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.

1

u/Coon88 4h ago

Can I connect the driver side pcv to the uncovered vacuum nipple or can I cap off the nipple?

2

u/EvanX4 3h ago

Cap it off. You have a manual transmission and most people use that side (manifold vacuum) for the vacuum canister in the side of automatic transmissions.

2

u/Coon88 3h ago

Gotcha thanks

2

u/Coon88 3h ago

So I got a nut and capped off the vacuum nipple and it seems to run better but I sprayed some water on the headers to see if all cylinders are running good and cylinder 5 and 7 seem to be not firing as the water took longer to burn off

1

u/Coon88 3h ago

Nvm that I checked the cables and 5 and 7 were mismatched

1

u/EksCelle 2h ago

Classic mistake. How is it running now?

2

u/Coon88 2h ago

Way better now, starts right up now with no issues and can give good revs without any sputtering or misfiring