(quoted from post at 14:29:57 05/04/12) OK, let’s clarify a few things since there is quite a bit of misinformation floating around on the web about adapters and what is really required.
First off, there is no special “orifice,” or “restrictor,” or “special filter” needed to maintain oil pressure with an N lube system. Open you parts books and look for this mystery restrictor. There is none. Pull out your filter element and look in the canister. Do you see an orifice? No. There are two ports in the housing which are tapped for 1/8-NPT. The fittings which thread into them are nothing special. They are an inverted flare fitting with a 3/16” hole through the center….this is the standard for that size/style of fitting.
What creates/maintains oil pressure in these systems is the fact there is several feet of small diameter tubing. Take the oil filter feed tube off and blow in it. It’s pretty hard to push much flow through it at all. So, the metering of oil through the filter is perfected simply with the architecture of the system and not through a calibrated orifice. The fact of the matter is you could put on virtually any head or filter and it would be transparent to the operation of the system and not affect the oil delivery to the bearings, etc.
With that said, both of the custom filter adapters for the N’s do include orifices. They include necked down regions which are 3/16” in diameter. Since these do not have any smaller cross sectional flow area than any other portion of the bypass filtration system on these engines, they really do no harm and are more to address the “myth” that a restrictor is needed in the N system than anything else.
With all that said, there are some nice benefits to the spin on adapter. In addition to the convenience of being able to buy filters at virtually any filter retailer (Walmart, Target, Farm and Fleet, etc), they make for a very nice reasonably mess free oil change. Probably the largest reason, however, is the fact you now have options in terms of the filtration you put on your engine. You can select a make of filter which provides far superior filtration to the original filter. If you look up the specs of the original filter, it has a 32 micron rating. Now take a Fram extra guard which has a 94% multipass test score and a 10 micron rating. 32 micron to 10 micron is huge. Add on the fact that you can now install a filter with more filtration media (remember that filtration efficiency is related to the face velocity of the oil through the media – the more media, the lower the velocity and the better the efficiency) and a spin on adapter will take your N to a whole new level of filtration.
I personally want to get the most number of hours I can out of an overhaul. If I can make a small investment to improve the filtration and reduce engine wear, I feel it will pay dividends in the long run in terms of down time true out of pocket cost.
