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Thread: Catastrophic engine failure???

  1. #1
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    Catastrophic engine failure???

    Hi all...I've been pretty silent because all has been well until recently.
    The year before last I upgraded to the Blueprint small block engine Model MBP3550CT which is basically a 350 .040 over with some fancy sounding parts. For exhaust i went with the Stainless Marine manifolds with the pretty stainless elbows. I don't have straight throughs though I have the rare S tubes that moves exhaust discharge to the water line.
    First year no problems ran really good...no serious issues.
    Second year (after warranty experatation) I started to experience a gradual decrease in WOT RPM's...Then it started to run like I dropped a cylinder. Diagnosis proved that I had wiped a couple of lobes on the relatively mild cam.
    Replaced the cam and lifters (flat tappet hydraulic) and it seemed to run OK but I couldn't keep water out of my crankcase...Not a lot...Just enough to milk up the oil. Reset the intake manifold...Still H2O in oil...Pulled off the heads and saw that both gaskets had issues and there was evidence of water in the back four cylinders, And it gets worse...Two broken pistons have pieces broken off between the outer top edge and the first set of rings. Numbers 5 and 6 are the damaged cans...Is this a classic reversion issue? The cam is not really radical and I checked with a couple of guys on the board and they assured me that I'd be OK. Are these Keith Black Hyperuetectic (?) pistons available with the apparently pedigreed rings available. This really sucks...I've been battling with this thing since August and I'm just about out of money and patience...Any suggestions would be greatly appreciated. Thanks,Mike
    Mike Pankok
    '86 Minx #44
    '66 14' Glastron Skiflite 50HP
    '75 MG Midget
    '01 Mustang GT Conv.

  2. #2
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    Marine cams

    A marine cam is unlike any other engine camshaft because the exhaust valve must be shut at top dead center to prevent water from being taken in on the intake stroke.

    In automotive engines the intake and exhaust valves are open at the same time in what is called "valve overlap." In this overlap situation the exhaust remains open past top dead center and the intake is open early before the intake stroke. This allows the intake valve to be fully open while the exhaust is exiting under pressure. In this automotive type engineering, the exhaust can pull some intake charge into the exhaust system and the cylinder which results in more power because the cylinders are more fully filled with the fuel air mix.

    Marine engines are engineered differently because of their proximity to water. Some manifolds and pipes barely above the waterline when the boat is not running. Water is also sprayed into the manifold not too far past the exhaust valves to cool the exhaust gasses for muffling and fire protection.

    If you are not using a bonafined Marine Cam you are very likely pulling water into the cylinders from the wet exhaust. This is called "reversion." "Injestion" is when sinking or a wave or other rocking of the boat back fills the engine from the sea.

    A bunch of guys saying a cam is "ok" is no way to qualify a cam. Who are the guys what is their marine experience? Crane Cams profile for say the 500EFI racing engine show the exhaust valve fully closed at TDC. This is no automotive engine cam.

    Tyler Crockett and other marine engine builders are using dry exhaust systems and getting away with automotive racing cams. This means the water is not sprayed into the exhaust gas to cool it. They use a water jacketed exhaust that dumps water overboard separate from the exhaust system - the exhaust gas is loud and hot and usually well above the waterline.
    Dr. d

  3. #3
    mrfixxall Guest

    fixx

    were do you have the timing set at?

  4. #4
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    Dr. David thanks for the lesson on marine camshafts. I was aware of this problem but not really clear on the exact cause. Makes sense now with your explanation.

    Thank you, this place is a rolling history and technical lesson. Wish I had more to contribute.

  5. #5
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    I had the ignition (Thunderbolt IV) replaced by my local marine mechanic...
    I believe he said his final timing was 38 degrees total...
    The stock ignition module didn't match the new motor.
    Mike Pankok
    '86 Minx #44
    '66 14' Glastron Skiflite 50HP
    '75 MG Midget
    '01 Mustang GT Conv.

  6. #6
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    38! Not on a bet for marine fine for street, to much unless everything is at absolute perfection very hard to achieve with today's available fuel. Why was the IV not a match for your engine? I run a pretty expensive stroker motor and use the stock IV as do many it is very reliable, all I did was add a hot coil. I think your mechanic handed you a bill of goods!
    No matter what your beliefs are "GOD BLESS AMERICA"

    Fully retired marine tech near 60 years in the biz.

