It rumbles and grumbles

[Terry,NJ]

I took a 150 mile round trip Sunday and am very disappointed. The vibrations, and rumbling at 50mph was not fun! Below that it wasn't bad, Not nice, but not bad. What is making this! It's almost a knock, but not quite. It's worse when you're going down hill or above 50 on the interstate and least when you're going uphill .I can't imagine what changes that much going downhill. The difference is quite dramatic. Just sitting and reving the engine will produce it too. These are my first model A s and I really don't know what a good one is supposed to sound/feel like.
Terry

[1crosscut]

The tail pipe where it goes through the hanger can make a heck of alot of racket that can sound as if it is from the engine. This has to be some what of a loose fit to allow expansion and contraction. Temporaraly slip a wood shim in there to take up the slack and go for a short drive to see if it solves some of your noises.

[Tom Wesenberg]

Is this a rebuilt engine, a good used engine, or just an old worn out engine?

[Terry,NJ]

Well I wouldn't call it worn out and it came with the car. It doesn't smoke or leak, It just rumbles, especially going downhill. It has good power, it was bored out to 4.000 and about .090 off the head. I didn't notice the vibration so much until I was on the interstate. Once I became really aware of it, I can't think of much else. I was going downhill and I pushed the clutch in and it smoothed right out as the engine came back to an idle.
Terry

Originally Posted by Tom Wesenberg

Is this a rebuilt engine, a good used engine, or just an old worn out engine?

[Barber31]

Hmmm. So that to me points to tranny issue? Maybe like worn out gears and clutch chatter? Curious to hear what y'all narrow it down to.

[29ModelA]

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Have someone ride with you and see if they can capture it on video.

Have you looked at your motor mounts, are the rubbers rock hard? You will get more vibes that way, and the A (at least mine) seems to have 2 vibration phases it passes through as I speed up. The vibration seems worse in these two RPM ranges for me.

[George Miller]

Sounds like the engine is out of balance. Lots of guys never weigh match the parts in the engine, plus they never check for crank shaft flange run out. If the flange is runing out you will have a 63 lb flywheel jumping up and down. not a good thing a 1800 rpms.

[Terry,NJ]

Dammit Grorge, Gimme something easy, willya? LOL Truth is, that's exactly the kind of stuff I was thinking of too. The big tear down stuff! Fortunately the FW is only 53 lbs. Something like a bent crank or a broken skirt on a piston. There may be a problem with the trans too, but the main issue is the engine.
Thanks, Terry

Originally Posted by George Miller

Sounds like the engine is out of balance. Lots of guys never weigh match the parts in the engine, plus they never check for crank shaft flange run out. If the flange is runing out you will have a 63 lb flywheel jumping up and down. not a good thing a 1800 rpms.

[George Miller]

Sorry I,m going to stick to my story.

[BILL WILLIAMSON]

Sounds pretty "normal" to me. Just think of how much stuff is mounted almost solid to the chassis & body. 45 MPH, seems to be the "cut in" speed for those sounds.
After puttin' in front & rear Float-A-Motors & a rubber tail pipe hanger, etc, Minerva wuz like a different car. Jist went HMMMM, at ALL speeds!
Bill W.

[1crosscut]

I'm with you Bill. Go for the simple things 1st. I was pleasantly suprised on how much fixing the tail pipe hanger vibration helped quiet things on my truck. Especially on deceleration.
Terry like you when I pushed in my clutch things smoothed out and got alot quieter.
Try the temporary shim in the hanger. Costs nothing and gives you a good excuse to go for a ride.

[Tom Wesenberg]

I think George might be right on this balance issue. A worn center main can also make quite a shake. You should be able to remove the pan, then use a jack to put upward pressure on the center of the crankshaft, then set up a magnetic dial indicator and set the pointer at zero. Now remove the jack and use a board or bar to pry down on the center of the crankshaft. This should give a good indication of center main clearance.

My center main babbit was gone when I bought my 29 Tudor. I didn't have to measure anything. I just had to look in the pan and at the sides of the center main cap, and I knew what had happened. No babbit really made for a good shake and rattle at any speed over about 20 MPH.

[TDO]

Worn tranny gears and bearings will make a lot of noise. A rubber hanger on the tail pipe will help a lot. Along with float a motor mounts. I don't believe you'll ever get rid of all the noise. The Model A wasn't design that way. Just keep on trucken and enjoy the ride.

[James Rogers]

Universal joint

[Mitch//pa]

Originally Posted by James Rogers

Universal joint

post # 1
just sitting and reving the engine produces the vibration

[Tom Wesenberg]

It is common for a loose bearing or piston to rattle more in an unloaded condition (coasting downhill) than while pulling a load (going uphill).

[Will N]

I have two Model As- one with a nicely broken in engine (don't know when it was rebuilt) and one with a newly rebuilt engine with less than 5,000 miles on it. They both vibrate more when going downhill with the throttle closed than they do on level ground or uphill with the throttle opened. I think it's just the nature of the beast.

[tuneman]

I have to agree with James Rogers on this one, I experienced the same issue.
Found it when taking engine and tranny out. It was so worn out, I don't know how it stayed together.

[Terry,NJ]

Thanks guys! A little up date, Last night, I did a compression test (and I won't disclose my actual readings, I suspect the gauge is bad) but they were all very close. I ran the test 3 times and got almost identical readings. The engine runs too good for the low readings to have been accurate.
While inspecting the exhaust system, I found that the manifold clamp bolts (2) were a little loose so I tightened them and I went underneath and looked at the clamp. It was tight! I made a rubber washer out of an old inner tube and put it between the frame and the clamp. Then I took an old rubber pad from a motor mount and cut a strip off of it and forced it in between the pipe and the clamp and tightened it. I took the car out for a ride (not on an interstate) and while it's still a little noisy, there is a definite improvement. I would have not thought of the tailpipe transmitting all that vibration.
Terry

[Terry,NJ]

Tuneman and James, Last year, I put some new parts in the trans. I had a spare Universal joint and it had a little play in it, about .004. At least that's all the shim I could get in. .004 seemed a little loose so I asked in the barn and I was told it was ok. I'm used to U.J.s having needle bearings with zero lash in them. As with everything else, Mod. A s are a little different.
Terry

Originally Posted by tuneman

I have to agree with James Rogers on this one, I experienced the same issue.
Found it when taking engine and tranny out. It was so worn out, I don't know how it stayed together.

[colin1928]

Originally Posted by George Miller

Sounds like the engine is out of balance. Lots of guys never weigh match the parts in the engine, plus they never check for crank shaft flange run out. If the flange is runing out you will have a 63 lb flywheel jumping up and down. not a good thing a 1800 rpms.

X2 Balance