Crankshaft oiling system modifications 1

[fabiom75]

3.4 liters engine 6 cilynders inline.

We bought a stroked crank that had a stright shoot oiling system. Previously we were using a 3 liters not stroked with cross drilled oiling system. The 3 liters engine was revving at 10500rpms with no problems. After 7k miles we removed it to swap it with the new stroked 3.4 liters and inspected it. Everything was in real perfect shape. Like new.

Now there are a lot of info about the straight shoot oiling system being better then the cross drilled one due to the problems that could appear at high rpms due to the centrifugal force.
The fact is that we have been able to rev a cross driled one for 7k miles at 10500rpms with no problems at all.

The new stroked crank came with straight shoot lubrification.
From a not expert point of view what made us worried was teh fact that the straight shoot on is going to pick up oil every 360 degrees from the mains while the cross drilled was picking it up every 180 degrees. The main bearings are 1/4 grooved.
At the same time the rod bearings are being feedded every 360degrees instead of 180 like in the cross drilled one.

We made some mods to the block and to the crank:

1) added a full 360 degrees grove all around the main cap/block (main cap for 180 degrees and block for 180 more degrees) this way we should have a constant feeding of oil thru the mains all te time thru the 360 degrees.

2) we made a pass thru hole on the rods journals to the exact opposite side of the journal. Even if I am not sure how this mod could be effective due to the centrifugal force (the oil should be able to go back to the opposite side of teh journal).

I would love feedbacks and comments.

Thanks

 

[SMOKEY44211]

Haven't we been down this road before in thread 71-168520?------Phil

 

[fabiom75]

Well we didn't alked specifically about this kind of modification on the crankshaft. we didn't discussed what could be the benefits and the cons.
It would be very interesting.

 

[franzh]

One issue when grooving main bearings is the belief that you are adding oil to the surface. Actually, the reverse is true.

Instead of having one large load surface, you now have two smaller load surfaces, minus the width of the groove. The center of the load surface is where the oil film is the "thickest", tapering off as it reaches the edge of the bearing insert. On many bearing sets, you may see the upper insert grooved and the lower insert flat.

Franz

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[fabiom75]

Franzh,

sorry for my english. Bu we DIDN'T grooved the BEARINGS at all. We left them stock.
We grooved the main CAPS and the block. To have a constant feeding of oil to the bearings...

Fabio