Vibration from Engine

[Drbrown]

Getting vibration .... mostly in the dash board area .... minor in engine compartment .... slight and occasional at rear. No vibration at idle (+- 500 rpm). Standing still, it starts above 500 rpm and disappears above say 1200 rpm. Its greatest when car is accelerating and moving. Disappears at about 35-40 mph.

Recently replaced front engine mount pads and suspect they are the cause. Did not replace the saddle pad under the tranny - looked okay - difficult to replace. Old front pads were spongy, compressed and bolts were loose. New pad and bolt kits came from Steele Rubber. Aside from the firmness and height of the new pads above the supporting frame, the items matched the originals.

My measurements: Front pads raised front of the engine about 3/8 of an inch. With effort, tightened castle-type bolts enough to get cotter pins thru. Did slight adjustment to the throttle cable at firewall. No problems with shifting linkage or clutch. Clearances around exhaust pipes "look" okay at stand-still.

Assuming the engine and drive train assembly (including the saddle pad under the tranny) accommodated the slight rise at the front of the engine, the only other "rigid" connect between the engine and frame/body are the anti-chatter rods under each side of the engine (front cross frame to bell housing).

Should I try to loosening the anti-chatter rod bolts a bit to see what happens ? Is there a torque setting for them. For that matter, I haven't even looked to see if they snapped (??)

Thanks for any advise.

[G.M.]

Check your plug wires and make sure two are not reversed. G.M.

[Drbrown]

G.M. .... Good idea. Will check plug wiring arrangement but think its okay.

Background: About 38,000 miles on rebuilt 59AB. Clutch engages and shifts smoothly. New Autolite 216 plugs; new rebuilt model 59 carb from Ken ct; new/rebuilt/tested crab points' distributor from Charlie NY. I cleaned all connectors on plug wiring. Vacuum meter reads steady 19.8 Hg @ running temp. Fuel pumps (mechanical and electric start/back-up) test at 3 lbs.

Vibration occurs whether engine cold or hot. Starts instantly. In neutral rev's smoothly up-thru to high rpm's. In gear, it will crawl-along smoothly in first gear under load at idle speed of 500 rpms. Aside from vibration, accelerating above 500 rpms the engine runs smooth and vibration disappears above about 1000-1200 rpms.

It appears to be a physical condition. I can try two things. (1) relax or tighten the chatter rods. (2) Loosen or tighten the bolts on the front engine pads .... It took an effort to tightening the nuts on the pad bolts enough to get the cotter pins installed. I hesitate to remove the pads and cut 3/8 inch off their height.

Interestingly, the engine/drive train operated fine on the old spongy front pads .... only held in-place by the weight of the engine and their bolts were just hanging thru the pads .... nuts were loose on them.

Who said "leave well-enough alone" ?

[flatford39]

Check your motor and trans mounts for wear and cracks.

[Ken/Alabama]

Put the old pads back in and see if the problem goes away.

[rotorwrench]

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The old Bell 47 helicopters I work on have two big rubber mounts on the engine cradle and four rubber isolators attached with a 4-way sprag rod set on the bottom of the engine. These things will get soft over time and mask main rotor vibrations. When you put new ones on is when you find out how much rotor imbalance you have. You end up having to track and balance the rotor as a general rule.

It sounds like you are having a similar problem. You may need to go ahead and replace that transmission mount too. Adjust the steady rods along with that and it should calm down unless you have a bad driveshaft carrier bearing or something of that nature. That rear axle pushes a good bit on the drive train and moves everything around a bit when you are starting out. This is where the clutch shudder comes in too. The steady rods work better if the aft mount is good. Only tightening part of it up will lead to more stress on the tight rubber parts with same sloppy tendency on the worn rubber parts.

[Binx]

Originally Posted by Drbrown

In neutral rev's smoothly up-thru to high rpm's. In gear, it will crawl-along smoothly in first gear under load at idle speed of 500 rpms. Aside from vibration, accelerating above 500 rpms the engine runs smooth and vibration disappears above about 1000-1200 rpms.

