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The FCC cranks balance factor is off by so much that it's not usable if you add tungsten to balance it out it increases the rotating mass of the engine and makes it kind of sluggish
 

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I tried to fix it three different ways

By adding tungsten only.
By adding some tungsten and then adding the rest of it in steel slugs in the flywheel.

The best results I had was I drilled out the one side and I had to drill out a lot and add a little bit of tungsten to get the desired 45% balance Factor the problem with this is I had to hog out so much that the crank lost its stuffer like ability what I mean by that is it no longer filled the entire void of the crankcase.

Moving along to problem two the FCC blocks a lot of the feed ramp area interrupting the flow of the engine.

And problem three the fuel charge has to be squeezed in between the connecting rod and the crank halves.

I have built about 12 of these engines over the years all different ways I speak from personal experience
 

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Hey I am all up for people trying new things just because my recipe was bad doesn't mean yours is going to be so give it a shot let us know what you did and how you got there.

45% balance Factor seems to be okay I agree with you 55% is the aim point anywhere between 45 and 55 is going to be the sweet spot for these engines sometimes getting them to 55 is just too much work.
 

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Just put it together and see how it runs no sense in wasting it full send it then build something else or use the parts to build another CAG.

Yes there are a lot of options out there but none as cheap as CAG engines where you can get a fresh one for under 75$
 

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Yea that's the problem with the FCC if you can get the BF more around 35% ( 50% is better ) it will provide better horsepower in the higher RPM band I would go ahead and drill it and try to fill it with JB weld
 
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