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Technical Small Block Chevy 12 and two timing tab issues

Discussion in 'Traditional Hot Rods' started by porkchop4464, May 25, 2019.

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  1. porkchop4464
    Joined: Jan 20, 2009
    Posts: 715

    porkchop4464
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    Dude, calm down. Caps really don't make a difference when typing. Okay, regardless of what I posted from Summit's own description, okay, okay balancer, rather. I will say, good thing you cleared all that up, cause that helps with my problem. Winner winner, chicken dinner!
     
  2. porkchop4464
    Joined: Jan 20, 2009
    Posts: 715

    porkchop4464
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  3. guitarguy
    Joined: May 26, 2008
    Posts: 105

    guitarguy
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    Just winging it here, but if the distributor went in as it should at the time of assembly and the crank was on TDC as you said, could the plug wires be off by one tower all around? That would be the only explanation I could have as to why it would show the mark in a different spot....of course it shouldn't run right either if the wires are moved.

    If not, I would make a piston stop (or buy one) and start the whole procedure over again to be sure. It doesn't take long to do.

    When you initially started it, If everything is aligned properly, did you have to move the distributor more than 3/8 of an inch either way to get the timing set? If so, it is more than likely the wires are off by one terminal or it's one tooth off on the distributor. To me from my experience building many engines, there really is no other explanation.

    Hope you get it sorted out.
     
  4. Rex_A_Lott
    Joined: Feb 5, 2007
    Posts: 875

    Rex_A_Lott
    ALLIANCE MEMBER

     
    Last edited: May 26, 2019
  5. oldolds
    Joined: Oct 18, 2010
    Posts: 2,680

    oldolds
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    Is there a vacuum advance on the dist? You need to pull that when you set timing. If you are not doing that you will have the problem you describe.
     
    31Vicky with a hemi likes this.
  6. DIYGUY
    Joined: Sep 8, 2015
    Posts: 598

    DIYGUY
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    from West, TX

    Hook up your timing light, start your engine, aim it at the balancer, adjust your knob on the light until the flashing mark coincides with zero on your timing tab. Looking at the dial on your light the knob now points to a number. That is your timing in degrees.
     
    David Gersic likes this.
  7. Any circle has 360 degrees
    Any 12 hr clock has 12 positions
    360 decided by 12 is 30
    12 o’clock to 2 o’clock is 60 degrees

    But if it’s actually 12:10 to 1:55 but eye balling it and calling 2&12 the amount of degrees will be different from 60.

    Just Incase I get more wishes granted ,,,
    I’ll say I’d prefer it if people would do a piston stop verification way before even use a timing light. AND NOT speak, talk, worry, look up, or do anything about adjusting degrees of ignition timing with a light prior to a piston stop test.

    Stock specs found in FSM are for stock engines. All those with stock engines raise your hand. Plus this wouldn’t be the first thread involving the exact same mystery about crate engines running best at 55*- there’s plenty. You could solve the mystery with a piston stop test and timing mark verification of marks and tabs then install the correct timing tape then get your light out. It still might not if your light is off by a little bit.

    Really that engine will dictate the amount of timing Advance it wants. Who gives a crap what it is measured at without a mark verification.
    Look at all these if’s that need to be 100% correct with Zero tolerance for error so the damn timing marks line up. There’s a USA drawn design and blue print that’s converted to metric and rounded off. Stack the tolerance up and it will be off.

    If the block was cast and machined
    If the crank was machined
    If the balancer was machined
    If the timing cover was stamped
    If the tab was stamped
    If the tab was welded
    If 10 different QC departments did their job
    If the matching parts were installed
    If nobody said “fuck it that’s close enough”


    And after thinking about all that for a second does anyone see any reason to fret about what a timing light says without a piston stop verification?
     
    Last edited: May 26, 2019
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  8. squirrel
    Joined: Sep 23, 2004
    Posts: 42,260

    squirrel
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    you need to put a piston stop in it, find TDC, and then you'll have numbers to go with how well it runs.

    Or take the front pulley off, and use a level and 45 degree triangle, and get the keyway lined up at exactly 45 degrees from vertical/horizontal, and then mark your tab as being at TDC. One of the damper bolt holes is in line with the keyway, making it possible to measure the angle pretty accurately

    btw mikeVV, the damper and balancer are the same part, but it performs different functions on different engines. On a 350, it's just a damper, but on a 400, it's a damper and a balancer. The thing about using the correct term is that it only works if the entire audience understands what the terms mean, and that isn't the case with most engine parts. So we have to just live with folks using the wrong term. Just like folks do in real life.
     
