Part 9 - Rotating Assembly Balancing - Shifting The Weight -In Depth Performance Engine Build 620+ Horse Power Street/Strip Pump Gas 454 Big Block Chevy
I used to balance engines in the 80’s on a Stewart Warner balancing machine very primitive compared to your machine. Back then, we did all the weight corrections on the crankshaft via drilling or adding mallory weights. Specifically on externally balanced engines , the reasoning was that if the flexplate/flywheel and or the harmonic balancer has to be replaced, the crank would be closer to being balanced, than if the corrections were done on either or both of them. If that is not the protocol nowadays, what changed? Great videos by the way!! I’m enjoying the fine art of engine building you are doing 👍🏻
The technique demonstrated makes good sense it seems to me. Without going too deep, there's one formula that sheds some light here: torque= force x distance x sine angle. So... if something wobbles 4" from midline or at the far end, we should be able to spot which one exerts more force/can do more damage - and that's the far end. That's without looking at resonance and frequencies for complex shapes where being out of balance generates its own feedback loop making the problem worse at certain speeds, but... I don't think we have to go there [and I'm also not equipped]..
Oh, and if you have actually spun up a couple of different external balanced flexplates, you'll find they are all over the map in terms of weight difference and weight position difference. The tolerance the aftermarket uses is pretty loose.
You can easily match up a new flexplate to the old one with the balancer. It would be pretty unusual to have to replace a flexplate unless you had a starter alignment/mesh issue you ignored.
This is the by the book right way and have had shops not want my balancer and flexplate. I wasn't comfortable with that because this way gets you something better than factory. There's a reason people used to tear down a new engine and blueprint it. Factory engines specs are all over as tooling wears. They didn't invest time for precision plus tooling runs a ton of parts before they end up so out of spec they changed it. Seen sfi approved faceplates fail but it's not common. Would at least buy a good flexplate since once it's balanced replacing it will cause premature bearing wear. Probably a better balancer too since the professional products balancers sometimes come apart at high rpm. The local speed shop wouldn't stock them for the longest time. Having them order one came with a warning then the price of an ATI. They had a grenaded on on the counter that let go around 7000rpm.
Just a thought, @ 9:25 could you also round the trailing edge of the counterweight instead of drilling deeper? any pro or con to that? im sure drilling is faster. Thanks p.s. - love the series! cant wait for the final vids to come out
Better let a professional handle this one. Skip to 0:57 mark in this clip and soak it all in: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-e9mf3Bypyk8.html
boy i be aggravated to max have to weld stater gears on the balanced flex plate or be doing a manual tans swap riding the 3sp od slush box annoyance and seeing a balanced flex plate .. lol ..K.I.S.S method ..but may be their is a resin i not seeing not to drill the crank it`s just 620 hp engine but am i missing something? thanks for videos be blessed men
Why does that make him a hack? I personally don't know the guy, but I thought he's taking a cast GM crank to 7k rpm... could it be he's trying to keep the additional welding/grinding heat out of the crank for longevity? I've never balanced either so this is a legitimate question.
What happens if the gears on the flexplate strip from an improperly installed starter. That flexplate is balanced for this engine only no replacement flexplate is balanced the same as this one.
Per yarrdayarrdayarrda below, if no two external balanced flexplates are the same wouldn't you run in to that anyway? Is there a way to "balance" the flexplate? Kind of like a tire machine? If you had that data I'd think you could replicate it over and over with no problems... but again I am not sure if that is even a thing. Judging by all of the videos up to this point, I don't think he is doing anything to intentionally be a "hack", hopefully he can chime in and shed some light on this. Thanks for your reply.
My BBC is neutral balanced meaning there are no weights on the harmonic damper and none in the flexplate I can replace either one and never have to worry that's the way it should be and that's the way most all competition engines are done.
This is all interesting, but I find the major flaw in bobweight calculations is that the formula doesn't represent what the crank actually experiences. I made a spreadsheet for one full rotation of a rotating assembly, with data points at every tenth degree. The standard bobweight formula only minimizes vibration (and stress/strain) if the center of mass of each connecting rod is one third of the distance from the big end center to the little end center; i.e. the big end weighs twice the little end. I have never found any production connecting rods that even come close to this ratio. They're usually 2.6/2.7: 1. I wonder if anyone has ever tried to actually make rods of this ratio, or if it's just one more example of "close enough...the masses will never know the difference" industry always gives the masses.
this is a stupid way to do it!! i guess when the ring gear gets chewed up by a bad starter you have to pull the crank out and rebalance in order to replace the flywheel.
