Piston Rings 68078776AA for Jeep Wrangler JK 3.6 V6

Piston ring set 68078776AA, also listed as 68078776AB, standard size, for the Chrysler Pentastar 3.6 litre V6 in the Jeep Wrangler JK from 2012, Grand Cherokee WK2 2011-2015, Dodge Charger and Challenger, Chrysler 300 and the 3.6 Grand Caravan and Journey.

One point to check with the customer before shipping, because it catches people out: Mopar sells this number in two pack sizes. Up to the 2015 model year the pack contains rings for all six pistons; from 2016 the same part number is supplied as rings for a single piston. The set we ship is the six piston pack, which is what a rebuild needs, so confirm the quantity when the order is for one of the later engines.

What is in the pack. For each piston there is a top compression ring, a second compression ring and a three piece oil ring made of two thin rails and a corrugated expander. The top ring is the one that takes the heat and the pressure, the second ring scrapes the bore and helps control oil, and the oil ring assembly returns the surplus to the sump through the drain holes in the piston groove. The rings are marked so they can only go in one way up, and the gaps have to be staggered around the piston, not lined up, or the engine will burn oil from the first start.

Fitting notes for this engine. The Pentastar block is aluminium with cast iron liners, and a re-ring is only worth doing if the bores are round, free of scoring and within the taper limit in the manual; a glaze breaker or a light hone is used to give the new rings something to seat against, followed by a thorough wash because the abrasive has to be out of the bores and out of the oil galleries. Check every ring end gap in its own bore with the ring squared up with a piston, file the gap if it is tight, and never file a chrome or PVD faced top ring on the coated face. Oil the rings and the bore, keep the ring compressor clean, and turn the engine over by hand before the first start.

Why an engine gets this far. Oil consumption that climbs to a litre every thousand kilometres, blue smoke on the overrun, low and uneven compression that improves a little when oil is squirted into the bore, or a broken ring land after a detonation event. On a Pentastar the usual companions are worn valve guides and a leaking oil cooler, so it is worth quoting the head work at the same time rather than doing the job twice.

Standard bore size only, no oversize. Twelve month warranty against manufacturing defects.