Balancing Rotating Assembly

[Jase]

i have a few of these buicks which are externally balanced (weight shaved from harm balancer and flywheel)

for my projects to go forward i need to make them internally balanced,

ie i'm going to have some flywheels made up alot lighter than standard for the gem,

and i need to add a blower pulley to the harmonic balancer on the ute.

So if the rotating assembly is balanced internally it will save me hugely.

I have heard of this being done but i don't want to deplete the strength of the part,

I can get stroker cranks with more beef if need be.

anyone struck a similar demon?

[Unclejake]

I am not 100% certain I understand the question - but you will not reduce component integrity by balancing a crank, rods, pistons or pulleys. It is also cheapish horsepower.

You can do the pistons yourself with a set of scales, and the rods with two sets of scales. The crank needs to go to someone with the right gear though.

[Spencer]

^ agree

Buicks are a 90 degree v6 right?

[Unclejake]

Yeah, I assume he means the vibrating Commodore 3.8 V6, unless he means the Rover V8 (or a Nailhead?)

[Yowzer]

Yeah 90deg they are.

[Poo]

ring Bob Mead (09) 8276481

Balancing Specialties

Unit 2 3034 Great North Road New Lynn Waitakere

he has lightened a couple of my flywheels (and made madrels). he is very well respected. and does full engine balancing.

im sure he will give a bit of advice over the phone.

[Spencer]

I thought it was only some three throw 60 degree v6's that used the dampener and flywheel to counter their primary inbalance. In a 90 degree v6 with a split pin crank shaft the primary inbalance is mostly countered by the crank, Balancing marks on the dampener & flywheel should just be for rotaional balance of these parts and not to counter any dynamic inbalance of the engine? I dont know jack about specifics of buick v6's though tbh

As above if your worried drop off your bottom end with the new flywheels to a balaning specialist ( I cant remember if ATL in frankton do bottom ends? if they do they are GC's)

[fuel]

if he's talking about the 3.8 Holden V6 then they are 60deg.

[Spencer]

cool anyone got a pic of the crank? tried to wiki buick v6 as I know nothing of them, when did they go 60 wiki is shit at explaining

[fuel]

hrmm shit maybe they are 90deg V6, I always thought they were 60deg. I guess that's one more reason not to bother with those boat anchors.

[Jase]

phil please moderate not opinionate

and stay on topic please

[Jase]

I am not 100% certain I understand the question - but you will not reduce component integrity by balancing a crank, rods, pistons or pulleys. It is also cheapish horsepower.

You can do the pistons yourself with a set of scales, and the rods with two sets of scales. The crank needs to go to someone with the right gear though.

thanks UJ the flywheel on a manual 3.8 has a rather large chunk cast out of it to balance the lot,

the autos have a beefy balancer with a similar chunk out of it,

i have an auto engine i'm converting to manual with a cnc'd flywheel,

i will run the auto balancer but have been told they still need work as you're adding more rotating mass

to the rear of the crank,

essentially i want to get a couple cranks balanced up so i can add new/different front pulleys and flywheels without throwing it all out.

[Gaz]

I thought that the point of balancing was to balance everything together rather than peice by peice. This is why I had my whole bottom end rotating componetry all balanced together rather than just the flywheel or crank. Had it done by a guy near hams actually.

Gaz

[Spencer]

Yea gaz I think his problem isn't to do with strictly rotational balance, more to do with the v6's being dynamically inballanced by design. Im guessing the notches on his flywheel and dampener are there to sort a secondary imbalance which is usually sorted by a balance shaft or left for the engine mounts, need a pic though

[Unclejake]

Yessum. It could well be that the crank counterweights on those engines are insufficient on their own and require an offset weight on the 'flywheel' to make them balanced. They always vibrated a bit in taxis for sure.

Slidenyo, the balancing procedure for pistons etc. is simply to get them all the same weight. Within 1 gram seems to be fairly standard. This is done by drilling a blind hole into the webbing that supports to gudgeon pin.

A good crank balance is done on a $75,000 machine that looks a bit like a lathe. The crank is rotated by hand a few times, then the balance machine tells the operator to drill a shallow blind hole(s) of a certain depth at one of more points on the counterbalance web. Structural rigidity is not compromised, but in truth will be effectively increased due to reduced harmonic loadings.

Pulley balancing is much the same. One ends up with holes drilled into the heaviest 'corner' of the pulley to even things out.

Balancing components on their own )as opposed to the complete rotating assembly) is a bit more expensive but absolutely fine AFAIK. With a flat plane crank on a four cylinder you can just take in the crank if that is all you want to balance. With a V8 you will need a bob weight. Usually the operator will ask you for a piston and conrod for the bob weight calculation.

I have no experience with V6 balancing but I expect they would want a bob weight.

I have had all my race engines balanced (and line honed) but I normally supply everything from the front pulley to (and including) the clutch

[Jase]

Thanks UJ i'm getting the picture now

i will then take in the two setups i want and get it balanced as a complete

bottom end,

the 3.8's are a bit coarse and i'd like to get them tidied up before

adding my power adders,

i think i may have to buy some engine building tools,

the whole reason around me asking was i was worried if i had a light flywheel cnc'd

there wouldn't be a way to balance the whole lot if it wasn't a huge cast lump

like the original.

so far

ute 3.8 super six cam chip and auto to be wade blown

gem 3.8 uprated rockers for more lift turbo and manual

[R100]

Was talking to the steel surgeon today as they run the 3800 in there stock cars. He told me he has never seen a standard flywheel with part of it shaved or notched for balance. All the ones hes come accross are just standard round flywheels. Because they are so hard to come across now he just machines up his own.

Hes made dozens of them and they are all just made from plate steel with nothing cut out of them.

So yeah im not too sure about whos right or wrong, only going by what he told me.

He makes them for $450 with ring gear, made to fit any clutch assembly. Also approx $500 for a steel bellhousing to fit any box you like.

Rekons with a bit of head work, and a good cam they go pretty good. They dont use the injection but fit a 2 barrel carb instead, this allows them to rev there tits off.