16v Heads, mixing and maching. Which is the best?

Discussion in '16-valve' started by Mike_H, Aug 27, 2007.

  1. Mike_H Forum Addict

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    ABF Head on a 9A Block - Good idea, or??

    I picked up an ABF head and some other bits from a CGTI Member, via ebay... I know the head physically fits on a 9A block, but was wondering what the pros and cons of this conversion are?

    I was thinking that fitting the ABF head on a short block might release the bigger power figures that ABFs seem to make, without the clearance problems.

    So how do the compression ratios work out? Are the inlet manifolds interchangeable between ABF / Kjet 16v's?

    Any other issues or pitfalls to be avoided?
     
  2. bigmac Forum Member

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    the inlet manifold wont be a problem. i know ppl that have put abf heads on the 1.8 kr , so i can't see it being a problem on your 9a.
     
  3. Mike_H Forum Addict

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    Yeah the 9A and KR heads/manifolds are interchangeable - do you know if your mates are using the KR type inlet manifolds with ABF heads?

    Any issues with compression ratio / pinking?
     
  4. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    It wont be a problem Mike as the later post 94 9A had the same 051103373D head with a tamer inlet cam. You can use the complete ABF inlet if running a Motronic or standalone. Else use KR or 9A jobs
     
  5. Mike_H Forum Addict

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    Yeah I was thinking the ABF inlet looked good for an MS installation - 3 pin TPS, fuel rail, etc...
     
  6. abf"d mk1 Paid Member Paid Member

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    but the ABF uses those unusual injectors, which may not be a problem. i,ve no idea.
     
  7. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    They are side feed injectors @225cc/min and 3bar . I know of a car that the digifant system was ditched in favour of a standalone. The engine is bog std and is very responsive comapred to a well sorted K jet car. You can read about it here.
     
  8. vw_singh Events Team Paid Member

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    Right people,

    I have been looking at the design of various 16v heads from the VAG range and have read numerous comments on what people have found to be better. So what do poeple think and why?

    i.e. KR bottom end with KR head? ABF head?
    9A bottom end with KR head? ABF head? etc.

    I have done some calculations on what would give more compression etc but would like to know what the rest of the techy types on here think.

    Also, what are the clearnaces like? How much cam you skim from a 16v head before its scrap or before interfearance becomes an issue?

    Gurds
     
  9. A.N. Other Banned after significant club disruption Dec 5th 2

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    C'mon techies, I was chatting to Gurds about running this thread - it should be up there with mr hillclimber's porting thread for usefulness ;)

    The Q is: what is the optimal mix & match job of KR/9A/ABF bits for maximum compression,preferably without having to machine anything.

    Starting point on the thread is head volumes. ABF heads appear to have less head volume, but correspondingly smaller cutouts on the pistons.

    Given that an ABF block is 236mm high, compared to the usual KR/9A shortblock height of 220mm there's a few things to factor in.

    The rod lengths are 144mm (KR/9A) and 159mm (ABF), so in theory that's 1mm of stroke-induced compression lost, because the block is 1mm taller. Obviously though, piston crown height is the critical bit, plus the cut outs.

    Thoughts folks?
     
  10. Hotgolf

    Hotgolf Paid Member Paid Member

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    This is always going to be difficult and vary vague when using stock parts
    For a start, lets go by casting numbers and not engine codes, as there was a bit of swapping and changing between the corrado/golfs/passats even with the same Kr code etc. I've seen numerous 026/027 and 051 heads on KR blocks. Then there's the 051 and 053's on the ABF's.
    There's no stroke-induced compression lost between ABF and 9a, as they have the same stroke of 92.8mm. The conmpression heights of the pistons have been altered to give the correct/similar deck heights.
    ABF heads have a raised centre section between inlets and exhausts, so compression should be higher due to this as the chamber volume has decreased. It will also increase squish. Smaller cut outs in the piston would then raise the compression further as there would then be even less volume in the cylinder.

    To answer the 'what is the optimal mix & match job of KR/9A/ABF bits for maximum compression,preferably without having to machine anything' qestion is going to be difficult, as the stock VAG parts are much of a muchness, and without altering deck heights or combustion chambers there's no going to be alot between the 16v heads, or 16v pistons.
    The only way of getting optimum compression is to start machining things.

    As for how much you can skim off a head. I've taken about 1mm, and I have high compression pistons. There's different ways of increasing compression without skimming thehead right down. For instance, you can machine the outer edge of the piston and leave the crown up, then deck the block down to suit. The piston crown will go into the chamber just like a JE and will be fine. As long as you haven't got major lift cams then you won't need to touch the cutout, but even if you have, you can always machine them down a little. I have 11.5mm cams and even with the block decked down and the ehad skimmed there isn't a problem as long as you have the timing smack on.
     
    Last edited: Nov 5, 2007
  11. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    I might add to to this that "the ABF" head or 051103373D/E (053 103 351 C casting) as stamped is also used on the ACE, ADL 1.8 16v, and post 94 9A.
     
  12. A.N. Other Banned after significant club disruption Dec 5th 2

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    So planting an ABF head on a KR block will give an instant gain in compression, for free, effectively. Comparing the actual ccs of both heads, chuck into a calculator and out comes a new compression on a KR.

    Add a 30 skim and greater gains are there for the taking, clearly.

    Head gasket differences, next?
     
  13. Hotgolf

    Hotgolf Paid Member Paid Member

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    It would be minimal really, probably less than 0.5:1, but I haven't worked it out yet on a compression calculator.

    As for gaskets and decking. 10thou off is approx. 0.3:1

    This is why I've said they mix and match parts.
    Toyotec, have you noticed any difference in German and Mexican 16v castings? There was quite a difference in the 8v ones.
     
  14. prof Forum Addict

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    if looking at base engines, then the different rod lengths may move the torque around.
     
  15. Hotgolf

    Hotgolf Paid Member Paid Member

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    Yes that right. Due to rod ratios/angles etc the engine charactersitics will change somewhat, as will different cam profiles.
     
  16. A.N. Other Banned after significant club disruption Dec 5th 2

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    But gaining x-amount of compression from an ABF head, then another 0.5:1 from a head gasket and we're taking about cheap-as-chips tuning, without forged pistons and the like.

    It's not sounding like rocket science, but simple bits to get hold of. eBay specials...

    What about factoring in any gains from 9As or 6As, but purely focusing on pushing up compressions. My guess is there's not a lot more to be had tho?
     
  17. A.N. Other Banned after significant club disruption Dec 5th 2

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  18. A.N. Other Banned after significant club disruption Dec 5th 2

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    ABF's quoted at 10.5:1?

    Also ABL was a 16V 1.8 motor in Seat Ibizas, running on Digifant. Wonder what head was fitted? Knock sensor probably fitted, so comps could be upped..

    All for the melting pot...
     
  19. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    Correct

    Runs 10:1, same head as ABF, post 94 9A and ACE except without ABF inlet cam.
    For Engine controls the configuration is a Dizzy for RPM trigger ( 4 window) and batch injection like an 8v ( two wires, 12v and ECU gnd to injector set).
     
  20. A.N. Other Banned after significant club disruption Dec 5th 2

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    So if the ADL's got the same head as an ABF, but runs 1.8, is it short block?
     

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