Timing chain and gear help!

Discussion in 'Small Block Tech' started by 19apollo74, Jul 24, 2016.

  1. 19apollo74

    19apollo74 Member

    Hi everyone, pretty sure the timing chain stretched and jumped time in my 70 350, any instructions on doin that job would be great or point me in the right direction.i would a appreciate it thanks.
  2. Bad Boattail

    Bad Boattail Guest


    Please put you name in your signature, we are all here on a friendly first name base :TU:

    Replacement of the timing chain on your 350 Buick engine is not different from other V shaped engines.
    Most important thing to know is how you have to line up the timing marks:

    Click image below and start reading at page 60-77 of this Buick Chassis Manual :Comp:

  3. alec296

    alec296 i need another buick

    You will be pulling the front cover off. I suggest a inspect and possible rebuild of harmonic damper. 46 years old . Don't pry on outer ring to get it off. Should come off fairly easy once bolt is removed.
  4. 19apollo74

    19apollo74 Member

    Thanks, i will tear into her tomorrow. The original motor is getting built ass we speak and I just bought this 70 motor,put about 1500 miles on her and it jumped time I believe.
  5. Bad Boattail

    Bad Boattail Guest

    You can check that first by looking at the position of the rotor and the mark on your harmonic balancer.
  6. ctlikon

    ctlikon Well-Known Member

    Don't forget to install the oil slinger before you reinstall the timing cover! :)
    BUICKRAT likes this.
  7. 19apollo74

    19apollo74 Member

    With the balancer lined up,the rotor was facing between number 8 and 4
  8. BigTodd

    BigTodd Well-Known Member

    Before you tear into the front end of your engine, could you share what kind of problems you are encountering with the engine performance? I've recently replace my timing chain and gears only to find out that was not the problem I was trying to fix. Removing the timing cover and all that goes with it can be difficult, broken bolts, leaks, oil pump issues and other fun stuff.

    Does the engine still run? Please describe what your problems are, it may not be timing chain related at all. We've got some pretty smart folks on here and the better you can describe your issues the better they can help diagnose the problem.
  9. alec296

    alec296 i need another buick

    Now turn crank backward until rotor lines with number I distributer tower see how much it moves
  10. 19apollo74

    19apollo74 Member

    The motor quit on me and wouldn't fire, I replaced module and coil and advanced the distributor and it actually fired but boy did it run bad, I just pulled distributor and I could feel there was a considerable amount of slack on the chain with a screwdriver
  11. BigTodd

    BigTodd Well-Known Member

    When I replaced my timing chain, I did the following:

    - #1 cylinder TDC on compression stoke lined up the harmonic balancer notch to "0" on the cover timing marks
    - Drained the radiator and removed the hoses
    - Loosen and removed the Alt, PS, AC and water pump belts
    - Loosen the shroud, then unbolted the fan and removed the shroud and fan together
    - Removed the transmission cooler pipes from the radiator, taped up ends to prevent tranny fluid drips
    - Removed the radiator top mount, then removed the radiator

    At this point I had plenty of room to work on the timing cover and harmonic balancer.

    - Using a 1/2" impact gun I removed the harmonic balancer bolt, removed the crank pully
    - Lightly tapped the harmonic balancer with a rubber hammer and it came off real easy, no puller required
    - Removed coil and mount, Removed small coolant hose (water pump to intake)
    - Marked distributor location with paint pen, and removed the distributor
    - Disconnected fuel pump gas connections, plugged so no gas would leak
    - I left the oil filter on so not to disturb the oil prime

    Now you can start removing the timing cover bolts to the block, I did not remove the water pump bolts or any oil pump bolts, leave them alone unless you plan on changing them. Unless you know you have bad oil pressure don't mess with the oil pump. Have a catch pan under the engine to get the coolant that will spill out once all of the other cover bolts are removed. Start with the two bolts on the bottom of the timing cover connected to the oil pan, remove those. Then work your way around removing the other timing cover to block bolts. Gently pry off the timing cover, don't torque on the cover, it is made of aluminum so be careful.

