Why new Rings, Why rough up a smooth bore?

[runthatjunk]

Looking for the science/technical reasoning behind this.

The question is if you have an engine that's not burning oil, high mileage, great looking bores with no ring ridge, why can't you just clean it all and put it back together.  Nearly every post I've read online says that new rings and scuffing the bore is mandatory.  Nearly every post I've read says if you don't it will be an oil burner.  Why?

It's on an 06 ford v6.  So fairly modern piston and ring package.  I couldn't believe how nice the bores looked,  It just seems a shame to rough up the walls that have been polished so nice.

The downside I don't know that i'm sold on the sintered metal cracked rods, the concentricity was only decent on about 2 of the 6 rods.

[Stangman]

I look at it like putting new pads on an old rotor, two surfaces that arent compatible. Same as a clutch disc without
resurfacing flywheel. Sure it might work but nothing like two new surfaces wearing in together. And rings aint the same as pads or clutch disc I was just giving an example. Besides too much work to shortcut. Just my opinion and you know what they say about them!.

[CaptCobrajet]

Crosshatch holds the oil.  Without oil, the ring will gall.  On your rods, if the bore is fatter at the parting line, run them.  If they are pinched at the parting line, do not.......

[Barry_R]

Sealed Power & Dana ran new rings on an old bore all the time in the lab.  Works fine.

Scrub the living heck out of it & go

But that assumes a perfect used bore - not something with a hundred thousand miles on it no matter how good it looks.

By that time the bore has most likely experience significant wear unless its something snoopy like nikasil etc.

In that situation the risk versus reward favors a proper hone effort.

[runthatjunk]

I get needing to hone them for NEW rings, if I was planning on another 100k+ miles that makes perfect sense.  What I don't get is that the same polished rings back into the same polished bores supposedly is crazy and will use lots of oil.  If it wasn't using oil before why would it start from simply removing and reinstalling the piston? 

And how the heck does a rod bore spread towards the parting line and tighten lengthwise?  One rod has done that by about .0015"

 

[shady]

well, I once had a 283 chev that had low mileage & was only driven to church by a 88 yo lady. (no kidding)  wasn't bad on oil when I got , but soon after started using a quart every 4-500 miles. Pulled the pistons out & sure enough the rings were stuck on the pistons.  Cleaned them up & removed the rings, cleaned the grooves & put the rings back on the same piston & put it back together. No hone no nothing. Work perfectly & used no oil after that. On cost was a gasket set & some carb cleaner.

[Barry_R]

[quote author=runthatjunk link=topic=6211.msg67751#msg67751 date=1531575874

And how the heck does a rod bore spread towards the parting line and tighten lengthwise?  One rod has done that by about .0015"
[/quote]

Because you (or the prior owner) has been beating the top of the piston with a BFH every other rotation for a million cycles of use.  Picture that half circle sitting upright on a workbench and you banging away at the top of the rod over and over and over.  Eventually it spreads out from the accumulated loads.

[chris401]

well, I once had a 283 chev that had low mileage & was only driven to church by a 88 yo lady. (no kidding)  wasn't bad on oil when I got , but soon after started using a quart every 4-500 miles. Pulled the pistons out & sure enough the rings were stuck on the pistons.  Cleaned them up & removed the rings, cleaned the grooves & put the rings back on the same piston & put it back together. No hone no nothing. Work perfectly & used no oil after that. On cost was a gasket set & some carb cleaner.

That is exactly what I did on my current 352. Ball honed, cleaned the pistons/rings and put back together. Leaks about 1 quart every 1,000 miles but not burning any. About 4 years and 8,000 on the engine.

[runthatjunk]

Thanks for all  the input, at the very least it shouldn't be a fogger driving down the road, and in THIS case that will be good enough for me.

[gt350hr]

  Pulling a rod and piston out and putting it back in the exact same bore has zero effect of ring seal as long as they aren't damaged in process. No need to hone unless the rings are replaced.