21 replies to this topic

[littlemissmagic]

+20 pistons are 1293 so what are +30?
as my engine has +30 pistons and was wondering what its been bored too?
Thanks

[fishey798]

1310cc i think!

[littlemissmagic]

oo i hope someone can confirm this as i could probably have alot of fun with this engine

[samsfern]

if 1293 is +20, and 1310 is +40, then +30 will be inbetween

[shorty]

is there a +30thou?

[samsfern]

30 thou is a standard overbore size

[shorty]

lol my memory seems to go 20 then 40 aha shows how much i pay attention

[Surfbluegarage]

+30 thou wld be 1310 if +20 is 1293 and +40 is 1330 not 1310.

[ministe]

I do believe its 1301cc.

[Surfbluegarage]

aahhh so whats a 73.5mm (1380) then in thou over?

[littlemissmagic]

so it is a 1310?
sorry for any confusion caused haha

[Surfbluegarage]

no i balls that one up it is a 1301 like stated above..
+20 =1293
+30 =1301
+40=1310
+60=1330

[littlemissmagic]

anyone know were i might find some piston rings for the seemingly rare overbore size of +30?
thanks for all your help

[mk3 Cooper S]

Yep + 30 is 1301. the top bore size for competition / class engines from memory.

I have a set of +30 ringless pistons and a set of new pistons and rings.
If you find out where you can them at a reasonable price then please let me know.

[samsfern]

possibly moss?