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  9. Maicobreako
    Joined: Jun 25, 2018
    Posts: 83

    Maicobreako
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  10. jaw22w
    Joined: Mar 2, 2013
    Posts: 667

    jaw22w
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    from Indiana

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  11. jaw22w
    Joined: Mar 2, 2013
    Posts: 667

    jaw22w
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    from Indiana

    Do to piston dwell at TDC, a dial indicator can still leave you a few degrees off. Piston stop is the absolute most accurate method.
     
    Maicobreako likes this.
  12. Who knows why ignition timing is advanced?
    Because it takes time, fractional seconds for a whole bunch of stuff to start moving and complete the hand off.

    The crank to move the the cam, the cam to move the distributor, the distributor to move the timing lobe, the signal to get to the coil, the coil to get to the spark to cap, cap to rotor, rotor to plug terminal, thermal to wire, wire to plug, plug to air fuel mixture, flame front to travel across the bore, fuel mixture to burn off, gasses to push down pistons.

    All that stuff eats up time and you want the last step of the process to happen at exactly and precisely the correct position. That means you’re going to begin the process before you need it to happen. Advance timing.


    Oh and what happens if something in that chain maybe takes a little longer? You’ll be needing more advance. Who’s got a faster processor in their module? Is it faster or slower than points?
     
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  13. squirrel
    Joined: Sep 23, 2004
    Posts: 42,260

    squirrel
    Member

    the time it takes for all that stuff to happen, is not really what advance is about...except the part about how long it takes for the flame front to travel across the bore. That's what advance is all about. It takes about the same amount of time at different engine speeds, but varies with cylinder pressure, so you need to start sooner to have it finished at about TDC, under different conditions of RPM and cylinder filling.
     
  14. Yep,
    The dial indicator method should be splitting the degrees of dwell as well for TDC. It could be useful if you needed the piston at the top and needed to know the exact crank degrees of dwell. Piston stop won’t do that
     
  15. David Gersic
    Joined: Feb 15, 2015
    Posts: 1,812

    David Gersic
    Member
    from DeKalb, IL

    Actual specs help a lot here. It’s a crate SBC, but that covers a lot of ground, from mild to wild. What’s the advertised compression ratio? Stock bore and stroke? Iron stock heads, aluminum heads?

    The cam specs matter. Got the cam card it came with? Or your receipt from ordering it?

    If you’ve verified TDC, then your timing tab is fine. You’re just running a lot of advance.

    Mine is similar. Stock 8.5:1 c/r bottom end, stock iron heads, and a cam with too much overlap for the engine. TDC verified, needs the distributor set at 35* advance to run, and there is about 20* mechanical advance in the distributor, so 55* all in by 2500 or so.

    Timing light, not dialed back, the mark on the damper is way up top hiding under the short water pump.

    You have a dial back timing light. Fire the engine up, pull the vacuum advance, and read the timing with the light. That and the actual engine specs are what you need to make sense of this.



    Sent from my iPad using The H.A.M.B. mobile app
     
  16. porkchop4464
    Joined: Jan 20, 2009
    Posts: 715

    porkchop4464
    Member


    Thanks ALL! Really. I now know what I have to do to get rid of this issue and have a foundation to really start tuning from. I have a few old plugs around in the shop, I will take one and pop a head bolt through and install in cyl 1.

    Never done it, so is it: get it in the bore, rotate assembly by hand (breaker-bar) 'til stop, then counterclockwise all the way back around 'til she stops again and measure between those two lines to get TDC?

    God Bless the Hamb for all it's smart asses, geniuses, and ne'er-do-wells (me included).

    The Pork
     
  17. KenC
    Joined: Sep 14, 2006
    Posts: 232

    KenC
    Member

    Dial indicator works too , but not in the way most would expect. Use it like a stop. Rotate to a number you choose, say .040 down the hole, mark the damper/balancer/round thing like you would with a stop. Turn the engine in the opposite direction until you reach that same .040. Mark the damper. Half way between the marks is TDC. Just like using a stop. The number, I used .040 is not important, just pick one, as long as you use the same both directions.

    I like this because it's easy to set up either with the head on or off with a mag base.
     
