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  1. #1

    Default Replace head gaskets as preventative maintenance?

    So I've stripped down my Crusader 454's for cleaning, paint, new manifolds/elbows, etc. I bought this boat in August. Stbd motor reportedly has +/- 400 hours and compression is as follows...

    1 125
    2 120
    3 112
    4 125
    5 115
    6 128
    7 115
    8 135

    Not great, but not awful either. Port reportedly has +/- 1,600 hours with compression that are not too different from this. I'm OK with my speed and fuel consumption. My question is this... since I'm staring at the heads, should I just go ahead and pull them so I can replace the head gaskets? Just seems like the right thing to do, and will eliminate that potential problem down the road for some time. Or is it a waste of time and money? What do you guys say?

    Thanks,

  2. #2
    Join Date
    Aug 2008
    Location
    Fairport, NY
    Posts
    1,670

    Default Re: Replace head gaskets as preventative maintenance?

    FWC? If so, I would do a valve job on Port and not touch STB.

  3. #3

    Default Re: Replace head gaskets as preventative maintenance?

    Yes, FWC. I had thought about doing valves on both, but your thought of just doing the high-time side is a good one. Thanks.

  4. #4
    Join Date
    Dec 2006
    Location
    Chaumont Bay, N.y., USA
    Posts
    5,469

    Default Re: Replace head gaskets as preventative maintenance?

    Or is it a waste of time and money?
    Ayuh,.... If ya rebuild the heads,.... Yes, you'll need new head gaskets,....

    Otherwise,...........
    Any Grease is Better,... Than No grease at All....

  5. #5
    Join Date
    Aug 2008
    Location
    Valparaiso IN
    Posts
    32

    Default Re: Replace head gaskets as preventative maintenance?

    Pretty sure the rule of thumb is no more than 10% difference, since you started now is the time to do it right. Look at your numbers, 3,5,&7 are all on the same side, I would want to know if it's rings or valves and proceed accordingly. Remember, it won't get any better. If money is tight then do the worst one now and the other down the road.

  6. #6
    Join Date
    Jun 2006
    Location
    Spotswood, NJ, USA
    Posts
    4,185

    Default Re: Replace head gaskets as preventative maintenance?

    Not knowing HOW you did the compression test makes it hard to answer .Did you test the odd side first and then try to test the even side with a weak battery? Was the carb wide open during the test? Was the starter able to spin the motor briskly with all the plugs out?
    Never just do 1 side, always as a pair ,saves money on the gaskets

  7. #7
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    9,800

    Default Re: Replace head gaskets as preventative maintenance?

    Tizor, as you know, your cylinder pressure numbers are low.


    Questions:
    ...... Did you use a pressure gauge that was equipped with a hose/fitting? In other words, the style that threads into the spark plug port via the hose/fitting????

    ...... If so, how many compression strokes did you allow each cylinder being tested pass through? (the hose/gauge pressure will be accumulative and must see at least 3 C/S cycles.... or approx 7 crankshaft revolutions)

    ...... Did you also perform a cylinder "Leak-down-Test" on this Engine? If not, do so prior to removing the cylinder heads! This can be an instrument that will help you determine where your pressure loss is occurring.


    FYI and FWIW re; pressure test:

    The 10% differential rule applies to the lowest -vs- the highest cylinder pressures for a given engine. In your case.... #3 and #7 cylinders!

    The carburetor throttle plates do not need to be fully open during the pressure test........ however, they do need to be open above what would dictate high idle RPM.

    The advice re; all spark plugs being removed and a having fully charged battery is good.



    .
    Last edited by RicardoMarine; 01-03-2018 at 08:24 AM.
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

    Please... no PMs! Post your questions on the forum.

  8. #8
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    7,158

    Default Re: Replace head gaskets as preventative maintenance?

    Actually, the numbers are 'servicable' per the GM updated 'compression test' procedure....

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