Question on Steam Holes

Discussion in 'The Garage' started by goldwing2000, Mar 19, 2007.

  1. goldwing2000

    goldwing2000 Guest

    Ok, just tore down my 400 4-bolt (3951511) and noticed a couple interesting things.

    First, it appears to be numbers-matching, or at least all the parts are from the same year ranges.

    Second, the valve seals were completely wasted and the intake valves all look like they have lava rocks on them. :rolleyes:
    Are there better seals to use than the little bands around the valve stems? I've seen umbrella-style seals but I have springs with dampeners, so I don't know if there's enough room in there for them.

    Third, it's been bored .030 over already. I hope the cylinders aren't too worn! :eek1:

    Fourth, five of the tips of the exhaust valve stems have serious chipping/erosion around the edges. Never seen something like this before. :thinking:

    Fifth, the head gaskets did not have steam holes. The heads have 'em and the block has 'em but the gasket didn't. This was the biggest surprise and my biggest concern.

    I've done some reading and it seems that some people use gaskets with steam holes and some don't.

    Pros? Cons? Discussion!

    Also, since I have your attention, is there any real down side to using the 76cc 333882 heads?
  2. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

    Dec 14, 2001
    Likes Received:
    Pleasanton, CA.
    If the head gaskets don't have steam holes the engine will over heat. You can run any head you want as long as you drill the steam holes in the heads you want to use.
    Have the block magnafluxed in the lifter valley as those 400's are prone to cracking there and especially if the engine was running without steam holes in the head gaskets.
  3. goldwing2000

    goldwing2000 Guest

    Well... I'll have to disagree with you, there. I ran this engine from 1997 when I bought it until 2005 when I bought my Blazer and it never over-heated.

    I can't imagine it was very happy about the obstruction but it always ran just fine. I had a mechanical temp gauge, so I know it never got too hot. *shrug*
  4. ntsqd

    ntsqd 1/2 ton status

    Nov 28, 2002
    Likes Received:
    So. CA
    What was the hottest dryest conditions that you ran it in?
    Out here I'm pretty sure it'd overheat in the Mojave in the summer.

    I've read of drag racers drilling the block w/ an airframe drill bit from the outside of the block ~1/4" under the deck connecting those steam holes. Then they tap & put an NPT plug in the 'access' hole. Anyone have any experience doing that?

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