Bad engine vibration -- HELP

Bob Johnson

Bob Johnson

Well-known member
I just installed the engine back into my pickup after a rebuild (a wrist pin came loose and messed up the cylinder wall). I am experiencing a major vibration.

The engine is a 1934 Model B engine with a counterbalanced crank. The flywheel is a Model A flywheel with 10 pounds removed. The 10 pounds was removed many years ago by the previous owner.

Before the rebuild there was vibration which occurred mostly during deceleration. It was most sever when decelerating from 55 mph to a stop (exiting the highway). The rear view mirror would shake and was useless during the deceleration. But the vibration was in what I would consider the normal range.

I was hoping that rebuilding the engine would reduce some of the vibration. But instead the vibration is worst. The symptoms now are the same but at a higher amplitude. It happens whenever I take my foot off of the accelerator. Such as shifting gears or slowing down. Going 55 on the highway down a fairly steep grade the truck rattles so much I am afraid something is going to fall off. If I push in the clutch and coast down the hill at 55 mph the vibration stops. If I coast down the hill at 55 mph with the clutch in or in neutral and I rev the engine I get some vibration but at a tolerable level (the same as reving the engine with the car not moving). Again the vibration occurs whenever the engine is slowing down and is MUCH worst if the car is moving and is in gear. It is also much stronger at mid to high rpms.

I did remove the fan belt and the vibration was about the same. I removed the starter and checked the flywheel with a dial indicator. The wobble was about 0.003" measured just inside the starter ring.

The engine work done was: Re-babbitt mains and rods (exchange rods and main caps), sleeve 2 cylinders bore all cylinders from 0.060" over to 0.080" over. New pistons, valves, valve guides, clutch disk, cam gear, replaced cam with re-ground cam. Valve seats re-ground. Crankshaft polished. Crankshaft, flywheel and pressure plate balanced (individually and together). Pistons weight balanced. Rod checked for straightness and weight. Head and block deck surfaced flat. Replaced kludged front motor mount spring plate and springs with new reproductions. I found one loose rear motor mount bolts.

The pickup has a Mitchell Overdrive.

It is very frustration to have spend so much time and $$ and have the engine not run as well as it did before. Does anyone have any suggestions?

Bob
 
Bob, after the flywheel was lightened (machines) a long time ago, ...was it re-balanced? I wonder if the pressure plate has a balance issue? Also, during this recent rebuild, were the reciprocating parts of the engine balanced during the recent rebuild?
 
Brent,

During this resent rebuild I had the crank, flywheel and pressure plate balanced. I was told they were balanced individually then checked as a unit. There were 3 new holes drilled in the counterweights of the crankshaft. The flywheel showed no new holes. The pressure plate had 2 washers wleded on to it.

The pistons were weighed and 2 of them had material removed to match the other 2. The rods were a matched set from the babbitt person. But I asked the machine shop that checked them for straightness to also check the weight of each.


Bob
 
When I did my Diamond B with a factory CW crank, I was told that 30# was normal removal on the fly wheel. My truck ran well, and 75 was not a problem on the interstate. I have a T-5 trany and hi gears in the rear with 16 inch wheels. Vibration is present but not objectional and normal, and no the engine parts were not balanced. Iceman
 
Bob Johnson said:
I just installed the engine back into my pickup after a rebuild (a wrist pin came loose and messed up the cylinder wall). I am experiencing a major vibration.

The engine is a 1934 Model B engine with a counterbalanced crank. The flywheel is a Model A flywheel with 10 pounds removed. The 10 pounds was removed many years ago by the previous owner.

Before the rebuild there was vibration which occurred mostly during deceleration. It was most sever when decelerating from 55 mph to a stop (exiting the highway). The rear view mirror would shake and was useless during the deceleration. But the vibration was in what I would consider the normal range.

I was hoping that rebuilding the engine would reduce some of the vibration. But instead the vibration is worst. The symptoms now are the same but at a higher amplitude. It happens whenever I take my foot off of the accelerator. Such as shifting gears or slowing down. Going 55 on the highway down a fairly steep grade the truck rattles so much I am afraid something is going to fall off. If I push in the clutch and coast down the hill at 55 mph the vibration stops. If I coast down the hill at 55 mph with the clutch in or in neutral and I rev the engine I get some vibration but at a tolerable level (the same as reving the engine with the car not moving). Again the vibration occurs whenever the engine is slowing down and is MUCH worst if the car is moving and is in gear. It is also much stronger at mid to high rpms.

I did remove the fan belt and the vibration was about the same. I removed the starter and checked the flywheel with a dial indicator. The wobble was about 0.003" measured just inside the starter ring.

The engine work done was: Re-babbitt mains and rods (exchange rods and main caps), sleeve 2 cylinders bore all cylinders from 0.060" over to 0.080" over. New pistons, valves, valve guides, clutch disk, cam gear, replaced cam with re-ground cam. Valve seats re-ground. Crankshaft polished. Crankshaft, flywheel and pressure plate balanced (individually and together). Pistons weight balanced. Rod checked for straightness and weight. Head and block deck surfaced flat. Replaced kludged front motor mount spring plate and springs with new reproductions. I found one loose rear motor mount bolts.

The pickup has a Mitchell Overdrive.

It is very frustration to have spend so much time and $$ and have the engine not run as well as it did before. Does anyone have any suggestions?

Bob
Click to expand...

My guess would be the front motor mount is to tight, maybe the wrong springs. Try backing the bottom nut off the front motor mount and see if that helps. How does the hand crank line up with the crankshaft ratchet nut.
 
Jim,

I did not check the U-Joint when the engine was out, my bad. How can I check it now?

