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Technical Compression check on my mopar flatty

Discussion in 'The Hokey Ass Message Board' started by El Tortuga, Apr 6, 2014.

  1. El Tortuga
    Joined: Aug 24, 2006
    Posts: 125

    El Tortuga
    Member

    Hey Guys I just bought a 47 Dodge Truck with a 230cu flathead. I did a compression check on it tonight because smokes blue off and on for some reason. I got 100psi on all cylinders and I used two different compression checkers to double check. Does this sound normal for one of these motors? Thanks for the info guys.
     
  2. tig master
    Joined: Apr 9, 2009
    Posts: 416

    tig master
    Member
    from up north

    Acceptable but blue smoke is usually worn valve guides.

    T
     
  3. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,657

    Rusty O'Toole
    Member

    That is excellent. "perfect" would be 110 - 120 depending on compression, yours is probably a low compression head.

    Has it been out of commission for a while? Or has someone filled it with thick oil? Either of these conditions will increase oil burning.

    I would change to 10W30 oil and drive it. Give it an oil change every 1000 to clean it out if the oil gets dirty fast. Does it have a bypass oil filter? They only need changing every 5000 to 10000.

    Questions:

    When does it smoke? Under acceleration (probably rings) when you lift off the gas (probably valve guides)

    Is the road draft tube clear and does it have the proper filter oil fill cap?

    Has it been off the road long?
     
  4. El Tortuga
    Joined: Aug 24, 2006
    Posts: 125

    El Tortuga
    Member

    Thanks Rusty, Yes its an old farm truck 47 Dodge 1/2 ton. It has sat mostly for a number of years. I haven't changed the oil yet or checked a whole lot out I just bought it. I just wanted to make sure I had something to work with that's why I did the compression check. I have only yard drove it, no brakes yet, so really don't know about what its like under actual driving conditions. It has major carb trouble but the blue smoke is getting pretty consistent. When I first brought it home it would smoke and then stop and start at idle really weird. I have had other flathead mopars and this motor feels strong despite the smoking that's why I did the compression check because it doesn't act worn out power wise. I will look at the draft tube further and the filter set up because it is been jacked with and doesn't look factory. An oil change also. It is a very typical old farm truck everything has been half assed. Thanks for the questions it gives me a little guidance.
     

  5. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,657

    Rusty O'Toole
    Member

    You say things have been half assed repaired, that would be the first thing to check out.

    But, if everything is as it should be, it is possible the rings are stuck from sitting. In that case you may need to break in the motor. Start by going for a drive of 10 or 20 miles, work your way up to longer drives. If you can take it out on the weekend for 20, 50 miles or more the rings should soon loosen up. The engine has to be thoroughly warmed up. You should notice the smoke lessened or stopped by the time you drive it 1000 miles. But, short trips won't do it, you need to get it completely warmed up.
     

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