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    Thread: Talk to me about big valve (40/33) 8V hydraulic CIS heads

    1. Member
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      11-18-2008 06:55 PM #1
      so, i am currently gathering parts for a minor engine project to be swapped into my '82 rabbit truck.

      the truck is currently running a stock 1.7L 8v CIS gasser engine.

      i recently purchased a 1.8L 10:1 high compression block and a separate 8v hydro CIS head, including a stock cam and an autotech 270 cam. some random knock sensor equipment was included (distributer and box).

      the head has this number stamped on it: 026 103 373 AA

      the seller and i were both under the impression that this is a CIS big valve hydro head. but when i got home and measured, the valves measured 38mm/33mm instead of the desired 40/33. not a big deal, as the price was a good deal for the cam alone.

      i have since concluded that this mystery head is from an '85...please correct me if i am wrong. but it seems that in '85, vw made the 38/33 CIS hydro head.


      ultimately, i would like to use a 40/33 big valve hydro head for this project.


      next time i go to the junkyard i'm digging for a 40/33...

      so, my question is, exactly what models and years did vw use the 40/33 big valve hydro CIS(-E) head?

      what numbers/letters will designate the big valve hydro CIS head? 026 103 373 G ???

      any additional related information is much welcome, i searched and searched and searched and couldn't find any solid information.

      thanks.


    2. 11-18-2008 08:20 PM #2
      I'm fairly sure that the solid lifter 40/33 valve combination only came (in the US)
      in GLI/GTI models 1.8 and few siroccos.
      Solid lifters are on the MK1 84 and earlier.

      Hydo lifters are on 85 and newer, cabirolets and mkII sciroccos, Golf GTI and Jetta GLI 8v models. up to 1992.

      Note where coolant flange between 1 & 2 is only a small valve head.


    3. Member dacolino's Avatar
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      11-19-2008 09:06 PM #3
      If you have a 38mm intake valve and 33 exh valve on a hydraulic lifter 8v, You have a VW Fox cylinder head. The head is essentially the same as a A2 but has smaller intake valves...There may be other 1.8l 8v's with small intake valves also that i am unaware of, but I was under the impression that foxes have small valve heads.

      check here (Adams page) for more info, where it says cylinder heads

      http://www.lunaticfringe.org/v....html


    4. 11-19-2008 10:23 PM #4
      Quote, originally posted by ny_fam »

      Solid lifters are on the MK1 84 and earlier.

      Hydo lifters are on 85 and newer, cabirolets and mkII sciroccos, Golf GTI and Jetta GLI 8v models. up to 1992.

      Sciroccos and Cabriolets didn't get hydraulic lifters until 1988.
      AFAIK, and I'm not expert on this, big valve hydraulic lifter CIS heads were for only on the higher performance 8v engines, i.e. GTi, GLi, Carat etc. And all digifant heads are big valve heads

      Quote, originally posted by ny_fam »

      Note where coolant flange between 1 & 2 is only a small valve head.

      Those are early style 1.5, 1.6 and 1.7L heads with solid lifters and and very small intake valves and they're not found on any North America VW after 1984.


    5. 11-20-2008 01:59 AM #5
      All Digifant's are 40/33 heads.

      Almost all CIS hydro heads are also 40/33, the exceptions being some 85 and 86 Golfs that ran on CIS basic and were upgraded with the CIS-E with a knockbox. I would guess that Jetta's with CIS basic up till 87 also had the small diameter heads. GTI's and GLI's 8v's from 85 on all had the bigger heads.

      CIS-E heads might be the best bet since most were German made and have supposedly the best castings and are fairly prevalent out there in the junkyards of America.


    6. Member
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      11-20-2008 12:25 PM #6
      Awesome! Thanks for the info, everyone.

      I ordered a MK2 Bently manual, that should help.


      Quote, originally posted by Das Kraut »
      All Digifant's are 40/33 heads.

      Almost all CIS hydro heads are also 40/33, the exceptions being some 85 and 86 Golfs that ran on CIS basic and were upgraded with the CIS-E with a knockbox. I would guess that Jetta's with CIS basic up till 87 also had the small diameter heads. GTI's and GLI's 8v's from 85 on all had the bigger heads.

      CIS-E heads might be the best bet since most were German made and have supposedly the best castings and are fairly prevalent out there in the junkyards of America.

