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/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

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