Oil Pressure Relief Valve - Three Bearing Engine

[Jamie]

Good evening.

Stupid question, no doubt, but does the three bearing engine have an oil pressure relief valve? I assumed that it would have one in the crankcase in the same place as the two bearing engine, but I have stripped it and cannot find one anywhere.

Jamie.

[David Stepney]

Yes. The three bearing engine’s oil pressure relief valve is in the same place as a two bearing engine. Just forward of the near side rear engine mounting and under the web that runs between the front and rear mountings.

[Jamie]

Thank you, David.

I wonder why my engine has had its valve removed, or left out? Oh, well, something else to add to the shopping list, assuming that the parts are available.

Regards,

Jamie.

[David Stepney]

Jamie, I can’t imagine why the relief valve is not present, but it wouldn’t have done the oil pressure much good. I wonder if this is the reason you are rebuilding you engine. And, yes, the bits are available from cherished suppliers.
Regards,
David.

[squeak]

Jamie some engines have been modified to redirect the oil flow by insertion of strategically located plugs in the oil galleries. Commonly for pressure feed and/or oil filter addition. It's important you understand exactly what's going on with your system before making changes. A long piece of wire and a poke around is a good start.

[Jamie]

David and Squeak: thank you for the information, advice and suggestions.

I have yet to start cleaning the crankcase or checking the oil ways, so I shall do as you suggest. It is odd the the front and rear bearings are poorly, yet the centre main and the big end shells and all of the journals are in fine fettle. Judging by the existence of modern sealants, helicoils and some judicious use of silicon sealant, three con rods with shells and one with a white metal bearing, the engine has been worked on at some time in the none too distant past.

The engine came to me as a sound, quiet runner, but well down on power. Initial checks showed that the head gasket had gone and the bores were in a very poor state. The cam follower adjusters were also quite substantially different in their adjustments, two especially so, suggesting that the valves were not likely to be opening and closing fully.

The fun continues...........

Jamie.
Jamie.

[Chris KC]

Quite so Squeak but the methods of adding an oil filter with which I am familiar still use the "standard" PRV layout (even if it may have been up-rated). Unless blanked off the oil supply will simply spill back into the crankcase.

Jamie, I think there are perhaps two ways to have full confidence in your engine, you either pay a respected engine builder to do it for you, or you do it yourself. If you are finding things you are not happy with one can only presume you will find more as you dig deeper.

[Jamie]

Jamie, I think there are perhaps two ways to have full confidence in your engine, you either pay a respected engine builder to do it for you, or you do it yourself. If you are finding things you are not happy with one can only presume you will find more as you dig deeper.

Paying to have the engine built is not an option, so I shall be doing it myself, seeking guidance when I can. The whole engine is now apart and, to be honest, there does not seem to be too mcu that is really bad about it; more, a number of irritating things: the missing oil pressure relief valve, the valves which all had different size, over-sized stems and three big ends with shells and one with white metal. The rest seems to be just wear and tear. So far.............

Regards,

Jamie.

[Tony Press]

Jamie, I think there are perhaps two ways to have full confidence in your engine, you either pay a respected engine builder to do it for you, or you do it yourself. If you are finding things you are not happy with one can only presume you will find more as you dig deeper.

Paying to have the engine built is not an option, so I shall be doing it myself, seeking guidance when I can. The whole engine is now apart and, to be honest, there does not seem to be too mcu that is really bad about it; more, a number of irritating things: the missing oil pressure relief valve, the valves which all had different size, over-sized stems and three big ends with shells and one with white metal. The rest seems to be just wear and tear. So far.............

Regards,

Jamie.

"there does not seem to be too mcu that is really bad about it;"

"over-sized stems and three big ends with shells and one with white metal."

I wouldn't have said that these are minor 'bad'  things
 

[Jamie]

Jamie, I think there are perhaps two ways to have full confidence in your engine, you either pay a respected engine builder to do it for you, or you do it yourself. If you are finding things you are not happy with one can only presume you will find more as you dig deeper.

Paying to have the engine built is not an option, so I shall be doing it myself, seeking guidance when I can. The whole engine is now apart and, to be honest, there does not seem to be too mcu that is really bad about it; more, a number of irritating things: the missing oil pressure relief valve, the valves which all had different size, over-sized stems and three big ends with shells and one with white metal. The rest seems to be just wear and tear. So far.............

Regards,

Jamie.

"there does not seem to be too mcu that is really bad about it;"

"over-sized stems and three big ends with shells and one with white metal."

I wouldn't have said that these are minor 'bad'  things
 

I agree: I was trying to be optimistic. Tongue in cheek comments are so hard to convey on a forum. The valves were a real nuisance as it took me a fair while to realise why I could not get them back into the new guides. The odd con rod has been replaced, as has the block which had water damage, pitting going right through the liners into the main block.....

Still, the sump looks good.

Jamie.