| Electronics > Projects, Designs, and Technical Stuff |
| Improvised oscilloscope probe for Automotive ignition analysis. |
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| Jim-0000:
[/quote] If it is a grey motor it will almost certainly have solid lifters. The modifications necessary to fit hydraulic lifters would be so profound that most people would just ditch the "grey" & go for a "red" motor. [/quote] Yes. Thanks for the post. |
| floobydust:
If there is a vacuum port right at the carburetor, you can connect a MAP sensor + scope and observe the vacuum dips for each cylinder, what the carb sees. Or add a port to the intake manifold. I'm thinking about the intake manifold volume and uneven pulsating flow because the runners are different lengths - some carbs freak out if the vacuum-ripple is great. |
| Circlotron:
Posting so I get updates. |
| Edison:
--- Quote from: floobydust on January 13, 2019, 04:54:42 am ---If there is a vacuum port right at the carburetor, you can connect a MAP sensor + scope and observe the vacuum dips for each cylinder, what the carb sees. --- End quote --- This is the principle management Ecotronic, in my case, the sensors were four - the vacuum was compared in different chambers (the Weber double carburetor). Your carburettor is not equipped with an electric needle choke? |
| Gregg:
1948 Chev pickup --- Quote from: floobydust on January 13, 2019, 04:54:42 am ---If there is a vacuum port right at the carburetor, you can connect a MAP sensor + scope and observe the vacuum dips for each cylinder, what the carb sees. Or add a port to the intake manifold. I'm thinking about the intake manifold volume and uneven pulsating flow because the runners are different lengths - some carbs freak out if the vacuum-ripple is great. --- End quote --- Floobydust: that is an interesting electronic troubleshooting method for a mechanical problem :-+ Another troubleshooting method, more old school, is to pull or short the plug wires one at a time when the engine is running rough to see which cylinder(s) are least affected by no firing. This may narrow down the search. Knowing the model of Holley carb may help us; each carb has its own quirks. Is this the Holley 32/36 copy of the Weber design? The vacuum leak test is still a good idea. At low idle, lean out the carburetor as much as you can and still have it running and spray some flammable carb cleaner at all gasketed intake areas and at all welded areas to see if the RPM rises. You can test your setup by squirting a tiny amount into the carb intake and noting the result. Two weeks ago I was helping a friend with a with a 1948 Chev pickup with a single throat Carter “rebuilt” carb and it was having similar symptoms. Installing the idle jet and emulsion tube assembly from the original carb solved the problem. |
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