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But how much? How do I check it? How do I know when I'm done? Is this an engine shop thing? Cley
I still got a couple of them to get ready to! Cley
Yes definitely a machine shop thing. Here's mine being done. It's not too expensive unless they have to start adding Mallory which is a heavy metal that's kind of expensive...
I ended up using quite a bit of Mallory because I wanted mine internally balanced. Most 360s or I should say all 360s are externally balanced from the factory, but my stroker is not...
I'm all set up for external balance in my car so it will stay that way I think. I guess I'll see how much the balance will cost . Cley
You can ask the shop how much an external balancing is before you do anything. Considering you know a few things, piston weight, the major player followed by rod weight, etc... My shop wanted me to have the balancer for the front & flywheel (4spd car) for the rear sent with everything. I had it done about 8 years ago. In these parts, (Lower New York = AKA Expensive living) my total was $325. Minor counter balance weight removed.
If you are externally balanced already, and you get lighter Pistons you'll need to remove weight. Depends on who does it, but when I have the option I take the weight out of the external parts of the balance job and not the crank. The less external weight you have to use the better IMO. You can also take the weight out of the counterweights. Who knows...you get it light enough, you may be able to make it an internal balance. Just need to get it up in the machine and see what it looks like.
L&K balance the disc as a unit. Pretty cool. I always zero balance the disc and then just leave it out. Either way, the disc needs to be accounted for. You'd be surprised how many don't even check it, let alone do it.
the machine shop I use charges 180 dollars for an external balance...internal that requires Mallory metal will hit 400 dollars... you have the cost of the Mallory metal plus the additional drilling of the crankshaft to press the Mallory metal.... just have it externally balanced....rod..crank..pistons with pins and clips.....one rod bearing...one set of piston rings...balancer...and weighted flexplate...
Simplified version....... There are 2 steps for a V8 or V6:Balance the rods and pistons to each other. Facotry KB's are quite close and for most builds you can use them as is. Rod balancing requires a special jig to measure the big and small end weight separately and then match them across all rods. Once that is done, you compute what is call 'bobweight'.4 bobweights of the proper weight are attached to the crank and its' spun on a special machine to tell the operator how to balance the crank. Most likely it wil be done by drilling metal out of the 2 end counterweights. With the 360, the external balance parts are needed to be part of that process: damper and flexplate and perhaps TC (depending on the felxtplate being used)This is all SOP for a properly equipped machine shop. The costs that 70aarcuda quoted are realistic for most of the USA. So I bet you do not save nearly enough to justify the lower KB price.
But the weight makes a big difference on how hisengine will respond and the compression height difference makes a big difference DBL check your deck clearances and dome/ dish/ valve relief volumes and check proposed compression with a couple of gasket choices BTW balance dude will have to add pin and rod bearing weights and rings when figuring bobweight You will be doing a weight removal not adding expensive tungsten
I used the KB107'S in my 360 and did not have any balance done! Many here will cringe but It was 14 years ago I was younger and very naive. Even thought when I got the KB's that they were just replacements. Engine is still running strong and always seemed smooth. Did get ring gap right LOL. I guess I got lucky.
Plus in the past wasn't very nice to this 360 and revved it like I stole it and then some. Today I know better. But like I said it is doing well.
I really think I'm going to go for the KBs and get the whole deal balanced. I'm looking forward to getting going on this build as soon as possible. Cley
Cley, I asked my machinist at Car Quest(I bought a 70 340 short block from) and he ballparked the balancing at $600. Where you are makes a difference. Trade prices are all over the map....literally. Dont assume US prices posted here. Good luck and have fun! My build is stalled but hope to get my arse out to the shop this winter.
There is one really good shop here in my area. Its run by older guys and they seem to know what they are doing. A few guys at the track recommend them to do Mopar stuff. I'll post the cost when I get it. Cley.
which shop is this Cley? it cost $500 to balance 3 years ago
LOL... well, all reports are that the factory balance range was not all that great... reportedly a range of + or - 25 to 30 grams. And the KB weight change in the 360 is a lot less of a change than for the 340 or 318; the stock 360 pistons were quite a bit lighter already than the others. Stock 360 bobweight is right around 2150 grams.... with the KB flat tops and stock rods, it changes to around 2078 grams. The weight difference is not going to be all that big, but the compression change WILL be a big change. Those old stock pistons are sooo far down in the hole LOL
Question....I'm thinking that the main cost in balancing is the labor in weighing everything and the computations as opposed to the actual machining?
A bob weight of 25-30 grams off from the factory would have been a good balance job. They won't shake unless they get up around 50-60 grams off, but it shows up in other ways. Like bolts coming loose, belts coming off. Stuff like that.
I would think there's some cost in the overhead of buying the machine to do it...
Nope. Most decent pistons are within a gram. Rods take maybe 10-15 minutes to balance. The math takes 5 minutes. Assembling the bobweights and spinning the crank takes the time. Especially if someone else has been in there before. Or, you are removing a ton of weight. The weight moves around the counterweights and does strange things when you remove a bunch. It just takes time. To get a balance job down to 10 grams is pretty quick. 5 grams takes a bit more and under 2 grams will drive you nuts. Plus, it isn't right until it repeats. Also, you just can't throw the bobweights on there.
We wish! Mallory metal now has far eclipsed the cost of labor. It's ridiculous.
OK my 2 cents on the balance you balance 100% of the rotating weight- you are not changing that you only factor in 50% (or so) of the reciprocating weight which is the rod small end, piston, pin, rings not an exact science so what? 50% of the difference in piston weight? so you end up overballanced a little figure out how much what impact does an overballance that size make who overballances Dilibertly and why? in which plane would any overballance shake be felt- H or V would motor mounts hide? may not make any difference I say if money's tight go for it