Engine vibration on 65 Rebuilt 289 2brl

[MadDogSkip]

My buddy has a 289 in his 65 that has been driving us crazy. we have been trying to figure out why it vibrates and runs with so much movement (shaking). The mounts are secure as tested with a bar. Is there something that could have gone wrong with the rebuild to cause this motor vibration?

At first we thought it was the driveline but the motor will vibrate when it is cold and running at high rpm idle.

Thanks for your advice...

-Dog out

 

[Ozsum2]

Well, if you have ruled out a miss, it could be because of the harmonic balancer or if they didn't balance the internal parts. They really should have weighed each part to get it right. The slightest difference could show up at a higher rpm.

 

[MadDogSkip]

How would one go about determining this imbalance? Any simple inexpensive ways?

 

[66P51GT]

First make sure all of the wires are attached and seated all the way down. Ask the engine builder what cam was installed. Early models have different firing order than late models. This determine how to connect the wires on the distributor. Double-check the wiring order on the distributor. Also, make sure the idle fuel mixture screws on the carb are adjusted properly.

To answer your question about the balance... the only way to check for an imbalance is when the engine disassembled. Each component needs to be weighed individually (piston, rings, rod bearings, and connecting rod). This is added up then bobs are attached to the crankshaft of equal weight. The assembly is then rotated with the damper and flywheel/flexplate. Much like balancing your tires, a computer indicates where to add or remove weight from the crank, damper, and flywheel.

 

[66P51GT]

Also make sure the damper is not damaged.

 

[6stang8]

Wrong harmonic balancer(50 oz) or wrong flywheel(50 oz) maybe?

 

[68stangman]

so it runs fine at slow idle?

 

[Ozsum2]

First make sure all of the wires are attached and seated all the way down. Ask the engine builder what cam was installed. Early models have different firing order than late models. This determine how to connect the wires on the distributor. Double-check the wiring order on the distributor. Also, make sure the idle fuel mixture screws on the carb are adjusted properly.

To answer your question about the balance... the only way to check for an imbalance is when the engine disassembled. Each component needs to be weighed individually (piston, rings, rod bearings, and connecting rod). This is added up then bobs are attached to the crankshaft of equal weight. The assembly is then rotated with the damper and flywheel/flexplate. Much like balancing your tires, a computer indicates where to add or remove weight from the crank, damper, and flywheel.

If it isn't too far off, sometimes they can grind away the excess weight.

 

[Ozsum2]

Also check the motor and tranny mounts for cracks.

 

[MadDogSkip]

so it runs fine at slow idle?

Yeah, she rusn real strong too (will burn off in first and chirp second with automatic tranny) She starts to vibrate above the eq idle speed of 50 MPH.

- Dog Out

 

[Ozsum2]

Yeah, she rusn real strong too (will burn off in first and chirp second with automatic tranny) She starts to vibrate above the eq idle speed of 50 MPH.

- Dog Out

So where do you feel the vibration.....on the steering wheel (front end) or seat of the pants (rear end-u joints-tranny mount)? Why do you think it is the engine that is vibrating? It can come from many sources.

 

[66P51GT]

If it isn't too far off, sometimes they can grind away the excess weight.

Even if it is way off it can be done. I purchased a used SFI 28oz. flywheel. Even though it was marked as a 28oz. it was found to actually be a 50oz. once it was put on the balancer. FPS was able to remove excess material to balance the assembly to 28oz. They also had to remove a bit from the nodular crank between the 1st and 2nd rod journal.

The same can be done to make the assembly a zero balance. However, it is best to start off with a crank that was designed for a zero balance to begin with.

 

[66P51GT]

So is the the engine or drivetrain? If it only vibrates at speed, then it is more than likely a drivetrain problem. Rough high-speed idle could simply be a carb adjustment.

 

[Ozsum2]

So is the the engine or drivetrain? If it only vibrates at speed, then it is more than likely a drivetrain problem. Rough high-speed idle could simply be a carb adjustment.

That's what we are all holding our breath to find out.