I am in the market for ACL coated bearings, and they seem to have two different types of standard size bearings.
One with standard oil clearance and the other with an extra 0.001" oil clearance.

I know a good oil clearance is for the main and rod bearings to be about 0.002". What is the advantage and disadvantage of running 0.003" oil clearance? 0.003" is still within the factory manual limit for both the rod and main bearings.

 

Bump

 

I remember searching these when I was building my engine, I just stuck with standard bearings and went with .0025 on the mains and .002 on the rods. If you get the extra clearance bearings and the clearance is too big then you're screwed and will need new bearings. Too tight with the standard bearing then you can just have the crank polished down to what you need.

 

Did you have good oil pressure? Because I'm at .002 on ross an .0015-.0017 on mains

 

.003" is very loose, on a fresh build i wouldnt go looser than .0023" or so.

 

Yes I understand that do you think .0015-.0017 is too tight on hi hp car on the mains? That's what I have.... On the rods I'm running .002 thanks on input in currently runnin standard h series acl on both

 

what kind of power and rpm limit? if its like 600whp and 8,000 rpm, id run .0015" without hesitation. 9,000rpm and more power? id try for .002"-.0025".

 

What I've always read is that looser is better, assuming you can get proper oil pressure. What type of engine are you putting together? On my 2.4 stroker, I did .002-.0023 on the mains and .0025-.0028 on the rods, with no oil squirters to divert oil flow. Using 20-50 VR1 I see 80 PSI before 2K RPM.
However, using an Evo block, and thus, oil squirters, you'd need tighter clearances to achieve proper oil pressure.
If you're just doing a drop-in piston setup, I'd use stock size main bearings, and .001 O/S rod bearings. The rods are smaller in diameter and put more stress on the oil film, so a thicker film is definitely more useful there.

 

nope not drop ins its build long rod 2.0 whole motors out ect. evo 8

 

Horsepower has nothing to do with clearance imo. Rpm range and how often you'll be in that powerband is what I go by. If you're road racing, I'd use more clearance. Higher rpm will yield high oil pressure, more clearance at the bearing will allow for more flow.

 

We run 0.03 to 0.04mm (0.0012" to 0.0016") on our drift cars which get hammered on the rev limiter ALL the time.

 

There's an example on the other side of the spectrum. Tighter clearance and high abuse and no issues.

 

So what is better for hi hp rpm builds ? Clearences wise what it the correct one lol I know the bigger clearence less oil pressure... If factory spec good for hi hp? Or should I get bigger clearence on main thanks

 

Drifting and hanging out around redline is very different from a high HP drag run. Sustained High RPM runs are more about keeping the rotating assembly stable, Smaller clearances mean the oil film is effectively harder. Good for stability, and keeping things running smoothly,not so good for high torque. Keep in mind that the strains of high RPM are compounded by higher cylinder pressures (torque) Larger clearances increase that oil film, effectively softening it. That little extra cushion can be the difference between spinning a bearing and finishing your trip down the strip.

 

what is really good main and rod clearences im not runnning a balance shaft or oil squirters its 4g63 block