RB20 boring & pistons

[littlemilla3]

Is it possible to bore the rb20det to 85 mm and use rb25 pistons? Are the pistons interchangeable if the bore is the same?

[rbsileighty]

No... but if it were possible... you still couldn't use the pistons b/c the wrist pins are not interchangeable either. Sorry bud...

Just remember boring to 86mm (stock 25's bore) from 78mm is a huge difference.

[dreamsOfSkylines]

if the wrist pins are not interchangeable how do people stroke the rb20 with the rb26 crank? Do they still us the Rb20 con rods?

[Yellow4g63]

They Use 26 crank and rods with custom pistons.

[oreofreak]

you cannot bore a rb20 no bigger the 82mm. Their several different way to stroke a rb20. To make a rb24 you need a rb26 crank, con rod, and 82mm customs pistons. To make a rb23 need a rb25 crank, and con rod, 82mm customs pistons. The rb20 block has to be machined for a rb26 and rb25 crank. It is a lot easier to use a rb25 that is already bored out to 86mm and a rb26 crank, con rod and pistons. You will then have a stroke rb25 which is a rb26 and no machining is required for crank or the pistons.

[s13sr20chris]

you cannot bore a rb20 no bigger the 82mm. Their several different way to stroke a rb20. To make a rb24 you need a rb26 crank, con rod, and 82mm customs pistons. To make a rb23 need a rb25 crank, and con rod, 82mm customs pistons. The rb20 block has to be machined for a rb26 and rb25 crank. It is a lot easier to use a rb25 that is already bored out to 86mm and a rb26 crank, con rod and pistons. You will then have a stroke rb25 which is a rb26 and no machining is required for crank or the pistons.

i strangely feel that i need to write all that down. maybe we should have a sticky on different rb configurations. starting with rb30 stuff. i would like an rb30 block with rb25 head. that would be very cool. i hear it will work.

[rbsileighty]

i strangely feel that i need to write all that down. maybe we should have a sticky on different rb configurations. starting with rb30 stuff. i would like an rb30 block with rb25 head. that would be very cool. i hear it will work.

25 head on a 30 block is said to be a direct fit, and doesn't like to rev much past 8k (still pretty high)... just fyi