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Setting your ignition timing

Discussion in 'Tips and Tricks' started by Mighty Milt, Sep 9, 2008.

  1. Mighty Milt

    Mighty Milt Moderator

    ther was a thread going around a while back, i can't find it now, but someone was asking about setting their ignition timing and found that it ran much better around 8* BTDC rather than the recommend 6* and something just struck me.

    when you are setting your engine timing on most models of cars you have disconnect the vacuum advance from the distributor and plug the hose with a screw or something. you will notice the engine RPM change and this is where you should be setting your initial engine ignition timing.

    on my 95 toyota truck EFI and my 91 daihatsu charade EFI you had to open up the relay box in the engine compartment and put a jumper wire across two terminals in what look an empty spot for a relay. this would change the engine rpm to set the initial engine ignition timing. the jumper wire was not a "trick" is was how the factory manuals explained to do it.

    when you finish setting the timing and connect the vacuum hose (or remove the jumper) make sure your distributor is advancing. rev the engine and make sure that mark moves, you should usually see (and this is a vague estimate) a minimum of 20* advance from idle to high rpm.
    Dan likes this.
  2. Dan

    Dan Member

    In reading through manuals, i remembered your post... found some references on timing advance for my 550's.

    vac advance starts at 3.15 (in.Hg) at 0 degrees and ends up at 20 degrees of total advance with a vac of 7.48(in.Hg).

    centrifugal/mechanical advance starts kicking in at 1500 rpm at 0 degrees and ramps up quickly to 14 degrees at 3100 rpm's then, tapers off to 24 degrees at 6000+ rpm.

    neither are in play at idle for my carbuteted engines.. i pulled the vac line and had no change in timing at idle and the mechanical advance didn't move anything until i revved it over 1500 rpm.

    your "vague estimate" is sounding like a well educated guess. good call!
  3. blue_miner

    blue_miner New Member

    im not sure if what im doing is right..but its holding up well

    here is what i do (using a portable digital tachometer)

    STEP 1. getting the 'operating' idling speed

    set the gears to neutral and engaged the handbrake. crank up your engine.
    wait until your engine is warm. switch-on one by one all electric current consuming device. i mean all, from headlights, hazardlights, radio, wiper motor (splash some water on the windshield for lubrication), etc. if your engine falters, adjust idle speed until ALL devices are operating. using the tachometer, record this IDLE SPEED. in my case it was around 950 RPM. power down the devices and go to next step

    STEP 2. now its time to mess with the engine timing

    loosen the distributor, and slowly rotate it. in doing the rotation, you will see your RPM readout getting lower or higher...adjusts where the RPM is getting higher then suddenly lowers. counter-rotate until the tachometer reads out the highest RPM you can get. your tachometer should be reading greater than the IDLE SPEED. tighten the distributor. you may want to verify your timing using a timing light. compare it against the factory setting indicated in your manual. you might be surprised.........of your accuracy..ehehehehehe

    STEP 3. now we mess with the carburetor...tsk..tsk..

    locate and adjust the FUEL MIXTURE SCREW until you get the highest RPM readout. at this time, your engine should be running aggressively...vroooooooooooooooooooom. the tachometer reading should be around 1000-1200 RPM. no, im not that crazy to stick with this kind of 'IDLE' speed.

    STEP 4. adjust the IDLE SCREW until your RPM readout is about the same as the readout in STEP 1.

    this shouldnt take 30 minutes of your time. try driving your mini truck around.

    if you do try this, kindly send feedback on this thread.
  4. torpedoman

    torpedoman New Member

    the average engine will preform acceptible at the factory reccomended setting. to set YOUR engine to preform at IT's BEST use a vacuum gague. at idle adjust timing for the max vacuum reading then back off for a slight drop on the gauge (about 1 in) this compensates for wear in all the gear train and other moving parts. If you have changed the cam in an engine it is the only way to set the timing to get the performance you paid for.
  5. Tinytoy

    Tinytoy Member

    Step#3 Would this not result in an overly lean setting? When we use to set up R/C plane engines you would lean out high needle to get max rpm's then hold the plane vertical to see if there was a rpm drop(too lean)
    These trucks are light ,but not that light! Any thoughts?
  6. Dan

    Dan Member

    I've set up these trucks with similar methods and was quite a ways off on the optimum settings. max rpm's on setting timing left me with no top end (overadvanced) and a lack of bottom-end responce/power on a too-lean mixture. I'm sure each engine sets up a bit differently but theres no way mine would run well if tuned by the rpm's method. maybe too much wear and tear on mine to compensate for. my rpms maxed out at about 18 degrees of advance but performs best at about 8-10, and about a half-turn back from max lean stopped the hiccup when i would throttle up from idle.

