I must order big end bearings. DMG ltd have different sizes in catalog ( standard , +10", + 20" , +30"...) Measure of crankshaft is 52,45 mm . What size should I order ?

 

Are you going to have a specialist machine shop grind the crakshaft, or merely polish the existing surfaces?

 

Hi Zarnca
The S-type of the 60s never had a 4.2 litre engine, only 3.4. and 3.8 litres, so the one you have must have been taken from another and probably later car. Do you know where the engine came from ? Normally bearing sizes are quoted as "-10", "-20" etc as cleaning up the crank journals on a grinding machine leaves them smaller in diamter.

 

This is 420G model 1967 with 4.2 engine. Now I received one information, that I have to order +20" bearings. Just want to be sure.

 

Aha, so not an S-type then ! Wow, you've got a 420G; there are very few of these cars left in the world now.

Yes, the 420G had the larger engine. If you've been told to get -20 bearing shells then it appears the crank has already been ground once to -10. Normally what size shells to buy is advised to you by the engine shop that is going to grind the crankshaft. If it has been reground once already, the shop that did this will stamp the bearing undersize on the crankshaft somewhere. Other thing is if the crank is so badly scored it won't clean up well at -10, so they'll grind to the next size. It all depends on the condition of the crankshaft when inspected.

By the way, the bearing sizes you have listed are in thousanths of an inch. Jaguar worked to imperial sizes then, not metric.

 

I found this in the SC Parts web pages: -

https://www.scparts.co.uk/sc_en/big-...t-1-16172.html

They quote standard size bearings of 2.086" so your bearings would seem to be to 20 thou. smaller as your 52.45mm in imperial size is 2.065.