The manufacturer probably thought.. it's plastic it'll eventually create its own backwash. I'm really glad you changed it. I would never trust plastic gears. Love the videos. Thanks
Just found your channel and I'm really happy that I did! Just started looking for a model T of my own. It feels really exciting! Never owned a pre-war car before but several more "modern" classics from the 1950-1990. I'm from Sweden and model T's are quite rare here. There are currently about 700 registered T's in the country and 50 000 were sold new, mostly assembled from parts right here in Sweden. Of course there wasn't a whole lot cars around back then and I've heard model T's made up about 1/3 of all cars over here in the 20's.
Austin 7 engines have a similar timing gear setup. Since there can be differences in centres of the two bores the timing gears were matched to the crank gear. We usually aim for 2 to 3 thou backlash from memory. I see someone else mentioned nylon is affected by moisture. When you 3D print it you have to dry it first since it absorbs moisture from the air.
Unfortunately, Nylon materials are sensitive to moisture, and can grow in size when they absorb water from the air. Can't say if the white nylon gear was once correct in size and has since grown due to high humidity, or whether it was machined incorrectly. In either case, it is yet another example of a reproduction part that isn't quite right. I am glad you had good luck finding an original Ford gear that will work for you. Old parts are very-often the best parts, as you know.
Getting everything down to the specifications is the way. Back when they would just slap em together throw on the cover and go. Some lived, some died. Good work
As others have said, I think the nylon has enlarged due to moisture or issues with the molding process (QA probably non existant, checked the master sample and some 'selected samples').
Usually new timing gears are machined a smidge larger to account for crank gear wear from what I have experienced. I just use whichever gear sets the correct backlash just like you did
Reproduction parts... always so close, but yet so far. I've got a NOS fiber gear (not the brown, it's the good black gear) I want try some day. Maybe next winter. Cheers
