If I realized that, I wouldn't post the things I did? I'm not arguing or trying to contradict the actual areas within the thermostat. I'm simply noting the path(s) the oil must take to get where it wants to go.
This sketch made by JRSIII in the other thread I linked in post #16 is a REALLY good sketch to show what's going on inside the t-stat when cold
With that picture, here's some locations within the t-stat to consider when cold. Cold is the issue we're most concerned with here, since the pressure will drop considerably when the oil heats up. Although there is the restriction of the oil flowing through the cooler but let's not get into that.
1. Note the alignment of the regulator window and this is most notable in the actual photo of the cut thermostat. The oil is encountering an edge and has to deal with this edge after it goes around the annulus of the t-stat casting and then upward 90 degrees to enter the regulator. Wouldn't this cause a pressure increase?
2. As the oil continues up through the regulator, it encounters the projection of the spring seat machined into the cap, and the spring itself. That said, the cap itself is indeed relieved around the seat and also up into the cap. These reliefs allow a more free passage of oil around and into the next annulus here. Again the oil has to change direction somewhat abruptly to exit the t-stat. But the change in direction is well managed by forcing the oil around that spring seat area.
Also worth noting is port/location #9 in the photo, which is the exit to the tank. Note how this diameter appears to grow as the oil exits the t-stat. That's a nice design to help minimize the losses as the oil leaves the t-stat.
Don't get me wrong here. I'm not implying the factory thermostat is a bad design. We'll not find a better thermostat when you consider its inlet and outlet port arrangement and the bypass/overpressure section it contains. I only wish that the t-stat had steel fittings like the later 964 t-stat.
I'm just saying that in the spirit of compactness, the thermostat has some tight areas that appear to create some pumping losses. The only reason I shared any of this is to point out to people that there isn't a free release back to the tank from the engine case oil sump. The thermostat has definitely has some tight turns in it. These turns are not smooth bends like a typical hose fitting. They're rather abrupt turns.
Take my comments for whatever they're worth- just observations and nothing more. I'm not saying my analysis of this contraption is based on flow testing and measurements. Just visual observations and my own understanding, which may be flawed in more ways than one, of how the oil is distributed throughout the t-stat.
Side notes:
I've said it before and i'll keep saying it. Anybody buying one of these t-stats used should very strongly consider opening it (BOTH caps) to replace the regulator and clean the inside. These units can contain a lot of garbage, especially in the bypass section. Oh, and have fun reinstalling the small cap atop the bypass section. That small diameter spring is a really stiff SOB.
Speaking of the caps, consider getting some replacement caps with hex heads. Mostly because it's difficult to get the caps off without nearly destroying them. I have needed to use a large pipe wrench carefully placed on the edges of the cap and a lot of force (heat included as well). The original caps with slots in them are also a cruel joke as far as using a tool for removal and re-installation.
Sure, you can make your own tool with some
strong (emphasis added) sheet metal contoured to fit the curved slots, along with some decent welding skills if you want to make a socket. Or you can grind a pair of thick chisels to the contour of the slots and use a wrench on the chisel. That's the tool I made until I came across the caps with hex heads. I say chisels plural because as luck would have it, the slots are NOT the same size on these two caps and therefore you need to make two tools.
If nothing else, at least you can still buy replacement slotted caps for not a lot of money. Or just contact Jimmy T here on the forum who sells some really nice custom machined & anodized hex caps for basically the same price as the original slotted caps, along with other cool things he makes. No affiliation with Jimmy on my part other than being a very satisfied customer.