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  1. #1

    Default leak down test results

    Here are the findings from a leak-down test: I had the compresser set to 80 psi and I set the regulator on the leak-down gauge to 70 psi

    Cyl #1 down 2psi
    Cyl#8 down 4psi
    Cyl#4 down 9psi
    Cyl#3 down 5psi
    Cyl#6 down 22psi (air is coming out of the exhast port on the lower unit)
    Cyl#5 Down 2psi
    Cyl#7 down 4psi
    Cyl#2 down 2psi

    All of the air that is leaking from #6 is coming out of the exhaust outlet on the lower unit. I am gatherng that I have a problem with an exhaust valve and/or since it is a fresh water cooled engine, possibly the head gasket. I am still burning large amounts of oil, and the plug from number 3 and number 5 have a white calcium crust on them. The remaining six look pretty good, chocolate/dark brown.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  2. #2
    Join Date
    Oct 2011
    Location
    maplevalley WA
    Posts
    7,284

    Default Re: leak down test results

    Have you tried using seafoam. Bring the engine up to temp and at a high idle pour half a can of seafoam in the carb/s and immediately shut the engine down. Let it sit for about 1/2 an hour or so and then start the engine and run it between 2500 - 3000 rpm until the smoke clears. The more carbon the more it will smoke but it will clean the rings, valves and head/s. Let the engine fully cool and see if your compression/leakdown numbers are any better. Have you checked the advance curve of your distributor is to spec?

  3. #3
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    3,119

    Default Re: leak down test results

    A leak down test is the best way to tell what is going on with your engine. A Compression test is inconclusive.

    Your leak down is telling you that you have a bad exhaust valve, a stuck exhaust valve, or a tulip-ed valve. There is nothing wrong with the head gasket. If there was you would have pushed coolant into the over flow tank. Time to pull the heads.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Let the insanity begin.

  4. #4

    Default Re: leak down test results

    Overflow tank? It is a freshwater/open cooling system. By looking at the plugs, it looks as if there are a couple of cylinders that have valves that have leaking seals, as well as the fact that there is a bunch of oil consumption. Our season is over in about three weeks, I will pull the heads and test them for warp, cracks and do a solvent test to see if any other vavles are leaking/stuck. In the meantime, with the boat out of the water, I may try a couple seafoam treatments and see if that fluctuates my leakdown percentage in that cylinder.

  5. #5
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    3,119

    Default Re: leak down test results

    Fresh water cooled = heat exchanger with antifreeze. Raw water cooled = bay or lake water cools the engine.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Let the insanity begin.

  6. #6

    Default Re: leak down test results

    Thanks for the clarification

  7. #7
    Join Date
    Oct 2011
    Location
    maplevalley WA
    Posts
    7,284

    Default Re: leak down test results

    When you pull the heads have them magna fluxed first if you suspect a crack you will have a better idea looking at the head gaskets close.

  8. #8
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    6,975

    Default Re: leak down test results

    I would agree with Chris in that your leak-down test reveals an exhaust valve issue.
    A good machine shop will make magnaflux testing protocol.


    The term Fresh Water Cooled engine is often used in a misnomer fashion, and is often misinterpreted.
    Fresh Water to some means an open system (raw water cooled) when running in river/lake water (apposed to salt water)... and Fresh Water to others can mean a Closed System.
    The Dog Gone Heat Exchanger manufacturing companies even refer to these as "Fresh Water Cooling" systems! Sheesh!
    To me, there is nothing Fresh about Ethylene Glycol and H2O.
    Ya can't drink it, ya can't wash your hands in it, and ya can't brush your teeth in it! LOL


    We should actually be referring to these as either an "Open" system (raw water cooled), or a "Closed" system (heat exchanger w/ ethylene glycol).



    If this is a Closed Cooling system, then yes....... a head gasket failure would likely be pressurizing the cooling system, and would reveal itself.

    However, the OP says that it's an open system...... I.E., Raw Water Cooled!


    .
    Last edited by RicardoMarine; 09-02-2012 at 10:00 AM.
    Rick ... aka Ricardo
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

  9. #9

    Default Re: leak down test results

    I think I am going to tackle this repair myself...I am pretty handy with a wrench, have a pretty good shop and I have a Merc engine manual. I have three to four weeks left until the offseason, I am going to pull both heads and check for warp and magnaflux both. I with then analyze the #6 exhaust vavle, as well as solvent testing all other ports. I may get lucky and end up simply having to do some lapping, or work free a stuck valve. Anything above that, such as pitted seats, or bad valve guides, I may have the head(s) sent to a machine shop.

  10. #10
    Join Date
    Oct 2011
    Location
    maplevalley WA
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    Default Re: leak down test results

    Sounds like you have a plan. Before you put it down work up an advance curve for your distributors.
    base timing and rpm
    every 500 rpm write down the timing advance and engine rpm and all in advance and make a graph to show the curve on both engines.
    your issue could be a problem with ignition advance you want to determine that ASAP so you dont damage the engine any more.

  11. #11

    Default Re: leak down test results

    Quote Originally Posted by kimcrwbr1 View Post
    Sounds like you have a plan. Before you put it down work up an advance curve for your distributors.
    base timing and rpm
    every 500 rpm write down the timing advance and engine rpm and all in advance and make a graph to show the curve on both engines.
    your issue could be a problem with ignition advance you want to determine that ASAP so you dont damage the engine any more.

    Only one engine, good advice, though...thanks.

