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Rebuilt engine no compression

Discussion in 'Intermediate CJ-5/6/7/8' started by rsbad454, Aug 1, 2013.

  1. Aug 1, 2013
    rsbad454

    rsbad454 Member

    NorCal
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    Has anyone ever experienced a no compression issue with a rebuilt engine? I have a 304 bored to 310, rebuilt heads,, edelbrock performer intake, cloyes double roller timing chain installed straight up, comp cams 252 cam kit, holley ta 470...I cranked engine over repeatedly and no luck starting, didn't even sound like it wanted to. I thought dizzy was off 180, but made no difference. I notice by pulling #1 plug out to verify tdc I wouldn't get any pressure on my finger. I only noticed some suction on down stroke. I put compression tester on and read zero with throttle wide open.I thought maybe comp pushrods could be too long, lifters are pumped up, cam timing off? I know I installed can dot to dot on chain sprockets with zero timing. Maybe. Sprockets were marked wrong....it's just very frustrating to sink all this time and money into something like this only to have a major issue. Any advice would be appreciated. Of all the engines I've built, never once had an issue like this.
     
    Last edited: Aug 1, 2013
  2. Aug 1, 2013
    nwedgar

    nwedgar Now with TBI!

    Newnan, Georgia
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  3. Aug 1, 2013
    rsbad454

    rsbad454 Member

    NorCal
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    Sorry phone was jacked.....
     
  4. Aug 1, 2013
    Mike S

    Mike S Sponsor

    Cameron Park Ca.
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    I would start with the pushrod length, then go to cam timing.

    Still with the cam timing way out I would think you should get some compression.

    An old spark plug, with an air chuck fitting welded/braised into it is a handy tool, install it in the head, set that cyl to TDC on compression stroke, feed it some air----and listen for leakage. Listen at the intake and the exhaust and the oil filler. Wherever you hear air leaking is telling what is not sealing correctly.
     
  5. Aug 1, 2013
    tarry99

    tarry99 Member

    Northern California
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    Who assembled it? When it was bored , did you measure the Piston to cylinder wall clearance? Did you confirm the correct ring package and check the ring end gap? Have you checked all cylinders? Pull the valve cover off and watch the valve action.........as you turn it over.......at TDC both valves on #1 or any cylinder for that matter should be closed..........if not you have a timing issue at the crank shaft. If they are closed then either wrong rings, Pistons or the valve job is not sealing. Or Head Gasket!
     
    Last edited: Aug 1, 2013
  6. Aug 1, 2013
    Corveeper

    Corveeper Member

    Chanute, Kansas
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    Your local parts store more than likely has an adaptor hose for this purpose. I got mine from O’Reilly for about $10.
     
  7. Aug 1, 2013
    jaysplace

    jaysplace Member

    North, South...
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    The hose on my compression gauge has a quick connect that hooks right on my air hose. The only thing I have to do is remove the needle valve out of the end with a tire tool.
     
  8. Aug 1, 2013
    rsbad454

    rsbad454 Member

    NorCal
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    The machine shop did the short block minus the cam etc....and they also did the heads with new valves. I have thought about using compressed air at TDC to verify valve closure and listening for air escaping anywhere. I won't be able to do anything until next week sometime.
     
  9. Aug 1, 2013
    tarry99

    tarry99 Member

    Northern California
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    Well at least you have some Ideas where to look. If you have already had a Compression Gauge on there and it reads 0 you have a pretty big leak somewhere , even with compressed air going into the cylinder it still may be hard to tell simply because the air is exiting so quickly during cranking or it is not even building air?...........Did you check all the cylinders? .............Head gaskets or sealing surface , Torque on the heads, Open Valves, Valves leaking,Wrong Pistons or rings for the bore............Good Luck!
     
  10. Aug 1, 2013
    jdarg

    jdarg Member

    SE Wisconsin
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    I'd get a piston TDC on compressing, pop the valve cover, and see if both valves are closed. At least you'll have a rough idea if its the timing set indexing or something else then. Hopefully its something really simple.
     
    Last edited: Aug 1, 2013
  11. Aug 1, 2013
    F Bill

    F Bill Member

    Abilene, TX area
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    Sounds like a valve lash issue.....or cam timing.
     
