Engine Build

[DeathSammich]

Hey, just wondering if doing a rebuild when is a cylinder bore necessary? And if a bore has to be done say 20 or 30 thou over, If using OEM oversized pistons is a tune required? Or is the oversizing negligible? The engine has 256xxxks in it and am not sure whether to hone it myself and re ring or take it to get rebooted and whether it would even be worth it. Was hoping to keep everything together and just remove the pistons. Cheers

 

[Pollushon]

You'd bore for a couple of reasons; performance or if the cylinder walls are damaged beyond what a hone can smooth.

If you bore you will need suitable pistons. A retune isn't mandatory but I certainly would get it touched up.

 

[vr304]

Really depends on what condition the bores are in as to wether it needs a reborn or not, u won’t know until you pull it apart

 

[DeathSammich]

Really depends on what condition the bores are in as to wether it needs a reborn or not, u won’t know until you pull it apart

And I'm guessing if it would like a rebore but you just hone it and put new rings in it itll just make things worse?

 

[Deuce]

And I'm guessing if it would like a rebore but you just hone it and put new rings in it itll just make things worse?

Possibly yes.
Maybe line up pistons and then see what machinist advises. Then purchase if required.

 

[Immortality]

There is an optimum piston to bore clearance, go much bigger and the engine will get noisy from the pistons rocking in the bores. If the bores are straight and not damaged or worn out in any way then a quick hone to deglaze is fine with standard type rings.

 

[gtrboyy]

Won't know untill you take heads off to look at bores.

If pitted or scoring marks visible mostly likely rebore needed

If can still see cross hatch from factory hone job or bore is glazed but minimal wear then might get away with honing & put back together after measuring wear.

Do dry & wet compression test beforehand to identify any cylinders to look out for & if smokey work out if rings,headgasket or whatever to save time later on.

Also before pop pistons out grab razor blade scrape carbon off top of bore so ringlands or bore dont get damaged.

What engine is it?
Sometimes better to build a good spare or swap it out then build your own...keeps car mobile & less rush or stress

 

[DeathSammich]

There is an optimum piston to bore clearance, go much bigger and the engine will get noisy from the pistons rocking in the bores. If the bores are straight and not damaged or worn out in any way then a quick hone to deglaze is fine with standard type rings.

Ahhh might explain the knock retard I was getting on my old l67 I had with forged pistons. There was massive clearence, could probably fit a knife down in. So if I were to rebuild it even with oversize pistons it will run off the stock memcal?

 

[DeathSammich]

Won't know untill you take heads off to look at bores.

If pitted or scoring marks visible mostly likely rebore needed

If can still see cross hatch from factory hone job or bore is glazed but minimal wear then might get away with honing & put back together after measuring wear.

Do dry & wet compression test beforehand to identify any cylinders to look out for & if smokey work out if rings,headgasket or whatever to save time later on.

Also before pop pistons out grab razor blade scrape carbon off top of bore so ringlands or bore dont get damaged.

What engine is it?
Sometimes better to build a good spare or swap it out then build your own...keeps car mobile & less rush or stress

Okay thanks! It's an l67. It would be easier to swap but getting a hold of an l67 is hard in tas and quite pricey

 

[EYY]

Just use an ecotec bottom end and get the tune right.