timing tabs and indicators

Discussion in 'Ignitions & starters and electrically related comp' started by grumpyvette, Jan 12, 2009.

  1. grumpyvette

    grumpyvette Administrator Staff Member

    these things are a deceptively simply but necessary component on your engine, they range from the cheap stamped steel, and non adjustable versions to the much nicer adjustable versions, ONE basic thing youll need to know is where TDC, 90,180,270 degrees are located if and when you get involved with tuning your engine ignition timing advance curve or adjusting valves if you do in with the engine not running, ignition spark should be bright blue and impressive, if its, weak,narrow, yellow or red theres a problem so research the cause, verify the coil and voltage
    stock timing marks are very limited in the extent of timing changes that can be indicated
    There are 3 timing mark locations on the balancers on SBC engines that I know of, therefore there are 3 timing tab locations also. Plus the tab location varies with small and large balancers as far as the distance from the crankshaft.
    READ THIS RELATED THREAD, ON FINDING TDC
    http://garage.grumpysperformance.com/index.php?threads/finding-top-dead-center.967/

    http://garage.grumpysperformance.co...evy-damper-is-designed-for-your-engine.11561/

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    RICK L posted this bit of info
    "#1 is the balancer TDC mark lines up with the keyway. This is the configuration for 1968 and older balancers. There are two timing tabs for this, one for 6"+ balancers, and one for 8" balancers. This would not include 400 engines since they were all made after 1968.

    #2 is the balancer TDC mark is 10 degrees CCW from the keyway, looking at it from the front. This is the most common location for 69-up engines, and that includes 400s. There is a bolt on timing tab that works with this setup.

    #3 is the balancer TDC mark is 30 degrees CCW from the keyway, again looking at it from the front. Only a few 69-up engines were made this way. You have to point the timing light through the gap between the water pump and timing cover. I don't know if any 400 engines were built this way, I really doubt it. I had a 76 350 truck core that had this balancer and timing mark on it. The tab was welded to the timing cover instead of the usual bolt on tab in those years. The balancer was also very light for an 8" balancer."



    I found this info posted several places
    The three most common locations for the timing mark on the damper

    The exact years of the type of damper timing marks overlap one another, depending on the exact application.

    The pre-1969 damper has the TDC line on the outer ring at the 2:30 o’clock position- or 2º before the keyway centerline- i.e. the line is to the LEFT of the keyway, looking at the front of the damper or engine. The keyway is seen in the ID of the damper nose.
    The damper used from 1969 to about 1984 has the TDC line at the 2 o’clock position- or 10º before the keyway. You'll find that aftermarket dampers are the 10º type, as are the bolt-on tabs sold by the aftermarket, unless they're adjustable.
    Warning Note: This includes the SBC 400, although the 400 damper is counterweighted because the engine is externally balanced. Do not mix and match internal and external balanced dampers!
    A third timing mark was used from (some) 1978 to about 1995, and nearly all 1984-1995. It is at the 12 o’clock position- or 40º before the keyway. This damper uses a timing cover that has the tab welded on at about the 12 o'clock position. Professional Products lists the years for this type damper line as being 1984-1995 and is a 6-3/4” diameter damper.

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    READ THESE CLOSELY RELATED THREADS

    viewtopic.php?f=70&t=4683&p=12672#p12672

    viewtopic.php?f=70&t=967

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    KEEP IN MIND that theres TWO totally different damper and timing tab locations that are correct on the SBC engines and you must use matched components for almost all years the ting tabs and dampers show TDC to be at about 2 o,clock, but theres a few applications that used a 12 o,clock timing tab and damper combo and you can,t mix&match the two types

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    the fact is that due to manufacturing tolerances a dot-to-dot install will frequently be a few degrees off! now most guys might never notice, but it can and frequently does effect the engines power band so getting it correct helps and eliminates one potential source of problems (be damn sure you verify the cams degreed in correctly and the ignition firing orders correct and all the distributor wires go to the correct cylinder,s spark plugs and distributor cap locations)
    obviously you need to have a consistent base line advance curve to work with,
    on most Chevy v8 engines that run cams designed for street/strip use Ive generally found a advance that goes from about 8 degrees at idle speed (800-900rpm in most cases) and smoothly advances the ignition to about 36 degrees or about 28 degrees advance from where it started at to reach 36 degrees at about 3200rpm , is generally a good place to start, or about 82 rpm increase per degree of ignition advance , up to about 3200rpm, where increase turbulence and squish tends to speed the burn process, you can then play with the engine and determine what changes MIGHT be require
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    WATCH THIS

