What do they mean by over bore

[treysawyers]

When building an engine block and you are changing your pistons, what does it mean when they say you can have it at 0.010 overbore or 0.020? Ive seen some websites that simply say you can get it at 81-84mm whatever they have? somebody pplease put me on. thanks

 

[nd4sped]

By request I am editing this post to be more specific.

A precision boring machine basically shaves teh inside of the cylinder sleeve. Thus increasing the inner diameter of the cylinder.

Over boring can be doen in 2 ways.

1. Boring out the stock sleeve to fit aftermarktet pistons. Which essentially weakens the cylinder sleeve.

2. The stock cylinder sleeves can be removed and a new thicker aftermarket sleeve can be put back in place of the original. This is a great way to go since the cylinder walls are already thicker than stock. They can also be bought with a larger bore already cast. Though if the sleeve is of stock porportion it can be bored out to fit your larger pistons.

There is also a cheaper way to go. You can have a much thinner sleeve that can be pressed over the stock sleeve. There is also another product out there that is similar called a Cylinder Brace that does the same thing.

This process has to be done extreamly accuratly or it will result in failure.

Hopefully this is better to understand.

 

[treysawyers]

I was kinda thinkin that, but how do i know exactly the size piston that goes in the over bore. like is 0.010 overbore the same as an 82mm piston, or an 0.020 the same as 83mm? thats what im trying to undertsand.

 

[HELP_ME]

umm bore piston? I only heard of porting throttle body... Dunno what it does...

 

[vandynamics]

A machine shaves the inside of the cylinder walls essentially making the bore larger. Though in turn you are making the walls thinner. But that is why people will have sleeves pressed into the block to reinforce the newly OVER BORED cylinders.

Thats what it is.

omg is this dude for real?

 

[nd4sped]

I was kinda thinkin that, but how do i know exactly the size piston that goes in the over bore. like is 0.010 overbore the same as an 82mm piston, or an 0.020 the same as 83mm? thats what im trying to undertsand.

If you dont know what bore size you have you can use a Inside Micrometer to measure the diameter.

omg is this dude for real?

Putting it simple thats what it is. So dont preech. If you have a better more informative answer then by all means post it up. But instead of wasting a posting, "omg is this dude for real?" post something that will actually contribute to answering teh question.

So if you want to just reiderate what I said and post the actual process that teh machine does. Help yourself.

 

[vandynamics]

If you dont know what bore size you have you can use a Inside Micrometer to measure the diameter.



Putting it simple thats what it is. So dont preech. If you have a better more informative answer then by all means post it up. But instead of wasting a posting, "omg is this dude for real?" post something that will actually contribute to answering teh question.

So if you want to just reiderate what I said and post the actual process that teh machine does. Help yourself.

well what you said is absolutley wrong. you bore/hone the sleeve. not the actual motor jug.

 

[nd4sped]

well what you said is absolutley wrong. you bore/hone the sleeve. not the actual motor jug.

Please go back and read my post. I said that it bores out the cylinder wall.

 

[vandynamics]

Please go back and read my post. I said that it bores out the cylinder wall.

im afraid that along with training motor repair. you also need to study motor termology and possibly grammer.

theres a difference between a cylinder wall and a cylinder sleeve. if you are going to teach someone. make it understandable and use the correct termanology. im not asking too much am i?

 

[nd4sped]

Ok let me be more precise so everyone can understand. Apparently Im not being thorough (sp?) enough.

So Im gonna edit my first post and retype it so no one is confused.

 

[vandynamics]

Ok let me be more precise so everyone can understand. Apparently Im not being thorough (sp?) enough.

So Im gonna edit my first post and retype it so no one is confused.

heres his first post for shits and giggles.

 

[Ravage70]

overboring will give u an extra 34.86 whp on any engine

 

[lanojp1]

overboring will give u an extra 34.86 whp on any engine

i sure hope you are joking...

 

[treysawyers]

im reading all these posts and my original question was still not answered. i know how over boring is done. i just want to know if when someone says they did a 0.010 over bore on their cylinders, does this mean that it was 0.010 inches or mm which ever. thats why before i said before if the stock piston is 81mm, would a 0.010 over bore mean that you would now use a 82mm piston.

 

[FRODO]

im reading all these posts and my original question was still not answered. i know how over boring is done. i just want to know if when someone says they did a 0.010 over bore on their cylinders, does this mean that it was 0.010 inches or mm which ever. thats why before i said before if the stock piston is 81mm, would a 0.010 over bore mean that you would now use a 82mm piston.

mm. there you go.

 

[nd4sped]

im reading all these posts and my original question was still not answered. i know how over boring is done. i just want to know if when someone says they did a 0.010 over bore on their cylinders, does this mean that it was 0.010 inches or mm which ever. thats why before i said before if the stock piston is 81mm, would a 0.010 over bore mean that you would now use a 82mm piston.

Just do a measurement conversion.

1 inch = 2.54 centimeters
1 centimeter = .3937 inches

Do the math and you will have your answer.

 

[Handlebars]

.020" is the standard overbore, which is 1mm. thats the most you can do on a stock sleeve.