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.

[Glamis400ex]

Thank you GPracer. I didn't think it was that difficult to grasp. Stock is 85mm...you have a 88mm. Do the math. Your 88mm piston is 3mm over and the limit of the stock sleeve. If your asking the exact amount of overbore like 2.9743mm....I can't answer that..only the machinist knows and if you REALLY wanna know, I'm sure he'll tell you exactly how much he bored the sleeve.

If you want to run 426 or bigger you need to have an aftermarket sleeve installed. They will press out the stock sleeve, bore the actual cylinder to accept a thicker sleeve, press in the new sleeve AND THEN you can bore to a 440 or 465.

[400exrules]

but what is the point of the sleeve, is it just so you can replace the sleeve itself if the motor blows or if you get a scratch or whatever...instead of trashing the whole cylinder?

[GPracer2500]

Originally posted by 400exrules
but what is the point of the sleeve, is it just so you can replace the sleeve itself if the motor blows or if you get a scratch or whatever...instead of trashing the whole cylinder?

The cylinder is made of aluminum and is far too soft a material to withstand having piston rings constantly scraping it. Sleeves are typically made of iron, I believe. Some cylinders get around having to use a sleeve by using a super-hard surface coating on the aluminum cylinder walls. Nikasil is an example but there are others. Hard coated aluminum cylinders wear very well but require special steps when an overbore is required/desired. This generally involves sending the cyclinder to a specialty machine shop to have it bored and re-coated.

[Glamis400ex]

yes, it's the part of the cylinder that is easily and cheaply replacable. When you have a moving mass (your piston) rotating up and down hundreds of thousands of times in a hole (your sleeve)....it's going to eventually wear out. Dirt makes it's way in there and causes wear. A sleeve is like $75 but the actual cylinder is close to $250. You wouldn't want to replace a cylinder every 2-3 years when the piston wears it out so you only need to replace the part that actually gets wear....the sleeve. The cylinder is just a holder for the sleeve. The sleeve is over 1/4" thick, so, if you do get some dirt in there and it makes some grooves, Honda makes the sleeve thick enough to accomadate a couple sizes larger piston. On a stock sleeve you can go with a 86mm...406, a 87mm...416 or a 88mm...426 and still have enough thickness to still dissapate the heat. When the walls get to thin from overbores they get REAL hot and either crack or warp. So that's why a 88mm is the max size you can go and still make it reliable. Any thinner on the sleeve walls and it'll crack.

Lesson over....

[WheelieMan4]

oooooooo sorry im not engine smart at all...i understand now

thanks

[GooseZ400]

awesome explanation glamis you know your s***

[Glamis400ex]

Wheelieman4,
No need to be sorry. You didn't understand so now you've learned something. I started out the same way.

GooseZ400,
Thanks.

GPracer2500 definately knows his $hit as well...:)

Glamis

[400exrules]

im going to get a 416 JE piston when i get the money, should i get the 10.8:1 or the 12:1? is their a big power difference between the two? could the 12:1 be run with a stock rod and stock studs?

[Glamis400ex]

If you want to run pump gas and run the stock rod, get the 10.8:1. The 12:1 will require a rod upgrade and race gas for sure. I have the 11:1 and I run a 50/50 mix of pump and race gas just to be safe.

You will most likely need studs even with the 11:1. I re-built mine the first time with new, stock studs and blew a head gasket after 5 hours. Just save yourself the headache and GET THE HD STUDS.

[boricua]

BAMM !!!

[400exrules]

Originally posted by Glamis400ex
If you want to run pump gas and run the stock rod, get the 10.8:1. The 12:1 will require a rod upgrade and race gas for sure. I have the 11:1 and I run a 50/50 mix of pump and race gas just to be safe.

You will most likely need studs even with the 11:1. I re-built mine the first time with new, stock studs and blew a head gasket after 5 hours. Just save yourself the headache and GET THE HD STUDS.

someone said to get a cometic flex steel head gasket because its really strong....would i still need the hd studs?

and what is the benefit of a thinner head gasket, doesnt it bump the compression up?

[GPracer2500]

Originally posted by 400exrules
someone said to get a cometic flex steel head gasket because its really strong....would i still need the hd studs?



Yes. The problem is the studs start to pull out of their threads in the cylinder. If the studs pull out than it doesn't matter how strong the gasket is.

[Glamis400ex]

The other benefit is that you don't need to re-torque the headstud nuts after 5 hours of break-in as you do with some other fiber gaskets.

I had absolutely ZERO problems with my 416, HD studs and flexsteel gasket set up. The studs and the flex-steel head gasket worked great.....but I did develope a leak at the head gasket due to my sleeve drooping about .001 and creating a void. I don't care how good a gasket is, if a void is created....you will leak. If the sleeve hadn't of dropped I would still be riding her, but alas, as I tore it down I had a pretty good gouge in the cylinder wall that could not be honed out, so I went to a 426 (88mm piston)

Glamis

[400exrules]

what caused the sleeve to drop?

can i install studs by myself with the tools i have?

[WheelieMan4]

i bought a moose racing gasket kit...is that going to hold up to an 88mm 11:1 comp?? and where can i find some HD Studs at?? Ive been looking and no luck...:ermm:

[Glamis400ex]

The sleeve dropped because sometimes they just do that. Usually heat related. I wouldn't install HD studs myself. Look at For Dirt Only or GT Thunder for studs. They can both do the drilling as well.

http://www.gtthunder.com/TRX400EX.htm

Glamis

[400exrules]

can gt thunder just do all of this for me? can i just ship them the cylinder and piston and can they install the hd studs, bore it, and install the piston for me?

[Glamis400ex]

Yes, if you read the link I posted...it says what you need to do.

Glamis