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Old 09-18-2015
owakip owakip is offline
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Default Low Oil Pressure fix

Been a while since I was on this forum last..but for a number of years I was dogged by running bearings in my Alpine powered 1960 Buckler race car. I have run both 1725 and 1600 cc Alpine engines consistently running Big End bearings in them.
To fix the problem I have used an Accusump, new oil pumps, drilled out the centre main oil gallery and oil galleries to number 2 and 3 big ends,beefed up the oil pressure by adjusting the oil relief valve made up complex baffles/windage systems for the sump, both lifted and lowered the height of the oil pick-up pipe in the sump. The engines always had great oil pressure (circa 60psi) until they were was raced hard... the end result was inevitably run big end bearings.
The FIX: A local race mechanic suggested it may be a cavitation problem with the oil-pump. Turns out he was right. Oil on the inlet side of the oil pump largely depends on gravity and a little bit of suction to get to the 2 gears that pump it through the engine. Once it gets on the other side of the gears the pressure ramps up to 60 psi + (depending what the oil relief valve is set at).
Any impediment on the inlet side of the pump significantly reduces the oil the pump has available to pump around the engine. The main impediment is the standard gauze filter on the end of the oil pick-up in the sump... The smaller the filter surface area and finer the gauze mesh the greater restriction.
The fix for me was to make a filter where the mesh size was around
4 mm... ie stops rocks but not the fine stuff... I figured the canister filter further down the line would deal with the fine stuff.
I also used a die-grinder to clean up the inlet track of the oil pump of all machining marks from when it was made.
End result 60 psi all day long regardless of how hard the car is raced.

I suspect much of the LOP (Low Oil Pressure) problems Alpine engines have historically had have at least in part been due to cavitation issues on the inlet side of the oil pump.

Hope this information helps someone else.
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Old 09-18-2015
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alpine_64 alpine_64 is online now
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That's very interesting info from across the ditch. Thanks for posting it.

I would say that the racing issues you have had and the lop that road alpines suffer is somewhat different. The road cars will suffer lop across the whole rev range including idle, not just as the car gets up to temperature or after hard use. This is generally is a result of worn clearance in the pump... This then leads to wear in the bearings which then becomes a vicious cycle until failure.

People would often do the adjustable oil pressure relief valve mod, but increasing the psi by the valve if you have lop is not actually fixing the issues, and also adding more pressure via the valve can cause issues as your increasing the pressure not the actual flow of oil.

Your modifications sound interesting and could well be worth considering on a fresh build, but is likely more useful in a situation like sustained high rpm in racing.

It would be worth hearing jarrids thoughts on this mod with his experience in the engines.

Also a hot rootes engined buckle would be a fun ride... What carb setup is it running?
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Old 09-18-2015
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jumpinjan jumpinjan is offline
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I assume this is the 1725 oil pump? And the pump as two styles of oil pickup screens. Which one are you using?
Yes, it's a good idea to smooth the pump cavities with a die grinder. I do that on all my rebuilds.
Jan
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Old 09-19-2015
owakip owakip is offline
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I only use 1725 motor oil pumps and I have made my own mesh screen (considerably coarser mesh than the factory ones).
I have been running twin 42 Weber DOCEs... but in the search for more HP I am currently building up a supercharged engine.
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