1929 Engine Questions

[mach0415]

I recently posted, concerning banger compression. I wanted to post, concerning rod bearings and pistons in a new thread. I Flipped her over about 45 minutes ago and pulled the pan. Seems like I need to clean her out good. Some sludge at the bottom of the pan and grit. I inspected crank and rods. Looks to be good. I need to take some measurements. At some point a rebuild was done, because there are remnants of slag splash on the rods and caps from a re-babbit pour. The rods and caps have been marked with punch dots for each associated cylinder number. I pulled #1 and #3 piston and rod to inspect bores and piston rings. Rings are free and bores look ok, but not perfect. No significant scratches, but some very minor rust "bruising" but no pits. Would you guys recommend honing and reringing it? Also, the pistons say "Mcquay-Norris" on them and have a full-length split skirt. Any light to shed on that? I have not checked specs yet, but on the tops of the pistons it says "P15"

[BRENT in 10-uh-C]

Re-ring it just because they are cheap if you think they may have lost some of their original tension. Something to think about is that when an engine has been run and then parked for awhile, then the dry cylinder walls will start rusting but the rust will disappear as soon as the engine is re-started again.

As for what I probably do is, ...do a very light, --and I mean VERY lightly, oiled honing just to break the glaze and create a crosshatch to cut the new rings. Fit the ring end gap and then re-install on pistons.

[Aerocraft]

Be careful if you do install new rings. The P15 most likely indicates .015" oversize pistons and you will have to carefully regap the ends of each .020" oversize ring. I would not recommend .010" oversize rings since the gaps will be too large. Years ago, we were able to buy pistons and rings in .005" increments. They are no longer commercially available. Gar Williams

[mach0415]

Thanks. What do you all make of the split skirt piston?

[Tom Wesenberg]

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Be sure to get all the honing grit out of the cylinders. Most ring and piston manufacturers will tell you to use hot soapy water to clean the grit. I usually use gas and white paper towels and keep swabbing them until the white towels stay white. I also oil the cylinders and let them set overnight then swab and oil them again. Most of the time that oil will float more grit to the surface.

In the 80's I knew a guy that rebuilt his Olds V8 engine, didn't get all the grit out, and wiped out the new rings in less than 50 miles.