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Old 03-13-2018, 05:17 PM   #1
daveymc29
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Default Float A motor and noise

I had a lot of drumming noise on a 31 coupe. I installed a good sound deadener most everyplace I could reach and still have a fair amount of noise and some of it seems to be related to engine speed and maybe even coming from the engine vibration to the frame. This car has float A motors instead of the stock motor mounts. I suspect the noise might subside if I install the originals with the new rubber insulation pieces, but wonder it I'd get the same result with a full set of new biscuits for the float a motors. Anyone have any experiences along those lines?
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Old 03-13-2018, 07:56 PM   #2
Art Newland
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Default Re: Float A motor and noise

One thing's for sure, it would be a lot easier to change the FAM doughnuts and give it a try.
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Old 03-13-2018, 08:34 PM   #3
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Default Re: Float A motor and noise

I am dealing with the same thing...I think. I have a 30 Coupe that produces what I would call a drumming that you can feel in your ears. This takes place around 15-25 mph in high gear. It is most noticeable at 20. It appears to be transmitted from the engine as there is a vibration that is most pronounced at about 20 mph. It resembles a exhaust drone except it follows a engine vibration through this range. I also have FLM mounts and I have tried different things to prevent the transmission of vibration from the engine to body. I loosened the transmission mount but nothing changed. Next I tightened the bell housing mounts one at a time and nothing changed. Next I loosened the mounts one at a time until you could turn the rubber mounts with your fingers. This seemed to make it better. I may try original mounts just for shits and giggles but do not expect to see any significant difference. I would have to believe there are others who have been through this (I hope) and found the answer. This condition is very unpleasant for putting around town.
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Old 03-13-2018, 08:59 PM   #4
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Default Re: Float A motor and noise

I had stock mounts for 30 years then put in floating rear but left front stock, can't say there was a hill of beans difference in the two. Floats big advantage seems to be it's easier to pull engine and replace.
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Old 03-13-2018, 11:14 PM   #5
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Default Re: Float A motor and noise

Quote:
Originally Posted by daveymc29 View Post
I had a lot of drumming noise on a 31 coupe. I installed a good sound deadener most everyplace I could reach and still have a fair amount of noise and some of it seems to be related to engine speed and maybe even coming from the engine vibration to the frame. This car has float A motors instead of the stock motor mounts. I suspect the noise might subside if I install the originals with the new rubber insulation pieces, but wonder it I'd get the same result with a full set of new biscuits for the float a motors. Anyone have any experiences along those lines?


Hey Davey,
I just changed out all of the rubber parts of my FAM rear mounts. It has been years since I installed them and had started experiencing a bit of clutch chatter. Reasoning that the engine angle had changed due to these rubber parts going bad, I changed them...including the rubber part at the top rear of transmission.
Snugged it all down as per usual and there was a noticeable improvement in engine angle and no more chatter. Pads were worn out !
My engine runs smooth, so as not to ripple a cup of water, when tuned good. And, it is not stock. A couple of other things that I did that also improved / eliminated, IMO, engine sounds from frame...B front mount which is also rubber mounted. I also installed a vibration crank balancer last year. It all adds to a balanced smooth running engine.
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Old 03-14-2018, 07:38 AM   #6
jerry shook
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Default Re: Float A motor and noise

A lot of the vibration comes from how they are adjusted. The adjustment is different on my 2 cars. It took me a wile to get the vibration out now no vibration.
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Old 03-14-2018, 08:15 AM   #7
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Default Re: Float A motor and noise

I have the same problem with excessive engine vibration which increases as the rpm goes higher. The car has newer FAMS that I inspected last week and found the doughnuts to be loose. Tightened them up and it made no difference at all. At the same time, I adjusted the timing and valves (had one too loose) and that didn't help either. It's not road related because the vibration is there by just revving the motor standing still.

I'll be following this thread hoping someone else comes up with an answer.

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Old 03-14-2018, 08:32 AM   #8
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Default Re: Float A motor and noise

Fought a rattle, FOREVER, it was a loose wood piece behind the Right 1/4 window. "Injected" some expanding foam & GONE!
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Old 03-14-2018, 08:42 AM   #9
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Default Re: Float A motor and noise

check the tail end of the muffler assembly and make sure its not touching the frame or to tight to allow expansion.
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Old 03-14-2018, 09:09 AM   #10
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Default Re: Float A motor and noise

Unknown noises help keep you AWAKE, on LOOOOONG DRIVES----
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Old 03-14-2018, 09:17 AM   #11
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Default Re: Float A motor and noise

Farrell,

Good point regarding the muffler assembly. I'll check that soon as I have time to get the car back on the lift.

