Advantage of an over bore

[BayState300GT]

What is they exact advantage of having an over bore like .20 or .30 etc? what if i kept it a stock bore, example, wiesco pistons with eagle rods stock bore. any major disadvantages?

 

[PIMking]

It basically will clean up the cylinder walls and make them strait and true.

 

[No_Skillz]

It basically will clean up the cylinder walls and make them strait and true.

Just to elaborate: sometimes a cylinder wall has seen so much abuse that it has scratches or gouges in it. It can't be filled in, only smoothed out by machining. Coupled with the fact that a slight bit of material is taken out when it is honed, you will need a slightly bigger piston to fill the space. There is no real performance gain.

 

[xe0]

What is they exact advantage of having an over bore like .20 or .30 etc? what if i kept it a stock bore, example, wiesco pistons with eagle rods stock bore. any major disadvantages?

edit: What he said ^^^

I wouldn't say it has an advantage. It is either necessary because the cylinders are out of round or damaged more then a hone can fix or it's not needed at all.

Adam

 

[BayState300GT]

ok thanks guys thats exactly what i was looking for if there was any kind of hp advantage

 

[TunaTalon]

Over boring will slightly increase the displacement. The percentage of power increase will be proportional to the increase in displacement.

See the thread at http://www.dsmtuners.com/forums/str...acement-various-combinations-bore-stroke.html for a table of displacements for different piston sizes and crank stroke.

 

[delta448]

http://www.dsmtuners.com/forums/str...acement-various-combinations-bore-stroke.html

Nice table, I made a similar list before I'd seen yours, but since you did rod ratios in yours, I just now decided to add them to mine as well.

http://www.dsmtuners.com/forums/stroker-tech/310730-anyone-have-any-experience-2-2l.html#post151632176

 

[Defiant]

Overboring for power is primarily a V8 practice, where you either have twice the cylinders to add up the difference, or have a thick enough casting that you can add significant swept area. On four-cylinder engines, as explained, it's done to make a damaged bore usable.

 

[mikEclipse99]

+1 ^. after dsms being 7, 8, 9+ years old those cylinders arent usually in the best condition so this basically machines them to be new again