How much do I need to bore over?

[WheelieMan4]

I'm getting an 88mm piston and i was wondering how much you all think that i should bore it...the cylinder wall is scratched and that is y i need to bore it out, so what would u all recomend......I DONT WANT TO GO MUCH, CUZ I DONT WANT THE CYLINDER THAT THIN....thanks!

[GPracer2500]

I don't get it. The piston size determines the bore.

[Glamis400ex]

Dude...you don't make one bit of sense. First of all, you don't say what size piston you have already in there. An 88m is a 426. If you're on the stock piston and sleeve go with an 86mm...that is a 406. I doubt a stock sleeve with a scratch would need to go all the way to a 87mm, or 416. Now, if you already have a 426 and it's scratched, you're probabaly outta luck. A hone may not do it.

I had a 416 (87mm) and had a gnarly gouge when I tore it down so I had to go to a 426.

I have had a very well respected engine builder tell me an 88mm bore on a stock sleeve is fine.

Glamis

[WheelieMan4]

ok here is what i was trying to say i guess....

i messed up my engine, to much dirt...i need a new piston and it needs to be bored because of the scratches......

so, im getting a JE 88mm (426) 11:1 piston, hotcam stage 2, and just wonder how much i should bore the sleeve over, to get rid of the scratches.....understand??? thanks

[400exrules]

i dont want to sound stupid but i am, what is a sleeve? i thought the cylinder is what gets bored. is the sleeve inside the cylinder or something? can you take it out?

[Glamis400ex]

YOU DON'T DECIDE THAT PART...your guy doing the machine work does. He will take a set of micrometers and measure the piston, add .002-.004 to it and bore the sleeve.

I don't understand why you think YOU get to decide the size of the bore? The piston diameter dictates the bore size. Just let the dude handle that part...you don't have any say in the matter.

The only say you have is wheather you want a 86, 87 88, or 89mm piston.

[Glamis400ex]

400exrules,

A sleeve is pressed in the cylinder. It's the part that actually gets bored out. When you run out of room, you can have the old one pressed out and a new one pressed in.

[WheelieMan4]

Well ok, i didnt know that at all...well if you have the 88mm, how much is yours bored over then?

[400exrules]

what do u mean run out of room, like if u have a 465 or somethin, and you need to rebuild, they'll put in a new sleeve since their wont be much room left, and you can bore the new one to whatever your want?

whats the limit on a 400ex sleeve

[GPracer2500]

Originally posted by WheelieMan4
Well ok, i didnt know that at all...well if you have the 88mm, how much is yours bored over then?

The size of the piston IS how much it's bored over. Stock bore is 85mm. An 88mm piston would be a 3mm overbore.