Piston rings for Series 80/81 and Eights

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Per Charles Friends questions about piston rings in the previous thread for series 80 I have dug out some old piston ring catalogs and contacted Grant Piston Rings to find rings for the 3 1/2″ bore engines – Series 80/81 sixes and 8 cylinders.

All sets assume 1/8″ height (vertical thickness) compression rings and 3/16″ oil ring grooves. Note the original Pierce spec in 1935 calls for .145 ring wall while these ring sets (and probably any after market piston) are standard .150 wall. I think the ring grooves are generally .155 deep which should be adequate to accommodate the normal piston cocking in the bore. Check to see that when pushed into the groove on one side the ring doesn’t stand proud of the piston. Hump expanders to increase ring pressure on rebuilds take up some additional depth and may not be a good idea.

Ring sets from Grant (grantpistonrings.com) for the Pierce series 81 (and probably 80 as well):

P2115, original application is for ’39 Packard 110 six cylinder

Top groove: 1/8” PL inside bevel cast iron oil ring

2nd groove: 1/8″ DS outside scraper ring

3rd groove 3/16” 3 segment chrome rail oil ring

set C2115 is the same except top ring is a chrome face inside bevel. This set is for a six cylinder and has the same number of compression and oil rings as the Pierce 80/81. These style rings have significant improvement in oil consumption and smoke reduction over the originals that were probably plain (rectangular) cast iron compression rings in the top 2 grooves and an early style flat faced cast iron oil ring in the 3rd groove as seen in Charles Friends pistons in the thread below. The “hump expanders” in his engine were probably put in at a rebuild to increase the pressure against the wall to compensate for some cylinder wear (a common rebuild practice). Plain compressions and cast iron oil rings are available for those who want to be authentic and have their Pierce smoke like it did originally.

For the 8 cylinder 3.5” bore engines the following ring sets would be applicable from Grant. The original application for this set is Allis Chalmers 4 cylinder D14 and G149 engines:

The P2746 with cast iron inside bevel rings in both the top and #2 groove, an outside cut scraper for #3, and a 3 segment chrome oil ring.

2 sets are required for an eight cylinder engine.

Set C2746 is the same except it is the premium set with a chrome inside bevel for the top groove. I don’t know for sure but I imagine the Pierce in this era originally used the same setup as Packard, a plain top ring, 2 outside cut “scrapers” and a cast iron oil ring.

Sorry I had to mention Packard yet again!

Jim

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