47 replies to this topic

[Northernpower]

This isn't a problem with worn bearings or a knackered oil pump (in fact its' the opposite, the engine is in great condition), it's to do with the head gasket. The SC 7 port head uses a different method of transferring the oil from the block to the rockers. You'll see from the photo it doesn't go through the head., it comes up through the normal oil gallery in the block but then it enters a trough machined into the head and travels along the head to the head bolt. It then comes up through the gap between the head bolt and the head and then comes out along another machined trough in the head to the rocker pillar and then up through the pillar as normal. It works very well.

 

 

 

I have an adjustable oil pressure relief valve and I want to know what's the minimum oil pressure I can run to be confident of getting lubrication to the engine. If I run too much it has a tendency to force the oil into the layers of the head gasket. I'm not going to remove the head gasket for a different type.

 

Discuss

 

 

[imack]

I don't have the book in front of me but from memory I think Vizard recommend around 60psi when driven stating higher oil pressure offers no more protection, requiring more power to drive the pump and raises oil temperature. I cant remember the suggested pressure at idle.
What sort of pressure are you currently running?

[Northernpower]

I don't have the book in front of me but from memory I think Vizard recommend around 60psi when driven stating higher oil pressure offers no more protection, requiring more power to drive the pump and raises oil temperature. I cant remember the suggested pressure at idle.
What sort of pressure are you currently running?

Not being funny when I say whatever I want. Currently running it at about 75psi when hot but obviously when its revving really high it does exceed that so what I'm looking for is a compromise.

Edited by Northernpower, 20 September 2017 - 09:39 AM.

[Spider]

After much searching, I found it!

 

http://www.theminifo...07866-oil-pump/

 

In terms of pressure, not nearly as much as you might think you need. Flow volume is important for the bottom end, but the top end, where you are presently looking is somewhat metered via the slots in the No. 1 Camshaft Journal.

[Northernpower]

After much searching, I found it!

 

http://www.theminifo...07866-oil-pump/

 

In terms of pressure, not nearly as much as you might think you need. Flow volume is important for the bottom end, but the top end, where you are presently looking is somewhat metered via the slots in the No. 1 Camshaft Journal.

Very interesting thanks, looks like I could run lower pressure. When I changed from the straight cut drops I asked about changing from my turbo oil pump to a standard one http://www.theminifo...-pump-decision/ and in the end kept the turbo one so I guess I'm going to have the volume. The camshaft was cross drilled on number one bearing. Do you think this will help?

 

EDIT: and obviously the crank is cross drilled as well.

Edited by Northernpower, 20 September 2017 - 10:26 AM.

[Ethel]

Like MS says, it's volume not pressure. The hydro dynamic wedge of rotating bearings make their own pressure. It's an instance where temperature# will give you more of a clue. We have pressure gauges as they tell us summet is up before the heat does the damage.

Probably not practical advice if your engine's in and running, but maybe machining for a sleeve dowel or O ring would be the best way?

# measuring it isn't easy as it's, the oil leaving the bearings more than the gallon sloshing about in the sump.

[Northernpower]

Like MS says, it's volume not pressure. The hydro dynamic wedge of rotating bearings make their own pressure. It's an instance where temperature# will give you more of a clue. We have pressure gauges as they tell us summet is up before the heat does the damage.

Probably not practical advice if your engine's in and running, but maybe machining for a sleeve dowel or O ring would be the best way?

# measuring it isn't easy as it's, the oil leaving the bearings more than the gallon sloshing about in the sump.

Yes I agree with you and hindsight is a wonderful thing, the easiest fix to try would have been to place a smear of RTV between the layers of the gasket in the area of the affected head bolt so it compresses into an oil tight seal and stops any futher oil progressing through the gasket. If reducing the oil pressure doesn't cure it, I'll probably try this as my next step.

 

Having said all that, I'm still not sure what is a safe pressure?

[Ethel]

That's a variable, bigger clearances and higher rpm will need more. If you're adjusting the relief valve to get there, you could attempt to get an oil temperature at current pressure as a baseline to watch the effect of reducing the pressure - going to be hit and miss with so many variables though. I think I'd be totally confident with 50 psi, but pressure that holds steady is a good indication.

[Northernpower]

That's a variable, bigger clearances and higher rpm will need more. If you're adjusting the relief valve to get there, you could attempt to get an oil temperature at current pressure as a baseline to watch the effect of reducing the pressure - going to be hit and miss with so many variables though. I think I'd be totally confident with 50 psi, but pressure that holds steady is a good indication.

I think I'll work on the principle of slightly reducing the pressure and watching to see how constant it is through the revs. I'll take your 50psi as the barest minimum but I'll do it in small increments from the existing.

[Ethel]

50 is my untested starting point wouldn't be at all surprised is you could go lower.

[Northernpower]

50 is my untested starting point wouldn't be at all surprised is you could go lower.

I realise there must be an element of pulling figures out of thin air on this one but I think I'll get a twitchy bum long before I get down to 50psi.

[Dusky]

Iirc the great Mr moke ;) runs 20 PSI at idle , My brain could be failing though as its getting older Everyday 😁

[imack]

Just checked the vizard book and he advises setting the oil pressure to 60 psi hot, say no more protection is offered with higher oil pressure.
I read this as suggesting pressure less than 60 psi potentially offers less protection.

[Northernpower]

Just checked the vizard book and he advises setting the oil pressure to 60 psi hot, say no more protection is offered with higher oil pressure.
I read this as suggesting pressure less than 60 psi potentially offers less protection.

Interesting, that gives me room to work. It's currently at 75 so I'll just slowly back it off keeping an eye out on consistency.

[imack]

"If I run too much it has a tendency to force the oil into the layers of the head gasket."

Out of interest, how do you know oil is being forced into the head gasket layers?