George,

When I put the bottom nut on the front motor mount I did tighten it real tight. The crank hole in the pulley lines up close.

Bob
 
I have a friend who is going through the same problem with his B Engine. It was also professionally rebuilt and all rotational components balanced individually and as an assembly. Vibration is still excessive. We were trying to remember or locate a post made several years ago (by Mike Flanagan I think) that discussed the importance of line boring main bearings in exactly the correct position, i.e., in respect to the cylinder bore. If not done so, vibration is almost assured.
My friend has done all the usual things to eliminate the vibration to no avail. His next step is to verify that the mains are line bored exactly correct. He is at the point where it might be wse to hide the guns.:)
 
:confused:Was the crankshaft checked for straightness. even balancing as you had done,could be bent. Was it the same crank in prior to the rebuild? with the frist vibration? Better work on the Town Car instead.:rolleyes:
 
Mains were line bored using the correct setup by someone who has done lots of engines.

The crankshaft is the same one as before. I had it polished (it did not need any grinding) straightened (it was off by about 0.003") and balanced.


Bob
 
a LONG SHOT, wAS THE FLYWHEEL REINSTALLED














A long shot, Was the flywheel bolt back in the correct position . ie not 1/2 turn out?? I have seen that done more than once, Check the universal, & front engine mount, May be too tight,
 
Bob Johnson said:
Brent,

During this resent rebuild I had the crank, flywheel and pressure plate balanced. I was told they were balanced individually then checked as a unit. There were 3 new holes drilled in the counterweights of the crankshaft. The flywheel showed no new holes. The pressure plate had 2 washers wleded on to it.

The pistons were weighed and 2 of them had material removed to match the other 2. The rods were a matched set from the babbitt person. But I asked the machine shop that checked them for straightness to also check the weight of each.


Bob
Click to expand...

Bob, I have never cut a Flywheel for weight, that you didn't have to drill a hole, or holes, to rebalance it. Washers on the pressure plate ok, as long as the plate was rebolted using the same position as when balanced. Having the rods checked for twist, bend, and off set is good, but if the rods were just checked for weight only, that has nothing to do with balance. Did you have all hard seats put in?? If your cylinders were bored with a portable boring bar, and the bar had been slid around on its machined surface, and not true any more, or the top of the deck has not been surfaced with the pan rail, and then bored with a portable boring bar, that is a big problem. You can get a big out of balance effect if the flywheel housing is not a 90 degree to the crank. Herm.
 
Bob Johnson said:
Jim,

I did not check the U-Joint when the engine was out, my bad. How can I check it now?
Click to expand...
You will have to pull the motor or rear axle. There is a way to test it somewhat Drive the car and decelerate so as to make it vibrate, when it is vibrating push the clutch in and rev the motor. If the vibration is in the motor you will feel the vibration increase as motor revs come up. If you don't feel any change the problem is behind the motor and probably in the ****** or ujoint. I could tell you how I know this but don't want to embarrass anyone.:o
 
newshirt said:
James, would a dry ujoint exhibit these symptoms? If so, would some shots of grease fix it?
Click to expand...

I have seen newer u joints with needle bearings get dry and tight from lack of greasing, but I have never seen a Model A u joint get tight from lack of grease. I've only seen them get looser and looser, which can cause a vibration while driving.
 
Bob, Since you had the vibration problem before the rebuild I would bet you have vibration from the clutch back to the rear axle. I would pull the the engine, replace the clutch, u-joint and pull apart and inspect the transmission. You might want to replace the transmission bearings and inspect the shafts for wear etc.
 
This is a somewhat common vibration, and I don't know the answer but I do know that the lighter pistons are, the less the engine vibrates. Many modern pistons are heavier than the original Ford pistons were. The lightest I have found are Ross, a bit pricey but very good pistons.
 
Herm,

The flywheel was cut for weight before I owned the car. When I took it in for the current rebuild there were no NEW holes. I marked the flywheel, crankshaft and pressure plate with bright orange marks for alignment BEFORE I took them in for balancing. I assembled them with the marks aligned. I do not know the exact procedure that was used to check the rods for weight. Hard seats were not installed. The valves, when closed, sit well above the block surface. I do not know what type of boring machine was used. I checked the flywheel housing per Les Andrews book and it was within specs.

James,

I have done a test where I decelerate to get the vibration, push in the clutch then step on the gas. There is an increase in the vibration when I rev the engine. However it is not nearly as much as when the clutch is out. It is about the same as when I rev the engine with the car not moving and the trans in neutral.

John,

I have a flat washer below the cross member under the front motor mount.


Bob
 
Bob Johnson said:
Herm,

The flywheel was cut for weight before I owned the car. When I took it in for the current rebuild there were no NEW holes. I marked the flywheel, crankshaft and pressure plate with bright orange marks for alignment BEFORE I took them in for balancing. I assembled them with the marks aligned. I do not know the exact procedure that was used to check the rods for weight. Hard seats were not installed. The valves, when closed, sit well above the block surface. I do not know what type of boring machine was used. I checked the flywheel housing per Les Andrews book and it was within specs.

James,

I have done a test where I decelerate to get the vibration, push in the clutch then step on the gas. There is an increase in the vibration when I rev the engine. However it is not nearly as much as when the clutch is out. It is about the same as when I rev the engine with the car not moving and the trans in neutral.

John,

I have a flat washer below the cross member under the front motor mount.


Bob
Click to expand...

If the rods were balanced, There should be some signs of metal being removed? Maybe the flywheel wasn't balanced from the first Guy? Your orange marks, did your balancer use those marks when he balanced, or balanced in a different position? Thanks Bob, Herm.
 
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