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Originally Posted by Invigor
Quote:
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Originally Posted by BMW Rider
Another problem common to the Dodge small block V8s was carbon build up in the exhaust crossover passage in the intake manifold. It results in the fuel not being properly vapourized due to the lack of heat under the carb. this would produce simptoms similar to what you describe. basuically you have backfireing beacause the fuel mixture is essentially lean since much of it is in liquid and un burnable form. This liquid fuel is then pumped duirectly through the engine out the exhaust resulting in a rich exhauast smell. It also tends to wash down the cylinder wall and cause excess oil consumption as well. The only cure is to remove the intake and clean out the carbon blockage.
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it does sound probable. the beast sounds ok when it idles, very hesitant when you give it gas..sounds like it's working really hard to get air...loss of power. I will add "possibly clean intake" to my list.
I've got, carb kit, set timing, and clean intake...whee! glad it's only a 2bbl |
It so hard to make a determination without seeing it first hand.
Check the ignition timing, if it is way off, then it is possible that the timing chain has jumped a tooth. It will be retarded since when the chain skips, the momentum of the crank will jump it ahead of the cam leaving the cam and distributor retarded. Usually when they go, they go to the point that the engine will not run, but it can just skip one tooth initially allowing the engine to still run sort of. Usually it won't be too long before it jumps another tooth or more and the engine will no longer run at all. Generally though, for timing to be the cause of backfireing, it will have to be too far advanced.
As for the carb jets being not set right, that is highly unlikely. The main jets are fixed orfaces and would have had to have been replaced to change them. The idle screws will only affect the idle mixture, and that does not seem to be your problem. It is possible that the float level is too high in the carb. This will have the effect of richening the mixture. this can be the result of a leaky needle valve or a float that has become too heavy, usually because it has absorbed fuel. But the backfiring is not a symptom of a too rich condition, but rather a too lean condition. If the only time it backfires is when you accelerate, it could be the accelerator pump not working properly and causing a lean out when the throttle is opened. Once the engine reaches the increased rpms, it will again run fine. Of course this means a thorough cleaning and overhaul of the carb is required.
Of course as is usually the case, there are multiple cuases combining to create the overall poor running. The timing may be slightly retarded due to timing chain stretch, the intake is cold due to carbon build up (almost a guarantee on that engine at that mileage if it has never been cleaned) and the carb is not in peak condition. There may be other factors such as the condition of the ignition system too. Check for bad wires, plugs, cap, rotor, etc. It may not be any one problem that is the major cause. And to top it off there may be more serious mechanical issues such as bad valves, camshaft, or other valve train component wear.
Like I said, so hard to diagnose whithout seeing it firsthand.