Jaguar S Type 3.0 litre

Who can help with this query - if I go onto the JEPC to buy main bearings for the above car .it refers to Grade 1,2 and 3 - each with a diff part number - What exactly are the grades standing for - is it the size of the bearing with grade 1 being standard size,2 being +10 and 3 being + 20 ?

You need to find and download my ENGINE COURSE 168 I had converted from my 3 ring binder Jaguar Training to .pdf.

It is ALL OVER the internet and Gus has it on his site. (

The bearing guide should be stamped on the side of the block.