Vibration

1938 Woody Cape Cod

1938 Woody Cape Cod

Senior Member
I just purchased a restored 31 sedan. Everything done correctly and first class.
It has Float-A Motors. It has an engine vibration sitting in neutral when bringing up the RPM's, with the clutch in or out. Also on deceleration. It seams
fine when driving along at a steady speed 30-45. Any ideas........Bob
 
A proven fact: anything or everything that goes around has a moment more like a
moment of insanity. Clutch in or out no change = that rules out drive line. So I bet
a dollar to donuts its the pressure plate / flywheel I doubt, but could be. My machine shop
has yet to find a new pressure plate from venders way out and I mean way out. My personal car engine all first class new a 59A V8 Findings = Flywheel ah couple grams:
pressure plate almost 90 and that aint going to fly with me. New plate and we had to
weld 90 + or minus grams a stack of washers on it because USA don't make nothing no
more, and those who do across the pond could care less. Hate to say pull the motor A's
are easy and have flywheel and pressure plate balanced.....sam been there on this.
 
Make sure the F-O-M's bolt is snug, or replace them with stock mounts. I replaced mine and the engine was as smooth as before and had less clutch chatter.
 
If all else fails, try a Harmonic Balancer Pulley. It certainly transformed my motor. These are made in New Zealand "These dampers are made by Murray Horn in Levin N.Z. His Company is Engine Restorations Ltd. His email is horn@xtra.co.nz
Murray says this is the best way to contact him.
The dampers are a straight fit to replace the standard Model A pulley. An added benefit is a shallow reverse scroll in the rope seal area to help contain oil."
 
1938 Woody Cape Cod said:
I just purchased a restored 31 sedan. Everything done correctly and first class.



It has Float-A Motors. It has an engine vibration sitting in neutral when bringing up the RPM's, with the clutch in or out. Also on deceleration. It seams fine when driving along at a steady speed 30-45. Any ideas........Bob
Click to expand...



Bob, just to poke fun at you, I like your first sentence however the verbiage in the second sentence does not seem to agree with the next paragraph! :D :D
ROFL.gif





While the above ideas all have merit, I tend to think by you saying the vibration is only happening during idle while accelerating/deaccelerating in neutral, my guess is the flywheel has been lightened a tad too much which is showing up from the impulses of each cylinder firing. When you are driving it, items such as transmission cluster, driveshaft, U-joint, wheels, etc. all are mass that adds to the weight of the flywheel which in-turn masks those impulses.
 
Brent..The car looks like it was done by a pro about 12 years ago with attention to detail. That's why the vibration doesn't make sense. Very few miles.....Bob
 
Harmonic Balancers are on most modern engines and I thought that they reduce the twisting action on the crankshaft. Does this have anything to do with vibration which seem common in the Model A engine? Jack
 
From my experience: Anytime you change the mass of the rotating assembly, the rpm range where the vibration is felt will change. The Murray Horn dampers do eliminate felt vibration with some engines. I used on on a project last about a year ago with good success.
Good Day!
 
Gonna dig this one up. How much vibration is considered "normal"? My Fordor does tend to vibrate a bit on decel but nothing that seems too bad to me considering how the engine is mounted.
 
big job said:
A proven fact: anything or everything that goes around has a moment more like a
moment of insanity. Clutch in or out no change = that rules out drive line. So I bet
a dollar to donuts its the pressure plate / flywheel I doubt, but could be. My machine shop
has yet to find a new pressure plate from venders way out and I mean way out. My personal car engine all first class new a 59A V8 Findings = Flywheel ah couple grams:
pressure plate almost 90 and that aint going to fly with me. New plate and we had to
weld 90 + or minus grams a stack of washers on it because USA don't make nothing no
more, and those who do across the pond could care less. Hate to say pull the motor A's
are easy and have flywheel and pressure plate balanced.....sam been there on this.
Click to expand...

My engine was balanced and everything proceeded well until the flywheel was checked with the pressure plate attached - a huge imbalance! The pressure plate needed considerable correction with weights attached.
 
1938 Woody Cape Cod said:
I just purchased a restored 31 sedan. Everything done correctly and first class.
It has Float-A Motors. It has an engine vibration sitting in neutral when bringing up the RPM's, with the clutch in or out. Also on deceleration. It seams
fine when driving along at a steady speed 30-45. Any ideas........Bob
Click to expand...

"Everything" was NOT done correctly and first class or it would not shake.
If it vibrates when idling, it has a first order harmonic. That generally means something is REALLY out of balance in the engine.
 
Just as a side note here while balancing is the subject, it is a VERY bad idea to weld weights on a clutch cover to balance it if you value your lower body parts.
The proper way is to drill the spring posts.
 
Perhaps start with the easy stuff 1st: as mentioned, fan, front motor mount tightness and springs (if original), replace FAM biscuits if 12 years old and side frame rubbers(vendors sell new ones. See posts 2,3,4. Are engine pans attached? Check front alignment of pulley thru the radiator shell and clearance of service brake rod to torque tube, etc.
Also, check the engine in neutral thru the spark rod range and see if vibration persists.
 
ALL engine vibrations are caused by MOVING PARTS.
If the engine is not running, there is no vibration. Changing engine mounts, muffler clamps,
brake rods, drive shafts and anything else can and does sometimes minimize or mask the problem by changing the resonant frequency of the vibration, BUT it does not address the root problem. BAD BALANCE JOB.
 
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