Need some help with a persistent engine roughness in my O-320b3b with a MS 1078-32 carb. Anytime-on the ground or in the air,hot or cold, rich or lean,-
I pass through the 1200-1400rpm range the engine stumbles. At first I thought it was vapor lock because its been hot so I hooked up heat shields on exhaust piipes and a blast tube pointing at the mechanical fuel pump. The engine still stumbles in the aforementioned range and once I am out of the range it runs fine. I pulled the plugs and they looked gray.
I have read posts about drilling the main jet on the carb. Does this sound like the type of roughness that would be caused by too small a opening on the jet? Causing me to run lean at low power? I asked the A and P who assisted me in building the engine and he was of the opinion that drilling the main jet was a extreme measure; he stated that he had seen instances where guys had passed pipe cleaners through the jet with good results. But he could not say if my symptoms could be cured by opening the jet.
The engine now has 33 hours on it and it runs up fine every time with minimum disparity in the mag drops and uses only a minimum of oil. Now if I could just get it to run smoothly at 1200 rpm! TIA.
I pass through the 1200-1400rpm range the engine stumbles. At first I thought it was vapor lock because its been hot so I hooked up heat shields on exhaust piipes and a blast tube pointing at the mechanical fuel pump. The engine still stumbles in the aforementioned range and once I am out of the range it runs fine. I pulled the plugs and they looked gray.
I have read posts about drilling the main jet on the carb. Does this sound like the type of roughness that would be caused by too small a opening on the jet? Causing me to run lean at low power? I asked the A and P who assisted me in building the engine and he was of the opinion that drilling the main jet was a extreme measure; he stated that he had seen instances where guys had passed pipe cleaners through the jet with good results. But he could not say if my symptoms could be cured by opening the jet.
The engine now has 33 hours on it and it runs up fine every time with minimum disparity in the mag drops and uses only a minimum of oil. Now if I could just get it to run smoothly at 1200 rpm! TIA.