brunner628

So a friend of mine was telling me about rod bearing math. Apparently you have to add numbers on the crank the hold the bearings in with something else blah blah blah ( i hate math ) Anyways before i knew this i just ordered Standard rod bearings from LCE. Has anybody done rod bearings on a 3.0 and could explain this. Thanks

Cyberman

How to use plastigage to measure clearances

thook

Hehehe.....yeah, screw the math. Just plastigage and compare the specs.

RMA

Yea just use the plastigauge .Dont know about the math your talking about.
This was taken from the fsm.

Measure the Plastigage at its widest point.
Standard oil clearance:
STD
0.024 – 0.053 mm (0.0009 – 0.0021 in.)
U/S 0.25 and U/S 0.50
0.023 – 0.069 mm (0.0009 – 0.0027 in.)
Maximum oil clearance:
0.08 mm (0.0031 in.)
If the oil clearance is greater than maximum, replace
the bearings. If necessary, grind or replace the cra–
nkshaft.
HINT: If using a standard bearing, replace with one
having the same number marked on the connecting
rod cap. There are three sizes of standard bearings,
marked ”’1”, ”2” and ”3” accordingly.
(Reference)
Standard sized bearing center wall thickness:
Mark ”1”
1.484 – 1.488 mm (0.0584 – 0.0586 in.)
Mark ’2”
1.488 – 1.492 mm (0.0586 – 0.0587 in.)
Mark ”3”
1.492 – 1.496 mm (0.0587 – 0.0589 in.)
Connecting rod big end inside diameter:
Mark ’1’
58.000 – 58.008 mm (2.2835 – 2.2838 in.)
Mark ’2”
58.008 – 58.016 mm (2.2838 – 2.2841 in.)
Mark ”3”
58.016 – 58.024 mm (2.2841 – 2.2844 in.)
Crank pin diameter:
54.987 – 55.000 mm (2.1648 – 2.1654 in.)
(k) Completely remove the Plastigage.

TNRabbit

You CAN do the math with a inner/outer micrometer beforehand. If you don't have one, it's not worth buying them, though.

thook

It's true........you can. You can mic' the crankshaft and the original bearing tolerances and split the difference in the thousandths, but the plastigage is so cheap tells you everything you need to know very simply. When/if you get the plastigage, though, get the green......at O'Reilly or someplace like that, make sure when you get it it's not all broken in pieces and you take care with it until you use it. It's real fragile stuff.

Mic's can also be used to determine things like cylinder wear or cam bearing tolerances, but then simply checking ring end gap and ring wear pattern or plastigaging the cam will serve the same. It's really whatever you want to do. I think mic's are really more suited if you are the one doing the machine work.........which likely you are not.