My Model A really vibrates

Question:

I have a 1930 Model A coupe with the original 4-cylinder engine. I have put in new pistons and valves and done some minor transmission work.

However, there is a very pronounced vibration in the engine when it is running. This vibration occurs when the car is in neutral and the engine rpm are increased. There is no vibration at idle. At mid-throttle it vibrates considerably throughout the entire car then levels out some at higher rpm.

I’ve done some checking around and have been told that the flywheel must be out of balance. If this is so, how do I balance the flywheel? Also, do you have any other suggestions? Thank you.

Answer:

There are several possible causes of the vibration you’re experiencing but the most likely culprit is one or more imbalances in the engine.

You state that you installed new pistons and valves but don’t mention whether you had any parts or assemblies balanced. Any good engine builder or engine machinist can balance pistons and other engine parts but this, of course, needs to be done while the engine is still apart. Pistons, connecting rods and other internal components can be machined to create match-balanced parts and reciprocating assemblies can be dynamically balanced to eliminate engine-damaging internal vibrations.

Effectively balancing a Ford Model A crankshaft can be particularly challenging, even for an experienced machinist. A flywheel can be out of balance and that alone may be the cause of the vibration you have. At the risk of sounding like a broken record, you don’t balance your own crankshaft unless you happen to be a good antique engine machinist with

the proper equipment. Whether that’s you or someone you hire, it is always a good idea to balance the flywheel and clutch assembly together as one unit and they should be balanced on your crankshaft.