  7. #7
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    First off...those KB Hypereutectic pistons are total bullsh*t.
    I broke the top of my pistons in the same way you're describing. The factory won't warrantee them. They'll tell you that the top ring was inproperly gapped. I did this 3 times before I met my present machinist who after describing to him what was happening, pulled a piston out of a box and said, "Is this what your piston looks like?" And yeah...the breaks were identical.
    Nothing will beat a good set of forged pistons, and the way we run our boats, we need 'em.
    Another thing they will tell you is that your spark timing is off. And if what the guy is telling you is true...there might be some truth to it.
    Check this out...
    http://www.boatfix.com/merc/Techbk/95/95HGB4.PDF
    Marine cams do have a special cam timing/lobe spacing to prevent reversion. I forget what the spec is, but look at the marine cam specs from say, Crane, or one of the other manufacturers. You will see the difference.
    Finally, not much can beat the Thunderbolt IV or V for exacting spark timing and spark voltage. It's one of the best marine applications out there.
    I had a client with the marine MSD and he had nothing but trouble with it, though the factory was really nice about things, he ended up getting rid of it and going with the Thunderbolt and never had a spark problem again.
    Sorry about your motor...
    GeneD
    007
    Formerly of Melbourne, Florida
    Permanent Resident of St. Petersburg, Florida
    1966 Classic 18-2+3

  8. #8
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    Added not the stock Merc recommendations are for stock setups, in our lighter boat and looking for better performance you can go higher. I have gone as high a 34 with good fuel, I found only a little above the 30 that I normally run. High ignition settings are spooky unless everything is spot on, in my opinion should not be used for every day running. Thinking about your cam, did you break it in in the recommended manner? Flat tappet cam should be broken in at about 2500 RPM for 15 minutes, you cannot get away with babying a flat tappet. Also it is highly recommenced that you run motorcycle oil which has a higher zinc content, zinc has been removed from automotive oils giving flat tappet cams a much shorter life span. Automotive oil is just fine for roller setups, but due to the loads on our engines roller or not only the best oils should be used. Many think our boats engine are much like our car engine, that could not be farther from the truth. Take the time to do decent research before you put it back together and use a knowledgeable marine mechanic, they know what even good car mechanics do not!
    No matter what your beliefs are "GOD BLESS AMERICA"

    Fully retired marine tech near 60 years in the biz.

  9. #9
    mrfixxall Guest

    Fixx

    ok 38* is too too muxh,,next ? who's cylinder heads? vortech's ?

  10. #10
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    you should stick to 30-32* total timing on fast burn or Vortec heads

    a 22* module and 10* initial should be plenty
    Charter Member - WAFNC, SBBR, KWOSG
    1955 Perfect Mate
    1986 Hornet III, 502-415 TRS

    www.donzi.org


  11. #11
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    -----"Brad Penn" oil (google it) for break-in oil. Made specifically for new flat-tappet cam motors. Have broken in several new cams with no problem......Bill S

  12. #12
    mrfixxall Guest

    Fixx

    Quote Originally Posted by BUIZILLA View Post
    you should stick to 30-32* total timing on fast burn or Vortec heads

    a 22* module and 10* initial should be plenty

    +1,,you beat me to the punch line

  13. #13
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    Quote Originally Posted by Dr. David Fleming View Post
    A marine cam is unlike any other engine camshaft because the exhaust valve must be shut at top dead center to prevent water from being taken in on the intake stroke.
    Hi Dr. D, your posts are always filled with a bunch of info, but just so bad info isn't passed on I've got to say this is not true. Unless you mean the top of the compresion stroke when everything is closed. ALL four stroke motors run some degree of overlap, how much there is says a lot about how much power you will make, how much you can get away with without reversion has a lot to do with the exhaust style and the engines internal sizes, mostly how much valve is feeding how much cylinder.
    Maddy's Daddy
    L.I.,N.Y.

  14. #14
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    I think I may be dealing with two separate issues here...
    I'm blaming the wiped cam lobes on the factory break in procedure.
    Rotella-T (high ZDDP content) then switch to synthetic (low ZDDP content).
    The manufacturer changed their recommendation and now warns of low ZDDP oil. It just seems strange that I beat the thing pretty good the first year and had no issues.
    As for the pistons...I'm thinking reversion with bad timing setting...
    My marine mechanic said he had to "power time" it. I don't know what that means but it doesn't sound good.

    The plan is to install high quality forged pistons and weld tails on the risers to divert the water as far back as I can. Timing will be set (by me) to the Blueprint specifications. Although I never experienced any temperature spikes I did notice a less than adequate impeller on my Alpha One water pump too...

    My plan is subject to change if you all think I'm doing something stupid...
    THANKS FOR ALL THE RESPONSES!!! Mike
    Mike Pankok
    '86 Minx #44
    '66 14' Glastron Skiflite 50HP
    '75 MG Midget
    '01 Mustang GT Conv.

  15. #15
    mrfixxall Guest

    Fixx

    extending the tips wont do anything with out seperating the water from the exhaust all the way through the s pipe to the tips..what is the correct cam spec's? just trying to save you from doing all the extra work that is not needed..

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