  12. #12
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    6,975

    Default Re: leak down test results

    Quote Originally Posted by nhuyck View Post
    ...... I may get lucky and end up simply having to do some lapping, or work free a stuck valve. Anything above that, such as pitted seats, or bad valve guides, I may have the head(s) sent to a machine shop.
    You have the cylinder heads off now, so you know just how much work it is to get into the engine this far.
    Why mess around with anything short of a complete cylinder head over-haul?

    BTW, should you find that these are both bad, be sure that you go back together with the same cylinder head combustion chamber volume.... assuming that this was correct prior.

    Quote Originally Posted by kimcrwbr1 View Post
    Sounds like you have a plan. Before you put it down work up an advance curve for your distributors.
    base timing and rpm
    every 500 rpm write down the timing advance and engine rpm and all in advance and make a graph to show the curve on both engines.
    your issue could be a problem with ignition advance you want to determine that ASAP so you dont damage the engine any more.
    Ditto this one!

    All too often we over-look how important the progressive ignition advance is, and how much damage incorrect advance can cause.
    We set BASE advance ONLY, and then we go our merry way.

    You should be able to find your OEM ignition advance curve specs.
    Follow this, and play it safe, or you may have a repeat!


    .
    Rick ... aka Ricardo
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

  13. #13
    Join Date
    Jul 2008
    Location
    , WV, USA
    Posts
    196

    Default Re: leak down test results

    If you have it down that far I would ditch the 2bbl setup for a 4bbl intake and carb just to have some added power once you get the other issue resolved. Might even look into a better cam. I know this has nothing to do with your valve issue but if it was me and I was already there I would add some more horses.

  14. #14
    Join Date
    Oct 2006
    Location
    Sherwood Park, Alberta, Canada
    Posts
    390

    Default Re: leak down test results

    Has the valve lash been checked on the engine?
    Bert

  15. #15

    Default Re: leak down test results

    Quote Originally Posted by 87concord View Post
    If you have it down that far I would ditch the 2bbl setup for a 4bbl intake and carb just to have some added power once you get the other issue resolved. Might even look into a better cam. I know this has nothing to do with your valve issue but if it was me and I was already there I would add some more horses.
    I enjoy the performance of the motor as it is, plus it gets fairly decent fuel mileage. At $4-$5 per gallon at the marina, I think I will leave the intake performance parts on the shelf.

  16. #16
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
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    6,975

    Default Re: leak down test results

    Speaking of valve lash..... when you go back together, I'd strongly encourage you to use the 8 stop procedure when setting your cam follower plunger depth (aka valve lash).
    IOW, don't be talked into using the 2 or 3 stop procedure. You will not gain the accuracy with the 2 or 3 stop.

    I'll also suggest that you do this prior to installing the intake manifold.
    If you want more details, ask.

    If not, then use the 2 or 3 stop, but I'd go back through them dynamically.

    BTW, forgive my old school technical jargin, but with hydraulic cam followers, you'll be setting the cam follower plunger depth and will have zero valve lash.
    + valve lash is typically reserved for mechanical cam followers.


    .
    Last edited by RicardoMarine; 09-05-2012 at 09:23 AM.
    Rick ... aka Ricardo
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

  17. #17

    Default Re: leak down test results

    Quote Originally Posted by RicardoMarine View Post
    Speaking of valve lash..... when you go back together, I'd strongly encourage you to use the 8 stop procedure when setting your cam follower plunger depth (aka valve lash).
    IOW, don't be talked into using the 2 or 3 stop procedure. You will not gain the accuracy with the 2 or 3 stop.

    I'll also suggest that you do this prior to installing the intake manifold.
    If you want more details, ask.

    If not, then use the 2 or 3 stop, but I'd go back through them dynamically.

    BTW, forgive my old school technical jargin, but with hydraulic cam followers, you'll be setting the cam follower plunger depth and will have zero valve lash.
    + valve lash is typically reserved for mechanical cam followers.


    .
    I have always adjusted valve lash by tightening the studs 1/2 turn past zero lash. I am not following the terminology of 2 or 3 stop, or 8 stop.

  18. #18
    Join Date
    Oct 2011
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    maplevalley WA
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    Default Re: leak down test results

    I think the 8 stop is the one I would use. Put the timing on TDC for # 1 cyl adjust valves at 3/4 turn past zero lash and follow the firing order put a thin screwdriver in the next plug hole and rotate the crank until the piston is TDC and adjust those valves do that for all 8 cylinders. Allways adjust the valve lash on a cold engine find zero lash and tighten all exactly the same. I`m reading 3/4 turn past zero but 1/2 is probably just fine with new lifters.

  19. #19
    Join Date
    Oct 2011
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    maplevalley WA
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    Default Re: leak down test results

    Oh yea find TDC on the compression stroke for #1 cyl stick your finger in the #1 plug hole and when you feel compression line the timing mark on TDC that is the starting point. The rest you use the screwdriver to find TDC for each cylinder.

  20. #20

    Default Re: leak down test results

    Quote Originally Posted by kimcrwbr1 View Post
    Oh yea find TDC on the compression stroke for #1 cyl stick your finger in the #1 plug hole and when you feel compression line the timing mark on TDC that is the starting point. The rest you use the screwdriver to find TDC for each cylinder.
    I was taught never to stick anything metal down the spark plug hole, it can make a nick on the pison head and create a hot spot/burr. I usually use something plastic that is longer than the stroke of the piston.

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