HV oil pump with wider clearances?

[Pablo]

I'm about to have my crank mains ground and I was hoping to get some thoughts on clearances vs oil pump style.

I like the idea of running a wider clearance especially with the stock crank on a higher HP build. I am shooting for mid to low tens with my combo and figured that a little more wiggle room on the mains would be a good idea.

So I was going to tell the machinist to shoot for .002 to .0025 on the mains. My concern with this is that with the stock modded pump/cover, that I won't have enough oil psi.

Why doesn't it make sense to run the HV pump and then adjust the oil viscosity to get the oil psi you want? It would seem to me that a lower viscosity would make more sense anyway. The torque required to turn the pump is directly related to the amount of restriction posed by the oil and clearances so with reduced restriction there is reduced load and hence reduced cam bearing load (I am also now running a cam without a groove in it so I think I will be better off there).

I understand that the more oil I am bleeding off, the more windage there will be but I would prefer that hp loss over having the crank flex enough to push through the oil wedge on a tight clearanced main journal.

I'd like to hear your thoughts on this for or against

 

[turbo nasty]

Biggest issue with HV pumps is the load on the front cam bearing and cam sensor drive. Not needed

 

[bison]

Id stay at the high end of the factory spec. The crank is going to flex and load the mains regardless of the clearances. The hyd wedge will just transfer the torsion directly to the mains. Adding clearance wont help.

 

[Pablo]

Thanks for the response bison. You always have good advice. That makes sense. If the hyd wedge were to fail due to tight clearance I guess it would have done so long ago.

 

[bison]

Thanks for the response bison. You always have good advice. That makes sense. If the hyd wedge were to fail due to tight clearance I guess it would have done so long ago.

With a cast crank you will still get some bearing wear at high hp on the center. The caps whole bottom end is moving all over when you make enough power to go 130+

 

[threerail]

whats a hyd wedge? I GOTTA ASK. never heard of that. when i was a kid it meant that someone yanked your shorts up to your shoulders!!

 

[turbobitt]

whats a hyd wedge? I GOTTA ASK. never heard of that. when i was a kid it meant that someone yanked your shorts up to your shoulders!!

Hyd wedge, or hydrodynamic wedge is what the oll forms between the rotating crank and static bearing. This wedge is what keeps your crank from contacting the bearing surfaces. Bearing clearance should be enough to allow for bending and flexing of the components but be small enough to allow the oil wedge to form. The load capacity of the bearing is strongly dependant on this.

Allan G.