Whats the standard YB piston diameter?

Thanks

 

86mm i think..

 

86mm pistons would slap somewhat.

standard bore size is 90.82mm

 

Thanks. Current low comp piston has 0.5 stamped on it, so my new high comp will be a 91.32mm jobbie then.

Thinking of going wossner 12:1 Mixed reviews online, anyone care to add?

 

I'm pretty sure that nash had woosner, with loads of trouble, ended up having to rebuild engine due to the pistons, noise and wear.
I assume(hope) you're going naturally aspirated if wanting 12:1, but not mentioned, forget 12:1 with a turbo, if sticking with turbo then the std mahle are excellent, people using these at 500bhp, my own ones did 200,000 miles!!
As to size there was 2 sizes used on the Yb engines, where the marking is by the dizzy clamp the numbers 2 or 3 relate to the pistons in that position with 2 being size 90.758-90.772mm, size 3 is 90.768-90.782mm, the important thing is the bore clearance but new pistons will be around 0.035mm - 0.062mm, you need to measure the bore wear first, my engine at 200,000 miles nearly missed the 1st oversize and jumped direct to 2nd oversize due to wear!!
tabetha

 

As above really but a std bore size is 90.8 and a .050 piston is 91.275 in mahle,wossners will be slightly different as they will need a bigger skirt clearance...


cheers danny

 

After a lot of tooing and froing I'm gonna go with NA..
The chap I bought the engine off had pics of the engine with head off and the pistons were stamped 0.5 The crank is scribed GGR so they may have done the rebuild.
Once I get the head off again I'll measure the bore size and take it from there.
I'll check those numbers by the dizzy too.
Thanks for your help! I'm gonna need loads more LOL!