Engine shaking at idle

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Old February 1st, 2021, 08:45 AM
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Engine shaking at idle

I replaced the radiator and had the harmonic balancer rebuilt and reinstalled, and painted the intake manifold while on engine (removed carb and other linkages and bracket and taped everything off), and now the engine shakes at idle. Set dwell, timing, idle fuel mixture, doesn't really improve. Any ideas? Carb was rebuilt, but was rebuilt and run before changing balancer and radiator and painting, and was running very smoothly. I'm thinking maybe the carb is flooding? There is also wispy smoke that comes out of the carburetor vents while running. Thanks for your help!
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Old February 1st, 2021, 09:26 AM
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Car is a 1966 Toronado, sorry, forgot to mention
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Old February 1st, 2021, 09:58 AM
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Could be your rebuilt balancer is out of balance. pay attention to the frequency of the shaking. Is it at crank speed or half crank speed. the balancer or a out of balance problem will cause a vibration at crankshaft speed/rpm, while a ignition or fuel problem will cause a will cause the engine to shake at half crankshaft speed as the cylinders fire every other revolution.
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Old February 1st, 2021, 10:04 AM
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I'd look at whatever got removed and replaced. I assume the carb came off to paint the intake. My money is on a vacuum leak.
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Old February 1st, 2021, 10:48 AM
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Originally Posted by gs72
Could be your rebuilt balancer is out of balance. pay attention to the frequency of the shaking. Is it at crank speed or half crank speed. the balancer or a out of balance problem will cause a vibration at crankshaft speed/rpm, while a ignition or fuel problem will cause a will cause the engine to shake at half crankshaft speed as the cylinders fire every other revolution.
I thought of that too... The thing is, I sent the balancer out to be rebuilt, and he aligned the outer ring to stock specs (inline with the crank keyway), so I wouldn't *think* that's the issue. It looks to be the correct balancer for the Toronado 425 (the "half moon" balancer). The only way I could see it being incorrect is if the previous owner had put a 330 balancer on the car, which I *think* has a different counterweight (correct me if I'm wrong)
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Old February 1st, 2021, 10:49 AM
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Originally Posted by joe_padavano
I'd look at whatever got removed and replaced. I assume the carb came off to paint the intake. My money is on a vacuum leak.
I'll have to remove the carb and check the gaskets and check for warpage
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Old February 1st, 2021, 10:50 AM
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Originally Posted by KaydenST
I thought of that too... The thing is, I sent the balancer out to be rebuilt, and he aligned the outer ring to stock specs (inline with the crank keyway), so I wouldn't *think* that's the issue. It looks to be the correct balancer for the Toronado 425 (the "half moon" balancer). The only way I could see it being incorrect is if the previous owner had put a 330 balancer on the car, which I *think* has a different counterweight (correct me if I'm wrong)
The 330 balancer is the same.
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Old February 1st, 2021, 10:52 AM
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Originally Posted by KaydenST
I'll have to remove the carb and check the gaskets and check for warpage
Before that you should put a vacuum gauge on the engine and see what the vacuum reading is at idle. Also look for any loose or mis-connected hoses. Verify ignition timing. Verify spark plug wires didn't get crossed. Again, what got taken off when you did all this work?
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Old February 1st, 2021, 11:01 AM
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Originally Posted by joe_padavano
The 330 balancer is the same.
I thought the 330 balancer has the timing mark at 9:00 relative to the keyway, and the 425 balancer has the timing mark at 12:00 relative to the keyway?
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Old February 1st, 2021, 11:04 AM
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Originally Posted by joe_padavano
Before that you should put a vacuum gauge on the engine and see what the vacuum reading is at idle. Also look for any loose or mis-connected hoses. Verify ignition timing. Verify spark plug wires didn't get crossed. Again, what got taken off when you did all this work?
The carburetor was removed, as well as vacuum lines. I only disconnected plug wires from the spark plugs because I removed and painted the valve covers as well. I'll double check to make sure I reconnected all the vacuum lines and make sure I reconnected the plug wires correctly. I get a vacuum reading of 15 inHg, but I am at 4,300 ft. elevation.
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Old February 1st, 2021, 11:33 AM
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Originally Posted by KaydenST
I thought the 330 balancer has the timing mark at 9:00 relative to the keyway, and the 425 balancer has the timing mark at 12:00 relative to the keyway?
1964 is the only year that the 330 balancer is different due to the one-year-only driver-side water pump inlet. If your car had a 1964 balancer on it, you'd never have been able to set the timing in the first place.
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Old February 1st, 2021, 11:35 AM
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Originally Posted by joe_padavano
1964 is the only year that the 330 balancer is different due to the one-year-only driver-side water pump inlet. If your car had a 1964 balancer on it, you'd never have been able to set the timing in the first place.
Gotcha, good to know
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Old April 27th, 2021, 08:36 PM
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Hey all, so I haven't been able to work on the car very much lately, but I found the source of my problem earlier today. I thought I'd post it up in case someone else has a similar problem. I feel stupid for not checking this out in more detail before, but a vacuum line had come loose in a spot I hadn't even thought to check, because I never touched it when I painted the manifold. It was at the vacuum tee under the driver side hood hinge where the headlights and I presume heater controls get their vacuum from. Thank you all for your help, car runs real smooth once again.
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Old April 28th, 2021, 05:05 AM
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Finding the problem and fixing it is half the fun...Drive on
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