What Crank???

[classical glass]

I,m still in the dark over what this crank is out of. It does not have a counter weight on the rear of the harmonic balancer and pulley and balancer are one piece. I do know the engine has chev pistons in (don,t know why) and runs very strong. Also can this assembly be replaced with a aluminum one? One last question if this is a 428 crank with chev pistons (wisco) stock bore, what will the cubic inch be for this engine? Sorry I don't have more info on this topic but either does the owner, who is 81 years old. But very sharp...

[olddog]

Originally Posted by classical glass

I,m still in the dark over what this crank is out of. It does not have a counter weight on the rear of the harmonic balancer and pulley and balancer are one piece. I do know the engine has chev pistons in (don,t know why) and runs very strong. Also can this assembly be replaced with a aluminum one? One last question if this is a 428 crank with chev pistons (wisco) stock bore, what will the cubic inch be for this engine? Sorry I don't have more info on this topic but either does the owner, who is 81 years old. But very sharp...

A 428 is the same engine family as the 427. The are both FE engines. Nearly the same cubic inch displacement, the 427 has a larger bore shorter stroke, and the 428 has a smaller bore with longer stroke, relative to each other.

By using the 428 stroke in a 427 bore block, you get around 450 CID depending on the final bore diameter after you clean up the block.

The 427 crank shaft was internally balanced from the factory, as most other FE engines. FE engines that shared the 428 crank shaft were externally balanced. I believe only the flywheel was weighted, with the exception of the Le Mans. The Le Mans version had a counter weight behind the harmonic balancer that is often called the hatchet. That engine had heavier rods. This all said, I could be wrong, and the harmonic damper may be weighted, but I do not think so.

Now days it is commonly practiced to drill holes in the counter weights of a crank shaft and weld in slugs of malory (SP?) metal. The malory metal is much more dense and allows them to balance out the rotating assembly all internally. Then a zero balance flywheel and harmonic balancer can be used.

So, this engine could be either internal or external balanced. The builder could have chose to do either. What you need to know is that if it is externally balanced, you cannot change the harmonic balancer or flywheel without matching the offset weight. Personally, I wouldn't change either unless there was a strong need. The rotating assembly may have been balanced with those attached, which is a more exact result. If it ain't broke don't fix it, cause the cure may make it worse.

It's a bit cheaper to leave it external balanced. Most people tend to assume internal balance is better, but either works, if done properly. When you get to the extremes of racing at the edge of maximum rpm, there are all types of little things that start to matter on balance, but that's for other people to worry about.