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Thread: 4age just will not time

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    4age just will not time

    hello
    i have been struggling with my 4age for a while
    i just cannot get the timing right


    i have read everything, tried everything and cannot resolve so here is where i am:


    4age 16v
    7rib block
    source is an ae86 rwd corolla
    big port
    it is mated to a t50 and mounted rwd
    corolla distributor
    hyperpack ecu


    the crank pulley and cover are setup as corolla, the pulley groove aligns to the cover at 0 . the crank wheel groove aligns to the block mark... so all the crank components align


    new piston rings, valves have been ground and seal perfectly, new head gasket


    both cam wheels align with back plate
    the cam studs are in the correct orientation


    the belt is on (and of and on and off many times)


    belt is tensioned as per manual, all marks align as per manual
    cam dimple is visible through the oil filler


    align the distributor dimples on the body and the cog


    insert dizzy..using a broken cap i can see that the arm is dead on position 1


    i have a custom fabbed inlet manifold with a pair of weber dcoe


    starting:
    not a smooth start, feels like i am sparking on multiple cylinders.. it turns but halts almost as if i am firing 1and3


    then suddenly off it goes, starts and idles ok....


    but, as soon as you get to 1000 it starts to backfire, miss, then as you push on, it almost levels out but starts to stumble again


    internet research would suggest that i am off a tooth on the cams


    they are absolutely dead on


    so i check the dizzy and with a timing light at 800/900 rpm i am about 35 degrees btdc


    so i move the dizzy one tooth up or down... both make it almost impossible to start


    so i read that maybe the dizzy cog is on wrong and that removing it and spinning it 180 will fix this...


    not wanting to do this i figured that instead i can stab the dizzy in 180 degrees out and wire up the plugs with 1 where 4 is etc


    this starts and runs but is no better.


    so at the moment it is all back as per manual and runs like a broken tractor


    observations:
    the trigger wheel is not in line with the arm, is this correct? i read that the trigger wheel is a push fit.. can it move ? where should it be


    questions:
    what other idea do people ?

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    Racer Decade Plus User wildo105e's Avatar

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    Re: 4age just will not time

    you say you have 40 dcoe carbs, where did thses come from ??? how are these set up. I have not read all the detail but you may be chasing the wrong thing ?? If it ticks over badly but gets better with revs you may be moving onto the main jets then ?

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    Bodger

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    Re: 4age just will not time

    35 advance at idle sounds like a lot. What is the static timing set at ?

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    Re: 4age just will not time

    Quote Originally Posted by mjr View Post
    35 advance at idle sounds like a lot. What is the static timing set at ?
    Agreed - that can't be right! @ 35 deg BTDC you'd be getting max cylinder pressure about 15 - 20 deg BTDC - I'd be surprised if it didn't bump back off static comp at TDC! Should be in region of 10 deg BTDC?

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    Bodger

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    Re: 4age just will not time

    "it turns but halts almost as if i am firing 1and3"
    classic over advanced ignition timing fault

    Info. about timing the Hyperpack unit:
    http://img.photobucket.com/albums/v7...4AGEMULTI2.jpg

    If you have 35 BTDC static then you could be over 50 BTDC when running beyond idle.
    Last edited by mjr; 08-05-2017 at 20:10.

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    Re: 4age just will not time

    so i read up on how to find true TDC.
    i created a spark plug hard stop. removed all the plugs. inserted the stop. rotate engine to stop clockwise. marked crank. then rotated anticlockwise to stop. halfway between the two marks is TDC.

    hoping for a new mark... i discover that TDC mark on the crank pulley is spot on...and so are my cam marks..

    so i pulled the cam covers and as expected my cam lobes are pointing in opposite directions... which is correct.

    so then i look for the dimples on the dizzy and they align perfectly

    so all my setup is spot on.... but it is definitely not running right.i will post in youtube and leave a link here... there is something very out... maybe the distributor itself ?


    https://youtu.be/qa2BoRRgE4Y

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    Re: 4age just will not time

    you say you have 40 dcoe carbs,
    Can't see that anywhere?
    But from the vid, there do seem to be some backfires through the carbs and it is a bit of a tortuous routed manifold - are the carbs set up or guesstimated? The slow cranking may not be ign. related? Could be battery / starter related and if coupled with carb tuning - all bets are off?

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    Re: 4age just will not time

    sounds like it has too much inital timing advance, but that might simply be the starter/battery/wiring isnt upto scratch. but theres something else wrong, once it starts it sounds way too flat, do you have an air filter/ airbox fitted? what jets/choke are fitted to the carbs?

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    Re: 4age just will not time

    sounds like it has too much inital timing advance, but that might simply be the starter/battery/wiring isnt upto scratch. but theres something else wrong, once it starts it sounds way too flat, do you have an air filter/ airbox fitted? what jets/choke are fitted to the carbs?

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    Bodger

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    Re: 4age just will not time

    Easy way to check initial timing is to retard the ignition by turning the distributor clockwise. From the sound on the video you would need to turn it a fair way. My 4age would do the same as yours with more than 30 degrees advance at idle. The ignition unit you have adds approx 17 degrees timing after idle. 4age likes about 34 degrees max advance and 16-18 at idle.

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    Re: 4age just will not time

    At last I got this working

    It was a couple of things
    1) faulty starter solenoid was the cause of erratic turnover
    2) I took the cam cover off and marked the distributor
    cog. I then pulled it out and discovered that if I turn the cog one tooth anticlockwise and then insert. Timing was spot
    on
    3) faulty timing light was flashing erratically. It turned out to have a cracked magnet in the pickup !
    4) idled OK. . But was very lean on progression. So I balanced the carbs and set them rich. They are now very rich

    But it now runs !!! Feels flat on acceleration. Definitely needs some tweeking so it is booked on rolling road next week

    Thanks for all your help

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    Re: 4age just will not time

    Flat acceleration turned out to be throttles only half opening. A new weber throttle linkage fixed that. A couple of hours on rolling road. .. now running perfectly !!
    Will post my torque curve.. it was surprisingly impressive.
    Last edited by Laikathedog; 31-08-2017 at 12:30.

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    Re: 4age just will not time

    Duplicate post
    Last edited by Laikathedog; 31-08-2017 at 14:09.

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