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2Ltr 1977 tune up challenge

Discussion in 'Engine & Transmission' started by D1VWT3, Apr 30, 2016.

  1. D1VWT3

    D1VWT3 Member

    Messages:
    50
    Location:
    Carwoola
    Hi all,

    I changed pushrod tubes and adjusted valve clearances .15mm cold and installed new plugs .7mm gap and set points 0.4mm and camper ran better than ever for two weeks.
    After that it lacked power and was running a bit rough.

    Inside the engine bay i noticed that the carbi linkage seemed looose. On inspection i needed to remove the auto choke cases and tighten both securing screws as one from each side had almost removed itself and the other were barely holding it all together.
    On reassembly it seemed that the syncronisation had to be adjusted and now its still rough and backfiring after a few minutes of idling.

    Timing for this engine is baffling. In the 'Bentely offical service manual timing varies from 7.5deg before tdc to 10deg after. They all state 'with vacum hoses attatched'
    Im assuming that it refers to Vac advance on dizzy, mine does not have a vacum advance.

    I have noticed small vacum hoses at the base of both carbies that have been blocked.

    The carbi syncing and tuning seems confusing but i have a tacho, airflow meter and timing light so surely i could do it.

    Any thoughts, please and thankyou
     
  2. peter drogi

    peter drogi Member

    Messages:
    68
    Location:
    bass hill
    Spark plug leads? In all the work that got down ....test the leads individually and see if one or more is no longer doing what its suppose to.
     
  3. cbus

    cbus Well-Known Member

    Messages:
    13,478
    Location:
    sunshine coast
    Bently is american and they had a lot of different anti pollution gear including advance/ retard dissys.

    Sounds like you have a 009 dissy ie no vac advance.
    As such your timing will be 7.5 BTDC

    Points often wear n close up from new in first few weeks.
    Symptoms being bad idle n low end power.
    Better at upper rev range.

    Recheck points and recheck timing for starters.

    Backfiring could be bad timing, poor fuel mix.?

    After doing points,timing.
    Check operation of chokes.
    They want to come off evenly within a few minutes.
    If the backfiring is not evident when chokes on but is once they are off and engine fully warmed up the its possible you are a bit lean for some reason.

    Unlikely to be base settings if you havent touched them.
    Check what you did on resync.

    Check for air leaks at manifolds and carb bases , hoses knocked off etc.

    If you have changed settings retrace what you have done.

    Search here for a good post on tuning carbs
     
  4. Mordred

    Mordred Super Moderator Staff Member

    Messages:
    3,005
    Location:
    Penna, Hobart
  5. oldman

    oldman Super Moderator Staff Member

    Messages:
    10,634
    Location:
    Avalon Beach NSW
    As posted above....get rid of the 009, a bus will never run as it should with a mech. advance dizzy.....they were meant to be on beetles.
    Matched, stock components in best possible condition will give you the most reliability.
    Good luck,
    Cheers,
    Mark
     
  6. Mordred

    Mordred Super Moderator Staff Member

    Messages:
    3,005
    Location:
    Penna, Hobart
    Not to undermine you Mark, but 009 dizzys were never fitted to any production car engine out of the VW factories. I think they may have been used on the industrial engines. As you said, they are very unsuited to buses particularly as they don't advance until the revs come up which doesn't help pickup. They are also known to flat spot on acceleration..

    Adrian
     
  7. oldman

    oldman Super Moderator Staff Member

    Messages:
    10,634
    Location:
    Avalon Beach NSW
    No probs. Adrian......had been told that by someone on here.....now know better:)
    Cheers,
    Mark
     
  8. kombiwhisperer

    kombiwhisperer Member

    Messages:
    146
    Location:
    fraser coast queensland
    Of course you guys are assuming that these part no. dizzys are the same as leaving the factory 35 years ago????

    You have to manually check each dizzy you use, especially in chinese flavour--Have on here from a southern parst supplier that has 36deg mech advance!!

    I prefer to run 005's original Bosch, they should have 15-18deg Mechanical advance in by around 3000rpm, plus 10deg initial fitted,
    will suit pretty much any engine, vacuum advance on top depends on how good the engine is at cruise, normally bugger all on a half worn out Kombi engine
     
  9. Mordred

    Mordred Super Moderator Staff Member

    Messages:
    3,005
    Location:
    Penna, Hobart
    No, I am not expecting them to be the same as when they left the factory, but at least they started out right, and have a greater chance than the chinese ones of being close to the original curve, rather than different from unit to unit as the come of the production line.

    I still hold that a vacuum advance on a bus is a greater advantage than a mechanical that gives flatspots on acceleration using the original carbs in good working order. They were designed to use a vacuum advance so hardly surprising they may not work as well with a different system. I sold a bus recently with a new 009 copy and petronix fitted to replace a very worn original and while fine on the highway, after numerous issues it has been replaced with a serviceable original which has sorted flat spots and odd running issues. I had heard about quality problems with them but now having experienced problems first hand I won't be recommending them.

    Adrian
     
  10. kombiwhisperer

    kombiwhisperer Member

    Messages:
    146
    Location:
    fraser coast queensland
    I'm with you with chinese junk, I will not use them, all they are good for is the people selling them making a profit

    Remember that vacuum advance is referenced to throttle vacuum and will only come on at cruise and is an economy device, and shouldn't be added into calculated spark advance.

    I have had trouble with those pretend electronic dizzy's(will not warrant my engines with them) not having sufficient spark current, and crazy dwell time which gives you the flatspots you refer to--gotta light the fire hard and fast

    We are planning a Dyno test session where we will test points, Petronix, then one of my electronic Bosch dizzys, all on same engine with same advance curve, should be interesting---also doing venturi size evaluation on the IDF's, hopefully to dismiss a few myths.
     
  11. D1VWT3

    D1VWT3 Member

    Messages:
    50
    Location:
    Carwoola
    I have discovered that i have lost valve clearance on inlet valve #3 cylinder. (for a second time after only 1hr drive and being set by mechanic as i began to doubt my skills)

    I am going to pull off the head next and look for a valve seat issue as it must be the problem,
    (i cant see the valves growing in length.)
    Im thinking about getting unleaded suitable heads and then doing a complete teardown and rebuild myself, Can't be tooo hard can it?

    If i can find a vacumn advance dizzy i think that ill get it fit it and hopefully see the improvement as now you mention it she does have flat spots on acceleration.

    Ill let you know of my findings and progress.
     
    Mordred likes this.
  12. saabman

    saabman Well-Known Member

    Messages:
    4,888
    Location:
    Goulburn
    yes if the clearance is getting smaler that is a bad sign :(

    I bought a chinese dizzy to try in the beetle a while back to replace the 009 - if your thinking about it - DONT - timing was all over the place

    I rebuilt mine get a good manual and follow the instructions I can recomed Tom Wilsons "How to rebuild your Volkswagen Air-cooled Engine"
     

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