  12. Aug 2, 2013
    rsbad454

    rsbad454 Member

    NorCal
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    Yeah, it's just disheartening to get this far, have everything looking good and sealed up, only to open it back up. Oh well....you live and learn.
     
  13. Sep 19, 2013
    rsbad454

    rsbad454 Member

    NorCal
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    Ok, I took a break from the Jeep for a bit, but decided to take another look at it. I pulled valve cover off and took rocker assembly off number one cylinder and used a remote starting button to bump engine around with my right middle finger over spark plug hole. I used my left hand to depress remote start button and two other fingers on left hand to feel pushrods as they cycled up and down with revolution of engine. My findings are when both pushrods are at the same level (should be at base circle) with number one piston at TDC and zero mark at TDC indicator on timing cover, I go to reinstall the rocker assembly, both valves are being opened slightly. I checked pushrods with stock units and they are the same length. Does anyone think the pedestals for rockers need to be shimmed?
     
  14. Sep 19, 2013
    tarry99

    tarry99 Member

    Northern California
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    I doubt both valves are opening.........If you have hydraulic lifters they will install at zero lash.............did you ever do a leak down test?........I would go get a cheap gauge from HF or borrow one..........get it on TDC ( if you can't feel any pressure pushing your finger off from air do it looking in the spark plug hole with a flash light......doesn't have to be exactly on TDC) then pump up the cylinder per instructions......... That is the easiest way to tell cylinder condition. If your hearing a large air leak try to isolate where its coming from. Where are you in Nor-Cal?
     
  15. Sep 19, 2013
    Jeepenstein

    Jeepenstein Me like Jeep..

    North Central FL
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    Yep, I'd get a visual on the rockers and valves and see if they are moving as should be.. start easy...
     
  16. Sep 19, 2013
    rsbad454

    rsbad454 Member

    NorCal
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    When I tighten both bolts to rocker pedestals I can watch valve springs on both intake and exhaust valves move. I get excellent compression when rocker assemblies are off at TDC. This is an odd scenerio.......
     
  17. Sep 19, 2013
    tarry99

    tarry99 Member

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    I'm still not clear how you are getting to TDC on the cylinder your checking............That should be viewed only in respect that the Piston is visually at TDC looking through the spark plug hole , irrespective of what the front Timing marks may point to. If it is in fact at TDC when you bolt the rocker assembly on and you are compressing valve springs it could be that your Cam to Crank shaft timing at the front timing chain could be off.

    When the motor was rebuilt was the Block decked or was the heads surfaced?.........meaning was any material cut off of either to correct flatness? And if so how much? You also mentioned that the new Comp push rod lengths were the same as the ones that came out. Did you change the cam Lifters? And I assume these are Hydraulic lifters is that correct? If lifters were changed , did you check there working installed height versus the old ones? Are your rockers non adjustable Rockers Arms? Did anyone rebuild the rocker assembly or have the shafts or rockers off of the shaft?

    It's hard for anyone to diagnose the problem via the internet.........what I would suggest is that you do a systematic check of all the Items mentioned above to verify each is in the correct position...........including if need be taking the front timing cover off. Some after market timing gear sets have bushings that can be placed in different locations within that gear to advance or retard cam and valve timing , not sure if you have that type. Perhaps you can check that via a part# that you purchased.

    I do really think that it is in Cam Timing.
     
  18. Sep 19, 2013
    rsbad454

    rsbad454 Member

    NorCal
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  19. Sep 19, 2013
    tarry99

    tarry99 Member

    Northern California
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  20. Sep 19, 2013
    rsbad454

    rsbad454 Member

    NorCal
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    I'm getting TDC by placing my finger at top of spark plug hole for number one cylinder while bumping engine over via a remote start button. While doing this, I have two fingers on top of pushrods for number one cylinder to feel when they lift and lower. When I feel and view pushrods are evenly matched in height ( lifters should be at base circle) and feel compression pushing past my finger, I go and look at damper also to verify zero on damper is getting close to TDC on timing cover. I also look into spark plug hole to view piston at tdc. This is when I go to put rocker assembly back on and tighten bolts slowly on intake and exhaust, I see the springs starting to compress on both. My guess is, pushrods maybe too long after rebuild, base circle may be bigger than stock.....
     
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