Thread: Rough Idle on my Chevy 350

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Pepi mentioned Marvel's Mystery Oil in the gas tank, which I've used in the past, but another alternative to consider is a pint of SeaFoam. Follow the directions on the can for the amount of fuel to mix it with, and it's best to add it to the tank first, then add the fuel to mix things up. I've also used SeaFoam straight out of the can, pulling the large vacuum hose off of the power brake booster and letting the engine suck the SeaFoam out of the can opening. Don't submerge, just put the end of the hose over the can opening, and tilt the can enough for the vacuum to slurp it up. Note, do this OUTSIDE, NOT in the garage. It smokes to high heaven!!

Originally Posted by rspears

Pepi mentioned Marvel's Mystery Oil in the gas tank, which I've used in the past, but another alternative to consider is a pint of SeaFoam. Follow the directions on the can for the amount of fuel to mix it with, and it's best to add it to the tank first, then add the fuel to mix things up. I've also used SeaFoam straight out of the can, pulling the large vacuum hose off of the power brake booster and letting the engine suck the SeaFoam out of the can opening. Don't submerge, just put the end of the hose over the can opening, and tilt the can enough for the vacuum to slurp it up. Note, do this OUTSIDE, NOT in the garage. It smokes to high heaven!!

To add to Roger's post - - - I had a 350 in my '55 and it got to dieseling so I used Seafoam according to instructions and "voila" problem solved.