Crank journal wear.

[Howieau]

Im purchasing some ACL race bearings soon for my engine. They come in standard, 0.25" and 0.5" - Mine crank journals are fine and show no sign of scratching or anything. Does that mean I order the standard size ones? Or do the journals wear over time and should go to 0.25"?

Is there some way I can measure my journals.

Cheers

Edit: My car has had no spun bearings or anything. There was slight scratching on the surface of a main bearing I think it was when I was pulling my engine apart but all crank journals are smooth as.

[twentyEight]

I have been meaning to ask the exact same question...

[TooF]

you should go take your crank to your machinist and the crank will probaly be need to be ground undersize. if it is in good shape to start with just grind it to 0.25 undersize.

[willwal98]

take it to a machine shop and the can put the micrometer on it and tell you exactly. Depending on what engine you have and what sort of life it's had it might be an idea to get them to double check it also. Mini's are really bad for crank wear because the engine and gearbox share the same oil and first gear is non-syncro. They also chew oil pumps because the pump is before the oil filter.

Edit: If I didn't type so much I would have got in first . I blame mini's for my long response too. Damn cars.

[ed]

Is there some way I can measure my journals.

and you are rebuilding this engine yourself? ok...

...go straight to a machinist, do not pass go, do not collect $200. at the very least you should linish the journals, and at the other end they may need regrinding to remove defects. in either case the wear needs to be measured with a set of micrometers and they will then tell you what size bearing to buy

cheers
ed

[amichie]

You measure the oil clearance with plastigauge. Calipers etc will only give you a ball park figure.

You should only use undersize bearings on a reground crank.

So your options are
1. Take it to a machine shop and get it meaured. Any decent machine shop will tell you they will need the rods and the block to measure it properly. Regrinding will cost approx $150 to $250 depending on number of cylinder etc.

2. Rebuild with standard size bearings and just a good clean up. If you do this there is no point in buying the race series bearings and you will generally be taking a much greater risk of reduced life span.

I would go option 1. But if you know the history of the engine and you know the crank has not been ground before and there is no sign of gooves on the journals etc then buy the standard size replacements. Worst case is you will be pulling it apart again and choosing option 1.

[mrshin]

Calipers and a micrometer are slightly different things...

[Andrew162]

Mini's are really bad for crank wear because the engine and gearbox share the same oil and first gear is non-syncro. They also chew oil pumps because the pump is before the oil filter.

my sister is putting a rebuilt engine into her Mini (heavy little bastard engine for the size ) as far as I know it's a stock block, fully rebuilt inc. dished pistons, 1100cc stroker crank and all the good guff. her engine should last a long time though, from the list of stuff on the invoice for the rebuild, it looks very solid.

sorry, slightly OT...

[willwal98]

Make sure you change the oil and filter more often than for a normal car. Also don't select first gear until the car is stopped completely unless she can double clutch.

[Andrew162]

haha, she's owned a Mini before.. this is a girl who used to reverse-clutch-start her last Mini (down our old front lawn) because it utterly refused to kick over for a cold-start.