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Timing way off, but runs great?

Discussion in 'The Hokey Ass Message Board' started by Mattilac, Dec 4, 2011.

  1. George/Maine
    Joined: Jan 6, 2011
    Posts: 949

    George/Maine
    Member

    If you are using and old timing light with no added gadgets to fucya up.Put the light on mark and drive it,if it runs worse your cam timing is off.make sure your advance isn,t stuck.
     
  2. porknbeaner
    Joined: Sep 12, 2003
    Posts: 40,988

    porknbeaner
    Member

    I alwasy though david Allen Coe was cool, he had nice wives.:p
     
  3. George/Maine
    Joined: Jan 6, 2011
    Posts: 949

    George/Maine
    Member

    I don,t know if you entered the wrong cam #or not but the one listed is for AMC. This would not change your timing at tdc but maybe running better with valves off timing mark.
    The cam maybe just marked wrong.Just something to check.
    From what i see on crankshaft the keyway should be the right 2 1/2 teeth for TDC
     
  4. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 4,618

    Ebbsspeed
    ALLIANCE MEMBER

    The timing chain being off a tooth or two would be of NO (ZERO, ZILCH, NADA) consequence with regards to ignition timing. When you set timing, you are establishing a relationship between the distributor shaft and the crankshaft. Granted, having the cam off a tooth or two will make it run like crap, but has nothing to do with the timing relationship between distributor and crank.
     
  5. Three Widow's Garage
    Joined: Jan 18, 2010
    Posts: 202

    Three Widow's Garage
    Member

    You might try checking your timeing light on a diffrent engine, see if it gives correct readings. The inductive pickup on the light might be picking up signals from adjunct
    wires? good luck JJ
     
  6. tubman
    Joined: May 16, 2007
    Posts: 4,188

    tubman
    ALLIANCE MEMBER

    It's got to be a wrong/slipped harmonic balancer or a wrong timing cover/tab. I have owned 7 SBC's in my life, and 2 of them had slipped harmonic balancers. That's a pretty high failure rate in my opinion. (The last slipped balancer was in a $5500 rebuilt 327 for my '67 Corvette). If the problem is a slipped balancer ring, these "If it ain't broke, don't fix it" guys aren't doing you any favors. If it can slip, it can come apart which can be problematic with water pumps, radiators, and other such things. (BTW, the "fresh rebuilt" balancer on the '67 327 turned out to have been a brief trip to the blast cabinet and a fresh coat of orange paint.)
     
  7. Certainly you've seen that the piston stop test verification showed the mark and tab are correctf if you've managed to see the don't fix it if it ain't broke guys; So WTF is this about..
     
    Last edited: Dec 6, 2011
  8. Thank you! I was about to write the same thing. Retarded or Advanced cam or not, it just isn't going to start at 35º of initial advance

    YEP! That or he's not doing the whole dead stop thing correctly (or both)
     
  9. Bad Banana
    Joined: Jun 20, 2008
    Posts: 769

    Bad Banana
    ALLIANCE MEMBER
    from Oklahoma

    Ok... I have been watching this thread since the beginning and I have pre-prepared myself for the flaming but here goes...:rolleyes:

    I personally have seen this exact situation many times. It has to do with the engine combination. The posters that say "it can't start like that" or "it should be pinging" have never run into this situation.

    The engines I have seen this on have low mechanical compression and are using a lot of camshaft lobe overlap. A good example of this is this engine

    http://www.summitracing.com/parts/NAL-12499529/

    Because it has low static compression and also a lot of cam overlap, the running compression is pretty low. An engine like this likes a lot of ignition lead and will not ping on today's pump gas. A lot of that has to do with the Vortec head design he is running (althought the engine I mentioned above does not have Vortec heads). Most of these type engines are very happy running for decades at 50-55 degrees total ignition timing because working cylinder pressure is not near pre-ignition or detonation. I usually just run an engine like this on the mechanical advance only and don't even hook up the vacuum advance. Put the total at about 50-55 degrees and don't worry where the initial is and just drive it.

    They also like a more aggressive accel pump shot as well. Most of them like to really pull hard at the higher rpms too. The O/P does not say what his exact engine combo is (if he did I missed it) but I am guessing it is close to what I describe. If I am wrong, then ignore me and carry on...;):D

    As for the dial back timing lights. They are not accurate at all in my experience. They can be repeatable but if you really want to know where it is, you either need to use timing tape, a degree wheel and mark it with a punch or saw blade, or spring for a crank trigger set up. The ignition timing on a set up like this isn't that critical.
     
