Wrong Head Gasket? Knocking after rebuild

Discussion in 'Classic Mustang Specific Tech' started by ks65stang, Apr 2, 2013.


  1. ks65stang

    ks65stang Member

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    OK so I had my 289 machined and bored .040+ and crank ground -.010 and I rebuilt the engine myself w/ rebuilt GT40 heads. I used the correct bearing, etc.

    I noticed a knocking after the rebuild, which sounded a lot like a lifter knock, and I went all over the engine w/ a stethoscope and was not able to pin down the knock. I started reading and thought it was rod knock so I pulled the pan and all the rods are nice and tight but I noticed the oil was a little milky.

    So, I started thinking maybe I have a blown head gasket? Maybe the GT40 head valves and my flat top pistons are hitting. Maybe I put a piston in backwards or maybe it’s just a bad lifter(s)?

    I pulled the intake and then the drivers side head (still need to pull passenger side head) and I found no evidence of the valves hitting the pistons or a backwards piston. I did discovered that the back cylinder was much darker than the other cylinders and the back plug was much darker. I then noticed the head gasket I used doesn't have holes for the back coolant passages (see pics)? Also in the photos all the cylinders look clean as I had to wipe down the cylinders because when I pulled the heads they filled w/ coolant, so I drained them, wiped dry and soaked w/ WD40.

    So in my amateur opinion......I used the wrong head gasket which caused the back cylinder (s) to get too hot, blow the gasket(s) and start allowing a small amount of coolant in the oil which screwed up my lifters and created the knock.

    What do you think?

    My plan of attack is to replace the lifters and reassemble w/ the correct head gaskets, add fresh oil and see what happens....

    Thanks in advance for your help.

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  2. ks65stang

    ks65stang Member

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    After searching for images of 289 head gaskets, I discovered I put the gasket on backwards....

    With this new info do you think my knocking was lifters damaged by water in the oil?

    So what should I inspect prior to re-assembling?
    #2
  3. woodsnake

    woodsnake Active Member

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    How long did you run the engine? Did you put in a performance cam kit?
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  4. ks65stang

    ks65stang Member

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    Engine ran long enough for a break in for the new cam. which is a Summit knock off of a Performer cam. Ran about 30 minutes during break in, a couple dozen other times for timing and trying to find my knock and 1 trip around the neighborhood. Longest run was 30 minutes for the break in and the rest of the runs were about 10 minutes or less, so it never got hot enough during these runs.

    I just pulled the other head and inspected all the cylinder walls and all look good. I pulled a few lifters and the cam lobes look good and little to no wear on the bottom of the lifters. Cam lobes are nice and sharp and look normal. I never had any signs of metal in my oil. I will take the heads to a machine shop this week to have magna fluxed to make sure I didn't crack them.

    As for the knock I'm still leaning towards lifters......it sure sounded like lifter knock....

    Do you oil soak your hydraulic lifters, pump them with a drill press and an old push rod to fill w/ oil or just lube, install and the prime the oil pump?
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  5. woodsnake

    woodsnake Active Member

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    Lifters don't usually make a knocking sound, if anything, they make a tick. The heavier "knock" sound is usually referred to in a bottom end/ connection rod kind of way. Did you check your bearing clearances before assembly? Any idea why you have the one plug that was so much darker in color than the others? I had a similar, "unidentifiable" knock, that sounded like it was coming out of my carb. One of my rocker arms had been set wrong, and the noise was actually backfire through the intake. I readjusted the lifters, and then had backfire out of the exhaust, because I now had a wiped lobe on my cam.
    This was my noise...
    http://s819.photobucket.com/user/woodsnake4462838/media/dbb25c9b.mp4.html?sort=3&o=10

    My third camshaft fixed the noise, but now I am having oil pressure issues, after the car warms up. It goes from 50 lbs cold, to 20 lbs when it warms up....
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  6. j69302

    j69302 Active Member

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    Pressure will drop as it warms up. What weight oil are you running? You might consider putting a thicker weight in.

    Also is this with a accurate gauge or a stock gauge? I have the original gauge and a auto meter gauge both installed, and while they both correlate together, but I don't trust either one of them as being anywhere near accurate.
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  7. ks65stang

    ks65stang Member

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    I did check bearing clearance during assembly w/ Plastiguage and everything was in spec. The darker plugs were in the hot (overheating) cylinders....so I'm guessing heat darkened them. There were no signs of oil or water in the cylinders. I have always had good oil pressure cold and hot. I have pedestal mount roller rockers w/ correct lifter preload, I will double check the pre-load again during re-assembly.

    I pulled the piston that got the hottest during break in, #4 and found no damage to the rod bearing, cylinder wall, piston or rings. My heads are now at a local machine shop that specializes in head work so they can inspect, once I get them back and no damage I plan to reassemble, fire it up and I will report back.
    #7
  8. Mr67Stang

    Mr67Stang Active Member

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    The "darker" coloration is the result of unburnt fuel building carbon deposits in the cyl. If it were burning hotter (too hot), it might be whiteish grey from ashy deposits. Rusty brown is the normal color deposited under normal burn.
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  9. ks65stang

    ks65stang Member

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    Head gasket replacement completed and at start up and idle the engine still knocked. I ran it for about 30-40 minutes, at different RPM's in neutral w/ no load on the engine and after a while the knock seemed to disappear and reappear but mostly disappear especially at higher RPM (could have been hidden by engine noise) I can hear some noticeable lifter noise when I first rev the engine up from idle to a higher RMP (2-3K) and then it settles out while maintaining the RPM. I assume increased oil volume from higher RPM is quieting the lifters.

    The engine is no longer overheating and temps from cylinder to cylinder seem to be in a reasonable range.

    I'm gonna let the engine cool and start it again tomorrow and see what it sounds like. The engine has no miles on it since rebuild and about 2-3 hours of run time. It might need to just break in? I have good oil pressure at idle and throughout all RPMs (60 psi cold and then ran about 50 PSI warm). I'm running 10W30.

    My dad will be in town this weekend and I'm gonna let him take a crack at it and get his opinion. I might just need to drive this thing for 250 miles and get my head out of the engine bay in my tight 2 car garage and see what happens.....Maybe I'm just paranoid...........
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  10. blown65

    blown65 Founding Member

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    I doubt it will go away with break in, if it does I'd be worried the next thing is the following boom.
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  11. 65-Fstbk

    65-Fstbk Member

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    Good luck with this....I can feel the frustration you must be experiencing. I will be building my motor soon and am anxious to hear what the problem was. I hope it's nothing too serious for you. Please let us know.
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  12. 65-Fstbk

    65-Fstbk Member

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    Just had another thought. When they rebuilt the heads did that include new springs? If not, maybe you have a bad spring that's allowing components to bounce. Not sure if that's realistic or not, just a thought.
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  13. woodsnake

    woodsnake Active Member

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    Did you (OP) listen to the link I posted?
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