooling of the oil is not good for the engine as it will be less efficient and cause more condensation build up in the sump by not evaporating off the water that is generated by combustion and finds it's way in to the sump. I found that the most efficient oil temperature for the F Vee engines was around 220*F and unless it is a hot day and you are cruising at high (4000 rpm) it is doubtful even then that most engines in a good state of tune would get that hot even with a stock cooler. Do not equate the need for a bigger, better oil cooler with the need for such on a race engine as being justification for one on a street engine which will never get subjected to the needs of a race engine and remember the oil viscosity used in race engines is also usually different and it is not subjected to stop/go driving.
I have always driven with a certain level of alacrity and I only have stock coolers and have yet to see my sump oil temp get to 220*F. Conventional oil breaks down at 250*F and synthetic around 300*F plus. The heads run at 325*F and the oil carries away a lot of that heat. This is why the oil needs to be changed because it is always gradually breaking down and no amount of cooling can stop it reaching breakdown temps at certain places in the engine.
Your needs and beliefs may differ, I just go by what I have experienced.

[Jacques Lefriant]

Hi David
You make a good argument for the thermostat that Porsche used in 1958 and for the use of multi viscosity oil that is available. However now i would have to recommend one of the aluminum coolers for most scenarios.
j

[Al Zim]

Meryvn the post you describe in your engine is the 912 post and usually it cannot be stretched. It also flows almost no oil to the filter. Oil works best when it is above 215 degrees Fahrenheit the impurities (also water) are removed due to the temperature. Over cooling the engine has been a concept that I have never considered. Present oils are substantially better than those available in the 1960's. Concerns about the ability for oil to withstand higher temperatures without breaking down are unfounded. Driving your 356 at 60 to 70 MPH (which I think is a speed that is safe) in 4th gear will not make heat. 90-100MPH will! Four areas of concern, A) is the fan working properly B) is the oil cooler clean C) How worn out is the oil pump drive gear to the cam D) what is the rod bearing to crank clearance must be correct for the engine to survive. Followi8ng factory recommended oil changes is a necessity. Aluminum oil coolers are nice to have, but in most not a necessity. al zim

[Edwin Ek]

David, what happens when oil breaks down? Do polymers shorten, perhaps thereby reducing lubricity?

[Al Zim]

The situation is not when the oil breaks down, it is the dirt and metal shavings from the wear in the engine that needs to be removed since there is not full flow oil filter on the engine. In dirty conditions the factory recommends oil changes at 1500 miles. If you were in very cold climates it would be more frequent than that. al zim

[Edwin Ek]

Al, thanks for replying. I was asking more generally- including cars, which have modern, efficient, full filtration.

[David Jones]

Edwin, you are opening a can of worms with that question. Short answer is yes but there is so much more to it. Synthetics will withstand higher temperatures for longer and as a result will not suffer oxidation due to thermal breakdown so the oil should in theory last longer. Problem is in the additives they still break down over time and heat cycles so once they are depleted it is time to change the oil. Ideally one should change oil by analysis but also by being aware of what the oil has had to do. Stop start driving is harder on oil than one continuous run at optimum operating temp. I have had to change conventional oil in the race car after one race because it ran a race over 250*F indicated oil temp for the whole race and it smelled burnt after the race. I have also run a whole race on synthetic with the oil temp over 270*F for the whole race and the oil looked and smelled OK.
There is so much information available on oils on the internet and so much disinformation out there that it is very hard to make an informed decision on oil. I now use Shell Rotella in all the 356 engines and Mobil 1 in the boxster. I have one engine with a full flow oil filter and two with the bypass. The engine with the full flow filter gets it's oil changed at 3K miles like the other two but that is because it has worn rings and guides and the oil gets contaminated faster so needs changing more often. Once it is rebuilt this winter it will probably get changed every 5K miles.

[Mervyn Hyde]

Thanks David. After this advice and the advice of others here, I have decided to let “sleeping oil coolers “ lie, and leave it in place as it works and does not overheat. Al I am a compulsive regular changer of oil and I also have been checking the sump plate for any form of sludge or build up. There is none. The full flow filter is an improvement that I may address at another time however.