0320 10:1 running Rough

Phillip Camarda

If the engine is running ROUGH it is not usually a vacuum leak at the carb seal. A vacuum leak tends add RPM to the engine and a slight leaning of fuel unless it is at one of the intake tube swedged tubes or the sump or gaskets.  Turn off each ignition system and see if the problem follows either the Magneto or the EI system. If it remains, you have at least eliminated the ignitions. This is a long shot, however, you may want to pull the oil screen or filter and look for cam particles. A warn lobe on a cam will cause this issue as well. If there is no lobe wear then I would do a compression check and verify that I have good compression and my valves are not sticking open or leaking. A compressed lifter body will also cause this issues. If the Ignition is good and the Cam is not warn and the compression is good with no valve leakage and the lifters are fully operational you need to take a closer look at the fuel flow delivery system. The carb could have a partially blocked idle jet. Sometimes when you get things overhauled mistakes can be made. Never discount the fact that the carburetor could have a partial blockage in the idle jet port or jet itself. Just have to ask this QUESTION: with your 10:1 pistons, you are running at least 100LL, not Auto-gas? 

P Camarda    

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