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Thread: My old 390 Tbird will only run at 45 btdc???
          
   
   

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  1. #1
    birdland's Avatar
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    My old 390 Tbird will only run at 45 btdc???

     



    I'm stumped -- this old car runs pretty good when the timing is at 45 btdc (at idle) This just bugs me,

    Here is what I have checked today.
    1. #1 tdc using a dial indicator.
    2. 0tdc on damper matches up.
    3. checked the marks on the timing gears. (it's a new chain)
    4. 150 compression in all cyls
    5. only have 5" vac at idle -- all vac ports plugged and the vac advance is unhooked.

    I'm going out to check the valves to see if they are tight right now.
    This engine looks like it was gone through reciently -- I only found the issue when I was cleaning up the eng compartment and pulled the cap off and noticed the rotor pointing at #5 instead of #1 when the 0tdc was indicated. I checked another forum and noticed a few other people were having the same issue. No one there had a clue what was happening (and, for sure, I don't either) Anyone here able to help?

  2. #2
    Mike P's Avatar
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    Not tryinger to be smart, but you are aware that #1 is on the passenger side bank (cylinder numbering is passenger side 1234/driver side 5678).
    I've NEVER seen a car come from the factory that couldn't be improved.....

  3. #3
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    live with it ..
    iv`e used up all my sick days at work .. can i call in dead ?

  4. #4
    birdland's Avatar
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    Yeah, but it just bugs the heck out of me that it's doing that.
    Last edited by birdland; 06-11-2011 at 05:25 PM.

  5. #5
    birdland's Avatar
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    #1 on the passenger side. Yep, I knew that --

  6. #6
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    Well I'm assuming a couple of things---checked tdc with dial indicator----sooooo, I assume the heads were off???? and since your so far off on the timing that you indicated where the piston topped out at???Not a positive stop type indicator????

    your using the correct firing order??? and what year timing gear do you have on the crank???they retarded the cam timing in early 70s with different keyway position

  7. #7
    NTFDAY's Avatar
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    Quote Originally Posted by jerry clayton View Post
    your using the correct firing order??? and what year timing gear do you have on the crank???they retarded the cam timing in early 70s with different keyway position
    My thoughts also jerry
    Ken Thomas
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  8. #8
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    Now I think we may be getting somewhere --- I don't know what year the gear on the crank is since this engine was together when I got it. How would I determine where the key way should be? I looked at pictures on the internet and all of them looked like the keyway was in the same position as mine (lined up directly with the mark) except for one that I saw that had several slots. Thanks, I'll look into that.

  9. #9
    IC2
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    Quote Originally Posted by jerry clayton View Post
    Well I'm assuming a couple of things---checked tdc with dial indicator----sooooo, I assume the heads were off???? and since your so far off on the timing that you indicated where the piston topped out at???Not a positive stop type indicator????

    your using the correct firing order??? and what year timing gear do you have on the crank???they retarded the cam timing in early 70s with different keyway position
    I don't recall retarded camshaft timing on the FE but for sure on the 385 engines(429/460) which was 6 to 9 degrees, depending on your info source.

    This sounds like whoever assembled this engine got the chain/gears off a tooth or two
    Dave W
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  10. #10
    jerry clayton's Avatar
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    I question the method/accuracy of determining tdc more than cam timing---also if its a point dist what the dwell is set at---

    With #5 being the next cyl in the firing order and questional accuracy of dwell, timing marks/tdc ----

  11. #11
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    I wrote this article on another forum for small block Chevies, but the procedure is applicable to any motor. If you used a dial indicator stem through the spark plug hole, that's where your problem began. But I still don't understand the 150 psi with 5 inches of mercury. It seems that if the cam was off enough to allow only 5 inches, it wouldn't make that kind of cylinder pressure when cranking.
    http://www.crankshaftcoalition.com/w...op_dead_center
    Last edited by techinspector1; 06-12-2011 at 02:02 PM.
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  12. #12
    R Pope is offline CHR Member Visit my Photo Gallery
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    45 deg. advance is sparking on the next cylinder on the cap. You are doing something wrong. Try moving your timing light lead to the next post.

  13. #13
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    Okay, it's 45 crank degrees, that's only 22.5 at the dist. Still halfway between the two towers, could spark to either one.
    45 degrees initial will kick back hard enough to damage the starter. I still think you are reading something wrong.

  14. #14
    IC2
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    Seems like a dumb question - but which plug are you using as #1? It's the RIGHT front. You said the rotor was pointing at #5, which would be the second cylinder on a Ford to fire and the front left - and the dist rotates CCW, opposite GM. If you are 45*, you are exactly 1 cylinder number of degrees off (360/8 = 45). FO is 1-5-4-2-6-3-7-8
    Dave W
    I am now gone from this forum for now - finally have pulled the plug

  15. #15
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    Quote Originally Posted by R Pope View Post
    Okay, it's 45 crank degrees, that's only 22.5 at the dist. Still halfway between the two towers, could spark to either one.
    45 degrees initial will kick back hard enough to damage the starter. I still think you are reading something wrong.
    Quote Originally Posted by IC2 View Post
    Seems like a dumb question - but which plug are you using as #1? It's the RIGHT front. You said the rotor was pointing at #5, which would be the second cylinder on a Ford to fire and the front left - and the dist rotates CCW, opposite GM. If you are 45*, you are exactly 1 cylinder number of degrees off (360/8 = 45). FO is 1-5-4-2-6-3-7-8
    Guys, Birdland posted this about seven months ago (five posts over two days) and has not been back since. I doubt seriously that we'll see any response from him at this point. Just my thoughts, not saying don't reply...
    Roger
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