In search of a better way to set injection timing.
I'm working on 2, 237's. Both with Ambac pumps. One with a fresh rebuild pump and another with a used pump swapped from another engine. Both engine data plates read 26 degrees at port closing. I have spilled timed both of them, to as close to 26 degrees as I could manage. Both engines are running good and sounding good. However, both engines smoke quite a bit of blue (unburnt fuel) at an idle, especially when cold. They clear up once i've got my foot into it under load. The injectors are also fresh rebuilds so it's unlikely that the spray pattern is poor. And neither engine uses much oil or has much blow by.
So...I figure my spill timing is out a couple degrees, probably retarded. instead of pulling the delivery valves a few more times and messing around rotating the engine with the hard to reach crank pulley on the Western model R's; I would like to try the pulse type/clamp on timing adapter with a strobe light. I have a Snap-on and use it on other model engines, no problem. I haven't tried it yet on the Macks.
If I clamp this to #1 injector tube, and read the mark on the crank when illuminated by the probe, should I expect to see the actual injection timing illuminated at an idle speed, or at a certain RPM? I know some engines with an advance mechanism in the pump (like some of the Roosa Master style Stanadyne pumps) require the engine to be at 2000rpm to accurately set timing.