Heavy crank pulley??

[BaldMenace]

Can anyone enlighten me as to why the crank pulley hub is so robust and heavy? I want to do something different and will be using different pulleys and want to make sure it's not essential.

 

[Chuck Leeper]

As long as the engine is externally balanced there will be some sort of "weight" on the balancer.
It may be a bolt on with an aftermkt balancer or cast in as in a stocker.
If you plan to use a light wt hub and bolt on pulleys, another scenario.

 

[BaldMenace]

As long as the engine is externally balanced there will be some sort of "weight" on the balancer.
It may be a bolt on with an aftermkt balancer or cast in as in a stocker.
If you plan to use a light wt hub and bolt on pulleys, another scenario.

My engine is internally balanced and I want to use regular V belt pulleys. My only belt driven item is alternator.

 

[WE2Regal]

Don't know exactly what your looking for but I came across an unusual v belt setup. Late 60's Jeeps and Buick v6 boat engines used a single groove v belt pulley for the alternator. The crank pulley has a very small diameter like an underdrive pulley and the water pump pulley is larger than stock in diameter. They are steel but surpisingly very lightweight. Especially the crank pulley. They were used with the early style short water pump in order to line up. But you would have to fab up the alternator mount down low on the driver side. The marine engine mounts it too low on the driver side and the alternator hits the frame. Jeeps mounted the alternator up on the passenger side head which might be in the way.

 

[BaldMenace]

Don't know exactly what your looking for but I came across an unusual v belt setup. Late 60's Jeeps and Buick v6 boat engines used a single groove v belt pulley for the alternator. The crank pulley has a very small diameter like an underdrive pulley and the water pump pulley is larger than stock in diameter. They are steel but surpisingly very lightweight. Especially the crank pulley. They were used with the early style short water pump in order to line up. But you would have to fab up the alternator mount down low on the driver side. The marine engine mounts it too low on the driver side and the alternator hits the frame. Jeeps mounted the alternator up on the passenger side head which might be in the way.

I have a set of those same pulleys and that's what I plan to use. Just need to use the short style water pump which is readily available. I'm going fab an alternator bracket for drivers side.

 

[WE2Regal]

You'll need various length spacers to line up the alternator pulley and the alternator adjustment arm bracket from the Jeep or boat engine. I've see them on Ebay.

 

[TIMINATOR]

On 86 and 87 engines the offset external weight is in the balancer. I milled mine to remove the weight and make the balancer symmetrical when I balanced mine internally.
Whether internal or externally Balanced that big cast iron pulley "spacer" needs to be balanced. Mine was off more than 5 grams, and that's more than double the aftermarket industry "standard" of 2 grams. I balanced my entire engine within a tenth of a gram because I am anal about stuff.
I also made the flexplate holes symmetrical before balancing too.
Externally balancing any engine puts abnormal stresses on the front and rear main bearings and the front and rear crank throws, causing premature failures there.
A well known crank mfgr. made this error for the first 15 years or so runs of stroker LS cranks. They failed to make ALL of the counterweights wider to offset the heavier/longer stroker rods, so those cranks required 3 slugs of heavy (mallory) metal in the rear counterweight and 4 in the front. This meant that the front and rear counterweights were trying to balance the middle of the engine too.
On street engine applications they usually worked well enough, but on high RPM applications, quite often the crank broke at the front crankpin, thru the oil hole. Finally after many nonwarrenteed failures, they re-engineered their counterweights like the newer companies products had. That was in about 2019. We have seen no failures since.
There is a funny ( kinda) story about the original run of 383 Chevy stroker cranks too. Not as catastrophic, but funny nevertheless.
TIMINATOR

 

[BaldMenace]

The crank pulley itself is heavy. It's got a cast iron part that bolts to the balancer. Never seen this before.

 

[~JM~]

Stock Crank Pully

rjcracing.com

Race Crank Pulley

rjcracing.com

 

[TIMINATOR]

That's the crank pulley spacer that I was referring to... It hangs off the front of the crank, is heavy, and the factory balance job on it isn't very close.
TIMINATOR

 

[GNTIM]

That's the crank pulley spacer that I was referring to... It hangs off the front of the crank, is heavy, and the factory balance job on it isn't very close.
TIMINATOR

I’ve been looking at a lot of the pulley spacers lately and all have balancing holes in them at different points. Some have multiple holes. I’m assuming they are there to balance the rotating assembly at the factory instead of just that part?

 

[TIMINATOR]

I believe those are there to balance the spacer only, and not very closely. The big offset weight on the balancer and the odd holes in the flexplate are there to externally balance the crank.
TIMINATOR