8 replies to this topic

[InnoCOOPER]

Can anyone help me with the size of this bearing please.  I expected to see + 20 not 200 or is that the same?.  The crank was re-ground under 1000 miles ago and and are in very good condition.  They are Mahle bearings.

 

The main bearings are + 20 oversize. Picture attached of big end bearings.  Bearing.JPG   74.84K   27 downloads

 

Help appreciated.

 

Nick

 

 

[Spider]

I'd suggest measuring the crank and getting the right bearings to suit, while sometimes looking at the old bearings can be a helpful indication, I wouldn't actually work from them. Never know, the last guy may have fitted the wrong ones or the last grind on the crank may have been off spec or it may even be worn and in need of another grind.

Edited by Moke Spider, 19 January 2016 - 07:15 AM.

[Cooperman]

When building engines measure, measure then measure again. It's call engineering! Never ever guess or assume anything.

The cost of proper measuring equipment is less than having to rebuild again because it was incorrect first time.

[InnoCOOPER]

Thanks and understand.  I have some Micrometers on order  I assume that when crankshafts are ground they are ground down in 010" at a time?

[Spider]

Yes, the usual and common sizes are in 0.010" increments, though you can get specials in what ever size you want, but I rarely bother.

[carbon]

As well as using micrometer to check crank bearing journal size, it is also worth using Plastigauge to check the clearances for mains and big-end.

 

Link: http://plastigauge.co.uk/

 

It's a soft plastic, you put a length of this between bearing journal and shell and then torque up the bearing cap to the recommended settings. Then remove the cap and measure the width of the deformed plastic to work out the clearance. Simple, but accurate.

[mk1leg]

that's the metric size

[InnoCOOPER]

Thx Mark...  Im going over to the UK  next week to get the block re sleeved probably going to go for 1275cc they will fit new pistons to my con-rods and also put in new camshaft bearings.  Then its good to go ready for me to rebuild...

[jaydee]

Honesty i cant see how can it be the metric size since that would be +6 thou or so