Bill, et al...
I called Carburetor Exchange and asked them for the specs on the fuel valve orifice for the Carter YFs they sell as replacements for the Chevy 235s. The tech told me they use a .0945 orifice, so it looks to me like they are splitting the difference between the Ford (.101) and Chevy (.081) specs to make it more economical for them to sell these things in bulk.
I also asked what initial fuel mixture setting they use. He said two turns out. This seems a bit rich to me. So, between the two specs, I think I am running very rich.
The tech also asked me if I had a PCV system or not, as this could affect (over time), the fuel blow-by amount that remains in the crankcase. I described the road draft system to him, which he knew as an "open tube" configuration, so it's at least possible the tech did not have a good feel for these old engines. But, he was trying to be helpful nonetheless.
I think that, while perhaps not the whole problem, the two rich running issues above, coupled with the fact that I drive only very short distances for testing purposes (and thus never develop a road "draft"), may be contributing to my experience of crankcase fuel contamination.
I will still be checking the fuel pressure and swapping out carbs this weekend, but may try to lean it out a bit first (set to 1 or 1.5 turns out) and see what happens.
Thoughts?
Jim