      Das Kraut, that is the kind of info i'm looking for. Thanks!

      Is anybody running the setup I desire? Does it put a smile on your face?


    7. 11-20-2008 12:37 PM #7
      all of the gl model jettas and golfs came with 38mm intakes. gti/gli models are only ones with 40mm intakes.

    8. 11-20-2008 04:17 PM #8
      Im running an Autotech 272 in my 1.8 Mk2. Gets on it but nothing to write home about

      The car is heavier than a mk1 and the 1.8 will be a nice upgrade in a Mk1 but if you want a smile throw the 3a Audi 2L block under it or an ABA 2L from Mk3 cars.


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      11-21-2008 02:28 PM #9

      is it possible to convert a big valve digi head to CIS?

      if so, what exactly would i need to do?


    10. Banned BillLeBob's Avatar
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      11-21-2008 03:11 PM #10
      Quote, originally posted by sriracha »

      is it possible to convert a big valve digi head to CIS?

      if so, what exactly would i need to do?

      Just change the injector inserts. Cheap and easy.


    11. 11-21-2008 03:17 PM #11
      Quote, originally posted by sriracha »

      is it possible to convert a big valve digi head to CIS?

      if so, what exactly would i need to do?

      Yes, it's easy. Just remove the digifant injector holders and thread in some CIS injector holders, like the one shown below. These particular injector holders were used ONLY in 1984 1.8L engines, these are from an 84 Scirocco. If your injection system is from an 84 or older, use these ones, make sure you don't get the holders for 83 or older engine, the thread size different they won't fit in a digifant head. If your fuel system is from an 85 or newer, use the holders from an 85-87, those ones are two piece brass and plastic holders.


    12. Member
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      11-21-2008 03:26 PM #12
      cool. thanks for the info.


      i could just use the injector cups from the 38/33 valve '85 hydro head i have in the garage.

      this opens up my options a bit. so, basically, i just need to find any post-'86 big valve hydro head, and i'm good to go?


    13. 11-21-2008 05:05 PM #13
      Quote, originally posted by sriracha »
      i could just use the injector cups from the 38/33 valve '85 hydro head i have in the garage.

      Yes, that'll work okay but it's not ideal. In the picture below, the pre-85 injector is on the left and the 85+ injector on the right. You can see the early style injector is missing the little cap on the end, the 85+ holders are designed to accomodate that cap so the early style injectors will be a little bit sloppy in the newer style holders. BTW, those holders pictured in my earlier post are cheap, about $3.00 each so you won't break the bank using the proper ones.




      Modified by ABA Scirocco at 5:08 PM 11-21-2008


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      11-21-2008 05:18 PM #14
      good call...thanks for pointing that out.

      could i use the injector cups from my '82 1.7L CIS head on the big valve hydro head?

      ...that would solve the issue of injector fitment, right?


    15. 11-21-2008 07:33 PM #15
      No, you MUST use an 84 or newer 1.8L part. The thread size on the 82 head is M24, the thread size on any of the 84+ 1.8L heads both CIS and digifant is is M22. IWO, the 82 parts don't fit

    16. 02-16-2010 09:19 PM #16
      Does anyone have the part number for the injector seats needed for the Digi to Cis Conversion?

    17. 02-17-2010 07:17 PM #17
      If you have injectors without the little stainless steel air shroud caps, use the inserts in group 2, if your injectors have the caps, use the parts in group 3 OR, remove the caps and use inserts from group 2. In either case, you might find it necessary to enlarge the bottom portion of the injector holes a little bit to fit the lower part of the insert.



      Modified by ABA Scirocco at 7:37 PM 2-17-2010

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      02-21-2010 05:55 PM #18
      all said and done, after the cost of all the injector parts and swapping the head to a 40mm type, I dont know if you'll really see much of a gain...

      anyone know of the power gains of 38mm vs 40mm? I heard it was like 1hp at best.....


    19. 02-21-2010 06:23 PM #19
      Quote, originally posted by ds1919 »
      anyone know of the power gains of 38mm vs 40mm? I heard it was like 1hp at best.....

      If you do nothing else to the engine, it probably doesn't make much difference after all most people don't get anywhere close to pushing the limit of their heads whether 38 or 40mm valves. But, if you're tuning the engine to it's limits, it's going to make a considerable difference.


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