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    use of a camshaft install handle generally reduces the chances of damaged cam bearings
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    YOU MIGHT WANT TO READ THESE THREADS ALSO

    http://www.familycar.com/Classroom/ignition.htm

    viewtopic.php?f=70&t=967

    http://www.corvette-restoration.com/res ... ing101.pdf

    http://stores.unleashedcustommachining. ... gories.bok

    viewtopic.php?f=70&t=875

    viewtopic.php?f=70&t=202

    viewtopic.php?f=53&t=562

    http://www.atiracing.com/products/dampe ... ctions.htm

    viewtopic.php?f=53&t=279

    viewtopic.php?f=52&t=130

    viewtopic.php?f=52&t=90
    SUMMIT RACING AND JEGS CARRY DOZENS OF DESIGNS[​IMG]

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    you can even find them with a built in timing light strobe
    http://store.summitracing.com/partdetai ... toview=sku
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    you generally use them with a timing tape like this

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    http://www.summitracing.com/parts/MRG-4599/?image=large

    http://www.summitracing.com/parts/MRG-4600/?rtype=10

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    http://forum.grumpysperformance.com/viewtopic.php?f=50&t=723

    http://www.summitracing.com/parts/MRG-4598/

    the use of timing tape on the damper is a huge help and yeah, the glue on the tape tends to get loose so use some contact cement sparingly, the contact cement works, but a simple spray coat of a clear lacquer spray paint sprayed over the tape and allowed to dry locks it on the damper fairly well also, or you can spend just a bit more, and buy a damper cover, and adjustable timing tab, just remember to verify TDC
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    they make these timing tabs for BOTH SBC AND BBC , and IN SEVERAL DIFFERENT DAMPER SIZES ,SO BE SURE YOU ORDER THE CORRECT ONE FOR YOUR APPLICATION, remember theres been both different damper diameters and two common and actually three different locations on the timing tab index location for small blocks, so make darn sure the damper you use matches the timing tab your using, by verifying top dead center and not assuming the parts you have are correct, some SBC dampers and tabs fit/index on the timing tab location at about 2 o'clock on the timing cover, a few at about 12 o'clock
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    this picture shows almost exactly where the timing mark should be when the timing light flashes at idle
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    start with the basics, verify tdc (top dead center)on the damper and timing tab are truly indicating TDC
    if it is it sounds like the cam was installed a few degrees out of its intended index with the crank rotation(easily done if installing it (dot-to-dot)


    keep in mind that if the cam was installed without degreeing it in, with a degree wheel theres at least some chance the cams indexed incorrectly and its installed several degrees out of sinc.

    viewtopic.php?f=52&t=966&p=1682#p1682

    viewtopic.php?f=52&t=90

    viewtopic.php?f=52&t=196
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    viewtopic.php?f=52&t=4548&p=12699&hilit=timing+marks#p12699

    one common problem I see many guys go thru is the result of not understanding what visual clues, or obvious symptoms indicate, when they see them.
    when your breaking in a new engine or cam, one common problem indicator is the headers running excessively hot
    EXAMPLE
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    btw notice the front header tube seems to be a bit cooler and each header tube as you move to the rear looks a bit hotter, thats because the engine compartment air flow cools the headers less effectively as its heated as it moves from the radiator rear ward

    the picture above is commonly the result of having Your ignition timing too retarded for the 2500rpm-3500rpm your supposed to be lapping a new cam in at for the first few minutes,or the ignition advance curve rpm is to slow with a light load. Under a light load combustion is a slower process. Some of the combustion is still taking place after the exhaust valve opens which will make the headers glow.
    if your running a LEAN due to either jetting, tuning issues or a large vacuum leak....the overly lean fuel/air mix tends to raise the exhaust temps, obviously an IR temp gun can be very useful in spotting this condition early, but its even more useful because it can easily tell you if only one or two headers are running significantly hotter, usually indicating a vacuum leak or tuning issue rather than ignition timing where all the header tubes tend to run hot.
    now obviously you should have verified the correct oil and coolant levels and verified your ignition timing and advance and firing order before starting it , or seeing the headers glow before letting the engine run very long
     
