I haven't seen this discussed here, some people claim that cross drilling crankshafts gives better flow and lubrication to the bearings, are there any studies confirming or disproving this?
Crossdrilled crankshafts
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Crossdrilling and grooving may provide more oil flow, but they also reduce bearing area.
Cross drilling is just one means that can be used to increase oil flow. However it only increases flow to the rod bearings.Some engines are cross drilled from the factory like the Toyota 22RE others had it in HD/marine applications such as the Big Block Chevrolet and FE Ford. The purpose of cross drilling is to provide rod bearing lubrication through 360 degrees of crankshaft rotation when still used with 1/2 groove bearings. This can also be accomplished with full groove main bearings but it significantly reduces bearing area on the lower main shell. Some companies even offer 3/4 groove main bearings to increase rod oiling but maintain bearing area in the highest loaded portion of the main bearing.
I guess it does have the advantage of carrying more heat away from the bearings though? , i just happened to notice while browsing google that my engine too is supposed to have a factory cross drilled crank and remember reading a thread on a forum about the advantages or disadvantages.
Originally Posted By: FordCapriDriver
I guess it does have the advantage of carrying more heat away from the bearings though? , i just happened to notice while browsing google that my engine too is supposed to have a factory cross drilled crank and remember reading a thread on a forum about the advantages or disadvantages.
There's a little bit of a misconeption here, in that the oil doesn't carry away heat per se, it gets hot, due to viscous shear, not carrying away the local heat. The heat from big ands and mains actually flows from the beaing INTO the rods and block, not the other way.
More grooving, or cross drilling takes away the local ability to build the many hundreds of psi that are needed to keep the parts apart, but as others have stated allows more access for the big ends to receive oil.
"Flow" in bearings isn't oil "pushed" through them, the oil supply has to be there, and the bearing receives oil from the supply, equal to the amount of leakage that it has (predominantly from the area building the hydrodynamic pressure).
This paper they made a transparent crank, and explored big end supply with different oiling arrangements.
I guess it does have the advantage of carrying more heat away from the bearings though? , i just happened to notice while browsing google that my engine too is supposed to have a factory cross drilled crank and remember reading a thread on a forum about the advantages or disadvantages.
There's a little bit of a misconeption here, in that the oil doesn't carry away heat per se, it gets hot, due to viscous shear, not carrying away the local heat. The heat from big ands and mains actually flows from the beaing INTO the rods and block, not the other way.
More grooving, or cross drilling takes away the local ability to build the many hundreds of psi that are needed to keep the parts apart, but as others have stated allows more access for the big ends to receive oil.
"Flow" in bearings isn't oil "pushed" through them, the oil supply has to be there, and the bearing receives oil from the supply, equal to the amount of leakage that it has (predominantly from the area building the hydrodynamic pressure).
This paper they made a transparent crank, and explored big end supply with different oiling arrangements.
Ah i see
I have cross drilled Ford cranks and broken them. I have cross drilled Chevy cranks and broken them. I have run full grooved bearing shells and spun bearings. It's a wonder I'm still tinkering. But mostly they all survived and ran well, or well enough.
Big Olds engines have oiling issues in hot boats where they can unload at WOT and bust up the lower end. Rods out the block can sink a boat, so we try not to
Cross drilling does not, in general, seem to offer any higher reliability ...
Big Olds engines have oiling issues in hot boats where they can unload at WOT and bust up the lower end. Rods out the block can sink a boat, so we try not to
Cross drilling does not, in general, seem to offer any higher reliability ...
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From a paper that was posted here a few years ago went something like this; " under stress, an engine oil will be reduced to its base oil viscosity".
What does that mean in the application of a wide spread multi grade engine oil like 5W50 in a high RPM engine?
HTHS is measured at speed, so the published value is the NET HTHS with VIIs aligned.
Let's assume that our 5W50 had an HTHS of 5.0 when fresh. Our BBF, BBC etc. is operating at 8,000 RPM.
Is our engine seeing an SAE 50, SAE 5W, or something in-between?
The old rule of thumb was 10psi of oil pressure for every 1,000 rpm.
I can't see how increasing oil pressure can help prevent bearing failure if the oil is too thin to maintain a hydrodynamic film.
What does that mean in the application of a wide spread multi grade engine oil like 5W50 in a high RPM engine?
HTHS is measured at speed, so the published value is the NET HTHS with VIIs aligned.
Let's assume that our 5W50 had an HTHS of 5.0 when fresh. Our BBF, BBC etc. is operating at 8,000 RPM.
Is our engine seeing an SAE 50, SAE 5W, or something in-between?
The old rule of thumb was 10psi of oil pressure for every 1,000 rpm.
I can't see how increasing oil pressure can help prevent bearing failure if the oil is too thin to maintain a hydrodynamic film.
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