bearing oil clearences
#1
Evolving Member
Thread Starter
iTrader: (1)
Join Date: Oct 2011
Location: Long island
Posts: 110
Likes: 0
Received 0 Likes
on
0 Posts
bearing oil clearences
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.
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.
#3
Evolved Member
iTrader: (71)
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.
#6
Evolving Member
Thread Starter
iTrader: (1)
Join Date: Oct 2011
Location: Long island
Posts: 110
Likes: 0
Received 0 Likes
on
0 Posts
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
Trending Topics
#8
Evolved Member
iTrader: (5)
Join Date: Jun 2007
Location: Lombard IL
Posts: 552
Likes: 0
Received 0 Likes
on
0 Posts
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.
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.
#10
Evolved Member
iTrader: (19)
Join Date: Dec 2007
Location: was Georgia, now williamsport PA
Posts: 1,001
Likes: 0
Received 1 Like
on
1 Post
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.
#13
Evolving Member
Thread Starter
iTrader: (1)
Join Date: Oct 2011
Location: Long island
Posts: 110
Likes: 0
Received 0 Likes
on
0 Posts
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
#14
Evolved Member
iTrader: (5)
Join Date: Jun 2007
Location: Lombard IL
Posts: 552
Likes: 0
Received 0 Likes
on
0 Posts
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.