1992 Chevy S10 4.3L V6 2WD

I read about putting SeaFoam in a gas tank instead of the crankcase because it takes away the carbon. I also read that is not necessarily a good thing in older vehicles because it will cause older motors to burn oil.

I put SeaFoam in my gas tank and now my truck blows bluish smoke on startup.

I believe that prior to doing this my motor was already burning oil. I also believe it has a rear main seal leak.

  1. If I chose to get a rebuild kit and rebuild my motor, do you think this will help my oil burning problem even after I removed all of the carbon?
  2. Do I have to rebuild my motor to fix the puffs of bluish smoke that come out of the exhaust pipe everytime I start my truck?
  3. Is a rebuild my only option here?
  • Have you burned through an entire tank of gas yet? Wait until you've replaced the gas (maybe a couple times) to see if it is a permanent problem. Oct 23, 2016 at 17:39
  • for no 3, if you don't want to spend the money I owned vehicle for a very long time with bad valve seals, I just kept adding oil when needed other than that it was perfectly fine and had good compression. But keep in mind it might damage your catalytic converter
    – method
    Oct 23, 2016 at 19:51
  • Yes i have used an entire tank of gas. My gas mileage lacks because I have an exhaust bolt broke off in the manifold so it leaks.
    – bchisum_11
    Oct 28, 2016 at 21:12
  • And that seems to be my issue but I prefer to fix it burning the oil as soon as possible. It still runs fine has good compression but I would like to save the cat as much as possible as well.
    – bchisum_11
    Oct 28, 2016 at 21:15

1 Answer 1


Usually the puffs of blue smoke on startup are actually caused due to leaking valve seals. These can be changed without the need for an engine rebuild. Changing them out also can be done while the engine is in the vehicle.

You could use this YouTube video as a source for directions for changing out the valve seals. The 305 will have the same valve train setup as your 4.3L does, but yours will have two fewer cylinders.


  • Remove valve covers
  • Remove the rocker arms (keeping them in order - they need to go back to the same spot)
  • Remove the spark plugs
  • Pressurize the cylinder
  • Using a spring compressor, remove the keepers, then the spring
  • Remove/replace valve seals
  • Replace the spring, retainer, keepers (repeat the previous 4 steps for all valves)
  • Replace rocker arms and adjust
  • Replace valve covers using new gaskets
  • Replace spark plugs
  • Thank you. That's great news. How much do you think I'll be looking at having to spend? Also is there a special tool needed to remove the springs and keepers?
    – bchisum_11
    Oct 28, 2016 at 21:22
  • You can find the parts at any parts store. Cost should be minimal. There is a thing called a on head valve spring compressor you use to compress the spring and take the keepers off. Plus, you'd need a fitting to pressurize the cylinder using an air compressor. These aren't something most people have laying around, but aren't uber expensive, either (as long as you already have an air compressor). Oct 28, 2016 at 22:14

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