SBD sandwich plate mod
I modified my sandwich plate back to standard in an attempt to regain oil pressure.
Basically, when SBD had all my engine parts before the last rebuild, they suggested this mod. It make the oil flow to the cooler all the time - thus keeping the oil cool.
After much disscussion here, it was decided that for a road application, this is most likely doing more harm than good.
Adding my poor pressure problems to this, I felt it was time to change back to standard. I was not planning of doing an oil change so I didn't want to remove the sandwith plate fully, especially as the pipe to the cooler are know for rounding off and being difficult to remove.
Instead, I removed the circlip off the oil temp thermostat housing so that I could replace the internals. I was expecting to find that SBD had removed the thermostat complately, but this was not the case. The stat that I removed was much longer and cause it to be open all the time. It was a bit fiddly to do, but I managed to replace it with a standard item.
This worked a treat and oil pressure - although still not great at idle, is now much better throughout the rest of the rev range.
The reason for this is that the oil is restricted more by not going through the cooler. The restriction causes a back pressure which enables the oil pump to build up pressure. Without this back pressure, the oil pressure drops off.
Those of you with a cooler may spot that oil pressure suddenly drops when the oil gets hot. I always used to think that this was because of the oil getting thinner, but on reflection, I am now thinking that it is due to a loss of back pressure when the oil temp thermostat opens. This makes more sense to me.
Any other thoughts?