Originally Posted by Westlotorn
The reason Fuel injection needs the 10 micron filter is to avoid plugging the injectors which need very clean fuel. A jet in a carb can pass much larger particles with no issue so the specs are more relaxed. More aggressive filtering can produce drag in your fuel delivery which is not an issue with a Electric pusher pump feeding fuel under high pressure but may be a big issue with a mechanical puller pump that is pulling fuel from your tank before it pressurizes it to the 6-7 lbs needed.
What Wes says in the above is exactly what I was concerned about.
The pump to carb fuel line in my car utilizes the all metal Fram 3727 filter. Napa, Wix, Purolator, and AC also carry this same filter in their lineup. All, including the Fram are 10 micron rated filters.
Now I'm wondering if using a 10 micron rated filter might be too 'tight', with respect to fuel flow resistance through the filtering media and using a puller fuel pump. With the exception of a recent bog/shutdown problem the engine runs fine, otherwise. A recent fuel pump pressure test with engine running showed 5.25 PSI, the minimum spec. .. . The fuel volume/time test as shown in the CSM wasn't done. I need to do that.
The top of the AFB was taken off to have a look inside. Interestingly, there were some rust particles resting on the bottom in both the primary and secondary fuel bowls. The carb has been rebuilt recently and was clean as a whistle inside, afterwards . It hasn't seen many road miles since being rebuilt. Seems a 10 micron rated filter should have trapped those rust particles.
Interesting that the 100 micron filter media you used worked just fine in keeping the AFB's clean.
Well, now what?. .. Might have to redo a new fuel line using a 40 rated filter.