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  18. blowby
    Joined: Dec 27, 2012
    Posts: 5,764

    blowby
    Member
    from Nicasio Ca

    If you make your own stop, grind a flat in the bolt so the air has somewhere to go.
     
  19. jaw22w
    Joined: Mar 2, 2013
    Posts: 667

    jaw22w
    Member
    from Indiana

    Never done it, so is it: get it in the bore, rotate assembly by hand (breaker-bar) 'til stop, then counterclockwise all the way back around 'til she stops again and measure between those two lines to get TDC?

    Yes that is the procedure. One additional thing I like to do. Loosen the rocker arms on #1 so the valves don't have the opportunity to hit the stop you just shoved in there.

    Yes that will work. But trying to hit that .040" precisely down in the hole may take a while. With the head off, I bolt a 1" x 1/2" steel bar to the deck across the bore with a hole drilled in the center and a stop bolt. Got to be way quicker than the dial indicator and cheaper too. Did you ever try to cut 4 pieces of steel in a chop saw exactly the same size by measuring, marking, placing it in the saw, and cutting it? Won't work. Put a stop on that saw and you will get 4 pieces exactly alike. Anytime you MEASURE ANYTHING you introduce some error. Same thing with the stop in the bore. You never measure anything.
     
    Last edited: May 26, 2019
  20. jaw22w
    Joined: Mar 2, 2013
    Posts: 667

    jaw22w
    Member
    from Indiana

    One more thing. Using the piston stop method you can put that TDC mark anywhere on the damper that you can see it and get a pointer to it.
     
  21. porkchop4464
    Joined: Jan 20, 2009
    Posts: 715

    porkchop4464
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    Got it!
     
  22. porkchop4464
    Joined: Jan 20, 2009
    Posts: 715

    porkchop4464
    Member

    Darn you, Jaw! It a BALANCER! What the hell! Get IT RIGHT:eek:) !
     
  23. porkchop4464
    Joined: Jan 20, 2009
    Posts: 715

    porkchop4464
    Member

    \

    David,
    Thanks for the comments, but unless I am seeing this wrong (which very well could be) isn't wherever my dizzy is currently locked affecting a true timing reading? Meaning, let's say I am actually at 15 BTC (don't know what it actually is right now) where my Dizzy is currently locked down. Now, I go and zero my light, and get a zero on the light, tab, and damper. In reality, I am still @ 15 BTDC and still don't have an accurate TDC to start from, correct? Again, not being a smarta$$ here, just seriously confused about what you explained. I know I am interpreting what you are saying wrong, however.
     
    Last edited: May 26, 2019
  24. porkchop4464
    Joined: Jan 20, 2009
    Posts: 715

    porkchop4464
    Member

    Agreed. I can hopefully even line it up with the tab I have on the engine currently at the traditional 2 o'clock location.
     
  25. porkchop4464
    Joined: Jan 20, 2009
    Posts: 715

    porkchop4464
    Member

    Will Do!
     
  26. DIYGUY
    Joined: Sep 8, 2015
    Posts: 598

    DIYGUY
    Member
    from West, TX

    Pork, use the knob on the light to zero the tab and pointer. Read what your knob is pointing to on your light. It might very well be 15 degrees
     
  27. porkchop4464
    Joined: Jan 20, 2009
    Posts: 715

    porkchop4464
    Member

    Sh@#T, now I am even more confused. I know it is simple, what is being explained, cause several people have mentioned something similar, but I am still not getting true TDC with this? I must be and am thick headed, I just am not understanding, guys. Sorry, really. Please, in baby steps and words.
     
  28. DIYGUY
    Joined: Sep 8, 2015
    Posts: 598

    DIYGUY
    Member
    from West, TX

    Not being a smart ass I promise. Do you know the flashing light will “move” when you adjust the knob on the light while engine is running?
     
  29. You can not find TRUE Top Dead Center with a timing light.

    Do you even have a dial back timing light???
    3F5997FF-E6E7-4847-8AD7-92A00E6E5FBB.jpeg EEC48B09-8501-49AB-898B-B94CBBEA98DF.jpeg
     
  30. Poppashelby
    Joined: May 26, 2019
    Posts: 1

    Poppashelby

    Let me have a shot at this. TDC has nothing to do with where the timing light is showing your mark. That mark is moved by turning the distributor. Do the deadbolt thing to find TDC. Leave it on that TDC mark, now you can make your line anywhere you want it ,and that will be your new TDC. put some white paint to see it good
     

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