I have had my engine recently rebuilt, about 1000 miles ago, and ever since there has been a vibration at about 4500 RPM. My snout on my Muncie M21 broke off... which i believe was due to the vibration... i have replaced it and do not want to have to do that again. the cluch is lined up and everything else seems to be in order.... could it be the crank shaft??? i need this fixed .... with it vibrating so bad i don't want to get on it... but god knows it is hard not to

 

can someone please help me???

 

Have you talked with the people who rebuilt your motor?

Vibrations can come from a lot of areas. You recently had the engine rebuilt. How much of the original engine was re-used?

Did you have the machine shop magnaflux the parts? Did they balance the rotating assembly, including the balancer and flywheel?

Did you install a new clutch?

What shape are the engine mounts in?

Does it vibrate around 4500 rpm, in 1st and 2nd?

 

To answer your Questions

The only old parts are the Rods (they said they resized them), Chrank, block, heads, distributor, carb, water pump.

The block was magnafulxed.

They said the engine was balanced, but I had the flywheel and the blancer was put on after the engine was done. So it was not balanced with those parts. The reason we put a new balancer on was to try and fix the vibration, but it did not fix the problem.

Yes we put in a new centerforce II clutch, pressure plate, and throw out bearing.

We put new motor mounts on.

It happens in 1st, 2ed, 3rd, but i have not had it at 4500 in 4th.

I was charged $150 for a balance. What does this include? My engine builder did not balance it, if an error was made it was by the machine shop.

 

$150.00 added to your machine shop bill probably did include engine balancing of the whole rotating assembly. I have to assume the machine shop and mechanic who did this for you are trustworhty, meaning you are comfortable that they do good work. Also, I am hearing you feel pretty confident that the vibration is coming from the motor area and not from the transmission back.

Does the vibration exist only under load or can you feel it in neutral and revving it to 4500?

This vibration seems to be more significant than what a fan blade, power steering pump, A/C compressor or alternator could cause. You could always disconnect all the belts and take the fan off and rev it, provided the answer is is yes to the question above.

Otherwise, if were me, my options would be to either:

1. Pull the transmission, remove the clutch/flywheel and have them checked for balance. The machine shop should be able to do this. Also, you could start the motor without the clutch and flywheel, to see if the vibration is still there. Again, provided you can feel the vibration under no load conditions. Of course you will need to properly support the motor in the back to do this.

2. Remove the engine and take it back to the mechanic or machine shop and have them put it on a motor stand and crank it up without the flywheel and clutch.

You have some work to do, but it is very important to fix this problem.

 

We had the flywheel resurfaced when the motor was put in, but i do not know if it was "balanced". Also i do not have A/C or power steering. I will see if it vibrates in neutral and make a post in a couple of hours.

 

Before you blame it on the engine, check the driveshaft, maybe the balancing weight broke off. I seen a couple of automatic trannies crack the tailshaft due to this

Marck

 

Well i just took the car for a spin to warn it up, and i made sure the oil was full, then i reved it in neutral. The vibration is still there in neutral. It is also there with the clutch in and out. So what's next?? By the way, not that it matters, but the vibration is actualy closer to 4300 RPM...anyways

 

I believe the weights are on there last time I was under the car.... which was long after this vibration started..... and since it does it with the clutch disengaged and in neutral, it cannot be the driveshaft, because it is not spining.

 

Did you check the damper? if the rubber oozes out replace it.

 

is the damper the same thing as harmonic balancer??? we replaced it and it still vibrates... it reves smooth then as soon as it hits 4300 RPM it just starts shaking..... this is not tooo good :confused:

 

Well, you've narrowed it down to the engine compartment and bell housing.

Will it rev past the 4300 and smooth out or do you not take it past that RPM?

Another thing that can cause an engine to vibrate is the ignition system breaking down at higher RPM. You might check your plugs to see how they look. This ignition system is the same one you ran before you rebuilt the engine and you have not modified anything, correct?

This vibration sounds significant. An out of balance harmonic balancer, flywheel or clutch disc/pressure plate can create vibration, but possibly not as bad as you make it sound.

In my opinion, you will need to at least remove the transmission and clutch, leaving only the motor and flywheel to spin and see if the vibration still exists. If so, you should remove the flywheel. If it still vibrates, then the entire motor should come out for re-inspection. Not what you want to hear, but you should not ignore this problem. You will have to back track to resolve it.

Maybe some of the engine builders on the forum will read this and offer some more ideas, before you tackle taking the drive train apart again.

 

yes it is the same ignition system, i try not to take it pas 4500 or so... but as far as i can tell it smooths out a little but is still there. It is more of a shaking vibration than just a vibration, if that makes sence

 

It might have the wrong crank in it had an engine builder do it to me !

 

it is the same crank that was in the motor before it was rebuilt

 

When I had custom exhaust put on my car, they did a BEAUTIFUL job, the only thing they forgot was an a/c compressor bracket on the bottom of the serpentine assy. They gladly fabbed another one for me, but in the meantime it had the same symptoms as you had.

Smooth as silk until 3500 rpm, then it felt like someone threw a wet towel into the serpentine belt. Shuddered so bad that you backed out immediately.

Did you check your drivebelt/accessories to make sure everything is bolted down tight and actually is re-installed?

 

Are you sure that the pilot bearing/bushing is in the rear of the crank?
If you have either a tin dust dhield on the front of the bellhousing or a tin inspection cover on the bottom of the bellhousing, remove it and start up the engine. Watch the flywheel assembly and see if you can see it wobbling. It is possible that the crank could be bent or the flywheel might be warped. I know you stated that it was resurfaced, but maybe it warped when installing(long shot here). I had a friend helping me once, he dropped a crankshaft and it landed on the flywheel end first then fell over. It didn't have hardly any visable marks on it, but it was bent. It had a vibration also from about 3300-3500 rpm and up. Just a couple more ideas, hope it helps. :cheers:

 

Just an idea, but have you made sure the exhaust isn't touching the body somewhere.Some vibration problems can be a real pain in the butt.

 

They all seem to be tight and lined up, what should i be lookin for?

 

how can be sure the pilot bearing bushing is in correctly or in at all?