De Carb Olds 307
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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, De Carb Olds 307 in Past Cadillac Vehicle Discussion; I was thinking of having my engine de carbed and i've heared a lot of different ways and methods to ...
  1. #1
    Jeppi94's Avatar
    Jeppi94 is offline Cadillac Owners Member
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    De Carb Olds 307

    I was thinking of having my engine de carbed and i've heared a lot of different ways and methods to do that. Like starting the engine up, let it warm up and spray a fine mist of plain water into the Throttle body, or using sea foam (never seen that product in sweden) Anyway, how do you guys do it and is it necessary?

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    csbuckn is online now Cadillac Owners Master
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    When I did it, I poured seafoam into the carb until it flooded and stalled, let it sit for 5 minutes and then started it back up and went for a drive. When it floods and stalls, you know a lot has made it into the combustion chamber where it's really needed. Probably the riskiest way but you get the best results.

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    deVille33 is offline Cadillac Owners Connoisseur
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    Re: De Carb Olds 307

    I have used the water trick by using a dish liquid bottle or other squeeze bottle, hold the carb at WOT. The water will keep the engine from revving out and make it labor. Sometimes when you do this, it helps to advance the timing slightly. Sometimes, however, when the build up is very bad (extreme), it is necessary to pull the heads and scrape the tops of the pistons. At this point it is also advisable to check the valve guides and seals.

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    gplesh99 is offline Cadillac Owners Member
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    Re: De Carb Olds 307

    What makes you think you may have to decarb?? Just curious.

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    Jeppi94's Avatar
    Jeppi94 is offline Cadillac Owners Member
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    Re: De Carb Olds 307

    The old man who had the car before me (he bought it in 2008) barely understood English and didn't know anything about checking error codes, couldn't read the manual or anything about the car, so he ran the car with a faulty map sensor, O2 sensor and an un adjusted TPS. When i changed the plugs, they were all white from running rich. From just changing plugs and fixing the MAP and TPS the car runs like dream compared to when i bought it. But i guess that it must be a huge amount of soot in the engine from that earlier abuse. I'm this kind of person who's not happy until my car is tip top looking like new, so i thought it might be necessary

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    outsider is offline Cadillac Owners Connoisseur
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    Re: De Carb Olds 307

    do what csbuckn says. that's how i do it on my 307

  8. #7
    Jeppi94's Avatar
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    Re: De Carb Olds 307

    The problem is that Seafoam is not around in Sweden, i can seriously not find it anywhere. I'm leaving the car to a mechanic tomorrow to let him replace the O2 sensor which must be drilled up, it's more or less welded into place. I will ask him what he thinks i should do and if he have heard of Seafoam.

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    csbuckn is online now Cadillac Owners Master
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    If you recently just corrected the rich problem, I'd drive it for a while to see if it cleans it out. Maybe look into the plug holes to see if there really is a carbon problem.

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    The Ape Man's Avatar
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    Re: De Carb Olds 307

    If there's no magic cleaner available I'd pour a half quart of Dexron transmission fluid into a full tank of gasoline for 2 tanks. Stand on the gas pedal at a few stoplights until 100 KPH a few times. Ignore the smoke it will clear up. Call it a day.

    Transmission fluid is made from fish oil and cleans carbon out of engines very well through the fuel system. Lots of mechanics used it before cleaners with funky names came out. It only takes a little........

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    csbuckn is online now Cadillac Owners Master
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    Seafoam works well.

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    sven914 is offline Cadillac Owners Connoisseur
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    Re: De Carb Olds 307

    I've done the water mist thing with my car, and it seemed to help. It's important to do it with a warm engine at higher RPM, and not to spray too much water, or there is a slight possibility that the engine might hydrolock.

    If you can find it, get a bottle of Gumout with Regane, and pour it into the gas tank when you fill up. It would work better if you only got a half tank (it's less deluded) but your car is going to run terrible.

    Sometimes higher grade gasolines have better additives to remove carbon deposits and clean the carburettor. Usually, if the engine isn't pining or knocking, switching to a higher octane won't improve anything, but some refineries add more solvents to the premium grade, than they do to lower ones. You might want to research which gas stations have the best cleaning agents added to their fuel.

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    mg-3 is offline Cadillac Owners Member
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    Quote Originally Posted by The Ape Man View Post
    If there's no magic cleaner available I'd pour a half quart of Dexron transmission fluid into a full tank of gasoline for 2 tanks. Stand on the gas pedal at a few stoplights until 100 KPH a few times. Ignore the smoke it will clear up. Call it a day.

    Transmission fluid is made from fish oil and cleans carbon out of engines very well through the fuel system. Lots of mechanics used it before cleaners with funky names came out. It only takes a little........
    Wow haven't heard of this one. How far back are we talking? When would this be inadvisable?

  14. #13
    The Ape Man's Avatar
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    Re: De Carb Olds 307

    Quote Originally Posted by mg-3 View Post
    Wow haven't heard of this one. How far back are we talking? When would this be inadvisable?
    I still use trans fluid on my 500 twice a year. Also fog anything not expected to run for a long time or anything that will be torn apart.

    1995 I Had a fleet of 18 Ford vans with the 300 inline 6. They all ran poorly just off idle after 125k or so. Used to introduce transmission fluid right into a vacuum line through a restriction. It would suck up a quart in about 15 minutes of idle. Smoked a lot. Always cleared up the performance issues. Same with late 80s BMWs.

    I mentioned it because the op said he cannot find Seafoam where he lives. It's probably made with transmission fluid anyway : )

  15. #14
    gplesh99 is offline Cadillac Owners Member
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    Re: De Carb Olds 307

    I see. If it had all those issues, may be worth it. I would take a peek inside the spark plug holes first, to see how bad it really is.

  16. #15
    jamespowers is offline Cadillac Owners Enthusiast
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    Re: De Carb Olds 307

    Quote Originally Posted by The Ape Man View Post
    I still use trans fluid on my 500 twice a year. Also fog anything not expected to run for a long time or anything that will be torn apart.

    1995 I Had a fleet of 18 Ford vans with the 300 inline 6. They all ran poorly just off idle after 125k or so. Used to introduce transmission fluid right into a vacuum line through a restriction. It would suck up a quart in about 15 minutes of idle. Smoked a lot. Always cleared up the performance issues. Same with late 80s BMWs.

    I mentioned it because the op said he cannot find Seafoam where he lives. It's probably made with transmission fluid anyway : )
    I have heard of putting Type F in the engine oil(and have done it many times) and running it for about 100 miles or so too. That cleans the heck out of the bottom end of your engine and can fix stuck valves.
    I have never tried it in the gas tank etc. I have put Seafoam in the gas tank and it does do a good job of cleaning junk out gradually.
    Is there a big difference in cleaning properties between Type F and Dextron? I was told to use Type F over 20 years ago so if one is better than the other now.....

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