Well here it is. I found and fixed a large vacuum leak (open connection on abandoned headlight vaccum tank). The car ran good before except a hesitation at take off - good power otherwise). Now with the leak fixed - the car bogs down ad misses during acceleration - not at take off. I am assuming that someone adjusted the carb not knowing of the large loss of vacuum at the storage tank. When I opened the connection up again, everything returned to the way it was before. Is this a timing issue or is it a simple adjustment of the carb - I am not real good at messing with the carb - but willing to do a little.
First things first. Check the initial timing, and the performance of the advances. This could be an issue of vacuum indirectly, in other words PCV, vacuum advance etc. Next, check to be sure that the carb is correct for the application. Then check the performance of the carb itself, power piston, secondary air valve, etc. Since I am not sure of the problem's actual conditions, part throttle, full throttle, hot or cold, we are shooting in the dark. I doubt that the carb is suddenly too rich, I suspect that the owner probalby guessed at what to do to overcome his unknown vacuum leak, and you will have to systematic in cleaning the mess up. Check the ignition timing and advances, and we'll go from there.
Thanks Ray. I am getting educated and will check all aspects of timing soon. Will Get back to you. Mike
I checked timing and it was about 3 deg. advanced so I adjusted back to tdc. Made a nice change, no more popping. I am happy with the performance except for the little hesitation at take off. Will mess with the carb this weekend. Also I think I should replace some of the components in the distributer - probably about time.
Mike, There is no way a properly set up BBB should like 0* degrees of timing. In general Buicks like a lot of initial advance, most of us run 12 to 18* initial timing with 32 to 34* total at 2500 rpm. Get a vacuumn gage, they are not expensive. Connect to a manifold port. Adjust the idle screws for the highest possible vacuumn. I have never heard of having too much vacuumn. If your engine likes a leak there are some other problems you need to find.
A note about advances; the problem is not one of initial, centrifugal, or vacuum. It is one of having the correct advance for the driving conditions, engine, and driving style. The intial timing adds to the centrifugal, and vacuum, if appropriate, and determines the actual time of ignition. Any combination of initial, or advance allowing the correct actual timing will work for the engine. I do, however, strongly suggest checking all of the advances to be sure they are working correctly. Changing the intial timing to fix another problem, as we all know, is not the solution. Ray
Note, Using a vacuum gauge may not be the most accurate method of adjusting mixtures as the gauges may not react as well to slight changes in vacuum. I have seen gauges that would not react to changes as much as 1/2", making it useless. Most tachs, especially the idle tachs wll work just fine, and will allow the adjustment of idle speed as well. Ray
As far as the timing - I observed the cent. operation as well as observing timing when the vacuum was hooked up. All seem to be functing when rpm is increased - aaccording to to the timing light. I havnt determined total timing as of yet, But at least everything seems to be operating correctly. Will mess with othe stuff this weekend. You all are a wealth of info. Thanks
Ok, I am happy with the timing. Have replaced cap, rotor, and points. Car starts, idles, and accelerates great EXCEPT at take off from a dead stop - where it bogs. Now I am getting into carb - as everything else is done - plugs, gap, wires, etc. I realize the carb may need a complet rebuild, but I will try adjustments first. One thing - there are four adjustment screws at the base of the carb when looking from he radiator side and the chassis manual is real elusive as to what they are - from left to right - what is the descripotion of each of these adjustment screws.
Mike, What carb do you have? Usually a bog just off of idle is not enough gas from the accelerator pump. This is an easy fix on most carbs with a rebuild kit. Take a look down your carb and open the throttle. You should see a good strong squirt of gas from the discharge nozzles. It should also happen very quickly (gettting gas with little throttle movememnt.) Ray does have a point about vacuumn gage adjustment. I always use a tach and vacuumn gage to adjust carb. One thing you should notice when adjusting the idle screws is as you adjust the screws in there should be a point where the engine will start to cut out and die. If you can screw the idle adjust all the way in you still have a problem. Good luck and let us know what carb you have.
