Is it worth going Crossflow?

Discussion in '8-valve' started by madasafish100, Dec 14, 2010.

  1. madasafish100

    madasafish100 Forum Member

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    I've been looking into this quite heavily over the last month, getting prices for parts and porting work. It's working out to be a weighty sum of money and I'm just wandering if it's really worth it.

    I've already got a strong counterflow 8v with big valves and well ported, is there any flow advantage with a Crossflow head or is the only real advantage having the carbs away from the hot side.
    I don't really want to pay out for a Crossflow head conversion to only gain 5 or so BHP. For the money I've worked out it will cost I could be well on my way to a valver.

    Opinions please all ye wise ones ( wink wink mr H with the flow test data if u have any?)
     
  2. Whittle Forum Member

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    the crossflow will never outflow a valver

    (well a well worked 8v would outflow a stock valver, but a worked valver would outflow the worked 8v)

    im staying 8v as i think it has more character!
     
  3. mr hillclimber Club GTI Supporter and Sponsor

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    Well, I'm not biased :lol:... but...

    The obvious advantages are... induction away from the rear radiated heat (controlable to a large degree tho), the inlet ports in the casting less likely to absorb heat from the exhaust ports, carbs or t/b's away from the clutch cable, the ability to fit decent filters... general ease of working on carbs at the front.

    Advantages yet to be played with... bigger ports as std, with more room to go bigger without breaking into the head bolt holes... this may help with feeding bigger valves.

    I'll try and get the inlet testing I've done to date up to show the direction it's going in.. so far so (very) good. On the std crossflow inlet, I'm seeing better flow with minimal work on it's 39.5mm inlet valve than a fully ported original type head on it's std 40mm inlet.

    The next step is more porting work, followed by a bigger valve.... I just need to grow an extra pair of hands to do more development work alongside customer work...[8-}]

    As for the 8v v's 16v flow.... the best conventional head I've seen to date made 103cfm, with big valves (42mm). The worst std 16v head (9A) shows 104cfm, ABF makes 110cfm, ported on std valves either 16v makes an easy 120cfm, with 137cfm possible with a "lot" more work and still on std valves... std valve size 8v's make 88-90 cfm.

    It's not all about flow numbers and bhp tho... a grunty 8v makes a swift road engine, and without big expense. And the crossflow will help where budget/something different is prefered.
     
  4. madasafish100

    madasafish100 Forum Member

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    Cheers Mr H, im thinking i may not bother going crossflow as it seems i will putting alot of money into some thing to not get much more power.

    A new carb manifold 180, porting of manifold about 50-100, rebuild parts 50, new hydraulic followers and cam 315 (as i run solid lifters) and porting of the head 500-650. Comes to a grand total of 1,175 thats minus head gasket, other gaskets and new head bolts etc

    im hoping my head with larger valves and porting will be making around 95 cfm and ive come up with a cunning plan to get around the clutch cable problem so i can fit a proper filter to it. Heat is not a problem as i have good heat shields in place, soon to be made better.
     
  5. mr hillclimber Club GTI Supporter and Sponsor

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    You can of course offset the cost by selling off the current head/manifold/cam, that would cover at least half, maybe a bit more.

    The cable can be mounted down thru the bulkhead and mod the pedal, I did this on mine. Or, a hydro conversion.

    If you have all the power/performance you feel you need, a good set up is maybe all it needs to round off the current conversion.
     
  6. danster Forum Addict

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    It will not cost 100 to port match the new inlet manifold. They are a very neat fit to the head flanges as std.
    315 for a cam is a little excessive too.

    If you are going solid tappet conversion then that will add to the cost, but the std hydros are probably well within operating range for all but race use.

    There is little point asking folks for their opinions on this because that is all they are. Until a few proper and optimised engines are put together to give real data, it is just pub talk.
    VR6Will's engine by his own admission was not running a high enough compression ratio to match the long duration cam he was using.

    I am just tidying up the valve seat area on my own crossflow head and putting it together with std valves to run and get a baseline figure.
    The cost of after market valves that are not optimised to the std valve seats is a further put off. Even the fancy valves appear to need back cut and fettled so more expense and time for an unknown gain. As Mr H has said, the initial test are good so may not even warrant going to the larger valves for certain applications.
     
