Float A Motor

[Lenny Bruce]

Hey guys good evening. Question of the day is….When I purchased my ‘30 Tudor the previous owner had installed a Float A Motor kit. No way of telling how long ago. I’ve heard from a fella the other day that the Float A Motor kit will actually eventually damage the frame causing it to weaken and sag? First time I’ve heard this so I figured I’d ask all you helpful folks. I’d like to prevent anything from happening if need be. Thanks everyone in advance your all very much Appreciated!!!

[nkaminar]

I don't think the frame with have any more tendency to sag with the float-a-motor mounts than the original mounts. Although there may be others who will disagree.

The frames sag at the rear motor mounts because in the past the car had hit potholes or perhaps curbs which caused the frame to bend at the rear mounts. This happened years before the float-a-motor was widely used.

One valid concern is the frame necking, or getting closer together at the mounts. The flywheel housing and original mounts acted as a frame member at the mounts to keep the frame rails in alignment. I don't think that this a too much of a worry though.

Another concern that has been mentioned is the engine rotating under torque but I also don't think this is too much of a worry if the float-a-motor mounts are installed correctly.

[Synchro909]

The almost solid connection from one chassis rail to the other provided by the flywheel housing and the solid mounts of the original arrangement helps the rigidity of the chassis. There is less twisting and flexing. On one of my cars, I went from Flota A Motor mounts back to the original solid ones. I immediately felt the improvement in the way the car behaved on the road. Apart from the rigidity of the Chassis the original mounts hold the engine in place much better. That means the front of the torque tube is held better and the rear end doesn't move around like it did and with the brake pedal mounted on the bell housing, having the bell housing mobile in the car might also affect the braking, not that I noticed much there.

[Lenny Bruce]

Wow that’s interesting. All I have heard as a newbie is the float A Motor kit reduces vibration.
Sounds like it’s the opposite.

[Conaway2]

Post #3 nails it. The original style rear motor mounts and flywheel housing form the 4th crossmember and increase the rigidity and strength of the frame.

However, the rear mounts generally have developed cracks over the years. If you choose to install original rear mounts, check them carefully for cracks and have them welded up if needed.

All four Model A’s I’ve owned have/had original rear mounts in them. Interestingly - I recently replaced a cracked rear mount in my roadster and noticed a reduction in engine vibration. But….a four cylinder engine has inherent vibration - having the engine balanced makes the biggest difference.

One other consideration - float a motor mounts also electrically insulate the engine from the frame - if you keep the FAM’s you might want to add a ground strap between the frame and engine/transmission.

Jim

[alexiskai]

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I've heard FAM fans and FAM pans. FAMs introduce several extra variables that can increase vibration. The rubber biscuits get hard over time. Over the years, the kits have used different materials, some of which aren't as good, and of course they can be installed wrong. You have to decide how much to tighten each mount individually, which can have a significant effect.

Since you already have the kit installed, my advice would be to check the health of the rubber components, make sure all the fasteners are tight, make sure the transmission support is installed correctly, and then leave it where it is unless you have a specific problem that you think removing it will solve.

[Lawrie]

I have just made up a set of rear floater mounts, I used the V8 front engine mounts, they Are really nice, I have just been out to the hyway in the A and its is very noticeably smoother and no vibes on deceleration, it hardly feels like my pickup.
I also have made up an electric distributor with a vacuum advance an have spent the after noon with a vac gauge in the car and the new dist on my test machine, so I could spin it up and map out the curve with and with out vacuum, one thing that impressed me was the engine still had good vacuum until you were over 55mph and used more than 1/2 throttle,
I now have a lot of good info on the advance curve and how much advance to drop off with the vacuum .
A good days work
Lawrie

[Keith True]

There is no electrical path through stock mounts,unless they are improperly installed,or something has worn through the rubber.The mounts and bolts do not touch the frame at any point,unless they are sagging.

[BRENT in 10-uh-C]

Wow, a bunch to comment on here....

Originally Posted by nkaminar

I don't think the frame with have any more tendency to sag with the float-a-motor mounts than the original mounts. Although there may be others who will disagree.

