Machining piston ring groove

[BK911]

Hypothetically, if one were rebuilding a 2.4E street engine and measured .005” for the top ring clearance, what are the options? New P/C’s? How about machining the top groove to accept 1/16”x84mm rings? I spoke with a gentleman from total seal that says they do this all the time. MUCH cheaper than new P/C’s.

How about for a 2.4S track machine?

Flame away!

BK

[john walker's workshop]

did you check the clearance with a new ring? they wear on their flat surfaces too. another way to do it would be to machine the groove to add a spacer shim like those thin, steel rails used in oil rings.

[BK911]

Mr. Walker!

Thanks for the response!

No I did not use new rings. After reading two pages of horror stories regarding new rings on old pistons with marginal groove clearances, I felt that was not an option.

I have measured the groove and the ring, and both are within spec separately. Unfortunately they are not when assembled.

You did mention machining the grooves for spacers. Can one deduce that machining for over-sized rings would also be acceptable?

BK

Not sure if over-sized should have be hyphenated, but I was always told, "When in doubt, hyphenate!"

[john walker's workshop]

either way would work. put the ring in the cylinder squarely by pushing it in with the piston crown and check for proper end gap. should be about the same as the original rings.

[zotman72]

When I did my first topend job on my MFI 2.4T engine, I used the spacer shim trick on my top rings. Had a machine shop in Seattle do it. New rings were used and the cast iron T cylinders were honed slightly to break up the old glaze. The engine's compression lasted about 10K, then things went downhill fast. When I tore down the engine to make an S, none of the rings were broken but I have to conclude that it was a wasted effort to extend the life of the pistons. I guess this is one data point to tell you to buy new pistons.
By the way, at the time I did this shim spacer thing, I shot an email to Bruce Andersen about it, and he told me not to waste my time (but I did it anyway....). HTH

On my S engine build, I used Total Seal rings for the top ring and stock (geotz?) rings for the bottom two. The S piston ring lands were in spec fortunately.

[BK911]

Mr. Walker! Thanks for the info!

Zotman! Wow, that sucks! Are you sure it was because of the rings? I still might give it a try. I can't see how it wouldn't work, but I'm not that bright!

Anybody else try this before? I'd love to have more than one example to base my opinion on.

Thanks!
BK

[zotman72]

Yep it was the pistons, I did a leakdown test before my tear down. Bubbling in the oil tank.... I also had a professional valve job done at the same time by German Precision when I did the topend job. So there is one datapoint for you. I have heard that MFI engines that are extremely out of tune, can cause top ring land wear due to way too much gas being dumped in the combustion chambers. My 2.4T motor back then, really was running awful with great backfire events. HTH.