6 replies to this topic

[mingy]

Nearly got my engine sorted (waiting for head to be finished)then i will pop it back int car.
Just thought i would ask you knowledgable lot if it,s worth using an adjustable oil pressure release valve, i know it,s just steady oil pressure i need but would it help to have some adjustment just in case.

[Cooperman]

Never seen the point. A properly built engine willhave good oil pressure. Once hot it will be the same anyway, as the relief valve will be fully closed when the oil gets hot.

[mingy]

Cheers for the info coops, what sort of oil pressure would or should i be looking at on a fully rebuilt engine and gearbox.
Its an A series 1275 block,offset bored to 1380 ( used original cast omega 73.5mm pistons out of old unit with new omega rings, modified 12g940 head 35.5 / 29 rimflow valves etc etc.
Should it show the same pressure on startup (cold) aswell as after running for a while,and will it drop slightly when iv,e run it in.
Your wealth of experience and no nonsense answers is always greatly appreciated.

[R1minimagic]

The oil pressure will always be higher when starting from cold than when the engine is warm as the viscosity decreases with temperature.

Typically around 60-80psi when cold and should drop to around 25-35psi when fully warmed up and idling.

The SAE viscosity of the oil you use will also have an effect especially when warmed up

[Cooperman]

At initial start-up from cold with a good 20w50 oil you should expect 75 psi to 80 psi.
As the oil gets up to operating temp the pressure will drop. When fully hot you shoulkd have 25 psi to 30 psi at 1000 rpm, rising to around 45 psi to 50 psi at 2500 rpm and not really less than 65 psi at over 5000 rpm. Those figures are just a guide and do depend on operating scenario. On a really hard driven car, say on a track at max revs, the pressure should hold up well at high revs, but drop to as low as 20 psi at 1200 rpm.
I hope this helps.

[mingy]

Much appreciated info, now then what type of oil should i use to run it in with and for how many miles, and then what final grade oil to use generally.
There seems to be conflicting views as to what oil is best,but i suppose some people may be using their mini for different purposes.
I was told Valvoline semi-synthetic is good but i would rather listen to people who have lots of past experience.
I just want to tootle about most of the time but may do my local hillclimb event next July for the sheer hell of it.

[Cooperman]

You can run in with any 20w50 oil and change it after a maximum of 500 miles.
For my rally Minis I always use Valvoline Racing 20w50 and for road Minis I normally use Castrol Classic 20w50.
In the end it's personal choice, but I stick with a good mineral 20w50. I'm thinking of trying the very expensive motor-cycle engine synthetic 20w50 some time.