Apr 102012
 

I have been working on the engine in my blazer for a few weeks now. I started by getting a crank kit to put in it and replaced all the gaskets when I put the engine back together. I got everything put together and set the timing and got it started. I noticed that after I started it that I have a slight knock coming from somewhere on the driver side of the engine. I first thought it was from the fuel pump but I removed it and started the engine while it was off and still had the knock. The pistons and ring are in good condition the valves and push-rods look good. I adjusted the rocker arms to specifications listed in my Chilton manual. I am currently waiting on a rebuilt carburetor to arrive because mine sat for awhile and doesn’t want to work properly. My question boils down to what can be causing the knock in my engine.

  4 Responses to “1985 chevy blazer s10 2.8l v6”

  1. It is possible that a wrist pin is worn.
    It is possible that you had play in the rod bearings… did you plastic-gauge them before installation?

    If you have the valve timing off.. the valve might be hitting the top of a piston.

    You can use a bore scope and look into the spark plug hole and hand crank the engine over an see what the valves are doing.

    Also, in some cases a blown exhaust manifold gasket can sound like a knock…. just a thought.

  2. I replaced the exhaust manifold gaskets. I also checked the clearance on the crank when I put it in. As for the valve timing I made sure that piston 1 was up and that the timing marks on crank and cam lined up when reassembling the engine.

  3. Sometimes if the oil pump isn’t primed properly before starting the engine it can take out a new bearing in seconds…

    if you are certain it is a knock and not a tick(lifter not pumped up all the way yet) then you may be looking at taking it back apart and inspecting. Make sure the oil pump and pick up tube are not touching something, etc.

  4. I guess it could be a tick because its not very loud and if you rev the engine up very far it quiets down to where you can’t hear it anymore.

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