Building a nearly stock 59 ab type engine and I’m just curious if it’s worth the effort and money to balance the engine. I’ve done this before on higher performance higher revving engines, but Not sure about this one. Let me know what you think
There are others with much more flathead experience than I have but when I had my stock 8ba built I didn't have it balanced. Maybe I got lucky but it idles smooth and runs like a top. Again, just my experience.
They are balanced when new,so as long as your working with the factory parts the engine came with,your good to go! But *****if your adding new rods an or new pistons,an new flywheel,those need to be matched to old factory parts= Piston Wt. match,in the case of a rod> Those need to match 2 ways to be best, Big end match and then total by only remove extra at top. Flywheel is factory>one plan,and can be done like doing a tire. As long as you match to old parts,then crank is still balanced.
That’s all good information. I’m using a crank and rods from the same engine, but new pistons at .060 over. If I assemble the rods and pistons can I just remove material from the pistons to get the same overall weight and weight at the piston end?
I've always been of the mindset that balancing enhances valve train stability, which isn't a hateful concern on mostly stock stuff that doesn't rev high, but that stability also enhances ignition quality (let the games begin). I think more critical is to find a "balance" of flywheel weight. Too light feels fun but takes away inertia. Inertia is a necessary quality in old engines. If it's in the budget balance is always a good thing.
Just because.............is why I would do it. I don't know that I would pay to have the whole assembly balanced because the effects of imbalance grow exponentially with rpm increase. Generally, Flatheads are not operating at those higher rpms even when an occasional run thru the gears occurs. So, in the rpm range most flatheads operate in, imbalance (within reason) should not be much of an issue. What I would do is buy a small inexpensive digital scale and get some enjoyment out of matching the weights of the components you plan to use. I built a few airplane engines in the past and it was a real eye opener. They have single plane crankshafts with the balance coming from opposing pistons. A local A&P had a bunch of engine spares from old engines and I had to search thru them for suitable replacements to build these engines. I took my trusty scale to his shop and began comparing component weights..........assuming that since it was an aero engine the production rods and pistons would vary only a little bit. Boy was I wrong! Now these engines only operate at 2700 rpms, so I guess the imbalance was acceptable. Still I matched parts as best I could and lightened some components to get them the same. As far as I know they never had any problems from those engines. So I'm saying.............Just because you can, you should at least match the component weights. If those 1940/1950 aircraft engines varied that much, I really have to wonder about auto engine components.
I agree with all that. I’ve matched weights before and it is kind of fun. Also it’s quite a bit cheaper than bringing the whole assy into a professional balancer.
But on a V8 you have to bring in one of those components and the flywheel to a crank guy for balance, he weighs your assembly and bobweights the crank accordingly, then adds/subtracts as needed from the crank/flywheel. I've read that inline cranks are sort of "inherantly" balanced in later engines (not a Model A, that's for sure) and simply making all 6 or 8 piston rod assemlies the same gets it done. On a flatty I'd have to think main bearing life is better if the whole gig is balanced. There's only 3 so any improvement in reciprocating mass/quality? And, if balanced will the flatty rev more if it has the valve spring tension to take it? This is a great topic.
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