AMC head V volkswagen head..differences?

Discussion in 'Engine & Transmission' started by Archeress, May 19, 2011.

  1. Archeress

    Archeress Active Member

    Messages:
    5,476
    Location:
    CALOUNDRA
    One of the original reasons why i asked all this was i ended up finding out that vw heads need gaskets but amc heads dont. So if anyone gets a full rebuild make sure yuo or the mechanic know which heads you have already..
     
  2. Archeress

    Archeress Active Member

    Messages:
    5,476
    Location:
    CALOUNDRA
    ok....to set this straight.

    My engine got a full rebuild.
    The heads were and still are AMC...all of them.


    Due to a previous rebuild about 7 years ago ( before i bought the bus ) the amc heads were machined to different measurements..That is to say that each head was different to the next and wrong to boot. This was a mob in brisbane as i have the previous owners receipt.
    Once this information was discovered my mechanic was on the ball.

    As a result...the heads were sent to mick of mick motors in northgate and he machined them to what was necessary. Bingo...i have a lovely sounding engine with apparently an american lumpy cam. sounds groovy.
     
  3. Mr Beckstar

    Mr Beckstar Well-Known Member

    Messages:
    517
    Location:
    Bateau Bay, NSW
    Has anyone got anything more to say on this topic? I’ve just found I’ve got AMC heads. Is there significant differences in the porting, combustion chamber shape, compression ratio, etc? Any issues with temperature, cracking, etc?
     
  4. Barry

    Barry Well-Known Member

    Messages:
    2,253
    Location:
    Abbotsford NSW
    It all depends..................*sigh* (stupid answer)

    If you were building the best motor you could afford you would buy new AMC heads and
    • replace the valves
    • replace the valve guides
    • replace the valve seats
    • minimum 3 angle valve job
    • match port and polish to your manifolds
    • check combustion chamber volume and match
    now.......... i reckon I have added 10HP and $2,500 to you engine
     
  5. Barry

    Barry Well-Known Member

    Messages:
    2,253
    Location:
    Abbotsford NSW
    I certainly wouldnt be "just banging" an new set on

    So somewhere between nothing and what I have listed above is what needs to be done
     
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  6. Mr Beckstar

    Mr Beckstar Well-Known Member

    Messages:
    517
    Location:
    Bateau Bay, NSW
    I’m just looking to have Harry running like a standard Kombi. I’m not looking for extra power. I want the same drivability as standard with standard carbies, dizzy, cam etc.
     
  7. KahunaKombi

    KahunaKombi Super Moderator Staff Member

    Messages:
    17,696
    Location:
    Bracken Ridge, Qld
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  8. cbus

    cbus Well-Known Member

    Messages:
    10,570
    Location:
    sunshine coast
    From my limited checking how good replacement heads are , it would seem the AMC are the pick .
    BUT, typical for much aftermarket gear now produced and as Barry has mentioned ,they do need a clean up to ensure good running and longevity.
    Checking the points mentioned is necessary.
    Seems ports do need a check for casting Dag's.
    Polishing is not actually to a fine polish. Such can be counterproductive at ' normal' velocities.
    Cutting to 3 angles is normal but apparently lacking in some valves?
    Seems valves and guides may be substandard.
    Probably some opinions that vary but for the price I consider better exhaust valves at least are a consideration if unsure.
    CC ing.( measuring volume of combustion chamber) is part of ensuring things are balanced and compressions are as chosen.

    Personally I am a fan of improved cams. There are better grinds now that give more power and economy without putting any additional stress on motor. Even without other changes.
    As per any build the carbs should be checked for jetting anyway.
    There seems to still be some issues with cam failures regardless of grind.
    Buy the best and attach cam gear with bolts, not rivets
     
    Last edited: Dec 29, 2017
    Mr Beckstar likes this.
  9. Barry

    Barry Well-Known Member

    Messages:
    2,253
    Location:
    Abbotsford NSW
    When Mr VW built motors he did some things well
    Other things he dropped the ball

    The valves, seats and guides are much better from Mr VW than AMC............ but if you are getting the sets replaced a 3 angle job does not cost more
    To me that would be a minimum

    The port and polish is an unlimited option that can be done by a competent home motor builder or by handing over $1,000's

    I believe you can buy AMC now without valves, guides, seats or spark plug hole
     
    David H and Mr Beckstar like this.
  10. Mr Beckstar

    Mr Beckstar Well-Known Member

    Messages:
    517
    Location:
    Bateau Bay, NSW
    Thanks for the great feedback. I don’t want to change anything unless I have to to bring back to a good relatively standard tune.

    I’ve got number 2 cylinder compression testing at 85 PSI whilst the others are all about 100 psi. The leak down test gives around 24-28 % on all cylinders. I compared valve lift height between number 2 and number 1 and they’re within 0.2mm of each other

    I’m still unsure whether I should pull the heads and barrels off. I don’t have an inside micrometer or other precision gear to rebuild the bottom end.
     
  11. Barry

    Barry Well-Known Member

    Messages:
    2,253
    Location:
    Abbotsford NSW
    Dont believe they are required
    You would give case and crank to a machinist to check out
     
  12. rstucke

    rstucke Well-Known Member

    Messages:
    459
    Location:
    Wamberal NSW AUS
    I bought AMC square port heads recently.
    I had to rework them.
    Combustion chambers and inlet and exhaust tracks were as rough as. A little minor polishing in those areas.
    I have a W&B valve grinder so re-ground the valves to the correct angles (45 & 30), one was not even concentric
    The valves were at 44 &29 and seats were 45 & 30 for an interference fit. My seat cutters 46 and 31 (hence the regrind)
    The original seats were one angle only and more than 3mm wide (I don't think they would have lasted very long before leaking).
    A couple of the air passages through the head (fins) had so much flash left in them cooling would have been more than compromised.
    Combustion chamber volume was surprisingly accurate.
    Compression ratio with std dished pistons will be low (7.4:1) unless you machine the step out of the combustion chamber. VW heads didn't have this instead using a spacer in there (prone to leakage and if left out 7.8:1 could be achieved with the correct shims under the barrels)
    I opted for flat top pistons and shimmed under the barrels to get 8.2:1. That with Webbers and a torque cam sounds angry when you rev it.
    The engine is in a test bed at the moment and won't go into Blitz until sorted (much easier than doing that in the vehicle)
    123ignition (programmable) coming with proper coil (an 09 distributor isn't going to be right for this engine (let alone any VW engine)but good for breakdown backup)
    [​IMG][​IMG][​IMG][​IMG]
    PC220027.jpg
     

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