Crank Main Bearing 0.003" Clearance

[driversdomainuk 8]

Hi

 

IMPORTANT AND ACCURATE HELP NEEDED...

 

Working with fellow competitor to rebuild MI16 engine.....main bearing clearance is 0.003" - with new bearings....IS THIS OK....?

 

Also what are the torque settings for the main bearings...is 38 ft/lbs correct..???

 

Thanks

 

Rob

[Cameron 16]

Haynes recommends 0.034mm - 0.075mm and yours is 0.076mm. I'd say that was out of tolerance so you might want to look at a re-grind.

[M@tt 77]

assuming its 1.9 xu9 alloy block

 

Main bearing running clearance

1905 cc engines** . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.025 to 0.050 mm

 

Big-end bearing running clearance - all models** . . . . . . . . . . . . . . . . . 0.025 to 0.050 mm

 

Main bearing cap nuts/bolts:

Retaining nuts/bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54Nm 40lbf ft

Centre bearing cap side bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Nm 18lbf ft

[driversdomainuk 8]

assuming its 1.9 xu9 alloy block

 

Main bearing running clearance

1905 cc engines** . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.025 to 0.050 mm

 

Big-end bearing running clearance - all models** . . . . . . . . . . . . . . . . . 0.025 to 0.050 mm

 

Main bearing cap nuts/bolts:

Retaining nuts/bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54Nm 40lbf ft

Centre bearing cap side bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Nm 18lbf ft

 

cheers

 

so what do i need to do...??

[B1ack_Mi16 67]

Grind the crank and use undersize bearings?

 

Or ask an professional enginebuilder what he reckons.

 

I know on my 2.3 engine the clearances are looser than peugeot specs due to my engine builder wanted more oil flow past bearings to help cooling...

[Tom Fenton 1,526]

Assuming it is new bearing shells, remove the crank and measure the journals accurately with a mic, the tolerance band is in the haynes manual.

[M@tt 77]

your gap is as cameron said .076mm so the gap is too big so you'll need to get the crank ground and fit the next size bearings. Your machine shop will be able to supply these.

 

HTH

[driversdomainuk 8]

your gap is as cameron said .076mm so the gap is too big so you'll need to get the crank ground and fit the next size bearings. Your machine shop will be able to supply these.

 

HTH

 

I am talking with a professional engine builder in a few days.....but on race engines this is possible. OK mine is not a full blown race engine but is not far off and is only used for motorsport...

[Mattsav 1]

Get the crank ground or you'll have major oil pressure issues. I wouldn't want to see more than 0.002" clearance.

[driversdomainuk 8]

Get the crank ground or you'll have major oil pressure issues. I wouldn't want to see more than 0.002" clearance.

 

What about using an uprated oil pump etc...as I know some race engines run this sort of clearance...it is just a real fag as I have bought some bearings (from someone here) and the crank has been reground...

 

Besides its an MI so without a dry sump it will go bang shortly.....!! (hard competition use)

 

Maybe it is time I start looking at Westfield Megabusa's...which was my plan but not just yet...

Edited January 16, 2009 by driversdomainuk

[Cameron 16]

"Uprated" oil pump won't help if the bearings can't hold the pressure anyway. Have you measured the journal diameters yet?

[Tom Fenton 1,526]

All the pump does is provide a flow of oil. The precise clearances between the bearing and the crank journal that the flow of oil passes through creates pressure in the oil system, due to the restriction in flow. This pressure is what prevents the journal from contacting the shells. If the clearance is too big then you won't have oil pressure, simple as that.

 

Solution is- measure the crank, then either get bearings to suit or have it ground and get bearings to suit.