Timing question

Discussion in 'Street/strip 400/430/455' started by '72 Skylark Custom 4bbl, Jun 18, 2020.

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  1. '72 Skylark Custom 4bbl

    '72 Skylark Custom 4bbl Well-Known Member

    It runs good, idles good, runs cool, has good oil pressure.

    Just not sure which piece of the puzzle I’m missing.

    Kyle
     
    '72 Skylark Custom 4bbl, Jun 19, 2020
    #21
  2. Bens99gtp

    Bens99gtp Well-Known Member

    You said b4 you had the heads worked on????? What was done to the heads???

    I had decent running small valve heads once......light porting......took them to the machine shop to have stage1 valves added.......car went .75 slower in the quarter........took another port job to fix the fact they just bowl hogged the heads to drop the calves in and screwed everything up in there
     
    Bens99gtp, Jun 20, 2020
    #22
  3. '72 Skylark Custom 4bbl

    '72 Skylark Custom 4bbl Well-Known Member

    Yeah. Made the decision while the engine was sitting. Kind of an after thought on my part. Plus I took it to a different place.

    Did bowl porting & a competition balance job. According to the flow sheet picked up like /0 CFM according to his flow bench.

    Kyle
     
    '72 Skylark Custom 4bbl, Jun 20, 2020
    #23
  4. 12lives

    12lives Control the controllable, let the rest go

    What tires are you running in the rear?
     
    12lives, Jun 20, 2020
    #24
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    So the porting did not pick up any flow?o_O
     
    LARRY70GS, Jun 20, 2020
    #25
  6. '72 Skylark Custom 4bbl

    '72 Skylark Custom 4bbl Well-Known Member

    275/60 on 15x10 rims

    Kyle
     
    '72 Skylark Custom 4bbl, Jun 20, 2020
    #26
  7. '72 Skylark Custom 4bbl

    '72 Skylark Custom 4bbl Well-Known Member

    Haha! That’s supposed to be 20 CFM!!

    Kyle
     
    '72 Skylark Custom 4bbl, Jun 20, 2020
    #27
  8. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    OK, that's better.:D Seriously though, you are missing something. I don't know what else to suggest, but based on my experience on this board, threads like this usually end when the OP, finally finds the problem, and it was something mentioned 4 pages back:D, and the OP invariably says, "not sure how I missed that":) I suggest you go back and check all the basic simple stuff, even the firing order, timing, dwell if you are using points, throttle opening, etc.. Jim's converters are awesome, and should put your engine right in the meat of the torque curve from idle. You should be melting tires.
     
    LARRY70GS, Jun 20, 2020
    #28
  9. '72 Skylark Custom 4bbl

    '72 Skylark Custom 4bbl Well-Known Member

    I’m pretty sure it’s something simple. Just have to find the missing link:). Could it be the throttle cable at the pedal? I’m going with the mark that the engine builder put on the TA balancer(he put it on the “nipple” of the balancer).

    I have a chassis dyno tuning session set up for July 10th hopefully that will help as well.

    Ken re-did this carb & distributor so other than adjusting the timing I’ve made no adjustments(distributor springs, idle setting, dwell, any of that stuff).

    Kyle
     
    '72 Skylark Custom 4bbl, Jun 20, 2020
    #29
  10. telriv

    telriv Founders Club Member

    I believe initial timing should be more than 4*BTDC at a slow idle of around 500-600RPM's. It should be more like 12*-16*initial at a slow RPM with no more than 32*-36* all in at somewhere between 2200-2600RPM's. with vacuum hose disconnected at the vacuum advance.
    Opps, forget that. Upon further reading it was the cam advanced 4*.
     
    telriv, Jun 20, 2020
    #30
  11. '72 Skylark Custom 4bbl

    '72 Skylark Custom 4bbl Well-Known Member

    Can I check dwell with the cap & rotor off? I tried having the wife bump the motor but the points never seemed to open. I’m trying to check with a feeler gauge as I have no dwell meter.

    Kyle
     
    '72 Skylark Custom 4bbl, Jun 20, 2020
    #31
  12. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    You don't have to bump the engine, turn the crank with a socket and breaker bar, and get it exactly on the point. Then look at the gap. Most good meters can measure dwell.

    https://www.amazon.com/Actron-CP767...=1&keywords=dwell+meter&qid=1592677527&sr=8-2

    Dwell affects timing, timing does not affect dwell.
     
    LARRY70GS, Jun 20, 2020
    #32
  13. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    It's either opening the throttle blades fully, or it isn't. Have the wife stand on the gas pedal, then you physically try to open the throttle more.


    This is the stock mark on a stock balancer, it's grooved.

    Stock Balancer.jpg
     
    LARRY70GS, Jun 20, 2020
    #33
  14. '72 Skylark Custom 4bbl

    '72 Skylark Custom 4bbl Well-Known Member

    F872C171-103C-46E0-9AE1-29F68C86A28D.jpeg You guys have been great.

    So even with me rotating it by hand the points never seem to open. I went almost a complete rotation.

    Yep paint mark on my balancer matches up so that’s good.



    Kyle
     
    Last edited: Jun 20, 2020
    '72 Skylark Custom 4bbl, Jun 20, 2020
    #34
  15. 73 Stage-1

    73 Stage-1 Dave

    I see you’re in Colorado... how far up in elevation?

    A dial back timing light can help as I found it easier to read when everything is lined up at zero.

    Also, are you reasonably confident in your current timing light’s accuracy?

    You’ll get this!
     
    73 Stage-1, Jun 20, 2020
    #35
  16. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    If you are at significant elevation, did you tell Ken that? The engine would not run if the points were not opening.
     
    LARRY70GS, Jun 20, 2020
    #36
  17. '72 Skylark Custom 4bbl

    '72 Skylark Custom 4bbl Well-Known Member

    About 5,400 feet. I have a Craftsman 14065 model.

    I would think so only a year or two old & rarely used.

    Kyle
     
    '72 Skylark Custom 4bbl, Jun 20, 2020
    #37
  18. '72 Skylark Custom 4bbl

    '72 Skylark Custom 4bbl Well-Known Member

    I did. I believe he said he was going to go one jet smaller if I remember correctly to heal with the altitude.

    Kyle
     
    '72 Skylark Custom 4bbl, Jun 20, 2020
    #38
  19. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    In general, an engine loses 3% of it's power for every 1000 feet of altitude gained. Your 370HP/470TQ was likely corrected power. You could be up to 15-20% down from those figures depending on weather.
     
    Last edited: Jun 20, 2020
    LARRY70GS, Jun 20, 2020
    #39
  20. 73 Stage-1

    73 Stage-1 Dave

    Did Ken set the distributor up and recommend the timing curve for the altitude too? I’d bump the initial timing, with the vacuum advance disconnected, 10 or so degrees and see how the engine reacts. If you have it at 12 degrees btdc now, I’d try 20 or 22.
     
    73 Stage-1, Jun 20, 2020
    #40
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