[RESOLVED] Q: Better to use standard size pistons or oversize?

[pj91gsx]

Is it better to bore out the block and put bigger piston when doing a rebuild on a 4g63t. Or is it perfectly fine to use standard bore for rebuild even though I am going to run the motor hard.

 

[tkelly27]

IF your cylinder walls are within tolerance, then use the standard bore. If they are damaged or out of spec, overbore them.

 

[_Launch_]

I'd highly recommend going with oversized pistons during a rebuild but like tkelly27 said if your cylinder walls are within tolerance, you can get away with a standard bore. The key word being if.

 

[tqmx1]

Also if the bores check out ok but your piston to wall gap is a bit loose replace the pistons. The skirts will wear down a little and with new pistons it should return the cylinders to new specs.

If not the worst thing is you will still have to punch it .020 over.

 

[Defiant]

It's pretty much a waste of effort to up-size the pistons on a 4-cylinder. You won't gain enough to see it. Save it for when there's enough wear or damage to the cylinder walls to need a deep cut.

 

[TunaTalon]

It's pretty much a waste of effort to up-size the pistons on a 4-cylinder. You won't gain enough to see it. Save it for when there's enough wear or damage to the cylinder walls to need a deep cut.

Over the limited range of possible bore sizes for the 4G63 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. As Defiant says, not much gain for just over boring.

 

[pj91gsx]

ok. That helps a lot thanks for the information.