  10. I don't think he has a lot of overlap, since he said he has 18" of vacuum - Overlap KILLS vacuum, so I don't think that's it.
     
  11. Roothawg
    Joined: Mar 14, 2001
    Posts: 18,631

    Roothawg
    Member

    I had a n HEI distributor that I bought brand new from Summit. It had 50 degreees of advance built into it. I still have it on the shelf. The Tech guys on the phone told me I was crazy and that there was no way it had that much advance built into it. I am going to send it to a reputable dist shop someday just to see what is wrong with it.

    The difference is mine pinged like crazy.
     
  12. Bad Banana
    Joined: Jun 20, 2008
    Posts: 769

    Bad Banana
    ALLIANCE MEMBER
    from Oklahoma

    At what engine rpm?
     
  13. And 150 on a compression test
     
  14. George/Maine
    Joined: Jan 6, 2011
    Posts: 949

    George/Maine
    Member

    One way the check TDC and you seem sure its right.
    Take the dist cap off and turn it till it points to number one ,then look at damper see how close you are.I never used the dialback timing light but think thats your problem.Another check get the right specs on cam pull off valve cover and check exhaust valve timing.If you pull the pulley off the key way is 2 1/2 to right for tdc.Keep doing the same thing try some thing else.
     
  15. Russco
    Joined: Nov 27, 2005
    Posts: 4,054

    Russco
    Member
    from Central IL

    So I have to ask how does it run at 10 or 12 initial and 36 total?
    I had a 327 with 9/1 comp. and a big solid that likes 45 total.
     
  16. Larry T
    Joined: Nov 24, 2004
    Posts: 7,678

    Larry T
    Member

    No, but when a camshaft is retarded (jumped a tooth) it will run sluggish, backfire through the carb, etc. and advancing the timing will help cover up the problem.
    Larry T
     
  17. Mattilac
    Joined: Oct 27, 2007
    Posts: 1,148

    Mattilac
    Member

    At 12 initial (according to the light), the vacuum drops way down, it barely runs, and I'll tell you why this is bizarre. When I first put the motor back together and had it in the car for fire up, I had the distributor set at roughly 12 initial to start with. Just to be clear, I did this by lining up the harmonic balancer mark with the 12° BTDC mark on the timing tab, then lining up the rotor end with #1 as close as possible. I got the thing started up, let it warm up for a while, check fluids, etc. Then I decided to time it (or at least get it closer to optimal) by ear. So I give the sucker a good twist further advancing it, and the motor's idle smoothed right out. I'm talking a good handful of advance, and then it purred. Sorry, I don't know or remember exactly how much more I turned it.

    To be honest, I really don't know what to think of it right now. My gut doesn't lean any which way. I can't see where I could be making an operator error, but I also can't see why a plain-jane 350 would have such a strange timing phenomenon.

    I could take a video of it running. Let me know if there's something you'd like to see. Thanks all.
     
  18. flatheadgary
    Joined: Jul 17, 2007
    Posts: 642

    flatheadgary
    Member
    from boron,ca

    matt, don't feel alone, i have the same situation with my 327. it will not idle at the stock marks. it is .040 over flat top, 461 heads, a .485 lift cam, a stock dizzy and dampener. it has to be advanced a good 3/4 inch from the stock marks to run. i also have done all the stuff i know and everybody else to no avail. i gave up and have drove it for over 2 years like this without any problems. i know how you feel though. the curiosity of why it does this is maddening.
     
  19. Bad Banana
    Joined: Jun 20, 2008
    Posts: 769

    Bad Banana
    ALLIANCE MEMBER
    from Oklahoma

    Still not seen the answer to this one. At a high enough idle and with the timing advanced far enough, my race engine will have 18" of vacuum too.

    The engine I linked to above has 175-180 on a cranking compression test. Cranking compression is different than running compression especially with more overlap in the cam.

    Exactly :D;)


    Bingo! There are a lot of these engines running around and they are fine. If it is pinging or bucking the starter, then you need to fix it. If not, just run it.

    We have a winner. What is the idle speed and engine vacuum with this timing setting?


