Possible for oil to leak from head gasket on SBC 350 gen 1?

Discussion in 'Engine Topic' started by hpp, Dec 19, 2017.

  1. hpp

    hpp New Member

    Jul 29, 2016
    New Jersey
    Hello. I have a 1974 SBC 350 with stock heads (462624). It just started leaking a lot. A steady drip every second or so. It is coming from the rear driver side. I spent a lot of time looking at it and am having a hard time digesting what I found. The engine is very clean as I removed, cleaned, painted it recently. Here are the things that are not leaking: valve cover, oil pressure gauge fitting, intake manifold, distributor flange. I can see oil weeping out of the bottom rear corner of the head at the seam between the head and block. I really didn't think this was a possibility. I can wipe it and see it seep out immediately. It's not running along the block from the intake. Seems incredibly unlikely to me that oil could leak from this spot.

    Has anyone seen this before? If the head cracked, would this be possible? The engine otherwise runs great. I would really appreciate your feedback and advice before I remove the head.

    I also understand that my head casting number is one of the bad ones that are susceptible to cracking. I have no experience with cracked heads.

    Thanks you.
  2. woody80z28

    woody80z28 Veteran Member Lifetime Gold Member

    Sep 8, 2004
    walton, ny usa
    I have had slight oil seepage that seems to be coming from the heads on both builds I've done with Felpro 1094 .015 head gaskets. We're talking very light seepage that accumulates over time though. I have never seen a drip like you're describing.
  3. badazz81z28

    badazz81z28 Veteran Member

    May 4, 2001
    Las Vegas, NV
    I would think not....There are no oil passages between the block deck and the head, only water. The oil drains back into the engine from the inboard side and falls down into the valley. Oil is either coming from the oil pressure sensor area, valve cover, the china rail on the intake manifold or worse a crack that leads into an oil passage that just happens to be in that area.
  4. cadillac_al

    cadillac_al Veteran Member

    Apr 22, 2015
    I think the oil is leaking out the back of the intake manifold and running down the slight crack between the head and block making it look like it is coming from the head gasket. Been there done that. I could have sworn oil was leaking from a head gasket but I knew it was very unlikely. I asked other mechanics and they said it isn't likely. After I looked at it long enough I realized there was enough of a gap for oil to travel in and make it look like it was coming from the head gasket. My money is on a leak at the very corner of the china wall.

    edit. Oh yeah, are these mls head gaskets by any chance? I wouldn't think so with stock heads but just a qualifier. Some of those gaskets will leak if they don't extend all the way to the intake gaskets/china wall.
    Last edited: Dec 22, 2017
    John Wright likes this.
  5. 77 cruiser

    77 cruiser Veteran Member

    Nov 17, 2006
    Frostbite Falls MN
    100_4502.JPG Could be the plug on the upper deck.
  6. biker

    biker Veteran Member

    I had this very problem with Felpro MLS gaskets on my 383 build. Same here, looked for all the world that the head gasket was leaking oil. Turned out the gaskets were a bit short of the china wall and seeped oil at those corners.
  7. woody80z28

    woody80z28 Veteran Member Lifetime Gold Member

    Sep 8, 2004
    walton, ny usa
    Hmmm...I wonder if that's the issue with mine. I was liberal with the RTV on the China wall, but I wonder if there was a little bit of a void in the corner... does it on both sides of both engines so it seems systemic.
  8. Todd80Z28

    Todd80Z28 Moderator Staff Member Lifetime Gold Member

    Jun 11, 2002
    Northern VA
    This. The hole with the pencil in it is a pressurized oil passage.

    I have the same problem, though not a drip a second. I've been too lazy to fix it... for 10+ years.:)
  9. hpp

    hpp New Member

    Jul 29, 2016
    New Jersey
    All, thanks for your feedback. For various reasons (holidays, sub freezing weather, work) I haven't had the chance to further investigate my leak. When I do, I'll update the post to let you know what happens. Thank you.

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