engine vibration part 2

[oldspert]

After getting replies about my engine vibration, I checked the rubber insulators between the frame and the rear mount. Looks like both sides are non existent. Worn away by years of driving.
Will I need a frame spreader to replace these? If so, I am mechanical enough (retired engineer) to build one.
Is there any info on using the Float-A-Motor mounts?

[Robbie Horn]

I replaced mine using a porta power between the bellhousing & frame rails one side at a time. The frame doesn't have to be spread very much at all. I still have vibration when I get over 45mph. When I get on the highway I add timing & lean out the gav & it runs smooth but starts vibrating at 45mph. Can go 44mph with no vibration. I think they all do that from other owners that I have talked to.

[mass A man]

A small bottle jack and a chunk of wood will do it too. The vibration could be normal if it's small, otherwise a bent or sagging frame might set up a vibration. The sag can twist the whole running gear out of alignment a bit to vibrate at some speeds.

[Banditorama]

Originally Posted by Robbie Horn

I replaced mine using a porta power between the bellhousing & frame rails one side at a time. The frame doesn't have to be spread very much at all. I still have vibration when I get over 45mph. When I get on the highway I add timing & lean out the gav & it runs smooth but starts vibrating at 45mph. Can go 44mph with no vibration. I think they all do that from other owners that I have talked to.

Mine runs nice and smooth at 45mph. It gets a little buzzy around 55mph, but no serious vibrations or rattles

[Robbie Horn]

Originally Posted by Banditorama

Mine runs nice and smooth at 45mph. It gets a little buzzy around 55mph, but no serious vibrations or rattles

Mine must have a lower rear end ratio than yours. I checked my u joints & they are tight. Been planning on removing the oil pan & checking bearing clearances. Hopefully it has some shims & if the bearings are too loose I can remove some shims. I've been trying to find a good rebuildable motor & also looking for someone in my area or kinda close that does babbit. Haven't had any luck on either. So I just keep driving & enjoying it , just stay under 45 mph.LOL I live close to Waco & once i get there 45 mph is fast enough to get around anywhere in Waco. I live in the country & have a path on backroads to get to waco witout getting on the highways.

[oldspert]

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I am going by the 29 I drove in high school in 1959. I lived 8 miles out in the country and drove into town every day. I know I could drive 55 with no problems. Of course the car was only 30 years old then.
When I bought that car I had to re-ring it and it had already been bored .080 so it ran very well.

[nkaminar]

Use of the Float-A-Motor is controversial. There is a contention that the rear of the engine forms another cross link for the frame and that the Float-A-Motor removes that link. The Float-A-Motor was probably a solution to worn out or non-functioning original rubber isolation pads in the back. Even with the Float-A-Motor mounts the rubber at the frame rails should be replaced.

[oldspert]

Originally Posted by nkaminar

Use of the Float-A-Motor is controversial. There is a contention that the rear of the engine forms another cross link for the frame and that the Float-A-Motor removes that link.

Agree that the cross link would be eliminated but would that be a problem since most of the A's on the road today will never see any hard bumpy roads that would twist the frame. I know mine will never see more than maybe a hundred mile tour on modern roads.

[BVZ24]

I went from a squished front and rear float motor back to stock and found I had significantly less vibration. The old floater pucks were crushed about 1/2 way and rock hard. The stock mount has rubber between the bracket and frame as the insulation, and the bolts shouldn't be cranked tight. I had a hard time finding rear mounts without cracks, eventually welded a cracked pair. The original front mount is already essentially a floater. Stock makes an engine swap a little more difficult, but how often should one do that?

[oldspert]

Originally Posted by BVZ24

I went from a squished front and rear float motor back to stock and found I had significantly less vibration. The old floater pucks were crushed about 1/2 way and rock hard.

How old was the rubber pucks in the float motor system?

[BVZ24]

Couldn't tell you. Inherited it that way. If I had to guess, as old as the restoration, 30 ish years.

[grudicil]

This discussion got me thinking. I replaced my original rear motor mount rubber pads when restoring the car in 1980 and I haven't given them a thought since. Should the rubber pads be replaced every few years to minimize vibrations between the engine and frame?

Gary