Bent Wrench

Toy for a big kid!

Valve spring pressure can be SWAG checked by using the heel of your hand to open valves.

A problem with a single runner would not be timing related. I'd look at the valve train and a compression check. Plug and wire/coil check. Check carb for a plugged low speed jet or passage.

The way I saw it done was on a constant flow injection setup. They ran a spring loaded check valve that opened up when the RPM got high enough (fuel pressure high enough) The check valve supplied injectors located at the mouth of the stacks. So they did nothing until the RPM drove the fuel pressure high enough then sprayed in the top of the stacks. With electronics you can do it lots of different ways. The gold cylinder is the check valve and it is tee'd into the main fuel feed The 4 hoses go into the air filter for the upstream nozzles. That is a custom built slide throttle valve.

Try wrapping this. We learned a lot. Not an easy deal. The hardest was the inside bends where the hood meets the fenders.

I'd put 50's in it and see what happens, it's really difficult to go off what others are doing, there area so many variables that will influence idle and low speed operation. Spark timing, cam timing, exhaust designs. You have done good by taking them apart, cleaning, and making everything match will give you a good baseline to tune from. If you cant dial it back with the mixture screws, It's likely that the low speed jet is too big. I think the Viton tipped fuel needle will provide better service and low speed operation. (a more consistent float level)

Harley has the same issues with their dry sump setups, the tank on many models is higher than the oil pump. They added a check valve on the pump output to hold back unforced flow.

Another thing happens when fuel is introduced up stream, it changes the weight of the air, this also effectively changes the tuned length of the runner