The frames sag at the rear motor mounts because in the past the car had hit potholes or perhaps curbs which caused the frame to bend at the rear mounts. This happened years before the float-a-motor was widely used.

One valid concern is the frame necking, or getting closer together at the mounts. The flywheel housing and original mounts acted as a frame member at the mounts to keep the frame rails in alignment. I don't think that this a too much of a worry though.

Neil, you kinda answered your own question with your opinion. When a Flywheel Housing is installed with original Rear Engine Support Brackets using reproduction rubber cushions, vs. with a housing installed with new FAMs and a Flywheel Housing, the frame has the ability to twist WAY more when you support the rear of the frame on a sawhorse just in front on the rear crossmember and lift the front of the frame by one frame horn. We showed this one year at one of the workshops we held at my shop. It was pretty eye-opening how much difference it made.

The cause of the frame bending/sagging is due to the added flex IMO. In the original way, the Supports are solidly clamped to either side of the Flywheel Housing with two fasteners and the load dissipated out over the entire end of the block. The opposite end is attached with three fasteners and the load dissipated similarly as to the opposite end of the Support block.

Originally Posted by nkaminar

Another concern that has been mentioned is the engine rotating under torque but I also don't think this is too much of a worry if the float-a-motor mounts are installed correctly.

This is where I think you answered your comment above. The #1 reason I feel that most do not understand the downfall of FAM is the main purpose of the Rear Engine Supports is to transfer the energy of the engine back to the tires and returns it thru the Wheels to the rear Axle Shaft Housings, up the Torque Tube to the backside of the Transmission into the Clutch Housing and finally the Flywheel Housing which is connected to both Frame Rails. The entire braking system along with both the front & rear suspension was designed on the engine remaining stationary in relationship to the frame.

So not only is the strength of the Frame channel compromised, but with the ability of the engine to move within the frame, every time the brake pedal is depressed, some of the pressure from the pedal is diverted to moving the engine on the mounts. In a mechanical system, surely we all would agree this is not good.

One final thing to contemplate, most frames that we see sagging or bent coming thru my shop typically also have a broken Rear Engine Support Bracket(s). I think the correlation comes as the pothole did not bend the frame, but instead I feel the sudden shock of the pothole initially cracked the Support Bracket which over time then allowed the Flywheel Housing to lose the inherent rigidity that it had. That overloads that area of the frame and causes the damage.

Originally Posted by Lenny Bruce

Wow that’s interesting. All I have heard as a newbie is the float A Motor kit reduces vibration.
Sounds like it’s the opposite.

Lenny, does it reduce vibration -or does it just mask it? That harmonic imbalance is still hammering on the rear main bearing either way. Maybe if you felt it, you would either drive faster or slower to move out of that harmonic area. If it is masked, then when in that speed range you are likely unaware you are damaging the engine even more.

Originally Posted by Conaway2

One other consideration - float a motor mounts also electrically insulate the engine from the frame - if you keep the FAM’s you might want to add a ground strap between the frame and engine/transmission.

I have not found this to be true. As mentioned above the method by which they were painted originally would make a good connection difficult at best. Most Model-As today that are sans the engine support pans get their engine grounding thru the connection of the subcomponents such as crossmember into springs, springs into spring hangers, and the torque tube and front radius rod connection at the clutch housing. Pretty wild when you think of the electrical paths a ground must find.

[Lenny Bruce]

I’m not having a vibration issue at the time. I had just recently heard that the float a motor kit will cause long term damage. I don’t want to replace them if not needed so I will just let well enough alone for now.

[Betterlifenz]

I removed the float a motor mounts from my 29 Murray Fordor and replaced with original. I was expecting more vibration with the change, but I have not noticed any difference at all! As they say - "original is best".

[WHN]

Originally Posted by Betterlifenz

I removed the float a motor mounts from my 29 Murray Fordor and replaced with original. I was expecting more vibration with the change, but I have not noticed any difference at all! As they say - "original is best".

For what it’s worth, I agree 100%. Original is BEST! On most things related to Model A Fords.

Enjoy.

[ryanheacox]

I got a set of FAMs for free and decided to try them out. I noticed only a marginal difference, nothing worth getting excited over. I'll swap back over to the stock mounts probably this winter. Bit of a pain of a job though.