Speaking of counter weighted cranks

[Patrick L.]

I did not want to hi-jack the other thread.

I'm just wondering if it is worth adding counterweights. Or not.

[Kevin in NJ]

If you have a properly balanced and properly rebuilt to factory specs A engine (and driveline) you would expect to be able to run 60 MPH for extended periods of time and get 50,000 to 80,000 miles with that engine.

So the answer is you do not need the counter balance to have a good running reliable car that will go tens of thousands of miles. The key is getting back to factory tolerances with the balance on the rotating parts.

The issue is when you have imbalances in the crank damaging the bearings.

Now a factory crank is somewhat imbalanced, but we know that long term reliability shows it will last for a very long time. This is based on decades of use of the Model A when it was a new car.

That being said.

If you have the money and really intend to push the car hard for tens of thousands of miles then spending the extra bucks for counter weighting may make sense. Properly done the counter weights will improve the balance of the engine.

Realistically, probably 90% of the counter balanced engines never see enough miles to make a difference. Just paying for a proper rebuild back to factory balance specs is your best money spent.

[Kahuna]

Agree with Kevin 100%

[MikeK]

Just to set the record straight about "balanced" cranks, all stock A cranks were very well balanced by Ford. This is well documented in literature and photographs. Adding dynamic balance with counterweights only serves to counteract a few thousanths flex along the centerline, which cams out bearings and fatigue cracks cranks. It does NOT result in any noticable, seat-of-the-pants improvement unless other problems have been fixed concurrently. New A engines ran smooth- 'till the center main cammed out. THAT is what adding counterweights fixes- the UNNOTICEABLE crank flex along its centerline.

If you want to watch a 30 second video of a crank dancing, even WITH both counterweights, a snout damper, and five mains, watch THIS. Only the main bearings hold it straight. Not having counterweights, even if the crank is in perfect dynamic balance does not prevent flex from centripital force. It only increases cyclic loading on the block mains.

Spend the money for counterweights or better still- a stiffer alloy counterweighted crank like a Scat.

[Patrick L.]

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OK, thanks