Oil pressure test

20 psi is low, as I believe the pressure relief valves are designed to open at about 55 psi then I wouldn't expect to see anything less than this on your gauge, hot or cold, except on tickover. Maybe the thick oil your using is disguising a problem,

Simon.

Tony, you did not mention the age, or model of your bike. Earlier models had scrolled rocker shaft oilways, and ran at a lower oil pressure. 5 P.S.I. minimum would be right for this system, with hot oil, bearing in mind that, the original recommendation for monograde oil was 30 S.A.E. winter & 40 for summer use. If you are in the U.K., if the pressure dropped to 5 P.S.I. at this time of the year, while using a 40 grade oil, something would be very wrong. 20 P.S.I. seems reasonable. Since you are happy with your set up, and were not asking for advice, what was the point of your post? John.

hi anthony i found your original post quiet informative so thank you for posting it and as this is a discution board not a Q & A then thank you for sharing the infomation

I am not sure if this is fact, but I once read in a bike magazine that when Norton first sold the Model 7 Dominator, it was fitted with an oil pressure gauge. The factory was inundated with complaints that the oil pressure was showing low. The factory then thrashed a model 7 showing no oil pressure round a test track with no apparent problems, so they got around the problem by not fitting an oil pressure gauge in subsequent years.

John previously wrote:

Tony, you did not mention the age, or model of your bike. Earlier models had scrolled rocker shaft oilways, and ran at a lower oil pressure. 5 P.S.I. minimum would be right for this system, with hot oil, bearing in mind that, the original recommendation for monograde oil was 30 S.A.E. winter & 40 for summer use. If you are in the U.K., if the pressure dropped to 5 P.S.I. at this time of the year, while using a 40 grade oil, something would be very wrong. 20 P.S.I. seems reasonable. Since you are happy with your set up, and were not asking for advice, what was the point of your post? John.

John

I imagine the point of the post was that Tony thought it might be interesting. I thought it was.

Alan

O.K. My apologies for the final sentence! John.

Tony,

your reference materialappears to cover engines designed with roller bearing big ends, ES2, Model 50, through to shell bearing big ends, twins.

The oilpressure and flow requirementsdiffer greatly between the two designs,so I assume the quoted figure of 5 psi is the minimum for a roller big end,not suitable for a shell big end where a minimum figure of approx. 15-20 psi at tickover with everything at working temp. is required.

I'll go with the factory recommendation of pressure relief valve opening at approx. 55psi., what has oil pressuregot todo with camshaft lubrication anyway,when the camsare fed by splash?

The factory did a publicity test in the late 1950s. They took an 88 engine on a test rig and bypassed the oil pump, running it on gravity feed (the centifrugral force of the spinning crank drawing oil in to the big ends) for 24 hrs at max power, with no harmful effects. So you could conclude that you don't need a huge amount of oil pressure for saisfactory lubrication, even with plain bearings.

Gave the Ingliston show a miss - too much going on at home just now. I will have a bike exhibited at the Lanark Classic show in May. Time to start polishing!

Gordon.

I have restored a '74 850 and found the crankshaft oil seal in the timing cover was 'blown' which turned out to be caused by the pressure relief valve being stuck. To me this suggests the purpose of the relief valve is to avoid the huge pressure starting from cold doesn't do any damage. I checked the big ends to be safe which were fine and fitted new shells so I am satisfied the pressure I get is correct which is about 70psi when cold dropping to 20 - 30psi when really hot. I have seen other comments on here saying the same. What surprises me is Norton having only an oil seal in the pressure line, especially after they doubled the oil pump speed in '66. I do keep a pressure gauge on it for safety.

I would be running multigrade oils in a shell bottom end. The oil gets to where it should quicker on start up. Norton recommended it for the twins and oil is far better than it was

Very interesting.

I have just bought a 1957 88. I think it is a good idea to have a gauge if one can be fitted. I need a diagram or photos of how to fit one please?

Took my 88 for a short first run this morning (six miles). Checked the oil was going round ect. It ran well but seemed hot when I got home. Air temp was 18 deg. I ran at about 50mph. Felt the oil tank. The top half was quite warm but the bottom was coldish. The oil level is a bit above normal.

How many miles before oil should be evenly hot?

John.