Engine overhaul - dynamic crankshaft balancing. Marketing hype, or worthwhile upgrade?
Posted by gumbley-goop@reddit | flying | View on Reddit | 11 comments
I'm comparing quotes from some big engine shops, and one of the standout differences is that one shop offers a "PRECISION DYNAMIC BALANCE of crankshaft assembly, connecting rods, pistons and pins". I asked the other shops I have quotes from if they do it, and all have said "No, we follow the Lycoming overhaul manual". It sounds like a meaningful upgrade? Am I sucker? A balanced crank I assume would have less wear over time...
In the details of the quote this is what it says:
Crankshaft: Balanced to within .5 inch ounces and must meet New dimensional limit tolerances. If required, it will be reground and nitrated. All will have new: bushing, bolts, nuts, keys, and bearings.
Connecting Rods: Resurfaced, Rebushed, and Honed to new tolerances. Weight distribution checked and corrected, any grind areas shot peened. Rods checked for stretch and alignment. All balanced within a maximum of 5 Grams. All will have new: Bushings, bolts, nuts, keys, and bearings.
Shit-Pilot@reddit
I’ve overhauled a dozen or so engines over the years and I have the crankshafts dynamically balanced. The balance on these cranks out of the factory is actually pretty shitty, and the 360/540’s especially already have issues with vibrations so having your crank/flywheel balanced dynamically absolutely can’t hurt. I have always wondered if Lycoming had bothered to do a better job balancing the rotating assemblies if they would have the issues with the crankcases cracking or fretting like they do.
320’s don’t seem to suffer from these issues.
Actually I have the entire rotating assembly balanced and matched when I put airplane engines together, it doesn’t tell you to do any of that in the overhaul manual but it absolutely doesn’t hurt. At the end of the day these are more like lawnmower engines slapped together than finely precise F1 engines like everyone thinks they are. They aren’t spinning at high speeds but I still do everything I can to balance them out.
tms2x2@reddit
Is a measurement "pretty shitty" a ISO standard? I wonder what the difference, before and after is. Just curious, I don't overhaul engines. Only cylinders and accessories. I never saw the benefit of getting a ton of yellow tag parts and assembling an engine.
aftcg@reddit
I've gone through a few engines in my day. Definitely can tell the difference between a mapped engine and an off the shelf OH. A few grams difference here and there end to to be a whole lot of IPSs. Especially with Lyc IO360s. They really love to be balanced. A good shop should be able to spin balance the spinny parts, and have enough recip parts to weigh the same or within a gram or two.
Polish the intakes and gami the injectors to make a fine dammed engine.
GMC9999@reddit
It sounds like a higher level of service. But what would be the additional benefit besides potentially a smoother running engine?
Flimsy-Ad-858@reddit
Less wear leading to longer overhaul interval.
Anything O-320 or bigger is going to be a minimum of $30k by the time it's overhauled and mounted, so if you can get an extra few years out of it, it's probably worthwhile.
I-r0ck@reddit
Lucking knows the engine best. If their manual says that it doesn’t need it, then it doesn’t need it.
SSMDive@reddit
My Uncle has a Corvette, bought it brand new. It was a decent car. Then he sent it off to an engine shop to be "Blue printed and balanced" which sounded kinda stupid to a 13 year old me.... Then he got it back and it was much better.
If the "factory" tolerance is something like 0.15, the "blueprinted" engine will be something like 0.015.
A guy a know built a Pitts. For the engine in the Pitts he went to a gigantic engine parts supplier with a scale. He selected 4 pistons that were super close in weight, then he did the same with connecting rods and everything else. That engine ran very smooth and lasted a long time.
So I can't speak to that shops claims. I can say that closer tolerances and matching weights has benefits.
tms2x2@reddit
Lycoming doesn't recommend it. Can't hurt if done properly. When I've dynamic balanced propellers it usually take less than 1 ounce. https://www.lycoming.com/content/what-engine-balancing
ThatOnePilotDude@reddit
I would just take it to one of the places that just follow the overhaul manual. The thing that is going to reduce the most amount of wear in the engine is making sure that the new bearings are on there/oil passages clear and properly breaking in the engine IAW OEM procedures.
BrtFrkwr@reddit
When all else fails...follow the instructions.
rFlyingTower@reddit
This is a copy of the original post body for posterity:
I'm comparing quotes from some big engine shops, and one of the standout differences is that one shop offers a "PRECISION DYNAMIC BALANCE of crankshaft assembly, connecting rods, pistons and pins". I asked the other shops I have quotes from if they do it, and all have said "No, we follow the Lycoming overhaul manual". It sounds like a meaningful upgrade? Am I sucker? A balanced crank I assume would have less wear over time...
In the details of the quote this is what it says:
Crankshaft: Balanced to within .5 inch ounces and must meet New dimensional limit tolerances. If required, it will be reground and nitrated. All will have new: bushing, bolts, nuts, keys, and bearings.
Connecting Rods: Resurfaced, Rebushed, and Honed to new tolerances. Weight distribution checked and corrected, any grind areas shot peened. Rods checked for stretch and alignment. All balanced within a maximum of 5 Grams. All will have new: Bushings, bolts, nuts, keys, and bearings.
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