Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Finding TDC in a small block... once again.

Discussion in 'The Garage' started by mrdrinksalil, Apr 10, 2007.

  1. mrdrinksalil

    mrdrinksalil 1/2 ton status

    Joined:
    Apr 4, 2005
    Posts:
    1,595
    Likes Received:
    0
    Location:
    Atlanta, Georgia
    Ok, I have an engine that hasn't been started in a long time and I'm not sure if the Dizzy has been messed with. Its a Chevy 350SB. I've read on here about the piston stop method of cranking one way, then the other and TDC should be between those two marks. BUT, how do you know what stroke youre on? Compression or exhaust? Don't I wanna set the dizzy so that the rotor is just before #1 cylinder when #1 cylinder is on exactly TDC of the compression stroke?
     
  2. mrdrinksalil

    mrdrinksalil 1/2 ton status

    Joined:
    Apr 4, 2005
    Posts:
    1,595
    Likes Received:
    0
    Location:
    Atlanta, Georgia
  3. Mudstud

    Mudstud 1/2 ton status

    Joined:
    May 29, 2001
    Posts:
    1,472
    Likes Received:
    1
    Location:
    Memphis, TN
    Yes TDC is on the compression stroke and there is a way to be certain you are on the compressioin stroke but I don't recall what that trick is right off. I suppose if you take the #1 plud out and stick a finger in there while a friend turn the motor BY HAND you should feel the pressure build and blow your finger out. Note that the #1 piston comes up to the top twice in a cycle so you can't go by just feeling it in there. Hope that helps or at least gets the ball rollin for this thread.
     
  4. dontoe

    dontoe 3/4 ton status GMOTM Winner

    Joined:
    May 7, 2004
    Posts:
    9,070
    Likes Received:
    0
    Location:
    Hickory, N.C.
    The rebuild book I used in the late Eighties to rebuild a 350 had an easy way. Don't remember exactly but something like #3 exhaust valve open and #6 Intake open..........I'll have to check it out next time I have the rocker covers off.............:p:
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,976
    Likes Received:
    189
    Location:
    Roy WA
    Easy way to know you are getting close to TDC is as mentioned. Pull #1 plug, put finger over the hole, turn crank until air forces out past your finger. You can use whatever implement you like (make sure it doesn't get jammed) in the hole to watch where the piston stops rising on the compression stroke. Should be darn near "0" on the timing tab.
     
  6. vortec

    vortec 1/2 ton status

    Joined:
    Jul 22, 2004
    Posts:
    1,472
    Likes Received:
    0
    Location:
    fort worth, texas
    x3

    that's how i do it.

    if you mean just feeling the height of the piston with a straw or something, that's exactly right. you can't differentiate between exhaust stroke and compression stroke that way. so the finger method works, because much less air pressure will be felt on the exhaust stroke than the compression stroke.


    the method isn't perfect, but i got mine to within 1-2 degrees with it, no problem.
     
  7. Kp

    Kp 1/2 ton status

    Joined:
    Apr 5, 2006
    Posts:
    135
    Likes Received:
    0
    Location:
    Tucson
    If you've got the valve cover off, you should be able to wiggle the rockers on the #1 cylinder. Both valves will be closed on the firing stoke.
     
  8. garlicbreath

    garlicbreath 1/2 ton status

    Joined:
    May 17, 2003
    Posts:
    1,136
    Likes Received:
    0
    Location:
    Denver
    Bingo.





    I have had several issues with just using the finger over the hole and ended up 180 out.
     
  9. mrdrinksalil

    mrdrinksalil 1/2 ton status

    Joined:
    Apr 4, 2005
    Posts:
    1,595
    Likes Received:
    0
    Location:
    Atlanta, Georgia
    well well well.... I guess I will just do the method with the piston stop and wiggle the valves to see it they are both loose. And check the pressure out the plug hole as well. Then I'll know what stroke im on. BUT once I get it set up at exactly TDC then where should I position the rotor and cap?
     