This reminds me of when Old Henry was having symptoms like this and it turned out to be a bad u-joint.

Lonnie

[Gary Tosel]

Since the engine is a little bit higher than with the old mounts, check the clearance of the exhaust pipe to the frame opening to see if the pipe is "grounding" to the chassis and moves when engine is under load.

[Drbrown]

Thanks for all these good comments.

G.M. Checked plug wiring arrangement and connections - all were okay. Also adjusted carb linkage for winter running and rechecked the idle screw settings using vac gauge. Ran engine no-load at stand-still up thru high rpm's .... runs very smooth; acceleration very responsive; no vibration. Tomorrow out on the road again.

flatford39: Two front pad mounts new and tightly bolted. Existing rubber "U" saddle pad under tranny looks good. Have its replacement. Took out floor panel but couldn't jack-lift tranny and drive tube high enough to remove/replace it .... need car on a lift to do it. I'll have it done by others. As rotorwrench said, that may even the engine-torque tube alignments out.

Ken/Alabama: Old front pads almost disintegrated in my hands; long gone. Alignment of the whole system slowly settled over last 70 years and stayed happy with itself.

rotorwrench: The clutch works fine; no chatter. Yes, thinking about giving new front pads time to settle-in and compress. Will check anti-chatter rods for equal tension and otherwise leave them alone. Might be able to check their tension by tapping with a hammer (like a tuning fork). Someone welded their front ends to the frame.

Binx: The U-joint, drive train and banjo were okay to this point. But .... ?

Have an unusual torque tube set-up .... no long drive shaft/tube with center bearing. Behind tranny, have U-joint/double clam shell with a very short torque tube (2 foot long or so), then a BW overdrive unit (acts as substitute for center shaft bearing); then an 8 inch tube section between the BW unit and banjo.

Gary Tosel: Exhaust pipes look okay but (as usual) are a tight-fit on driver's side. Driving over-the-road MAY cause them to hit frame. Will check mufflers and tail pipes but the source is up-front.

Will up-date .... Dan

[G.M.]

Someone mentioned U joint. Was on an AACA tour years ago and the AACA
president asked me how hard is it to pull the rear the U joint was making
loud noises. I told her you have to pull the rear and they didn't want to get
into that. I told her I had U joints that were dry and made that noise and to
try greasing it. They shot a tube or more of low melt chassis grease in and
went on to complete the tour with no noise. Two years later on another tour
the U joint was still quietly working. G.M.

[37don]

When you run out of ideas you might check the runout on the outer edge of the flywheel. I don'meen to send you on a wild goose chase but I had a slight shake at Idle and got progressively worse the faster you went. It got a little better when the rpm got up around 2000 and above. This engine was in the car when I bought it and when I removed the trams I found no dowl pins and about .022" runout at the outer edge of the flywheel. When I lintalled the flywheel in my new engine ( built by Ol' Ron ) I measured less than .002" in the same spot. By the way my new engine has 38500 miles on it and runs like the day I installed it. Thanks Ron! May not be you problem but it is a last resort idea that worked for me.
Regards, Don

[Drbrown]

37don .... I'm not getting any shaking. The engine turns and accelerates very smoothly through the rpm's. Haven't done any internal engine of tranny work that would have set something out-of-balance.

Today I purposely ran it hard around the city, trying to stress it a bit by accelerating through the gears. It seemed better after that. As rotorwrench suggested, maybe these new front pads need to settle-in.

[V8COOPMAN]

Originally Posted by Binx

This reminds me of when Old Henry was having symptoms like this and it turned out to be a bad u-joint.

Lonnie

A "bad u-joint"? That's funny! I'd say that that U-joint had surpassed "DESTROYED" status. DD

[Binx]

Just this once V8COOPMAN don't be "that guy". Help Drbrown fix his car. Let the butthurt go.

Lonnie