Ring Clearance
Turbo Mini Forums

How critical is piston ring clearance? On the top ring I have clearances ranging from 0.0035" on one piston to 0.007" on another piston (0.0035 being the top limit in the haynes manual). Second ring clearances seemed ok but I haven't checked them all properly yet.

I am putting new total seal rings in these pistons and they are standard turbo pistons.

What are other people's experience on ring clearance? Should I even be considering running with these?

As long as the ring clearance is not stupidly huge and they are above minimum clearance, they should be fine. The varience is likely to be the difference in cylinder size. I assume you have had the bores honed? the machine shop should be able to tell you what the finished size is, not what it should be.

Are you talking about the ring gap Sprocket? I mean the gap between the ring and the groove, as shown in this picture (although I measured it with the ring installed).

Ah right

Ring grooves sound like they are worn, but if they are still within the limits, they should be OK for a short while yet.

Ultimately, you should be considering a new set of pistons, and Avonbar do some nice shiney Accralites at a very good price

The thing is they are double the top limit mentioned in the haynes manual. I can't find anything else on here about gap clearance, so it got me wondering if it is an issue or not?

I have another one to match the one I sent you if that one has better tolerances and another random one.

im lead to believe if the gap is excessive it will tend to pump oil up from below the ring as it moves back and forwards, i spent a good while in with my machine shop matching up a set of rings for my first set of pistons
although i never had it done, they said machining the groove up to the next size and buying in new thicker rings is straight forward

Yes i moved to the darkside

Instagram @jdm_brett

Thanks for the offer Andy, but after rechecking them it appears all four are out of tolerance. The smallest clearance being 5 thou, largest 7 thou. I need to decide my next move which is either fit them as is but plan for buying pistons in the future, or buy new pistons now :(

Edited by metroturbo on 16th Jun, 2010.

Just sold a decent set of pistons to Tadge. They are hard to come by these days. Andy will be able to confirm this

Personaly if its a fairly standard motor, I would see how you get on and consider new pistons in the near future.

As for thicker rings, I wouldn't think you could get any thicker rings considering the Turbo rings are already thick, and hard to come by.

i had no problems sourcing rings for my first build i picked the rings out of 4 different sets and payed for one my machine shop had a book(i preusme all have) there was the p/n and dimentions to literaly a million different rings

Yes i moved to the darkside

Instagram @jdm_brett

metroturbo, I don't think there are huge risks to have such clearance. The consequence is that you'll get a faster build up of carbon deposit inside the groves, so at some stage rings won't seal a expected. But if you control well the richness and don't spend your time idling in the traffic it should work for a while.
Actually what's important is to have a good flat surface on the bottom of groves, the ring is pushed toward it to seal the chamber.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

Thanks for the replies. I only do a few thousand miles a year, so I'm going to give it a go with what I have.