  7. Tinytoy

    Tinytoy Member

    fuel mixture screw

    Is the fuel mixture screw set up clockwise to go lean (screw into carb) and counterclockwise to enrich. The screw interferes with the flow of fuel?
    There was a post on a different site stating ballpark air/fuel mix was 2.5 turns out from completely screwed in.This is the top screw on a carry 660 carb.
    Last edited: Dec 28, 2008
  8. Tinytoy

    Tinytoy Member

    :eek: I see this conversation has already happened once or twice.Set up like a needle valve, controls the rate of fuel.clock wise lean ccw rich;)
  9. torpedoman

    torpedoman New Member

    yes screwing it in closes off fuel out allows more to flow, most carbed engines uoe 2 1/2 turns out as a starting point and most of the time it is too rich but they run that way so you can adjust from there, engine must be at operating temp to do the tuning," lean drop tuning" turn in until max r.p.m. is attained back out until you get at least 25rpm drop the hardest part is to do it very SLOW turn and give it a chance to take effect. too lean will be too hot and burn pistons and valves too rich fouls plugs used plugs should be tan in color. Crude check= run engine at 2000rpm for a couple of minutes turn off ignition while running at 2000 pull plugs and color check.
  10. johnnymac

    johnnymac New Member

    i failed air care

    how can I check timing with a timing light? Thanks
  11. project_x

    project_x Member

    What were your aircare numbers?

    I failed my emissions too. I had high hc and high co.
  12. johnnymac

    johnnymac New Member

    air care #246 allowed tested 646
  13. Mighty Milt

    Mighty Milt Moderator

    if you fail your emissions test, you can usually bump the timing up kinda high, then turn the idle and fuel mixture down a bit to compensate. what that does is make the engine run kinda hot. hot is clean, it burns all the crap out. it worked every time on my big block.
  14. fupabox

    fupabox Active Member

    Milt is correct on the timing I do it for emissions on my volvo turbo every 2 years for inspection then back it back off a few points so I can run on reg gas without pinging. When I forgot to put it back before the test once it failed the test...rebumped timing and good to go
  15. o8k

    o8k Member

    The manual (from lulu ) for my carry shows the air/fuel mix screw looking like a peg w/ 4 holes in it, rather than somthing i would expect (phillups, standard, allen, etc). Am i an the right place? Do i need some special tool to turn it?
  16. project_x

    project_x Member

    Mine is a standard slot but you had to get at it with a rachet, or a with just a bit in your finger tips.
  17. Tinytoy

    Tinytoy Member

    that is a tamper proof cap, ditch it and there will be a slotted cap screw underneath:)
  18. o8k

    o8k Member

    Ah ha! apparently it worked, it proofed me from tampering... :D
  19. candyk123

    candyk123 Guest

    does anybody have the factory timing numbers for the '91 mits Bravo 3g83? I'm having a mechanic take a look at my Bravo sometime soon. I'd like to have the proper numbers for him to put it back the way it should be.

    When I bought my Bravo Van, The thing shook extremely bad. The steering wheel vibrated terribly, leaving the hands feel a bit numb. So I took it in to this mechanic, from the place I bought the vehicle from. I asked him to do whatever he could about the shaking, and he said he'd take care of it by adjusting the timing. I had no idea it would cause trouble in my baby. Now my red light is on in the tach, it's blowing out wicked white smoke out the exhaust, and I'm wasting gas. I know absolutely beyond the shadow of a doubt that my fuel efficiency is screwed up. last $20 fill I only got 63 or 68 km out of it, compared to my usual way beyond 100km when I first bought it. I'm certain the problem is timing.

    Any suggestions?
  20. Dan

    Dan Member

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