Morris Minor Owners Club

After full engine rebuild on 950 engine. Rebore to +40 New big end shells, Pistons, rings, valve guides,valve stem seals. Engine starts easy, ticks over well,Pulls and runs very well. My only consern is when driving at 40mph the oil preasure gauge shows around 65 to 70 lbs i am worried this may be to high and could it do any damage to engine,seals ect. Is it possible to reduce preasure a bit . Would an extra washer under oil preasure valve make spring a bit weaker therefor allowing plunger to open up sooner ? Just a thought i am no expert, Would like to hear your views. This is when engine is warmed up properly.

Can you tell us what the pressure is when engine cold @2000 rpm, and what oil you are using.

That's PERFECT oil pressure - if it is with hot oil after a run. Adding a washer would raise the pressure even higher - which you DO NOT need to do! Be happy with it!

blues2rock wrote:Can you tell us what the pressure is when engine cold @2000 rpm, and what oil you are using.

20/50 engine oil used. At 2000rpm from cold shows 85psi Then after 10 miles and engine warm it reads 68psi and at tickover after 10 miles reads around 40 psi . i am going to remove the oil preasure spring and measure the length should be 2 7/8 inch. Thanks for answering .

It's perfect = don't do ANYTHING.

I think the workshop manual shows relief valve opening at 60lb and a MINIMUM 15lb at tickover hot. as above leave it alone,there will be hundreds on here who wish theirs was showing 68 when hot,its where it should be.

Too much oil pressure when cold can er ode the lead flashing on the shells sometimes. We had a lot of problems on some of our engines that operated in cold climates with this and had to fit a double relief valve system to alleviate it. Dont rev it too hard until it is warmed up and it will be OK.

Thankyou for replys, good advice i will leave alone thanks again.

I've never heard of the possibility of 'erosion' - High pressure with cold/thick oil has been known to tear the oil pump shaft away from the rotor - some designs are only 'press fitted' with no key. And bore lub will be limited anyway on start up. So yes -for whatever reason you chose to believe - it is always wise to warm an engine at low revs

Too much oil pressure when cold can er ode the lead flashing on the shells sometimes. We had a lot of problems on some of our engines that operated in cold climates with this

Sounds like the oil was too heavy. Seen it lots of times. The cold, thick oil just can't circulate.

Maybe in canada in winter,but over here,not a great problem,not had much frost yet,only had to clear screen three or four times so far this year.long may it go on like that

If it's nice and oil tight you could try some slightly thinner oil 15/40 perhaps.
No doubt this will bring howls of anguish from some people but I think 20/50 was probably the only multigrade available at the time so it's unlikely others were tested.

The thinner oil could certainly be considered - the correct oil for the engine is SAE 30 - so 15/40 will be fine in a good tight engine. I see what you mean 'katy' - if the oil is so cold/thick that it will not circulate - then yes the bearings will be rubbed/scored. I thought you all plugged your engines in with sump heaters in Canadian winters...... And yes -even up here this winter at 600 ft. I have only scraped the screen twice so far - and even that was light frost. It's the Global Warming !! Bring it on I say!!

I thought you all plugged your engines in with sump heaters in Canadian winters......

That's the norm when the temp drops to about -15ºC or so. 10W30 is usually rated to -18ºC (0ºF) and most newer cars use 5W30 so not too much of a problem nowadays. A lot of people use the "remote start" to start their cars and let them warm up before driving.
Sometimes the block heaters or power cords fail or there's no place to plug in, sometimes people start their engines and rev the sh*t out of them, sometimes they think 10W30 is all they need and then start their engine at -30 or -40 and then wonder why the rods started knocking or worse yet have let go and punch a hole in the side of the block. (threw a rod we say).
YMMV

Yes - my nephew in Edmonton uses the remote start for his truck - and his Focus. Not legal in UK - vehicle must not be unattended with engine running....at least - not on the highway. He keeps his ATVs in a nice warm garage...

MarkyB wrote:If it's nice and oil tight you could try some slightly thinner oil 15/40 perhaps.
No doubt this will bring howls of anguish from some people but I think 20/50 was probably the only multigrade available at the time so it's unlikely others were tested.

Gotta support Mark.
20W/50 is too thick.
It was invented for knackered engine / oil burners.
Thinner multigrades were available.

Gotta add that new engines were run in on "Running In Oil" in the 60s.
It was a monograde in the 60s.

Some here from Castrol: -
http://www.ebay.co.uk/itm/Castrol-Runni ... 2586c539a9

Some here from Morris: -
http://www.ebay.co.uk/itm/Morris-Golden ... 4d2cafe742
.

smithskids wrote:Too much oil pressure when cold can er ode the lead flashing on the shells sometimes. We had a lot of problems on some of our engines that operated in cold climates with this and had to fit a double relief valve system to alleviate it. Dont rev it too hard until it is warmed up and it will be OK.

Gotta support Smithskids.

I can distinctly remember a 60s/70s diagnostic chart showing damage to thin wall bearings caused by too high an oil pressure.
According to folklore of the period excessive oil pressure could unseat thin wall bearings.
I tended to put it down to mechanics not fitting the shells correctly in the first place.

Contrary to modern folk lore, high pressure isn't the be all and end all.

Engine oils main functions are
1) Take heat away from the bearing.
2) Form a skid for the crankshaft to float on.

Oil flow rate through the bearings is much more important than oil pressure.
High oil pressure means a low flow rate through the engine.
.

Castrol XXL for oil burners.

123 wrote:

smithskids wrote:Too much oil pressure when cold can er ode the lead flashing on the shells sometimes. We had a lot of problems on some of our engines that operated in cold climates with this and had to fit a double relief valve system to alleviate it. Dont rev it too hard until it is warmed up and it will be OK.

Gotta support Smithskids.

I can distinctly remember a 60s/70s diagnostic charge showing damage to thin wall bearings caused by too high an oil pressure.
According to folklore of the period excessive oil pressure could unseat thin wall bearings.
I tended to put it down to mechanics not fitting the shells correctly in the first place.

Contrary to modern folk lore, high pressure isn't the be all and end all.

Engine oils main functions are
1) Take heat away from the bearing.
2) Form a skid for the crankshaft to float on.

Oil flow rate through the bearings is much more important than oil pressure.
High oil pressure means a low flow rate through the engine.
.

So conversely does a lower pressure mean a higher flow rate?

If the bearing clearance has increased you do get an increase in oil flow until the flow capacity of the relief valve settings and the pump are reached. Our oroblem on the medium speed diesels was cold start up 90-100 psi causing erosion of the flashing on the aluminium tin bearing shells, plus sometimes the oil filter pack would collapse due to the excessive start up pressure on one side of the oil filter and the subsequent passage of dirt out of the filters being carried in to the bearings. Some ships had electric lub oil pumps and the start up pressure could be controlled at say 30 psi until the engine warmed up then the pressure could be regulated to 60 psi normal running pressure. With an engine driven pump you have to rely on the relief v/v system to keep the pressure within safe limits. Getting back to the original question though nothing wrong with the pressures you have quoted.