Lack of Vacuum and Carb issues

[RamD50]

Last week my truck came back after getting the brakes redone by my mechanic. They ran diagnostics and found that I have a lack of vacuum, my carbs are out of sync, and the engine diesels hard on shutdown. What can I do to fix this?

[pennyman1]

get a carb synchronizer gauge - you put in on the inlet to each barrel of the carbs and adjust the flow until they are drawing the same. I suspect your rear carb is drawing far less that the front carb and is causing all the problems. #4 cylinder is where the weber / mikunl intake pulls vacuum from, so check and be sure you have good flow.

[Rickdees]

What pennyman1 said, there are many videos out there

https://youtu.be/GaTRyHxvneY

[RamD50]

Thank you for the info, I've looked into getting an airflow tool and have watched a few how to's on the subject. Could this also be the cause of my dieseling issue? Or could I be running too high fuel pressure? (Holley Red electric fuel pump reg'd down to around 5psi)

[pennyman1]

that is too high for the carbs - 3 - 3.5 PSI. Remember, flow is more important to webers / mikunis than pressure, but too much pressure will cause issues.

[RamD50]

Thanks, I'll reg that down next time I work on the truck.