Re intermittent misfire

[vivapete3]

Hi all, can anyone help! My HC 1256CC has an intermittent misfire, looking at the engine at tick over, it runs smoothly for approx 5 to 6 seconds then the engine shudders momentarily then goes back to smooth tickover & repeats the shudder after 5/6 seconds,I have checked the electronic ignition and timing all appears well. Out on the road the car runs OK Smoothly , a local mechanical reckons a valve may not be opening or shutting in sync with the other valves, also when the engine has been running for a while then is stopped the engine won’t restart for about for 10 to 15 minutes could this be connected to the misfire, any advice would be very helpful, cheers, Pete.

[1972nail]

Sounds like an air leak to me. check that the carb and manifold bolts are tight. Also, if it's the long air filter type, check that the thermostatic valves in the nose of the filter is operating correctly and not flapping loose.

Could also be a lack of oil in the Stromberg dashpot. Top up with a light oil like 3 in 1 oil.

[vivapete3]

Sounds like an air leak to me. check that the carb and manifold bolts are tight. Also, if it's the long air filter type, check that the thermostatic valves in the nose of the filter is operating correctly and not flapping loose.

Could also be a lack of oil in the Stromberg dashpot. Top up with a light oil like 3 in 1 oil.

Many thanks for those ideas, not thought to look at these other areas, cheers Ulster, Vivapete3.

[redfirenza]

there is a small pipe connected to the top of the inlet manifold when you pull the pipe off the stub the hole into the inlet manifold is even smaller about 1.5mm I think, it used to be common for this to block up, what about the coil?