    Your choices are:
    1. Drive it as is.
    2. Pull the damper and mark it acurately at 35-40-45-50-55-60 degrees using a degree wheel or timing tape and get a better reading with a non-dial back light.
    3. List the engine combo with accurate compression ratio, camshaft part number or specs, intake, carb, distributor etc and what engine vacuum you have at specific ignition timing and engine rpm.
    4. Keep this thread alive with 4-5 more pages of "it can't be that" or "it must be this" without any real data to support any of it.

    I'll lead a horse to water but I ain't gonna stand on it's head and make him drink it... :cool:
     
  20. I had a 360 mopar that had stock miserable compression (probably 7.5:1) and a 284/484 cam, it ran well with a lot of timing, and pulled like a mother at upper rpms. It never bucked the starter or pinged, and I could mix super and regular gas without issue in it.

    That said, I brought the compression up to a true 9.5:1 and then it pulled like a freight train right from idle (A lot less timing too)
     
  21. MAD MIKE
    Joined: Aug 1, 2009
    Posts: 346

    MAD MIKE
    Member
    from 94577

    TIMING MARK LOCATION
    TIMING MARK CALCULATION LINK
     
    Last edited: Dec 7, 2011
  22. Sheep Dip
    Joined: Dec 29, 2010
    Posts: 1,572

    Sheep Dip
    Member
    from Central Ca

    When in doubt use a vacuum gauge.
     
  23. porknbeaner
    Joined: Sep 12, 2003
    Posts: 40,988

    porknbeaner
    Member

    Ebb
    I have been trying to tell people that for ages on the ignition timing and relation to the crank as opposed to the cam shaft.

    I run my cam shafts slow by a degree or two myself, but a tooth in either direction on a smll block may cause issues with the valves and piston tops. I guess it depends on the quench area.
     
  24. George/Maine
    Joined: Jan 6, 2011
    Posts: 949

    George/Maine
    Member

    If you want to take the time and check this its not that hard seeing you put it together. On the TDC mark
    Mark 28degs BTDC now in other direction mark 20 degs ATDC.
    With the valve cover off look at the tdc both valve closed,now one full turn to tdc past to 20 degs the exhaust valve should just be closing.Now 2 nd test turn is clockwise dirrection same dir till you get to 28 BTDC the intake should just be opening.
    I know they will run one tooth off maybe two.
    I,m sure if you have used your timing light before is ok.
    I think you are off 1or 2 teeth off.
     
  25. Mattilac
    Joined: Oct 27, 2007
    Posts: 1,148

    Mattilac
    Member

    Bad Banana,

    Idle was around 1000RPM. Cranking compression test was done with the engine cold. I've been trying to give you all the data I can provide. I do not know the compression ratio, but I can tell you everything else about it.

    Pre-'86 small block 350 (casting # 3970010) w/ stock dish pistons
    Iron Vortec heads (casting # 10239906)
    Comp cams 268H (specs here: http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=15&sb=2)
    Edelbrock RPM Air-gap intake + #1405 600cfm carb leaned out 8% in cruise mode
    Stock HEI distributor
    Hooker headers

    I will check the actual vacuum and idle numbers again at 12 initial. Thanks to everyone who has contributed.
     
  26. porknbeaner
    Joined: Sep 12, 2003
    Posts: 40,988

    porknbeaner
    Member

    Somehow I think that 1000 rpm idle does away with runs great, unless you have one helluva a gnarly cam. With dish pistons you can't have much in the line of compression, like around 8:1.

    Probably better disregard anything I have said previously. I haven't given you any good advice. Other than to loose the dial back timing light. The only way you can tell your real total advance is to mark you balancer or with a timming tape.
     
  27. budd
    Joined: Oct 31, 2006
    Posts: 3,479

    budd
    Member

    firstly i don't think a SBC will run off a tooth on the timing chain. i have been present when two or three SBC have been turned off and would not restart because they had jumped a tooth, secondly i think your timing readings are just messed up for some reason and it's not really 30 and 60, my guess might be your getting induction crossfire on your timing light, maybe.
     
    lbcd likes this.
  28. john walker
    Joined: Sep 11, 2008
    Posts: 1,065

    john walker
    Member

    are the wires to the distributor switched?
     
  29. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 4,618

    Ebbsspeed
    ALLIANCE MEMBER

    Induction crossfire would be a minimum of 90 degrees off, (plus or minus whatever the "real" advance is) assuming the false signal was coming from wire #8 or #2.
     

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