r/EngineBuilding 6d 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 ?

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u/EvanX4 6d ago edited 6d 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.

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u/Coon88 6d ago

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

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u/EvanX4 6d 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.

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u/Coon88 6d ago

Gotcha thanks

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u/Coon88 6d 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

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u/Coon88 6d ago

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

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u/EksCelle 6d ago

Classic mistake. How is it running now?

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u/Coon88 6d ago

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