I'm rebuilding a stroker that has some scoring on the cylinder walls. The Machine shop says the motor is alreadr .020 over & will need to be bored again to get rid of the scoring. This will put me at .040 over stock. Will this be an issue in the long run? Can this motor handle 30 or so PSI without any problems? I can't seem to find any related info so I thought I'd ask. FYI this motor will be running a BBK full & eventually E85. Possibly down the road I may upgrade to a Red, but I doubt it. Thanks for any input.

 

IMO, it will be ok. I dont think mitsu would build a turbo charged motor & put thin cylinder walls in their engine.....

would a 85.0mm bore be stronger than a 86.0mm bore in a evo 4g63 block...Yes.....Will you ever challenge the integrity of the cylinder wall strength with the build you have going 100% of the time to really make a big difference..... I know im not.

I plan on doing the same, as the block i obtained is already +0.020 & needs some work.

I recently over-revved my motor & it spit out a rod 10 days later...so i plan to cut up my ventilated 4g63 block & post the wall thickness of the cylinders that i measure.

i will also measure my 4g64 block as well....

if going 0.040 on the bore was forbidden, i dont think mitsu would have made replacement pistons of the size...

 

Thanks for the reasurance. I did'nt think it would be a big deal, but I wanted to make sure there weren't any horror stories first. Not much info on the .040 over bore on here. Thanks again & good luck with your build.

 

there was a thread on this a few weeks ago, do a search. The general opinion was that its fine.

 

I did search but found almost nothing.

 

https://www.evolutionm.net/forums/ev...5-40-bore.html

 

I typed .040 instead of .40 in the search thread title box which is why I didn't find it.