Piston Ring Question
01-25-2019, 05:14 PM
#3
As long as the rings themselves are in good condition, I would say it's safe to reuse them. On engines I've rebuilt (BMW M20, etc), I've been known to carefully remove the rings and clean the passages underneath prior to reinstalling.
01-25-2019, 05:23 PM
#4
Nordschleife Master
Rings won’t be compromised and as long as they aren’t damaged you shouldn’t replace them. I guarantee that your compression numbers will be worse if you fit new rings without first honing your bores. Just fit those pistons complete with existing rings back were they came from.
01-25-2019, 06:37 PM
#5
Drifting
I would remove the rings from each piston and place them in a zip lock bag marked to the corresponding piston, ie piston 1 is the closet to the radiator.
Clean the pistons, rofs, and rings with odorless paint thinner and blow dry each component. Reassemble to match rings with piston and arrange gap or each ring per manufactures spec.
Clean the pistons, rofs, and rings with odorless paint thinner and blow dry each component. Reassemble to match rings with piston and arrange gap or each ring per manufactures spec.
01-25-2019, 09:54 PM
#6
Rainman
Rennlist Member
Rennlist Member
Mike,
Have heard from a number of 944 engine builders that as long as the cylinders aren't tapered or actually worn oversize that it's OK to stuff new rings into existing bores.
Did that myself in 2006, no issues on oil burning or power production.
Know of a guy here in LA, loooongtime 944 racer who prepares the bores simply by wiping them down with a scotchbrite pad lightly, cleaning, and inserting new rings on pistons.
Have heard from a number of 944 engine builders that as long as the cylinders aren't tapered or actually worn oversize that it's OK to stuff new rings into existing bores.
Did that myself in 2006, no issues on oil burning or power production.
Know of a guy here in LA, loooongtime 944 racer who prepares the bores simply by wiping them down with a scotchbrite pad lightly, cleaning, and inserting new rings on pistons.
01-25-2019, 10:17 PM
#7
Nordschleife Master
However if you reuse the rings in the bore you won’t have to measure anything and compression will be exactly as it was before. Assumed op was asking if they could reuse the rings and imo that’s the option I’d go for.
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01-26-2019, 04:09 PM
#9
Race Car
Old rings will wear in the width profile, they slam against the upper and lower of the ring grooves as the piston reverses direction.
Definitely check that widths are in spec, then side clearance while installed in the piston.
T
Definitely check that widths are in spec, then side clearance while installed in the piston.
T
01-26-2019, 05:17 PM
#10
Thanks folks. Turns out I’ve got no choice but to replace as when I pulled piston #1 out of the bore I discovered the upper ring broken. This poor engine.
Some history on it. I purchased this block (16v) from Plyhammer as a year ago I discovered wall scoring on my running engine.
Whomever owned it before clearly didn’t do any maintenance other than oil changes. The internals look surprisingly clean as do the cylinder walls.
However I discovered what I concluded to be cam teeth at the bottom of the oil pan, frozen pullies, fairly toased bearings, and the block was covered in caked on oil grime.
This is is my 2nd engine build (1st was for our 83) and I did re-ring that with no issues. I was just more curious in case they were in spec.
In the end there is some good info in this thread. Thanks all.
Chris
Some history on it. I purchased this block (16v) from Plyhammer as a year ago I discovered wall scoring on my running engine.
Whomever owned it before clearly didn’t do any maintenance other than oil changes. The internals look surprisingly clean as do the cylinder walls.
However I discovered what I concluded to be cam teeth at the bottom of the oil pan, frozen pullies, fairly toased bearings, and the block was covered in caked on oil grime.
This is is my 2nd engine build (1st was for our 83) and I did re-ring that with no issues. I was just more curious in case they were in spec.
In the end there is some good info in this thread. Thanks all.
Chris
01-26-2019, 05:27 PM
#11
Race Car
If the block had work done, cylinders are supposed to have a chamfer that aids in installing rings and lessen chance one is broken during install.
T
T
01-26-2019, 06:08 PM
#12
Drifting
Or at the previous engine rebuild, the installer was not careful with the ring compression and released compression force before the top ring was securely square inside the cylinder wall. That is why I always use a fixed ring compression because I do not have enough finesse with an adjustable one
01-26-2019, 06:37 PM
#13
Addict
Rennlist Member
Rennlist Member
They are pretty easy to break, I doubt it was broken while in use, if so the bore would be trashed. More likely carbon and bore ridge broke it upon removal.