Float-a-Motor Issue, a Lesson Learned

J

JayJay

Well-known member
While crawling around underneath my new-to-me 1931 Town Sedan I noticed that the nut on the main Float-a-Motor bolt was almost falling off. When that nut is not tight there is nothing really keeping the engine from rotating on the bolt during load.

The nut is an aircraft nut with small notches cut into the base of the flange (see photo). When the nut is snug against the washer and the rubber doughnuts are slightly compressed (per the installation instructions) the axial force from the rubber doughnuts keeps the notches dug into the washer beneath it and it won't rotate. What I surmise happened is that over the years the lower rubber doughnut has gotten compressed and the bolt lost that axial force. Normal driving introduced enough vibration to allow the nut to back itself off. I checked and the other side was just about to allow the same thing.

This doesn't seem to me to be the most robust of designs. To make sure that the nut stays tight to the bolt you could use nylon-insert nuts. Or, you could do the cheap solution that I did and install jam nuts.

Either way, the lesson learned here is that you should be sure you check these nuts periodically to make sure they aren't about to come loose.

(The photo/diagram of the Float-a-Motor is a screenshot of the directions that Bratton's allows you to download. Thanks, Bratton's!).

Best wishes.

JayJay
 

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Mine from Snyders came with Nylock nuts as standard, not the the type you show. (Being a pessimist I used some Threadlok too.)
 
The person I bought the car from had owned it since 1984, and it had been restored prior to her buying it. So those Float-a-Motors could be 40 years old. Not surprising that things have evolved. I looked for 7/16"-14 nylock nuts at my local hardware store and they didn't stock them, so I went with the jam nuts. I'll look for the nylock nuts next time I head to the Big Orange Box.

Threadlock seems like a prudent addition. I'm going to replace the rubber doughnuts as the photo shows the lower one squeezed out. When I posted that photo I also noticed that there are some wires pinched in the mount, something I didn't see when I was under the car. Those are turn signal wires installed by the previous owner. Clearly there was enough movement in the motor mount with the bolt loose to allow those wires to get pinched. I loosened the bolt, jacked up the engine and freed the wires. Fixed for now.

JayJay
 
Surprised nobody has mentioned replacing the rubber from time to time. I have F-A-M on both cars and have replaced the rubber on both of them twice in 21 years. Of course I drive both cars all the time.
 
Just an FYI ... Nylocks are great, but they are technically not reusable, .. well more than a couple of times, but we all do it. The Nylon insert wears out and wont hold the nut locked in place.

Also, the Float bolts should never be loose enough to easily rotate. If so, tighten them to the point that they don't. Also keep in mind that the engine and trans need to sit at 3.5* angle to the frame otherwise you'll have shifting issues. If the engine angle is off because the rubber is worn, replace the rubber pucks.

Regards
Bill
 
Regarding Float-A-Motor Mounts, the rear mount reacts the engine's torque, and the front mount reacts fore-aft drive-line forces and engine torque. You should have both Float-A-Motor Mounts.mounts.
 
Even the old originals can crack or the rubber pads deteriorate. A person should look at the motor mounts from time to time. The torque tube and engine both push and pull around at all the mounts during operation. It's a wonder they last as long as they do.

I remember a casual friend that complained about his 67 Mustang fan cutting the radiator hose till he figured out that one of the motor mounts had delaminated. He'd romp on the gas pedal and go buy a radiator hose.
 
I once had a Model A that the brakes stopped the car good but were very hard to push, then one day I noticed that when I pushed the brake pedal the gear shift would rise up. Upon inspection I found missing bolts where the rear motor mounts bolt to the frame, the transmission was sitting on the brake crossover shaft.
 
BillCNC said:
lso, the Float bolts should never be loose enough to easily rotate. If so, tighten them to the point that they don't. Also keep in mind that the engine and trans need to sit at 3.5* angle to the frame otherwise you'll have shifting issues. If the engine angle is off because the rubber is worn, replace the rubber pucks.

Regards
Bill
Click to expand...

I was told by a respected individual in the Model A world that the float mounts should only be tightened so that you can just barely twist the top disc with your fingers. Any tighter will hasten the deterioration of the rubber disc.
 
Lightman7 said:
I was told by a respected individual in the Model A world that the float mounts should only be tightened so that you can just barely twist the top disc with your fingers. Any tighter will hasten the deterioration of the rubber disc.
Click to expand...

Mine are tightened 1/4 turn past the wiggle. Just enough to stop the bolt or rubber pucks from turning.

Per instruction #7:

7. Install a rubber biscuit between the frame bracket and the flywheel housing bracket that you have just installed and let the motor down. Now install another biscuit on top of the flywheel housing bracket with the aluminum disc and drop long bolt down through the center of the locking nut. Tighten until biscuits are just starting to compress. Do not overtighten!

Guy's, If your pucks can barley turn, the rubber is not compressed by any means. Close, but no cigar.

Also the instructions mention an aluminum disc, ... mine are cast iron.

Regards
Bill
 
BillCNC said:
...

Also the instructions mention an aluminum disc, ... mine are cast iron.

Regards
Bill
Click to expand...
I suspect that there have been some variations in configuration of the F-A-M over the years. For example, if you look at the pic I posted above from the Bratton's instructions, it shows the lower rubber puck residing in indentations in the frame-side bracket casting. On mine the frame-side bracket isn't a casting, it appears to be angle steel, and doesn't have those indentations for the puck (see that in a picture I posted also). Perhaps I have "imitation" F-A-M, or maybe mine are so old that the manufacturing methods have changed. I'll know better when I get the replacement pucks. If they don't fit then that will be an issue.

BTW, the F-A-M on the engine I helped a club member install this morning looked like the Bratton's picture and had nylocks on the bolts. Don't know when those were purchased, however.

JayJay
 
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