1965 401 oil filter housing problem discovered.....

[dlmwtvl]

So,
  I just finished another 401 assembly.
Started the engine, and set the timing.
I set the idle to 2000 rpm, and let it run for 15 minutes. (Cam break in)
No issues whatsoever. Excellent oil pressure.
   The next day, I started it again, set it to 2000 rpm for 15 minutes.
Again, no problems.
After 15 minutes at 2000,  I let it idle for a few minutes, and shut it down.
I was happy.
Ten minutes later, I went under to drain the break-in oil, and change the filter.
When I touched the oil filter, it was almost cool to the touch...……
The oil pan had 6 quarts of 180 degree motor oil, and the filter was full of oil, but cold oil....
The oil filter housing, has a bypass valve, which is supposed to open, when "the element becomes restricted enough to produce 4.5 to 5.5 pounds
difference in pressure between the inlet and outlet ports"
Mine was opening with the drag of a brand new Wix 51049 filter and 10w30 motor oil.
The oil was not being filtered, at all.....
The bypass valve spring, simply fatigued, from 55 years, and all those heat cycles...

  I had another housing, that felt firmer on that valve. I put it in, now, it is filtering the oil.
Does anyone have a part number for the spring, and the little fiber disc, to renew these oil filter housings??
I wonder how many of these valves are malfunctioning out there?
Debris going around the engine and never getting filtered out...
Anyone got a sticking oil pump pressure relief valve????? This condition would cause that, and so much more!!
We change the oil and filter, and, assume the filter is catching the debris.

   I always cut open the break-in, oil filter.
There is always something in them.  I do remember one,  that was completely clean...… I mean, nothing....I was proud of my clean work, but, still puzzled that there was nothing.... This could be the answer...…..
The Horror...….

[telriv]

To filter ALL the oil I usually plug the by-pass.  BUT you need a good filter that can carry the volume required which I believe the Wix filter does.

[dlmwtvl]

Tom,
I found replacement springs, by size and rate.
I went with a 7.5 lbs./inch spring.
I dare say, the one removed, was less than 1 lbs./inch.
It's filtering oil now.  I only use 51049 Wix filters.
What is your technique for plugging the by-pass?
Thank you,
David

[65GSConv]

This is interesting. With a WIX 51049 oil filter, which does not have an internal by-pass value, and with plugging the oil pump body filter bypass valve, the only safeguard against oil over-pressure is the oil pump body pressure relief valve (which according to the 65 GS Service manual, should limit total pressure to either 33 PSI or 40 PSI (both values are stated in the service manual, likely only one can be correct, and I don't know which is). I'm wondering if today's oil filters are built differently than back in 1965, in that today's oil filters have a great restriction to oil flow in order to reduce the nominal micron filtration size. I've seem some oil filters of today with internal by-pass valves having a rating of 14-18 PSI; this is a heck of a lot higher than the 65 GS's oil filter bypass build into the filter housing of 4.5-5.0 PSI.  And given the pressure relief on the 65 GS oil pump body is either 33 or 40 PSI (let's say 40 PSI), that means only 22-26 PSI is left for the rest of the engine if the oil filter was reaching its maximum capacity. I just wonder if today's oil filters increase pressure sooner in use because they are filtering smaller particles that the original filters left go through. An oil filter that takes out smaller particles appears to be good for the engine, but only to a point until it reduces oil pressure to the rest of the engine. This may mean shorter oil filter change intervals on these engines to keep pressure drop across the filters as low as possible.

Anyone have any data on the old original oil filters to know what the pressure drop data was on them compared to, say, the WIX 51049 of today?