Cory M

What would cause the rings to fail and break apart on 5 of 6 cylinders? Engine is a 3.4L race motor, JE pistons, QSE cylinders, not sure who the ring manufacturer was. Happened approx 2 years after full rebuild. Engine is at the shop now. Seems like a weird failure to me, any ideas?

Mike Murphy

Wow. Did this happen all at once, or did power and oil consumption go down gradually? I don't much about these flat-6 engines in terms of ring failure, but excessive heat and/or pre-detonation can be the cause in other engines.

Peter Zimmermann

Cory: You don't say how many hours are on the engine. That said, the only place that I trust to analyze your issue is Engine Machine Service (EMS) in Los Angeles. It might be worth it to you to box up your parts and take a trip north to show them what you've got. Their phone number is (310) 641-7019, and you want to talk with either Bill or Dick.

Cory M

I can estimate the hours, but I don't know for sure. Figure about 20 events, about 2.5 hours per day, roughly 100 hours. The engine was actually running fine but developed a miss at higher RPMs, the miss may have been an electrical issue. While at the shop to fix the miss a compression check revealed one cylinder was about 25% lower than the others, but the others looked okay. A small piece of a ring was found when changing the oil and the decision was made to open it up. No detonation issues and historically it hasn't run hot. The temperature sending unit died so the gauge didn't work for 2 events though. Wasn't running hot the weekend the miss started. Oil consumption didn't increase significantly either.

I have an idea in my head of what may have caused it but I'd like to hear other opinions first.

Steve Weiner-Rennsport Systems

Hi Cory,

Assuming for the moment that the ring gaps were measured and adjusted when the engine was built, the main reason rings get broken is when the engine detonates.

There are many many other tell-tales that an experienced engine builder can spot to confirm this.

theiceman

Very interesting. I rememeber one of the local guys know with a very similar issue. The rings broke on all 3 cylinders on the same side of the engine. I don't think we ever figured out why but he rebuilt it and it has been fine.

JET951

i dont think you found a piece of ring in the oil, think about it how did that piece of ring get past the piston? does the piston have a hole in it to allow the ring piece to fall through?

g-50cab

What rings? I know a few engine builders that will only use deves (is that right?) rings with JE psitons - they throw the ones that JE supplies away.

JB Racing in florida had their own version if my memory serves me correctly.

Cory M

This isn't my engine. The owner told me it was a piece of a ring he found in the oil and one cylinder is scored pretty badly.

I don't know the brand of rings.

Charles Navarro

I try at best to stay clear of Deves rings. Haven't had the best of luck. For most of the larger bore sizes, JE supplies Goetze (OE) sourced rings for the 911 application, or at least that's how I use them.

JE has lots of excellent rings in its catalog, you just need to know which to use. I've used just about every ringset they offer from a 77mm bore to a 107mm bore with nikasil bores with excellent results!

I vote for detonation being the cause of your failure.

g-50cab

Sorry that's it Charles - Goetze not Deves - I must have seen an ad lately for deves as they were the first one that popped into my head.