I have a 51' 263 with hydraulic lifters running on 6 volts. Engine has 47,000 miles on it. Engine was "freshened up" at 37,000 miles. Lifters cleaned, bearing clearances checked, carb rebuilt, new coil, cap, rotor, points, wires, compression check etc... Engine was running really well for a couple of seasons until last fall during a 300 mile road trip where it developed the stumble. Prior to this it had a recent exhaust manifold leak (that has been fixed several times before) that I thought may have caused the intake to also leak. Both intake and exhaust have been fixed but the problem still exists. The engine also seemed to have a sticky lifter at the beginning of last season but freed up after a few longer trips. Engine runs well at idle and strong in park when giving it more throttle. The problem occurs only under load and particularly at the shift points from 1st to 2nd and 2nd to 3rd. It is a 3 speed manual. I have tried or done the following: Replaced inline fuel filter between tank and (2 year old) mechanical fuel pump Replaced inline filter between fuel pump and carb Checked timing Cleaned and checked point gap Cleaned and checked plug gaps Checked plug wires Checked distributor lead wires Cap and rotor look good Adjusted existing carb throttle screws Switched carbs with no change Vacuum advance holds suction and moves freely Bi-passed mechanical fuel pump with electrical pump Performed a compression check not perfect but actually is slightly better than my original prior to engine install. (rings freed up?) What am I missing? Sticky lifter(s)? Poor valve spring? Burned valve? Weak dizzy springs? Sticky dizzy weights? Need help!!
Missing under load is more often ignition than carb. When someone asks my help on old stuff, I say, "Clean both ends of both battery cables. Replace with new brand name spark plugs, plug wires, cap, rotor, points and condensor. Then I'll be glad to take a look at it." So far, nine time out of ten, this solves the problem and I never see the car. The tenth time, I put my AFR O2 sensor on it. Fifty years of thinking I was tuning carbs and I only learned how much I didn't know when I got an O2 direct reading meter. jack vines
I have tried 2 different carbs, Second one had new accelerator pump and power piston. Could either be bad out of the box? Looks like I get a good Squirt looking into the carb and opening the throttle.
How old is the fuel????? If over 6 weeks old, regardless of what expensive miracle-in-a-can was added, could be the problem. Assuming you have already burned out last seasons fuel, and refilled with fresh fuel, I would look at voltage regulator setting, and generator output. Not really a lover of multiple fuel filters either. Not that I think it will make any difference (don't think the carb is your problem), but it might help to know if you have the Carter (tag number ?) or Stromberg (stamp number ?). Jon.
're your manifold issues. If you have them off for any reason in the future, take them as an assembly to your favorite (automotive or industrial) machine shop and have the ports surface ground to true them. Ray
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