Rear Engine Mounts

[ursus]

After decades of use, most Model A's have some degree of sagging at the rear engine Mounts. Which side suffers the most from this effect, left or right, and is this partly caused by the twisting force of engine torque?

[nkaminar]

Caused by bad roads and big bumps.

[Joe K]

My experience is the problem isn't the engine mounts, but rather the obese driver.

And there is something about that spot, perhaps being sundered by the bolts attaching the engine mount to the frame?

Joe K

[History]

The weight of the transmission is also there, including an any forces vertically on the torque tube. The frame was made to be able to twisted as it traveled over the terrain of the time which would be “off-road” today at the least. All the weight that connects to the engine mounts combined with the inertia of that weight adds up over a bump and either cumulative or one big bump, ditch or overload of driver bends it and it stays there. My opinion,,,,,,,,,

[katy]

Back in the 1950's, my second car was a Model A coupe. The brakes required a very heavy push, but being young and inexperienced I never gave it a lot of thought, "that's the way they are" kinda thing. One day sitting at a light I noticed that when I pushed the brake pedal the transmission raised up, foot off the brake, transmission went back down. Upon checking I found the right rear motor mount was missing the bolts that connected it to the engine. The transmission was sitting on the brake cross shaft. After sourcing and installing the missing bolts the brakes were much easier to push.

[rotorwrench]

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Frame sag is just another word for a bent frame. With so much water under the bridge, it's hard to say if it was rough roads, weight overload, or wreck damage from a quick trip into a ditch. If these old cars could talk it may be more like a wail and a scream. I've seen left, right, and both sides bent. When found, it's best to start thinking about straightening it back out before it gets worse. If it's cracked, reinforcement may be needed to keep it from falling apart in the future. 90+ years aren't always kind to them old bones.

[ursus]

Originally Posted by rotorwrench

Frame sag is just another word for a bent frame. With so much water under the bridge, it's hard to say if it was rough roads, weight overload, or wreck damage from a quick trip into a ditch. If these old cars could talk it may be more like a wail and a scream. I've seen left, right, and both sides bent. When found, it's best to start thinking about straightening it back out before it gets worse. If it's cracked, reinforcement may be needed to keep it from falling apart in the future. 90+ years aren't always kind to them old bones.

My coupe has a steel plate welded in just aft of the right side mount. I am wondering if reinforcing one side in this manner could make the other side more likely to sag.

[rotorwrench]

They generally don't bend unless unusual stress is applied. Hot rodders usually box the frame if they adapt a heavier motor with higher performance. The basic A-V8 conversions back in the late 30s & 40s usually used a 1932 Ford K-member in there to reinforce that area. For a stocker, a fish plate can be used but that's an individual decision.

[nkaminar]

The hood on my car did not fit well and I suspected a sagging frame. I lifted the body a few inches to remove the front fenders to paint them. I discovered that all the rubber pads had compressed to about paper thin. I sighted the frame and it was straight. I replaced the rubber pads and added more to adjust the alignment of the doors. I guess the wood had compressed in places. Anyway, it fixed the fitting of the hood.