I bought a 59A flathead that was used as a stationary generator it's whole life, it was supposed to be a great running motor. I pulled the heads to take a look at the bores, all bores look good, there is no lip at all on any of the cylinders, the thing is standard bore 3.1875' (3-3/16'). After cleaning off the tops of the pistons I found that one piston has a very small section missing on the edge of the dome, exposing the top piston ring. Another piston had a crack about an inch long, extending down to the edge. The block looks to be a '39 Mercury 239, it has a 46-48 crab distributor and Ford 59A heads. Apparently this was not uncommon for a stationary / commercial engine at the time. I'm no expert, I don't really know if this is true or not. I believe the pistons in it are steel, 3 ring, standard bore P/N 99A-6110-A. I can get my hands on a couple of slugs, I was hoping to swap these out with a new set of appropriate rings, and hone the cylinders. I have included images of the tops of the pistons, and the block deck surfaces. Any advice on pistons and rings to use would be great. Thanks. Chris.
No sleeves Flatjack, the pistons are definitely steel. Although I will go home and try the magnet test tonight, thanks.
58custom, I believe it's '39 Mercury block that was use as a commercial / stationary generator. It's not unusual for these to be factory relieved to cope with detonation issues...
I have seen a few like that. All stationary engines, which would be left to run for long periods, without supervision, and with minimum maintenance. You can see that it was done entirely by machine, given the precise nature of the cuts. No sign of the hand-of-man. Although that one looks like it has only about 135-hours on it! Even so, I think I would track down some aluminium alloy slugs.
The last engine that I pulled apart for inspection and leak repair had 135-hours on the meter. It looked just about the same inside, except it was just TWO YEARS OLD! How that one looks that good at 78-years is a miracle. That is quite the score!
gimpyshotrods, I thought you may have had a crystal ball over there... Nice observation, I was told that it had done very little work since new You definitely think I should just get some decent alum slugs and rings, and rebore?
If you even need to bore it. Measure the bores, and inspect them carefully. If a hone job is all that it needs, just do that. No point in reducing service life and spending money for no reason. I do recommend something other than steel slugs. Whenever possible, I like to take as much unnecessary weight out of the rotating assembly. A steady state, governed stationary engine will do just fine over time with a heavy slug. You, presumably, will be putting this in a car or truck, where you will need to have it rev-up, with a fair degree of responsiveness. The heavier the rotating assembly, the slower it will rev-up.
Thanks man, good advice. I have an Isky 1007B cam and adjustables coming as well. I figure I could mill the heads for a little more compression fit the cam and lifters, hone the cylinders and re-ring the pistons and also check main and rod bearing. Hopefully I can cut some laps with the lads. Looking to go AV8 on my 29 roadster, and not miss out on another season.
Might be a good idea to balance the assembly(including the flywheel/clutch), as you're changing the internal weights of the pistons. Re-balance is always a good idea, as it makes for a longer lived/smoother running engine.