hey... just wondering how far can you bore out a b20z? will 85mm still be safe to rev to 8k on a built motor?

i mean my buddy did a b20vtec...his was bored out to 84.5 and he was revin past 9K and it is fine...

Define "built" ,...I mean,if you upgrade the bearings (ACL,cheap and good) and the rods/pistons,...Basically upgrade the internal rotating assy., and should be fine.

BTW: B20 vtec is amazing,...I remeber the first time I saw/heard a built one run an EG hatch,...They pulled out to line up,and the b20 walked a little showing off,.. I just stood there in awe ....Hands down,the most amazing sounding honda I've ever heard

yea man...i remember when i first rode in it...he hit vtec and i almost shit my pants haha

thanks thats all i wanted to kno.... im having the block built with crower rods and cp pistons. everything is going to be balanced. it was either build the b20 or get my 1.8 sleeved to accomodate the larger bore. or should i just sleeve my 1.8 so kno one will kno that it'll really be a 2.0? still undecided.

i would not do that with out sleeving a b20 block they crack ......at high comp...

The cylinders walls are already thin, you bore it out to 85 and you just make them even more thin... it'll break a lot sooner.

Get the 1.8 sleeved to 85mm and you'll be set.

I have seen an 85mm, stock wall B20 hold together pretty good. It was NOT boosted and thats a totally different problem. I would have to say if you are going to bore it, get a capable tuner. Ultimately its life is going to require a great tune. The stress on the cylinder walls comes from the piston/rod assembly not being exactly at TDC on the combustion stroke. In a normal, unaltered motor there is a fair amount of forgiveness in the cylinder walls that allows for a little bit sway from them.



When you bore an already thin wall you narrow the tolerances that those walls can deal with. This is going to increase your need for a near perfect timing tune. Alot of people think its the piston that goes through the wall or a rod breaking that is the cause when in actuality it is the fact that the timing is off and the pressure is displaced from the wrist pin and the crank to the cylinder wall itself. This is what cracks the walls.

thats some really good information IBleedJDM thanks for posting man!

Any time hope its useful to someone. By the way who likes my PAINT skills?

haha well it is good to know that you can color inside the lines

Thats just when I'm on the computer you see me a crayons don't get along. I dip them in elmers glue and eat them thats why the nurses won't let me do crafts!

hey guys thanks for all the help...