Flathead CO level at idle.

[Tony Smith]

Originally Posted by kevin powles

Hi, Can anyone tell me the correct Carbon Monoxide level at idle to expect on an 8BA flathead running a holley 94 carb. I have set her up using a colourtune, idle speed and timing are spot on but I am running about 6% CO at idle on a hot engine, which I am thinking is a little high.

1949 was not a high point in the history of designing fuel-efficient and low-emission engines. I don't have any original specs for the emissions as I don't think they originally bothered to record them.

If your engine is running smoothly without blowing smoke, you can try to reduce it a little by turning the idle screw to the leanest point, or even replacing the jets with a smaller size, but you might have to just face the fact that these engines pollute a bit.