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  1. #1
    suck my wake's Avatar
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    No Compression on New Rebuild

    Has anyone that has rebuilt any of these 4-tec's had an issue with the rings being bad right away. Brand new oversized pistons and rings and low compression on one cylinder, barely 50 psi and it still runs just runs like it has a miss. I checked everything and all I can come up with is bad rings................has anybody ever encountered this issue???

    New Rings are on the way

    Before you ask:

    Checked all the valves even the other cylinders
    checked and re-checked the cam timing
    checked the lift on all cam lobes
    new bore and hone, cylinders are mint
    head and deck are straight no warpage


  2. #2
    Got Boost? psycho rxp's Avatar
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    Quote Originally Posted by suck my wake View Post
    Has anyone that has rebuilt any of these 4-tec's had an issue with the rings being bad right away. Brand new pistons and rings and low compression on one cylinder, barely 50 psi and it still runs just runs like it has a miss. I checked everything and all I can come up with is bad rings................has anybody ever encountered this issue???

    New Rings are on the way

    Before you ask:

    Checked all the valves even the other cylinders
    checked and re-checked the cam timing
    checked the lift on all cam lobes
    new bore and hone, cylinders are mint
    head and deck are straight no warpage

    What valve spring retainers are u using?
    Any problems installing the pistons or rings into the cyls? (maybe a ring broke,or something?

  3. #3
    suck my wake's Avatar
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    Quote Originally Posted by psycho rxp View Post
    What valve spring retainers are u using?
    Any problems installing the pistons or rings into the cyls? (maybe a ring broke,or something?
    This is a completly stock rebuild, the motor is not modified. The only mods to this ski are an X charger and RRFPR.
    There were no issues with the install but they are coming back out today, I'll know the ring condition soon.

  4. #4
    If you have the tools, you might do a leakdown test on the motor. That should tell you where the problem is. If it's rings you should hear air escaping into the crank case. If the valves are the problem you'll hear air coming out of the intake or exhaust. If the head gasket is not seated you'll hear air coming into the coolant tank.

    Mark

  5. #5
    suck my wake's Avatar
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    I did that and the only place that you can hear air is "bubbleing" in the crank case. BUT on every 4 tec motor that I have worked on you can hear that same noise. Like when you put the riva valve kit on, same noise. I don't think that the factory rings seal all that well to begin with compared to most hp aftermarket ones.

  6. #6
    When I rebuilt my motor I had 165 psi compression on all cylinders cold, before the motor was run and broken in, and and 135 psi hot. That's with a decked head and racing cam advanced 3 degrees. Sounds like a ring or honing problem. That sucks.

    Mark

  7. #7
    Gone in 3.0 seconds... RXPT400's Avatar
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    When you installed the piston rings you are supposed to place the gap of each ring within 120 degree of each other to get a good compression reading maybe that is where your compression is escaping if the gap on the rings are lining up straight down in order. just double check on that.......

  8. #8
    suck my wake's Avatar
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    Quote Originally Posted by RXPT400 View Post
    When you installed the piston rings you are supposed to place the gap of each ring within 120 degree of each other to get a good compression reading maybe that is where your compression is escaping if the gap on the rings are lining up straight down in order. just double check on that.......
    I always set the rings up @ 120 degrees of each other, this is not just as simple as that. Wish it was

  9. #9

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    Quote Originally Posted by suck my wake View Post
    I did that and the only place that you can hear air is "bubbleing" in the crank case. BUT on every 4 tec motor that I have worked on you can hear that same noise. Like when you put the riva valve kit on, same noise. I don't think that the factory rings seal all that well to begin with compared to most hp aftermarket ones.
    Did you cut the valves or seats? If so you might have the valves too deep in the seats, causing them not to seal when the engine is running. In some cases this problem can't be found in a non running engine because the hydraulic tips of the rocker arms aren't fully extended. Check the valves installed height or look for a stuck tip.

  10. #10
    suck my wake's Avatar
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    Quote Originally Posted by JEBLASINI View Post
    Did you cut the valves or seats? If so you might have the valves too deep in the seats, causing them not to seal when the engine is running. In some cases this problem can't be found in a non running engine because the hydraulic tips of the rocker arms aren't fully extended. Check the valves installed height or look for a stuck tip.
    Nope, the head wasn't messed with other than cleaned and inspected

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