external balance
Registered User
Joined: Jun 2010
Posts: 3,613
From: Rogues Island, USA
Are you talking about Mallory Metal? I'll assume you are.
Whenever you change the internal components you change the assemblies balance. IE going from a cast piston to forged. A forging is heavier and you need to compensate for that by adding weight closer to the rotating assembly. You could make the crank counter weights heavier by welding to them but it's easier to add a plug of Mallory Metal. Welding the counter weight is imprecise because you don't know exactly how much material you've add and the weight involved, In other words you might have to go back and add more or grind away some that you added. With Mallory Metal you know it's weight beforehand and can place it precisely. Mallory Metal weighs approx. 2.1 times more than steel. If you remove an once of steel and replace it with MM you know you've increased the weight by 1.1 ounces. 2.1oz MM - 1.0oz steel = 1.1 oz more of MM.
Hope that helps
Whenever you change the internal components you change the assemblies balance. IE going from a cast piston to forged. A forging is heavier and you need to compensate for that by adding weight closer to the rotating assembly. You could make the crank counter weights heavier by welding to them but it's easier to add a plug of Mallory Metal. Welding the counter weight is imprecise because you don't know exactly how much material you've add and the weight involved, In other words you might have to go back and add more or grind away some that you added. With Mallory Metal you know it's weight beforehand and can place it precisely. Mallory Metal weighs approx. 2.1 times more than steel. If you remove an once of steel and replace it with MM you know you've increased the weight by 1.1 ounces. 2.1oz MM - 1.0oz steel = 1.1 oz more of MM.
Hope that helps
Last edited by TripDeuces; Jul 8, 2014 at 09:59 PM.
Thread Starter
Registered User
Joined: Mar 2010
Posts: 1,309
From: South-central Pa.
Are you talking about Mallory Metal? I'll assume you are.
Whenever you change the internal components you change the assemblies balance. IE going from a cast piston to forged. A forging is heavier and you need to compensate for that by adding weight closer to the rotating assembly. You could make the crank counter weights heavier by welding to them but it's easier to add a plug of Mallory Metal. Welding the counter weight is imprecise because you don't know exactly how much material you've add and the weight involved, In other words you might have to go back and add more or grind away some that you added. With Mallory Metal you know it's weight beforehand and can place it precisely. Mallory Metal weighs approx. 2.1 times more than steel. If you remove an once of steel and replace it with MM you know you've increased the weight by 1.1 ounces. 2.1oz MM - 1.0oz steel = 1.1 oz more of MM.
Hope that helps
Whenever you change the internal components you change the assemblies balance. IE going from a cast piston to forged. A forging is heavier and you need to compensate for that by adding weight closer to the rotating assembly. You could make the crank counter weights heavier by welding to them but it's easier to add a plug of Mallory Metal. Welding the counter weight is imprecise because you don't know exactly how much material you've add and the weight involved, In other words you might have to go back and add more or grind away some that you added. With Mallory Metal you know it's weight beforehand and can place it precisely. Mallory Metal weighs approx. 2.1 times more than steel. If you remove an once of steel and replace it with MM you know you've increased the weight by 1.1 ounces. 2.1oz MM - 1.0oz steel = 1.1 oz more of MM.
Hope that helps
Lots of people told me I had to get it off a engine of the same years because the older engines are externally balanced while the newer ones are internally balanced and some are a combination.
railguy
Registered User
Joined: Oct 2004
Posts: 7,743
From: Forest Ranch Ca.
What year Blazer and what size engine? I thought most all Chevy engines after sometime in the sixties were internally balanced, I know I've swapped flywheels and flexplates on numerous SBC with no problems in the past. Maybe I was just lucky....Tedd
Registered User
Joined: Jun 2010
Posts: 3,613
From: Rogues Island, USA
You can easily pick up a flywheel/flexplate at any auto parts store for fairly cheap money. I know Chevy had both internal and external balanced engines but I don't know enough about them to comment. I'm sure a Google search will give you the answer you need
Registered User
Joined: Dec 2010
Posts: 192
From: Milwaukee, WI
There is an important difference between a simple rotating balance and torsional compatibility. Balancing a wheel/tire is a rotating balance. The torsional compatibility of an engine rotating assembly takes into account firing impulse spacing (think Harley v-twins), bank angles, and other rotational components (a torque converter for example), and weights of components (pistons and rods), among individual engine characteristics. Engine RPM has an effect-a range of RPM makes the torsionals harder to control as opposed to a generator set that runs at a constant speed.
Back to the vibration dampener, crank and rods, and flywheel example...those components are balanced similar to a tire and wheel for a rotational balance. the vibration dampener, torque converter, and any flywheel weight determine the correct torsional balance for a given installation.
And yes, incompatible components from a torsional analysis, if operated at the wrong speed for a long enough time, will (not might) come apart.
Back to the vibration dampener, crank and rods, and flywheel example...those components are balanced similar to a tire and wheel for a rotational balance. the vibration dampener, torque converter, and any flywheel weight determine the correct torsional balance for a given installation.
And yes, incompatible components from a torsional analysis, if operated at the wrong speed for a long enough time, will (not might) come apart.
Registered User
Joined: Jul 2011
Posts: 139
From: Ventura, Ca
Most engines that are external balanced, meaning there is a weight on the flywheel and damper, have it because there wasn't enough room for more counterweight inside the engine. The crankshaft counterweights can only be so big before there is contact at bottom dead center in the rotation and there isn't room for more width because of block clearance.
One example would be the small block chevy. All except the 400 are internal balanced but in 1986 when they went to a one piece rear oil seal, the extra counterweight you see on the flange for the flywheel was lost for the sealing area. There wasn't room to add weight to the crankshaft inside the engine so the 1986 and newer small blocks are external on the rear only.
Take an Oldsmobile 350 which has heavier components than the Chevy 350 and shorter stroke and you can see that there wasn't room for more counterweight and the engines needed to be external balanced.
One example would be the small block chevy. All except the 400 are internal balanced but in 1986 when they went to a one piece rear oil seal, the extra counterweight you see on the flange for the flywheel was lost for the sealing area. There wasn't room to add weight to the crankshaft inside the engine so the 1986 and newer small blocks are external on the rear only.
Take an Oldsmobile 350 which has heavier components than the Chevy 350 and shorter stroke and you can see that there wasn't room for more counterweight and the engines needed to be external balanced.
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