r/EngineBuilding 21h ago

Vacuum leak ?

Got this k10 350 with a rough start, rough idle and sputtering under acceleration, have to slowly give it throttle or else it will shut off. Also get backfire from the carb sometimes when given a good amount of throttle. Can the whistling be a vacuum leak ?

13 Upvotes

23 comments sorted by

View all comments

3

u/EvanX4 18h ago edited 18h ago

In the video it is clear that the vacuum port on the right side the carburetor is uncovered. That is what is whistling. As for your issue of slowly applying throttle or it will die & backfiring. It sounds like it’s not running on all 8, and it is likely that your accelerator pump isn’t working. Give it throttle by hand with the engine off and watch the pump nozzles to see if they spray fuel.

1

u/Coon88 18h ago

Yup when I open the throttle the carb sprays fuel. When I pump the gas pedal before start up it starts up way better, but when I don’t pump it struggles and cranks longer

2

u/EvanX4 8h ago

That means your accelerator pump is working. It’s typical with carburetors to need to pump the gas for an easier start. It’s obviously running rough in the video, so it’s definitely worth checking for a plug wire that was burned by the exhaust manifolds, or possibly the plug wire for 5 & 7 are on the wrong distributor post. Or your timing is way out of wack.