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highcking

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About highcking

  • Birthday 08/13/1950

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    Luray, Va

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  1. Jon - thanks. I’m running with standard breaker points. I do need to look at fast idle. Buick specifies 1500 on the top step of the cam. That’s very fast, but I guess it shouldn’t stay there long, especially in hot weather.
  2. Too hot today, 90 degrees, to play with the choke setting. I did try running the car with idle screws at one turn out, very lean. Would not idle. It will idle at one and a half turns but I already knew that. Because the bogging problem seems relatively insensitive to these various adjustments, I may need to pursue the carb base vacuum leak. Manifold vacuum is over 17 and steady and I hear no hissing, but tomorrow I’ll listen with an engine stethoscope. I assume a very small leak at the base gasket can disturb the air fuel mixture at low rpms. Spraying the base to find a leak is actually not simple due to things in the way and air coming from the fan.
  3. The Buick manifold design sends hot exhaust gases through the body of the carb. Cadillac likewise. A Carter AFB is made of aluminum which is quickly eaten up by exhaust gases. Both Buick and Cadillac shop manuals call for a blockoff plate to prevent this. The plate itself gets hot and transmits that heat to the carb body, but not as fast as direct contact with exhaust gas.
  4. Ben - yes on the carb heat manifold. It has been blocked off. Ken - good point about manifold vacuum. The Buick has an oil pump vacuum booster that is piped directly to the intake manifold, I forget exactly how at the moment. In my experience with three 58 Buicks, these don’t work worth a darn. With my current car I got caught in a sudden rain shower, and sure enough, the wipers would virtually stop when I accelerated. Back in the day, Trico sold an electric vacuum booster pump that actually held vacuum steady at 15 or more inches. Later today I’ll try the choke reset and lean out the idle screws as you suggest. It’s a hot day today in Virginia which will affect the choke setting slightly. I’ll also check the fast idle and check once again for a tiny base gasket vacuum leak. Bill
  5. A few tries today in good weather. Accel pump is spurting on both nozzles as it should, I checked using a snooper scope. Choke manipulations: factory setting is index, I tried two rich and two lean, no discernible impact. Choke back to index, I tried idle mixture screws at 1-1/2, 2, and 2-/2. No effect. Let me be more specific on the phenomenon. Cold engine, start car, idles smooth, touch throttle gently, engine lags for a few seconds or dies. Jam throttle down, there is a momentary hesitation but engine does pick up pretty fast. I have one other option, try the other AFB rebuild I have on hand. Nuisance to swap, though. I never liked Rochesters on this car.(
  6. Ken - very helpful! I’ll continue to pursue along those lines. The internet is packed with threads on the AFB flat spot, on many different cars.
  7. Pushing the choke to rich settings didn’t help, nor did setting the idle screws a turn richer. Let me be a little more specific about what’s happening. Start cold engine, goes to fast idle. Weather is warm so this may be around 1,000 rpm. Vacuum is at about 18, good for 58 Buick. Run just until fast idle is off, then shift to drive and gently squeeze the throttle. Engine will either die or sag way down. If the latter, it recovers after a few seconds. This behavior continues until engine is warm and choke is open. Could this be a rich stumble rather than lean stumble? Tomorrow I plan to look at the accel pump action.
  8. I had that thought too. I’ll try the choke adjust first, maybe one notch. If it doesn’t improve, I’ll reset the choke and try idle screws.
  9. I’ve finally gotten the Carter AFB on my 58 Buick Roadmaster to function well … with one exception. When the engine is cold, even minimal throttle forward or reverse kills the engine. Five minutes’ warmup and the flat spot disappears. Car runs and accelerates fine after that. My feeling is that it’s a slight fuel mixture problem at idle. Accelerator pump issue would continue on a warm engine. Thoughts on this? Bill Lursy, Va
  10. I have a baffle plate the looks just like the gasket. I have another that is just a plain square open in the middle.
  11. I have that flange gasket. What does that baffle look like? And what is the correct order of installation?
  12. Yes, it has that feature. I believe it’s a correct AFB for the car.
  13. Well, I tried the gasket first and the shim on top, no sealer. Bad seal, lots of leakage. Also I found out the at shim I used (new) was razor sharp and sliced open my finger. In light of what I pointed out above, that the gas passages don’t line up between the manifold and the AFB carb, it’s not clear to me what the benefit of the shim is.
  14. Adam - thanks. I have two AFBs both the same. But as you can see, the rusty Rochester has the groove in what you’d think is the “proper place.”
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