boring questions

[Oldshell4481]

im going to get my cylinder bored .50 over and putting a new piston in while i get this motor rebuilt, what will last longer and be more beneficial to the motor,, a 10.25:1 or a 12:1 piston, im more worried about longevity of the engine and less maintenance than power. and when i get this bored do i need to do anything to the top top end of the head (where the valves are)????

[bigredhead]

without a doubt.. the 10.25:1 will be easier on the bottom end and everything else..

[Oldshell4481]

alright thats what ill get

[bigredhead]

plus you can run pump gas.. . high octane fuel gets expensive i hear !!

[Yamahauler]

Is .050 over the next oversize you are on? or are you boring it .050 over from stock?
You should only go to the next oversize (.010 or .020 over, depends on your machine) so you have room for more bores if need be.
Boring it out .050 over will give you 199cc instead of 192, so its nothing you will notice

[Oldshell4481]

i looked in DK and it only showed pistons for a .050 overbore, no .010 over or .020 over..

[grundlegrabber]

Sometimes different companies offer different overbore sizes. An overbore size that might not be available from Honda might be available from Wiseco or Sudco, etc. If you are going with a high compression piston, you may not have that many choices of piston manufacturers and bore sizes. With a stock compression ratio piston there are probably more choices. Definitely would not suggest a 12:1 piston. That's a super high compression ratio that will require you to run race gas, and will also be a lot harder on the motor. At 10:5 to 1 you can still run high octane pump gas, and you get noticeable power gain with minimal stress on the motor.