  10. Mudstud

    Mudstud 1/2 ton status

    Joined:
    May 29, 2001
    Posts:
    1,472
    Likes Received:
    1
    Location:
    Memphis, TN
    Find #1 TDC
    Slide the distributer in to the engine with the #1 terminal in the right spot- (The rotor will be facing toward the front left corner of the engine (Driverside front piston). The cap will only go on one way so you gotta make sure the way the cap goes on the rotor is at that terminal on the cap.)
    Put the cap on and all other plug wires and try to fire the engine. It it just spins and spins you are 180* off in which case you take the cap off (leave all the wires in place) and rotat the dist 180* and slide it back in. Before doing this though, since you turned the engine over, you'll have to establish TDC on #1 again.


    You really outta locate a book and check the illustrations if you are unsure. You'll need a book to make sure you start your plug wires correctly. Prolly wouldn't be good to have them messed up and try starting it.
     
  11. mrdrinksalil

    mrdrinksalil 1/2 ton status

    Joined:
    Apr 4, 2005
    Posts:
    1,595
    Likes Received:
    0
    Location:
    Atlanta, Georgia
    What do you mean Point it towards the #3 cylinder? isn't the firing order 18436572 ? Wouldn't I want to point it towards the #2 cylinder and it would rotate to the #1 a little when I dropped it in?
     
  12. Mudstud

    Mudstud 1/2 ton status

    Joined:
    May 29, 2001
    Posts:
    1,472
    Likes Received:
    1
    Location:
    Memphis, TN
    This is too hard to splain without illustrations but I'll try once more. The number one terminal on the dist will be facing the front of the engine toward the drivers side = front left corner of engine. In other words, it will be facing the front of the engine just to the left (as viewed from behind) of center. It has nothing to do with where it's physically facing- it has everything to do with where the dist meshes with the cam. Hope that helps clear it up. A book will explain all this in a glance.
     
  13. mrdrinksalil

    mrdrinksalil 1/2 ton status

    Joined:
    Apr 4, 2005
    Posts:
    1,595
    Likes Received:
    0
    Location:
    Atlanta, Georgia
    4xcrazy- yeah i know how the cylinders are #'d. And I was right with the firing order. It fires #2 cylinder then #1, then 8,4,3,6,5,7 and so on. I was trying to figure out why to point it to 3 when you were trying to fire on #1
     
  14. mrdrinksalil

    mrdrinksalil 1/2 ton status

    Joined:
    Apr 4, 2005
    Posts:
    1,595
    Likes Received:
    0
    Location:
    Atlanta, Georgia
    I think I will be good to go now. I have been building this damn truck forever now and its bout time to fire up the engine. I'm really nervous and dont want anything to go wrong. I've got a lot of time and money into this truck. I messed a lot with the 25 year old wiring and for some reason can't get power to the starter sylinoid when I turn the key. Any ideas on that one?

    heres a pic of the engine..

    [​IMG]

    [​IMG]
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,976
    Likes Received:
    189
    Location:
    Roy WA
    You should ALWAYS have power to the solenoid, that's where the battery cable goes. :)

    Purple wire is the "start" wire (typical) so make sure it's got juice when you turn the key. I don't believe that one is fused, but I could be wrong.
     
  16. mrdrinksalil

    mrdrinksalil 1/2 ton status

    Joined:
    Apr 4, 2005
    Posts:
    1,595
    Likes Received:
    0
    Location:
    Atlanta, Georgia
    Yeah, I can't get power to that purple wire when I turn the key. What should I look for now?
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,976
    Likes Received:
    189
    Location:
    Roy WA
    Everything else got power? The two (typical) wires running from the battery lug on the solenoid to the junction block to the fuse panel are hooked up and have power?
     
  18. mrdrinksalil

    mrdrinksalil 1/2 ton status

    Joined:
    Apr 4, 2005
    Posts:
    1,595
    Likes Received:
    0
    Location:
    Atlanta, Georgia
    Yup, checked that. I have two power wires that are hot running into the fuse block.
     
  19. garlicbreath

    garlicbreath 1/2 ton status

    Joined:
    May 17, 2003
    Posts:
    1,136
    Likes Received:
    0
    Location:
    Denver
    Make sure the shifter is truly in park or nuetral also.
     
  20. 76zimmer

    76zimmer Flyin Rat Premium Member GMOTM Winner

    Joined:
    Nov 14, 2005
    Posts:
    23,030
    Likes Received:
    1,347
    Location:
    Kzoo, Mi
    PM Paul Ryoken...but check the starter switch to see if you got power there. Do you have a wiring diagram? and what year again?
     

Share This Page