oil clearances

what is acceptable oil clearance for rod and main bearings for a street engine? is plastigauge a reliable source for checking? any help is appreciated?

 

Use plastigauge. The time spent will be worth it. Get the green and do both the mains and the rods. Keep the clearances tight. .002 to .0015 This is just my $0.02 but I don't know what kind of engine. Good luck and maybe find some specs on the engine.

 

Mobucket, Like asking "how long is a board?" The acceptable oil clearances will vary with the bearing and engine design.The Olds rocket in one chart had a recommended rod clearance of .0005-.0025 for 1960 but earlier listed .001-.003. many of our current engines list .0005-.0015 and recommend 5w,20 or 0w,20 motor oil.My 1933 caterpillar gas tractor allows rod bearing clearance of .007-.013--babbit bearings and max rpm of 750.For a street engine I try for the middle of the factory recommendation with excellent alignment and smoothest possible finish.
I find plastigage a very revealing tool to show the actual clearance across the bearing.Of course it is the final test after using mikes or bore gage on bearing bores and shaft.Plastigage gives very repeatable readings if care is taken to control the placement of the thread and unwanted movement of the bearing & shaft.

 

Mobucket, PS if you need specs on a specific engine just ask.Some of us can deliver.

 

working on a olds 324. i pulled the rods and mains and the bearings that came out were .001 and i already had std. bearings. so i checked ( with plastigage) #3 and#4 main and came out at .0015. is this ok. if it is marginal can i use a heavier oil to help with the clearance?

 

.0015 should be fine.

On most engines, when it gets over .003 then you need to worry about it.