K Series 1.8 Con Rod Big End diameter: 51.68mm +/-

[PACR]

I'm trying to find what the range of acceptable sizes are for K Series 1.8 con rod big end diameters. I can find the journal sizes and tolerances for the different journal grades - from the pdf engine manual. I can't find the big end diameters and tolerances for the different rod grades 5,6&7. It looks like 51.68 is nominal from the aftermarket rods on offer - but unfortunately they don't quote a tolerance band +/- for their rods.

Does anyone have the tolerance band sizing for the 1.8 rod grades? Or is there a 'known' size range for big ends that's acceptable?

Many thanks 

Piers

[oilyhands]

It's in the internal rover k series engine manual which I have somewhere around, as I recall the differences in the rod grade sizes are *the same* as the differences in the grades of the crankpin sizes. As it is, at the moment *genuine* graded bearings are near impossible to source, there are many that purport to be size graded, but they are just after market 'std' bearings reboxed as a size grade. All after market bearings are effectively 'blue' grade (intermediate), in my experience around 80% of bearing requirements are blue.

I nornally use Mahle Motorsport big end bearings (blue grade), the difference in sizing is minimal so bearing clearance is normally within acceptable limits.

Oily

[PACR]

Thanks Oily. I span a bearing again (you helped me out with advice and parts for this a couple of years ago) and took the crank, a spare crank and the rod / piston assy to a nearby engineering shop. It seems the spare crank is straight and has cleaned up with a polish. The chap who was checking the rods (in case the spinning bearing had caused damaged) left a note saying he thought the big ends were not standard size (they were from a 160 engine I used for parts so don't know full history) but all the same when he was checking for bearing availability. I don't know what size they actually are hence trying to find out the tolerance for when the chap's back in on Monday. Seems to be +/- 0.01 from 51.68 if it's same as the journals.