8v cylinder head porting with flow test results

Discussion in '8-valve' started by mr hillclimber, Nov 8, 2009.

  1. mr hillclimber Club GTI Supporter and Sponsor

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    Not really, the exhaust can be made a little larger but the rest is the same.
     
  2. mr hillclimber Club GTI Supporter and Sponsor

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    :lol: .... yep, not as easy as it looks eh!

    That would'nt have been a compression test, that was a cc check to work out the compression ratio.

    You dont want the finish too polished, it's the shape not the finish thats important. I use carbide burrs to rough out (lubricated with WD40), 40 & 60 grit flap wheels and a final blend with 60 grit in a split rod, you dont need anything finer than that.

    The split rod has to be run at a slower speed, you cant use it in a die grinder at 27,000 rpm.
     
  3. Golfsburg88 New Member

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    I would like to thank U for the 8V head port thread, you gave me some hope

    Please can you make a thread of VW 16V head, vs the Honda B16A head?

    I own an ABF, and i think VW failed to make a 16V head with a hgh flow

    The 1.6cc 16V B16A of the Honda have extreme flow, please can you illustrate why? and how can I make our 16V head flow like the Hondas?

    Thank you alot :)

    Your fan from Egypt
     
  4. Golfsburg88 New Member

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

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    Some flow data from CCC, Oct 1994.

    Stock inlet: 75cfm
    Stock exhaust: 55cfm

    Bored inlet port / flowing throats & seats: 90cfm
    Offset bored exhaust port (lower edge std) to 28mm from just under 25mm: 2cfm gain
    + throats & radiused port corners: 61cfm (standard valve)

    Latter referenced standard valve, so by inference the rest were too.

    No WG references.
     
  6. Tristan Forum Junkie

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    very slowly and carefully !
     
  7. mr hillclimber Club GTI Supporter and Sponsor

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    I've found similar too Chris.... on my bench, stock inlet (EV in the case of the head tested) show's 71 cfm, the exhaust only 44-45 cfm. On a G60 I tested, I saw 76 cfm, and the exhaust the same at 44-45.

    There will be differences in castings too, so the above may not mean a G60 head is better in stock form. When both heads were ported, both came out at 88-89 on the inlet, the exhaust....similar final result to Dave Walker's finding's, but after a lower starting point... there's an article coming soon with that in... do we REALLY need big exhaust valves to make good power... ;)
     
  8. A.N. Other Banned after significant club disruption Dec 5th 2

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    Cool. Other info mentioned was:

    Most manufacturers working to a 70% inlet:exhaust ratio (no news to us)
    Their Golf had 73% std
    Having opened the inlets up, they then balanced the ratio back only as far as 67.7% (can be worked out from the earlier posted numbers)
    Tim Stiles says larger exh valves works like magic on Golfs / reduces tendency to pink.

    Shall await tests with interest :thumbup:
     
  9. mr hillclimber Club GTI Supporter and Sponsor

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    Oh there's lot's of em!

    On the ratio front... down to 68% is the accepted norm for road type engines, though 70% is around the average, with a bit more... 72-73% the "required" norm from a race engine... though thats not set in stone either.

    In fact, a recent head I did had 67.5% exhaust flow compaired to the inlet, but made over 190hp from a 2ltr 8v in hillclimb/sprint trim... which I dont think is lacking much!

    My own ex hot rod head with bigger valves than above has only 62.5% exhaust flow, yet makes only 3-4 hp less than the above engine from 200cc less capacity.
     
    Last edited: Sep 29, 2010
  10. A.N. Other Banned after significant club disruption Dec 5th 2

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    Ex hot rod... Razzer floated the topic of hot rod motors in convo the other day.

    Any idea where it came from?
     
  11. mr hillclimber Club GTI Supporter and Sponsor

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    The original engine it came from has history from John Toovey (hot rod/short circuit specialist), who re-built it at some point. But during a conversation with a cam company when trying to i.d the profile, it turns out it's a Mass cam profile (another hot rod specialist).

    The head has "A S" stamped on it, the head honcho of Mass in the heyday was Alan Sherwood (Alan still builds engines, mostly historic BDA's, but no longer owns Mass). Recent flow testing though shows it can be improved... the head I did for my local hillclimb man is 3cfm better on the inlet & 10 cfm better on the exhaust... all on smaller valves... though power of both engines is all but identical.
     
  12. A.N. Other Banned after significant club disruption Dec 5th 2

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    Good stuff. From what Razzer was saying, quite a few of these VW motors were circulating succesfully in hot rods at one stage. Thread potential at some point I think.
     
  13. mr hillclimber Club GTI Supporter and Sponsor

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    They were very sucessfull. "Claims" of up to 230hp were touted in the day, but I'd like to see it on a known dyno... recent dyno testing suggests a bit less in the real world, but still strong power considering limitations of valve size V's capacity.

    But here's a story... when my engine was in full hot rod trim, and owned by a chap called Rob Higgs, a friend of mine's customer at the time used to race with him. Said racer ran a 225hp 16v Vauxhall XE which due to the spec & regs was rev limited. At 7.5k, and in a space framed national hot, you can imagine the noise inside, well, my friends customer used to say "I can hear Higgsy revving that fo%ing VW engine behind me as he reels me in"!
     
  14. A.N. Other Banned after significant club disruption Dec 5th 2

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    Razzer I think had some numbers for power, but these engines were what sounded like proper steel things :thumbup:
     
  15. mr hillclimber Club GTI Supporter and Sponsor

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    Some were, mine always had a std VW crank but steel H section rods, forged (Cosworth) pistons, the above mentioned head, steel cam buckets, 48 Webers. I still use all the above apart from the crank (which broke when in use in a grass racer). They used to break valve springs regularly (Iskendarian's) when using the big hotrod cam (which I still have), but we cured that with a better spring and a tamer cam.
     
  16. fthaimike Forum Addict

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    Interesting German 16v video here on cnc porting:
    [YOUTUBE]FDNOB4XLAH0[/YOUTUBE]

    Google translation of txt post from forum it was in:
     
  17. TonyB Paid Member Paid Member

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    That's interesting. I know it is done that way but I've never seen it before.

    You take your time and get the port dimension data just right for the CNC programme and you have enough tolerance built in for the port wall thickness. Then you just need a jig set to suit the head and taken as a given that the factory machined faces are a constant then you just bolt it on and press the button, tidy:clap:
     

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