    Last edited by a moderator: Aug 25, 2017
  2. grumpyvette

    grumpyvette Administrator Staff Member

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    ALWAYS CHECK YOUR FIRING ORDER SEVERAL TIMES!
    you might be amazed at the number of times , that simply stopping,dropping back to the basics, and inspecting,carefully verifying the function and installation of each component used leads to finding, isolating and correcting problems.
    I recently had as neighbor install a 4/7 swap cam, who spend several hours trying to get his weekend toy to idle correctly, before he asked for my help, and mentioned, that he had verified the firing order several times, 1.8,4.3,6,5,7,2...........
    only then to get this stupid grin,after telling me he had checked EVERYTHING SEVERAL TIMES! after realizing after fighting for several hours what the problem was..
    SBC cylinder numbering;
    -2-4-6-8
    1-3-5-7


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  3. grumpyvette

    grumpyvette Administrator Staff Member

    FIRING ORDER CHART
    Heads up! from
    http://www.donzig.com/tech.html

    These firing order diagrams show rotor rotation direction and give the location of the number one spark plug wire lug on the distributor cap. The location of your number one lug may, and in fact, most probably is, different from that shown. Your number one lug is which ever lug your rotor is pointing at when your engine is positioned so that the number one cylinder is at top dead center at the end of the compression stroke, not the exhaust stroke.

    To identify the alignment of the timing marker and the "zero line" on the harmonic balancer which represents top dead center at the end of the compression stroke, just remember that it occurs just after the intake valve closes. Remove the valve cover so that you can see the valves for the number one cylinder. Identify the intake valve. It is aligned exactly under the runner of the intake manifold. The exhaust valve is exactly aligned with the exhaust port of the cylinder head. Take precautions so that the engine can not start accidentally as you rotate the engine (i.e., take out the spark plugs). Rotate the engine and watch the intake valve go down. Keep rotating the engine until you see the intake valve just begin to come back up. Stop, your close. Look down at the timing marker. Rotate the engine just enough more to bring the "zero line" on the balancer into alignment with the timing marker. Your engine is now at top dead center on (at the end of) the compression stroke.

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    1. Determine the total amount of degrees you wish to run in the engine.
    2. Determine the total amount of degrees your ignition
    3. Through additions & subtractions, find out where to set the crank BTDC, and do it now!
    4. Find out where the number 1 cylinder segment is in the cap and mark on the outside case of the ignition with a marker.
    5. Find out where last cylinder segment in the firing order is on the cap and mark that on the outside of the ignition case.
    6. Line up all intermediate oil pump drives and gear drive so as to place the rotor approximately � of the way between #1 cylinder segment and the last segment in the firing order when the ignition is firmly seated on the manifold or block surface.
    7. At this time you should check the play between the intermediate shaft and the ignition or the block and the thrust face on the gear. Some play or clearance must be present. If not when you tighten your ignition down, you might be jacking your oil pump gear through the bottom plate of your pump.
    8. Put the retaining clamp on now and just snug up the bolt / nut retainer so you can move the ignition with a slight amount of resistance.
    9. Hook up the buzzer to the primary wire and a good ground and turn it on. The buzzer may be buzzing now or it may not , don't worry at this time.
    10. Determine which way the rotor rotates and hold back against it with your thumb and apply a few ounces of pressure.
    11. Turn the outside case of the ignition against the rotation until the buzzer just stops. You might have to do this 2 - 3 times to get the feel of it, but the mag will fire just as the buzzer stops (this is when the points open).
    12. Tighten up the ignition retainer bolt / nut until the ignition will not turn.
    13. To check if your right there in the ball park ignition wise, reach up and grasp the rotor and turn it the way you did before. It should quit buzzing and now buzz with the alternate application and reduction of pressure on the rotor.

    (btw when using a spark plug in the cylinder head style piston stop tool
    if your standard strait probe/stop tool is not touching the piston due to the shallow enterance angle

    youll want to remove ALL the spark plugs and back off ALL the rockers
    on not only cylinder number one ,
    but all the cylinders
    ,
    so you can feel the engine as it moves/rotates
    yes youll need to adjust valve when your done finding TDC
    http://garage.grumpysperformance.com/index.php?threads/adjusting-valves.196/


    and make sure the cars not in gear so that the engine can be rotated much more easily when done manually,
    this prevents the valves in cylinder number one from opening and removing the other spark plugs greatly reduces resistance due to compression.

    yes your problem, is FAR from rare and in fact its very common most guys simply take an old spark plug,
    put it in a vise and bust out the old porcilian center and re-thread the interior of the remaining metal hex.
    or buy a tool like comps
    https://www.summitracing.com/parts/...-_-comp-cams&gclid=CJ3wuuyJ8tACFYOFswodCKYKvw
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    you then buy a 6" threaded bolt, screw it into the plug body
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    with similar thread pitch and thread that fully threaded bolt about 3" of that bolt entending past the spark plug base,
    and heat and bend it with your propane or acetolene torch in a shallow curve,
    now BRAZE or weld a cheap socket head wrench to the bolt head so it can,t move off the bolt and indexed so ,
    its pointing strait up when the bent internal part of the piston stop points strait down ward

