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  1. #1

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    Question 4Tec Low Compression 60% leak-down - Confused

    Looking for everyone’s technical input.

    08 challenger 230 with twin 215s

    One engine has been using coolant and oil. I taped an overflow bottle to the coolant reservoir and did a WOT run and the bottle was full - indicating a head gasket as I suspected.

    Visual inspection I see oil running out around the head gasket, valve cover gasket, water pump hole, oil cooler o rings…etc. pretty much if it has a rubber oring or gasket it leaks. So I degreased the engine so it was spotless if oil. Ran it again and oil appeared around the HG and the valve cover gasket within a day.

    Today I brought the boat home, did a compression and leak down test. Unfortunately these were done stone cold after the boat has not run for a week. I also did the same on the good motor to compare results. I am confused how it can run!

    Engines cold:

    Bad motor:
    35psi, 55psi, 55psi
    All plugs out.
    Leakdown - 50%, 60%,60%
    I can hear air through the dipstick hole since I took it out.

    Good motor:
    90psi, 90psi, 90psi
    All plugs out
    Leakdown - 10%, 10%, 14%

    I am in the process of pulling the head on the bad motor but what I was trying to see is if the rings are shot. I really don’t want to have to rering it unless I am sure.

    Since I know the HG is shot how can I really tell if the motor needs new rings or not when the HG seems to be leaking.

    The motor NEVER smoked blue or anything. It always started right up and ran great. Boat always did ~ 50mph and the only reason I am pulling the head is due to the coolant loss and I am not sure about the disappearing oil. I figured it’s a different issue , and not the rings. Only because it goes through about a quart every weekend 2-4hrs of runtime. If it were burning it I figure I would see it blue on the trailer or on plane. Here is a picture of the plugs.

    One plug just looks wet because the spark plug tube had oil in it that ran down the threads amd I could not tip it up straight before the oil got to the electrode.

    Tore the head off amd the HG the black rolls off like gelly. Possibly the problem? Someone was in there before since I could tell the m6 head bolts were half rounded over.

    i really don’t want to pull the block and rering it if I don’t have to.

    thoughts
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  2. #2
    Site Admin Green Hulk's Avatar
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    Quote Originally Posted by turbosl2 View Post
    The motor NEVER smoked blue or anything. It always started right up and ran great.
    I would say that your rings are fine, your issue is just the head gasket.
    Also, go back with these ARP head studs, the stock head bolts suck
    https://www.4-tecperformance.com/ind...roducts_id=546

    don't forget new rocker shaft bolts
    https://www.4-tecperformance.com/ind...roducts_id=822

    head gasket
    https://www.4-tecperformance.com/ind...roducts_id=823


  3. #3

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    Quote Originally Posted by Green Hulk View Post
    I would say that your rings are fine, your issue is just the head gasket.
    Also, go back with these ARP head studs, the stock head bolts suck
    https://www.4-tecperformance.com/ind...roducts_id=546

    don't forget new rocker shaft bolts
    https://www.4-tecperformance.com/ind...roducts_id=822

    head gasket
    https://www.4-tecperformance.com/ind...roducts_id=823


    I hope so! The cylinders look fine visually but it did use oil (but leaking like a faucet everwhere around the head) and gurgled through the oil during leakdown test(as i mentioned above). I suspect if the gasket is in that bad of shape like i have it could leak everywhere, lol. There was no visual indication the gasket was leaking in a certain spot, but EVERWHERE, lol. The plugs to me...feedback welcome, i figure would show signs of oil burning if it were the rings.

    You are giving me what i want to hear thats for sure, dont want to pull it apart for no reason.

    I actually just ordered all the OEM stuff. Now i wish i got the studs and not the bolts. Maybe i will just order the studs anyway.

  4. #4

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    how much do you trust your compression tester? Those numbers on both engines are extremely low.

  5. #5

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    Quote Originally Posted by toxicgun View Post
    how much do you trust your compression tester? Those numbers on both engines are extremely low.
    not very much based on how it runs like new, lol! Just more interested in comparing both engine numbers. New head gasket is installed. Just waiting to put the rest of the engine accessories back on and we shall see if the HG coolant leak is fixed it. Also pto bearing had no clamp around the boot to bearing. Figure this is my oil problem. Coolant leak was def filling overflow and gasket is shot due to overheating I suspect…based on the black coating rubbing off like jelly.

  6. #6
    gone fishing sucks2bu's Avatar
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    I bet you are using a harbor freight compression gauge. I have two sets I bought when I forgot mine at home and went out of town to work on customers skis. Both sometimes read right other times read 90 psi only.

    Change your h/gasket and go have some fun. Your engine is fine. Ohhhh on the head studs. I tore the threads out of a block using them. Be careful.

  7. #7

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    Quote Originally Posted by sucks2bu View Post
    I bet you are using a harbor freight compression gauge. I have two sets I bought when I forgot mine at home and went out of town to work on customers skis. Both sometimes read right other times read 90 psi only.

    Change your h/gasket and go have some fun. Your engine is fine. Ohhhh on the head studs. I tore the threads out of a block using them. Be careful.
    Yup it is. That’s why I am not to worried about it. I just hope the HG fixes the leakdown test results, obviously from the pics it was leaking everywhere, lol.

    I do appreciate the vote of confidence it does make me feel better. All head BOLTs (OEM) are installed and torqued to spec and holding well. Lots of oil helped. We shall see

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