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Back in the day you could buy high pressure oil switches for a BMC Mini that went out when the engine was idling. Sometimes like a cylinder pressure gauge it's often best not to know. The factory dash oil pressure gauge on my W124 Merc had a maximum reading of 45 psi so anything higher was superfluece.
I did fit a pressure gauge back in the late 70s, Smiths iirc, I seem to recall it used to run at 80psi, came in useful one day as whilst on a run down the motorway it suddenly dropped pressure like a stone, turned out the oil filter, which was a pattern filter, had collapsed and went into a spiral shape as it did so. Never fitted anything but genuine Honda since on a SOHC.
" I wonder why Honda, in this instance, chose not to have the oil pressure switch situated at the top end"The cylinder head is effectively "open bath" lubrication with the pressure just delivering the oil rather than being a constant pressurized film as the crankshaft bearings are. After the restriction going from gallery to the head there's not that much pressure to monitor, if failure occured (blocked preventing oil getting out) the pressure would rise not fall, but then if too high pressure was present the relief valve would open on the pump. So you'd not see the error from monitoring system easily.It does look odd though as essentially there are two different delivery systems combined and split as noted, base mains etc and head system all occupying the same engine
Quote from: K2-K6 on October 04, 2021, 10:00:06 AM" I wonder why Honda, in this instance, chose not to have the oil pressure switch situated at the top end"The cylinder head is effectively "open bath" lubrication with the pressure just delivering the oil rather than being a constant pressurized film as the crankshaft bearings are. After the restriction going from gallery to the head there's not that much pressure to monitor, if failure occured (blocked preventing oil getting out) the pressure would rise not fall, but then if too high pressure was present the relief valve would open on the pump. So you'd not see the error from monitoring system easily.It does look odd though as essentially there are two different delivery systems combined and split as noted, base mains etc and head system all occupying the same engine A few million years ago I worked for a motor parts wholesaler, and we did a steady trade in selling camshaft kits for the Ford OHC Pinto engine. I think I'm right in saying that they also used the "spray bar" system to lubricate the top end, but, I never did find out if the problem was down to poor lubrication or other factors. I seem to have a vague memory that the cam lobes wore prematurely.
I had an amp meter and a oil pressure gauge mounted in a pod above the speedo/tacho so they were easy to see. The oil pressure take off was mounted where the current pressure switch was on a T piece so they both worked, it meant cutting out part of the chaincase guard but it did work.
It was a long time ago, late 70s or early 80s IIRC. The actual readings I don't accurately recall, more the position of the needle, IIRC the gauge went from 0-100 ( i just looked up a picture of one, I thought it went higher so that's why I said 80psi) and the needle used to sit almost vertical when running but a little past, which made me think 80psi sounded about right, but based on the pic 55-60psi is more accurate, it used to go down on tickover to approx 20psi and around 40psi when very hot but TBH it didn't sink that much as back then we all used 20/50 oil so it was thicker to start with.