    RELATED THREADS

    http://garage.grumpysperformance.com/index.php?threads/cam-degreeing.9010/#post-35474

    http://garage.grumpysperformance.com/index.php?threads/vertex-ignitions.1320/page-2#post-69524

    http://garage.grumpysperformance.co...et-it-to-last-cam-install-info.90/#post-31431

    http://garage.grumpysperformance.co...ter-1-for-timing-ignition-cam.966/#post-18999

    http://garage.grumpysperformance.com/index.php?threads/turning-your-crank-manually.5933/#post-18274

    http://garage.grumpysperformance.com/index.php?threads/cam-degree-equipment-tools.1759/#post-4441
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    now you can stick the bent bolt into the cylinder, thread the bolt body into the head and once its seated in the head,
    you can easily index the bent part to point down into the cylinder where it will contact the piston as it rotates
    which a strait bolt would not do due to the shallow enterance angle
    be aware that you need to be able to feel the engine stop when it contacts the probe tip, if you don,t manually turn the engine fter first removing the other spark plugs ,
    and backing off the rockers the resistannce to rotation the valve train and compression have will make felling the piston contacting the piston stop difficult,
    and you damn sure don,t want to bend or break the piston stop.
     
    Last edited by a moderator: Apr 16, 2017
  4. busterrm

    busterrm solid fixture here in the forum

    Aftermarket timing tabs and TDC

    I was looking at another site, and there is a fella asking a question about his balancer and tdc. Well, all these guys are saying that depends on the year model of the engine. The guy building the engines says its a Dart block. Well, Indycars and I have them too, so my question is: The normal way of finding TDC and using a bolt on adjustable tab is what we need to do right? That is what I do with all my engines and not had problems yet?
     
  5. Indycars

    Indycars Administrator Staff Member

    Re: Aftermarket timing tabs and TDC


    That's what I did, was use an adjustable pointer. Actually I forgot to
    install the pointer and calibrate it before I put the heads on, so I had
    to make a piston stop from a spark plug.

    http://www.summitracing.com/parts/sum-163800







     

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  6. busterrm

    busterrm solid fixture here in the forum

    I plan on doing mine before the heads go on. I want to visibly see the piston at TDC, going to use my dial indicator to verify True TDC. Then just use a bolt on adjustable tab and be good with it.
     
  7. Indycars

    Indycars Administrator Staff Member


    I feel it's more accurate to use a piston stop than a dial indicator. The indicator leaves the decision up to you when the piston hits zero movement. That might leave you wondering where to make the call for a couple of degrees. You can see from the chart below that there is plus/minus 2° (4° Total) where the piston has only moved .001 Inch.




    You can use this link to download the Excel file and do your own calculations with the exact geometry for your engine.

    viewtopic.php?f=99&t=4385

     

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  8. busterrm

    busterrm solid fixture here in the forum

    Actually I use both the piston stop(bridge type over the bore), and dial indicator. I use the bridge to get it close, then fine tune it with the dial indicator on the bridge. I get it real close! It usually takes me about 2 hours to get it right. I don't care for something coming in contact with the piston, so I use a bolt(3/4 drilled and tapped 1/4-20 in center) that I made a phenolic bumper as the actual piston stop. The phenolic piece is drilled for a 1/4-20 bolt and countersunk down into the phenolic material, the bumper is about 3/4 thick. The 1/4 bolt has a small screw head on it. I have been thinking of using the short bolts for the roller cam retainer plate you and got at Fastenal. I would have to grind it down to a smaller diameter. In my line of work, it's easy to get all the stuff to make one. I have even thought of using a piece white nylon for the bumper.
     