What would happen if the previous owner installed the timing gear one tooth away from where it should mesh with the crank pulley? Would the motor run ok but with a lot of vibration and is it worth pulling the timing cover to check this? Some time ago, I pulled the cover to check the gear because of a noise which turned out to be a cracked fan blade. The lash seemed to be ok and there was little to no wear on the fiber teeth but at that time, I neglected to check the alignment of the markings on the two gears. I have owned the car for almost three years and it has always had a vibration problem even after changing both front and rear mounts.

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Old 03-14-2018, 09:33 AM   #12
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Default Re: Float A motor and noise

One tooth off your engine will run but not very well. This can be easily checked by looking at the valves and piston as the piston passes over TDC on the overlap stroke. Remove the side cover and as the piston passes over TDC one valve should be just opening and the other just closing by equal amounts. I have new FAM mounts. I have eliminated the bottom spring on the front mount by replacing it with a rubber shock bushing which fit as though it were made for it. Next I am thinking about the exhaust system.
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Old 03-14-2018, 09:58 AM   #13
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Default Re: Float A motor and noise

daren007,

The engine runs pretty well except for the vibration. Acceleration seems normal and I can get 55 mph with no problem. There is no backfiring at any speed or at deceleration and there is no overheating problem even on the hottest days of summer. When I adjusted the valves last week, I first did a 10 min leak-down test on each cylinder and all four held with no leakage but I guess that could happen even with the timing gear off one tooth.

Hopefully it is the exhaust system which I need to check first chance I get. Any other input would be appreciated.

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Old 03-14-2018, 10:54 AM   #14
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Default Re: Float A motor and noise

Installed float-a-motors this Winter, I have not noticed any added noise, but now my motor is level (bent/broken stock mount)
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Old 03-14-2018, 05:47 PM   #15
daren007
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Default Re: Float A motor and noise

I do not believe it is a resonance but a drumming / buffeting type noise passed on to the body from the engine somehow. Today I isolated the exhaust and there was no difference. I will keep trying.
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Old 03-14-2018, 05:58 PM   #16
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Default Re: Float A motor and noise

Sometimes the choke rod rattles, engine splash pans, oil fill pipe cap and throttle/advance rods. The FAM's need new donuts or biscuits when they get hard and compressed and just tighten enough to stop the top donut from rotating and perhaps another 1/2 to 3/4 turn more. That's a starting point because a few adjustments may be necessary. Some of us prefer the stock front mount with the correct length springs .
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Old 03-14-2018, 07:19 PM   #17
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Default Re: Float A motor and noise

never been a fan of FAM other things to check...contact between the throttle assy and firewall, transmission touching the floor boards, torque tube touching brake cross shaft engine will move for and aft too much with FAM's
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Old 03-14-2018, 07:23 PM   #18
daren007
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Default Re: Float A motor and noise

Front mount with correct length springs....Who has the correct length springs along with correct tension.
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Old 03-15-2018, 09:23 AM   #19
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Default Re: Float A motor and noise

Remember, FLOAT-A-MOTORS have been used successfully, for MANY YEARS, they're a VERY OLD Design. They're really NEAT, when you have to remove or replace an engine!
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Old 03-15-2018, 01:51 PM   #20
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Default Re: Float A motor and noise

Quote:
Originally Posted by jerry shook View Post
A lot of the vibration comes from how they are adjusted. The adjustment is different on my 2 cars. It took me a wile to get the vibration out now no vibration.


'how they are adjusted' !
IMO, this is more true than not.
The engine should NOT rock in any fashion. If it does, these mounts are not secured/tightened adequately to function properly. I've seen where some are afraid/convinced, that if pulled down tight that will cause problems. Just the opposite is true In my experience. Changing 'donuts' is easy and inexpensive, so even if you crush the donuts somewhat...at least the engine is not going to rock if done properly.


It is also very important, when tightening, to try to compress/tighten BOTH sides equally.
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