Heat riser on Packard 356 engine

Yep, without the help of the exhaust gases (diverted by the heat riser) heating up the hot spot on the intake the fuel will not vaporize as well when cold and the engine runs rich. Running rich also doesn't help with the cylinder wall lubrication so it's worth spending the time to replace the spring.

Thanks JT. That probably explains the blowby gas coming from the breather as well,I suppose, if gas is getting into the oil and then is vaporized as the engine heats up. I'll get a spring ordered right away.