Originally Posted by
Crankshaft
Red is back on the road and going rather nicely.
It took a bit but while it was out I did a bit of trying to work it all out and found that the L28 has two crankcase breathers, one at the top into the rocker cover and one at the bottom front bottom of the crankcase. This one goes through the PCV valve into the inlet manifold. That means the manifold sucks an unmetered flow of air through the engine and into the manifold.
No wonder I couldn’t tune it. A welsh plug replaced the outlet and a 1/4 brass plug blocked the manifold. Now the only air that gets into the manifold comes through the brakes or the carby.--