Warm idle air/fuel adjustment

[Jowe]

After wakening the beauty from winter hibernation, I took a 90 km drive to warm her up and check everything in order. Despite of that the rotary switch for the fan blower fell off when turning , the ride was a real joy and the engine was pulling really good. However, I noticed that the idle was a little low when warm, some 600+ rpm. So, I tried to adjust the idle air valve by opening it up (by the prerequisite that the engine is running rich) but the idle didn't go up at all. Then I made the split linkage test and, as expected, when opening the throttle only, the idle went up. Why didn't the idle air valve do the job? What other adjustment to increase air? Other status: cylinder head torqued, valves adjusted, compression 140-160 psi, clean spark plugs.

[Tyler S]

I had a similar issue. when I removed the intake manifold to rebuild the head I found that most of the small idle ports in the intake runner were partially blocked with carbon buildup. This limits how much air the engine can get at idle, limiting the range of the idle air screw. Remove the Idle screw housing with the big nut,  There is a hex welsch plug on the manifold at the opposite end near the fire wall you can remove to take a look through the runner with a mirror and a light. You may need to remove the manifold to clean it properly.

[Jowe]

Good idea. I will do that and report back. Thanks!