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351W Foaming Coolant / Head Gasket?

Discussion in 'The Hokey Ass Message Board' started by AAFD, Dec 20, 2010.

  1. AAFD
    Joined: Apr 13, 2010
    Posts: 585

    from US of A

    Got an OT truck with a 351W. Bone Stock.

    Truck has been parked for almost a year, but ran great before it was parked. A couple months ago I went to start up the truck and move it, but the starter just went "THUNK". I tried to turn the motor by hand and it didn't move. So I started looking for another shortblock to replace this one. Today I figured I would pull the plugs and soak the cylinders and see if that was the culprit.

    When I removed the #3 spark plug, a drop of water hit the exhaust manifold. Hmmm. So I look at the plug and it's rusty inside. So I blasted the cylinder with air and it sprayed out some water. First thought...blown head gasket. I soaked the cylinders in PB Blaster, MMO, ATF/Acetone. Gave it about 20 minutes and cranked the engine and it spun. So I soaked it again, gave it another 20 minutes, and it spun free. I cleaned up the plugs and installed them, ran the motor for about 20 minutes. It poured smoke out the tailpipe for about 10 minutes then cleared up. Temp was good, oil pressure good, ran great.

    So I changed the spark plugs for new ones, changed the oil & filter, added some MMO to the oil, and topped off the transmission & brake fluid. While it was idling I popped the radiator cap to check it's level and the coolant was foamy. Hmmmm.

    I aired up the tires and took it around the block, came back and got my wallet, then headed to the gas station. Drove about 10 miles and it never got hot.

    There was no trace of coolant in the oil, no trace of oil in the coolant.

    I'm wondering if I have a cracked head or a blown gasket?

    Any ideas? I'm thinking of trying to find some better heads anyway because I have a cam/lifters/pushrods/double roller timing chain/headers/billet hei dizzy/intake/carb all new sitting in boxes but was hoping I could limp this critter along for a while before I dug into the motor to install the new parts. It would make sense to do everything all at once.
  2. I wish that I could tell you the answer to this question but I'm just learning about mechanics as I go along with my car. I have a 351W and C6 in my '54 that I'm learning and cussing at all the time. If you decide that its too much trouble to repair and want to get rid of the parts you bought, let me know.
  3. Merlin
    Joined: Apr 9, 2005
    Posts: 2,546

    from Inman, SC

    A crack is possible but I would lean more towards a blown head gasket that is blown between a water passage and the cylinder since nothing is present in the oil.
  4. grapp
    Joined: Aug 16, 2008
    Posts: 457


    Rent/borrow a pressure tested and test it!~

  5. stealthcruiser
    Joined: Dec 24, 2002
    Posts: 3,748


    There is a kit made, that detects combustion "gases", in the coolant, but not sure of the name of it.......................It works in the "litmus paper" fashion, as you didp the strip of test paper in the coolant.
  6. You need to find a combustion gas tester. I have a tube that you put colored liquid in, if it turns color, you know for sure that you have a head gasket problem
  7. I walked out to my truck one day (yblock) and it gave me the same THUNK! Cylinder #2 was full of water from a crack in the head that opened up. Remove the head and check for cracks or a blown gasket. It was about $200 for me to get the crack pinned, head milled and get a new valve seat put in. plus the cost of gaskets.
  8. p.s. get a pressure tester and hook it up to your radiator to determine if there is a leak...
  9. AAFD
    Joined: Apr 13, 2010
    Posts: 585

    from US of A

    I tested compression in all cylinders and got 140 across the board. Don't have any other testers, but can probably borrow one although it really doesn't matter because something is definitely wrong and either way the heads need to come off. I'm doubting it's a cracked head only since it has never gotten hot, but not ruling it out. Seems more likely to be a blown gasket. I'm going to try to locate another set of heads that perform a little better than these terrible 80's heads and in the mean time, pop these heads off and see what the issue is.

    Thanks for the replies folks.
    Last edited: Dec 20, 2010
  10. I'd bet on a bad head gasket or possibly an intake manifold gasket that is letting water into the combustion chamber. You could give it a dose of Block Saver and buy some time, but for reliability it should come apart and have everything looked at closely.


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