Lotus Elan and Lotus Elan Plus 2 Forums

Davidb wrote:Thank you Rohan!

From Keith Dixon's paper:
"As a rule of thumb, it is reasonable to allow for a pressure drop of 10% for each right angle change of direction {of oil flow} ."
That is what I was trying to overcome/avoid.

So Rohan, it does mean that the flow is increased-which is a good thing-but pressure would be unchanged?

I am still trying to understand why I am getting 60psi oil pressure with the new standard pump and was getting 55 psi with the old, standard pump (measured with a stand-alone gauge)?

Davidb wrote:Thank you Rohan!
So Rohan, it does mean that the flow is increased-which is a good thing-but pressure would be unchanged?

Davidb wrote:Update.
So today I finally got back to working on the Elan engine. When Covid19 struck and all events were cancelled I simply left the car and worked on other things-repainting the house, gardening etc...(Yuk!)

Here is what I found.
I removed the new oil pump and thanks to tips on this forum it was easy. I supported the engine, removed the two bolts that hold the r/h engine mount to the chassis, jacked up the engine and slid out the oil pump. ( I did remove the end plate but found it was unnecessary because the pump came out/in anyway.
I examined the pump and compared it to the old pump. Finally I realised that the oil pressure relief valve on the old pump was stuck open! I had not noticed this before since I found the oil pick up pipe fractured and concluded that was my only problem.

P1090132.JPG

So now I examined the new pump to find the cause of the high oil pressure. Was it a HP pump in a STD box or what? What I found was that the oil pressure relief valve spring had an arc to it-unlike the original pump where the spring was straight. I examined it closely and finally realised that the spring was installed incorrectly. It uses a retaining plate-which is shaped like a washer but the centre hole is actually punched out as a protrusion that locates the spring. The spring had been installed incorrectly and instead of sitting with the spring surrounding the protrusion it was sitting on the edge of the protrusion thereby reducing by an eighth of an inch the fitted length of the spring and increasing pressure. I jammed a Philips screwdriver down the hole in the retaining washer, there was a "twang" and the spring was in the right place. Here is how the spring would have looked out of the pump:

P1090132.JPG

So cleaned and refitted the new pump and spun the engine over on the starter-with plugs out and the carbs still unfitted and I get 45lbs oil pressure! I also found that the threaded section that the oil filter threads onto was loose in the oil pump.

I think the lesson here is to check these pumps thoroughly before fitting!

(I dunno why there are two copies of the oil pressure relief valve photo...)