TO-20 Rod Bearings

[dpalmerNH]

I am currently doing an engine rebuild on my Ferguson TO-20. I pulled the pistons out today and in looking to find out what size bearings they are. All I could find is the number "Z120G 306M". I'm not sure whether I should order standard, .010, .020, or .030 Rod Bearings. Can you help me?
 

[PackardV8]

Mic the crank.
 

[trac]

They will be marked if they are over sized.
 

[2tractors]

Those are standard, meaning original.
 

[John(UK)]

There will always be a size stamped in the back if it is oversize, if there is no size given then they are standard....John(UK)....fergusontractors@hotmail.com
 

[PackardV8]

"Z120G 306M". So then could "306M" possible mean 0.306mm???? Which would be about .012" under. I've overhaulded a few "modern day" engines with metric undersize stamped on bearing shel inserts. But it was somewhat encyptic just like the "306M". First time i ran into it it took me by surprise.

Dpalmer. The only way to know FOR SURE is to mic the crank. Mic reading is bible. Everything else is just reference symbols.

Keep us posted on your findings.
 

[PackardV8]

Also note that EACH AND EVERY journal of the crank must be determined for size. It is not uncommon (especialy among older engines) to find maybe only ONE journal that is undesized and or variations of std or undersize combinations along the crank.

IN more modern times now that everyone wants to sell the customer everyting on the shelf many 'kits' and as well as individual parts are sold as sets only. But older rebuilds could have miscellaneaous undersizes in bearings, oversizes in pistons, valve stems etc.

Gotta use a MICROMETER on the parts. Anything else is guess work.