  9. vettman040

    vettman040 New Member

    Guys, I have a 496 Chevy BB. I bought it already built and assembled. It is a 90-91 block with 2 piece rear main seal. I bought a brand new GM balancer for 454/502 (externally balanced) that is degreed, a timing cover for an 8" balancer that went to a BB (don't know the year of cover). I'm having a heck of a time trying to timing the engine to run smooth. I set the timing gears at #1 TDC and the balancer at 0 degrees before installing the timing cover. I installed the distributor to fire number 1 but it's having a hard time starting, and if it runs, doesn't run good even after trying to set the timing. I'm setting at 12* initial and centrifugal coming 36-38* with vacuum disconnected. I have tried to move the distributor CC one tooth to retard and forward one tooth CCW to advance, can't get it running right. After it heats up, lopes really bad trying to restart, if fact sometimes won't start at all.
    I've read the posts here and began thinking that possibly my timing pointer and or balancer is not aligned right. Because the engine is in the car (65 Corvette), what's the proper procedure for locating TDC on the #1 piston. BTW, the engine is is hard to turn by hand (breaker bar on the front balancer bolt).
    I'm at wits end trying to get this beast running right. Any help/suggestions would be life-saving at this point.
     
  10. grumpyvette

    grumpyvette Administrator Staff Member

    like in most cases, where your looking for a cure to a problem, you need to isolate and test each potential area, that might be the source and verify its correctly functioning, you need to verify exactly what your dealing with before making any assumed required changes.
    obviously you start, with the basics , by verifying that the damper and timing tab indicate true mechanical TOP DEAD CENTER, then you need to verify the cam timing by degreeing in the cam, once both are verified correct youll need to properly adjust the valves and then verify the ignition advance curve

    viewtopic.php?f=52&t=966

    viewtopic.php?f=52&t=90

    viewtopic.php?f=52&t=5482

    viewtopic.php?f=52&t=3816

    viewtopic.php?f=52&t=90&p=16617&hilit=degree+wheel#p16617

    viewtopic.php?f=55&t=109

    viewtopic.php?f=52&t=196

    viewtopic.php?f=52&t=181


    Where are you located?
    there might be a local member willing to help you out!
    you should find THESE LINKS USEFUL,
    Id suggest reading the links, and sub links posted above and not just skipping thru them in a quick skim through
    then
    adjusting the timing mark on the timing tab and damper to reflect true TDC,
    then degree in the cam,
    Id also suggest theres a good chance the valves are not properly, adjusted or theres a valve train clearance issue,
    once youve done a compression check,and verified cam and ignition timing youll look for tuning issues, vacuum leaks , look for ignition system and fuel supply problems
     
  11. Loves302Chevy

    Loves302Chevy "One test is worth a thousand expert opinions."

    Forget about adjustable and expensive timing pointers. If you can properly locate TDC, (you are already degreeing your cam - aren't you?) then here is how I do timing pointers:
    You don't have to try to get one of these to fit and be accurate or cover up everything with one of these. Ever try to time your engine with this setup?
    I'm using an inexpensive 2 piece aluminum cover where just the cover can be removed, exposing the entire timing set, but the front of oil pan does not have to be dropped to do it because the front seal for the oil pan remains in place.
    With the timing cover and harmonic balancer bolted in place, set the crank to perfect TDC (use your degree wheel). Since I just finished degreeing the camshaft, without moving the crank, lock it in place and install the balancer - NO HAMMERS. Then all you have to do is use a center punch to mark the spot on the timing cover that aligns with the TDC mark on the balancer. My StreetDamper is counterweighted, so make sure you allow enough clearance.
    I used a stainless steel M4 x 0.7 mm screw for my pointer. Determine how far you want the pointer to protrude from the cover and cut the head off and sharpen to a point. I used 2 SS nuts & flat washers, 1 each on the inside and outside. You will have to check for clearance on the inside that the nut might contact the timing chain. Measure or use clay to check. If it does, then just don't use the inner nut and washer. This cover is almost 1/4" thick where the pointer is located, so there will be enough threads. If everything is good, then drill your hole with the proper tap drill. Then tap the hole. Assemble your new pointer to the timing cover and use red loctite on all threads to make sure it never loosens up. Cut off any excess screw threads flush with either the inner nut or cover. You now have the most accurate and easy to read timing pointer that will not rust - and even better, you did it yourself! Congratulations.

    TIP: Apply a ring of Permatex to the inside of the harmonic balancer hub before installing on the crank to prevent an oil leak, especially along the keyway slot. Place the Permatex about 3/8" further in than where the end of the snout will end up. It will roll into a bead as it is pressed on. Use anti-seize on the snout. Be sure to oil the seal and make sure that the lips of the seal do not get folded in. A dental pick works well to carefully straighten it out. Then use you finger to smooth the sealer, if you want to. Mike.
     

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  12. Indycars

    Indycars Administrator Staff Member


    Thanks for the great idea and pics!!!

     
  13. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member


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    Last edited: Feb 18, 2016

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