Re: Weird Surging
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It could still be a fuel supply issue, such as a pin hole in the fuel line between the pump and the tank or any other sort of leak. A non-working fuel cap vent might cause it.
It's possible the vacuum advance could cause it, or a lack of lubrication on the distributor rotor or too much lubricant on it. Too much or too little fluid in the transmission could cause it. Some automatics are very sensitive to fluid level. Some cars have the wrong dipstick in the transmission. Long shots: A problem with motor mounts or with the throttle linkage could cause a feedback effect. A problem with the fuel flex line or fuel pump linkage might cause it, as could a defective fuel pump diaphragm or spring or valves. A weak or broken valve spring might give a surging effect. Clogged exhaust?
Posted on: 2/6 19:37
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Re: Weird Surging
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When I first purchased my 1956 Caribbean it was running a single Rochester 4-bbl and had the surging symptoms you describe. Ultimately, the solution was to replace the carburetor main jets with a set one step richer.
PS - I've still quite quite an assortment of those jets, let me know what # you wish and I'd be glad to check.
Posted on: 2/6 20:05
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Re: Weird Surging
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I had the exact same problem with a 1972 Thunderbird. Main jets one number richer eliminated the surge and improved performance.
Posted on: 2/6 20:07
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Re: Weird Surging
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Just can't stay away
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Hooking up a tachometer would show you if the enngine speed is is fluctuating and help you in your diagnosis.
Posted on: 2/7 11:42
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Re: Weird Surging
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Quote:
As far as I know, not unlocking at 3/4 throttle is normal. Do you have the throttle lever extension on the transmission? I don't think this is surging related, just commenting on the transmission. Transmission problems (for fairly obvious reasons) often happen at a certain RPM, certain gear, certain temperature, etc. Since it happens the same in all possible states I think the transmission is fine.
Posted on: 2/7 17:06
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1955 400 | Registry | Project Blog
1955 Clipper Deluxe | Registry | Project Blog 1955 Clipper Super Panama | Registry |
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Re: Weird Surging
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Try disconnecting the vacuum advance line at the carb and plugging the port.
Posted on: 2/7 20:45
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Re: Weird Surging
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Try driving it with the air cleaner off. I had running problems on my '51 when running at higher speeds, which I eventually traced to the matting inside the air cleaner. Took me four months to figure it out after doing a lot of the things you mentioned in Post #1.
Posted on: 2/11 5:21
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Re: Weird Surging
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Just can't stay away
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The carburetor is definitely not lean. Rich, actually. I live at high altitude and left the standard jets in it because it's not rich enough to hurt anything and it allows me to drive to lower altitude without damaging the engine from being lean.
It's not the gas cap. I've driven with the cap off with no change. It's not the vacuum advance. The old vacuum advance didn't work and it still surged the same as it does with the new vacuum advance. It's not the points or condenser. I've been through several sets. No change. It's not the fuel pump. Three different fuel pumps all acted the same. Nothing is out of place or clogged in the air cleaner. I soaked that whole thing out with kerosene and thoroughly inspected it before I ever drove it. No valve springs are broken. I looked at them all when I had the valve covers off not long ago. The fuel line is not clogged. I can blow a high volume of air back through it. Pinhole air leak, maybe, but usually that makes the pump lose prime when the car sits and I do not have that problem. Motor mounts are good. Throttle linkage is good. Exhaust is not clogged. Carburetor bowl vent is sealing properly and adjusted properly. I wonder if it's some sort of fluttering in the air cleaner or carburetor. I can imagine the oil in the air cleaner getting sucked up into the gauze then draining back and getting sucked back up again in a fluttering rhythm. Something similar could happen with the air and fuel flow in the carburetor as well. Some models of four barrel carburetor can get secondary flutter. I might switch a pleated paper air cleaner onto it or disable the secondary barrels of the carburetor and see what happens. It is definitely a weird one.
Posted on: 2/23 0:52
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1955 Patrician.
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Re: Weird Surging
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Sounds like it is time to hook up a gauge to the DirectDrive port and watch the pressure. Also hook up a tachometer as bullish—ter suggested. If you don’t have someone to monitor and record the pressure, rpm, speed and surge, setup a video camera to record the test and look at the data after.
Posted on: 2/23 2:31
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