Is there a difference between zero balance & internal Balance?

[BT SNAKE]

I hear guys talk about this and sounds to me like there might be some confusion here. So
what's the scoop?

Hersh

[CobraEd]

Zero balance means no external counterweights needed on the flywheel or dampner to offset an inherent "imbalance". The imbalance is Zero or none. Internal balance is pretty much synonymous meaning that there are no EXTERNAL weights needed. It is "internally" balanced to zero or neutral.


So, . . having said all that, the two terms are synonymous.


.

[RICK LAKE]

BT Snake Hersh zero balance is what the rotating assembly is what you want. Has the least vibration when the assmbly is spinning. You want the complete rotating assembly, this is the dampener, spacer, crank, rods, pistons, flywheel, rings and bearings. You either add or remove weight to balance the assembly to "0"
External balance motor have an outside weight on the dampener and possible the flywheel also. The danpener has weight added or drilled out to balance the assembly, same with the flywheel. IMO the problem with external setup is that if you have a problem where you need to replace the flywheel or dampener you need to have it balanced to match the motor. If you get an internal motor balance you just need to match the old weight of what you are replacing. The is a SMALL fudge factor for maybe a couple of grams. to keep the motor smooth. This is for a street motor, 6,000 rpm limit. Over this number and you need an internal balance with all the parts to help extend the life of the motor. If you have money, ATI will custom balance the rotating assembly with the motor running. Nascar guys have this done to have motors live at 9,400 rpms. Rick L.

[CobraEd]

This is why the older 302s with 28 oz external balance are better than the newer 5.0 engines with 50 oz external balance. The greater the external weight that is needed means that the engine is inherently more "out of balance" and you are trying to compensate for it so that the driver does not "feel" the vibration. Any imbalance is bad for the engine although the external weights make it livable for the average street driven car.


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[Rick Parker]

Zero balance is a term used to describe when all the attached items added to the crank such as flywheel, vibration dampner, clutch etc do not have any imbalance (attached weights)within them to offset an imbalance in the spinning crank, rods and pistons, pins and rings. The crank counter weights have enough mass to offset the weight of the rods, pistons, bearings, rings, and clinging oil. THEN any "0" balanced flywheel, or damper can be attached (or changed) without the necessity of rebalancing the entire assembly.
There is less stress on the main bearings if it is "0" balanced and it is generally smother running.
An externally balanced engine such as a 289/302 can be converted to internal balance by the addition of slugs of Mallory metal (heavier by volume than iron) pressed and welded into holes drilled into the crank counter weights.

[BT SNAKE]

Thanks Ed & Rick,

I built a 347 stroker and had it internally balanced. I ordered a fly wheel from Performance racing Warehouse for the motor and told them I needed a flywheel for internal balanced and they sent me one with a removable weight. I know I have to take the weight off but am I going to have to zero balance the flywheel.
Also I got a harmonic dampener that zero balanced from Professional Products.

Hersh

PS,, Thanks Rick Parker, you were posting the same time I was.

[CobraEd]

Originally Posted by BT SNAKE

Thanks Ed & Rick,

I built a 347 stroker and had it internally balanced. I ordered a fly wheel from Performance racing Warehouse for the motor and told them I needed a flywheel for internal balanced and they sent me one with a removable weight. I know I have to take the weight off but am I going to have to zero balance the flywheel.
Also I got a harmonic dampener that zero balanced from Professional Products.

Hersh

You are set to go. Run that sucker up to 10,000 RPM


.

[Excaliber]

As I recall the reason internal (or would that be zero ) balance motors are prefered in racing circles over external balance is, "crank whip". Adding weight to either end of a rotating crankshaft increases the whip or wobble of the crank at higher rpm. Removing, or adding, weight toward the center of the crankshaft helps to stabilize the whip at high rpm's.

...theres a physics in law in there some where, mass at the end of a stick or mass in the middle of a stick sort of thing.

[Karl Bebout]

Hi Hersh, are you putting that 347 in the GT40? PLEASE tell me you're not taking the mouse out of your roadster!

[BT SNAKE]

Hi Karl,
Noooo ! The mouse stays right where it is but I am going to put on some alloy heads soon. I'm
replacing the SBF in the GT with this home built 347
stroker. I started collecting parts last April because the price for a long block were a bit high for my budget. I bought a block off of Craig's list and some 185 AFR heads too. I built several motors when I was younger, mostly SBC. I will say that engine builders that are good earn their money. What a pain when you have to setup to build a motor for yourself. I begged borrowed and rented all kinds of tools. I am glad I did it but I'm sure next time I'll let the piggy bank get a little fatter and have it done. Did I mention my hands are sore as hell and there is grease embedded in them for at least 6 months.

Hersh

[zrayr]

Originally Posted by CobraEd

You are set to go. Run that sucker up to 10,000 RPM


.

just curious what will your estimated maximum rpm?

Z.

[BT SNAKE]

Z,
I'm looking for torque mostly because I'm not getting out of the corners as fast as I would like.
I'm hoping for about 420 FT LBs at 5200 RPM. I figure the max RPM to be about 6500. I have a friend with a 347 that is carbed and he gets close to this. I have 8 barrel injection so I'm not sure what the final numbers will be until the dyno.

Hersh