Topic: Top-end rebuild....new rings or not necessary?

[BlackMax]

The engine is out and the head is being re-built. I found some rings for this motor (supposedly anyway). 

My mechanic says the existing rings are "fine" and within specs.  He says no reason to replace rings. 

Now, I've had people tell me both:

"you must replace the rings once the pistons are out" and I've also heard

"if everything is fairly fresh, you should be fine for years to come.  No reason to mess with rings."     

Disclosure:  My cylinder walls are smooth with ZERO lip.  It appears (at least to the eye and touch) that they are not worn at all, and thus should be round.  The previous owner said the motor had 10K miles on it....but  then he also said it ran great (the guides were TOAST).

Opinions?

[fuzzybutt]

if you have the rings, why not just put a new 60 degree crosshatch on the cylinder walls and throw em in. break in takes longer with that angle but the motor will last longer that way

[bryanj]

If the ring end gap in the bore is within spec and the ring side clearance in the groove in spec dont change them

[markjenn]

Not groking the "must replace rings if pistons are out" rationale.  If you put it back together and you left the rings on the piston, I can't see any reason why you couldn't reuse rings.  Some mechanics say that if the ring is removed from the piston, it should be replaced, but I don't think that's a hard rule.

If you don't know the history or mileage of the motor, I'd replace rings and hone.  If you do and the time in service is reasonable, I'd leave well enough alone.

- mark

[heffay]

if you see markings in the cylinder... at least a hone is necessary.

last 3 (only 3  ) sohc4 motors i've taken apart looked pristine on the inside while looking fairly worn on the outside. 

you can usually tell on dis-assembly whether things are fitting together correctly... if not they present themselves more on re-assembly.

so no... not always necessary.