    Once the cover is off, set it aside. Look for your timing marks on the top and bottom timing chain gears. If they are lined up then the chain did not jump a tooth. If they are not lined up the chain jumped. My chain had not jumped but it did have a lot of play in it. My two timing marks were lined up on the gears. I made absolutely sure that I did not disturb the cam or crank location. Those two dots must be pointing at each other on the chain gears. If you find your timing marks off because of a jumped tooth you will need to remove your timing chain and gears, then put the gears back on without the chain and line up the timing marks, cam timing mark pointing down, Crank timing mark pointing up directly pointing at each other. Then remove the gears, grease and hang your new chain on the gears and reinstall. Be sure to reinstall the fuel pump eccentric on the cam, and oil slinger on the crank. Properly torque the cam bolt. Double check your gear timing marks are still lined up. Check your timing cover crank seal, replace if needed. Clean up the timing cover and clean off the old gasket material. Install new gasket and reinstall the timing cover. Reverse the steps above and reassemble the front end of the engine. Be sure the timing marks are still lined up on the harmonic balancer and cover timing marks still set to "0". Install the distributor so the rotor is pointing directly at the #1 spark plug post on the cap.

    I left the shroud and fan off, and only put water back into my radiator in case I found anything wrong while tuning and had to get back into the cover. Once I got the correct advance dialed in, I drained the water, put in coolant and installed the fan and shroud. Good Luck and take your time.
  12. 19apollo74

    19apollo74 Member

    Thanks for the detailed instructions Todd, the new timing chain and gear should be in tomorrow. I give you an update after a few days.
  13. OZGS455

    OZGS455 Oh what a wonderful day!

    Thanks Todd, Im looking at removing repairing and refitting my timing chain cover ino the very neat future so its nice to have the proceedure laid out step by step for me
  14. OZGS455

    OZGS455 Oh what a wonderful day!

    ok Im into it now, specifics on my thread but using this for reference.
    so the fuel pump can stay bolted to the cover for now>?
  15. Stevem

    Stevem Well-Known Member

    Do yourself a favor and on putting things back together also install a Cam key to advance the Cam 2 degrees, as stock type replacement chains give up 2 degrees in very little run time!
  16. alec296

    alec296 i need another buick

    Remove fuel pump from cover.
    A cam key with advance will also advance the harmonic balancer. Not a good idea. Buy a better gear set if needed.
  17. OZGS455

    OZGS455 Oh what a wonderful day!

    theres actually 4 bolts holding the timing cover to the oil pan not two as stated above,
    got those last two bolts out now and its come off ok
  18. stk3171

    stk3171 Well-Known Member

    if the large gear has the plastic teeth missing best pull the oil pan and clean pickup screen.
  19. telriv

    telriv Well-Known Member

    Everyone drains the coolant & thinks no more about it until they go to remove the cover & coolant spills out & into the oil pan also leaving a mess to work around or clean up later.
    What i do after you think all the coolant is removed is to jack up the rear of the vehicle as high as possible. What this does is increases the level in the front & as much as 1-1 1/2 gallons more come out. After that finished draining now you can lower the rear to normal height. When you go to take the cover off little or no coolant will come out to make a mess or go into the pan. Makes things so much neater & easier to work around without having to cleanup a bigger mess than nec.

    Tom T.
  20. OZGS455

    OZGS455 Oh what a wonderful day!

    Anyone following those instructions I followed needs to know theres 4 bolts holding the oil pan to the timing case, not just the front 2 obvious ones,
    And the radiator dont need to be removed, plenty of room to work with it in.
    Thankfully I didnt cause too much damage tryna force the cover off with the back 2 pan bolts still connected.
    4 thou warpage where I tried to hammer a chisel in the side down low to pry it out. was filled by the gasket and sealant.
    Its fairly obvious when I had a good look as to why it wasnt budging.
    No real damage done.

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