  7. drunkenalan Paid Member Paid Member

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    As Dan says there isnt many proper Xflows out there this months golf+ has a mk1 with a cross puts out 160 ish, I havent seen a xflow that would convince to me that the x flow design will work any better than the original counter flow head.

    and TBH the head design is xflow but the position of the valves isnt, if you see what i mean..
     
  8. skint_golfer

    skint_golfer Forum Member

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    from what I've seen of my old 8 valve's internals I'd have to agree, theoretically a crossflow will flow much better but thats dependant on valve placings and size, inlet and exhaust port design etc etc and VW are not renouned for spending a lot on R&D for theses engines.

    infact comparatively the crossflow design is better than the counterflow design but neither is any good when compared outside the VW world.... and neither would be as good as a standard abf :thumbup:
     
  9. skint_golfer

    skint_golfer Forum Member

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    incidentally I've been doing a bit of research for my engineering dissertation on variable length inlet manifold design so that last comments not just plucked out of a bucket of 8v hate!:lol: I've actually read books and stuff [eek][:-B]
     
  10. danster Forum Addict

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    Pub talk. ;)

    http://www.clubgti.com/forum/showpost.php?p=1911029&postcount=41

    Std un ported crossflow head with a SH cam and digifant management. :thumbup:
     
  11. mr hillclimber Club GTI Supporter and Sponsor

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    Yes indeed... George's is a very good example of how well the std crossflow head works.

    Forget all the old pics you may have seen with a "crossflow" style head (be it any maker's... Ford, VW etc) flowing in one side and out the other... it just does'nt work like that.

    An engine draws air in through an open valve... it does'nt know, or care how it gets in or where it comes from... front or back of a head will do. After the explosion has taken place, the spent gasses need to get out... again, they dont care where a port goes once past the valve head, they just need to find the exit... and I doubt they will remember what side the air/fuel mix came in.

    So when you next see a picture of any "crossflow" style head flowing in one side and out the other... just laugh out loud and shout "what about the combustion process in between"!

    And the ports wont be opposite each other as the valves are side by side, but again, it does'nt matter.

    Anyway... off the soapbox... as soon as I get the flow figures up you'll see the potential, and why engine's like George's work so well in basic form. A std crossflow head only flows 5-7cfm less than a ported conventional head, but with better mid flow, and when ported, they match the top end flow of a ported old style head, with better mid flow... and all from a 0.5mm smaller valve... so far.
     
  12. madasafish100

    madasafish100 Forum Member

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    This is exactly what has put me off....... 160BHP is probably not a great deal more than what im getting now and that is with lots of port work according to the article, a special grind on the cam and full throttle body, mappable set up.

    I think i just need to stop rushing this and wait to see what kind of figures are available before i commit. Its not a case of needing more power, it was mainly so i can fit a decent filter and im going to play around with the clutch set up so it will enable me to do this.

    the main reason of the thread was to see what people thought and the two 8v masters have set me on the straight and narrow.

    Cheers guys :thumbup:
     
  13. mr hillclimber Club GTI Supporter and Sponsor

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    160hp... who ported the head/built the engine... stevie wonder?

    Dont let others failings put you off. If I'd done that, I would'nt be porting heads ("you cant just port heads, only pro's can do that/get results"!) or we would'nt be running DCOE's ("carb's dont work on an 8v/make any more power"!) or using lairy cams ("it's pointless using more than a 304 as they dont make anymore power and become undrivable"!).

    My advice would be to see what power your current set up really makes after a proper set up, that will cost a lot less that another head + parts, setting up again etc. As long as it performs the way you want you have a result.

    If you want to move forward from that, then there are other options to consider. Same with the cam situation... you could still run a decent hydro profile for fast road/track day use, or I'm sure with a bit of work we could make the mechanical set up fit/work.
     
    Last edited: Dec 15, 2010
  14. danster Forum Addict

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    Stevie Wonder Racing Co. :lol:

    I would be very superstitious of that power output myself. ;)
    [YOUTUBE]2OJsYwLs7yE[/YOUTUBE]
     
  15. madasafish100

    madasafish100 Forum Member

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    Hahahahahaha :thumbup::clap: aparantly the name of the guy is Jim Paine of race power motor sport who is "renowned for building slick 50 engines"
     
  16. mr hillclimber Club GTI Supporter and Sponsor

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  17. danster Forum Addict

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    Was it a 1.6? [:s]
     
  18. mr hillclimber Club GTI Supporter and Sponsor

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    [:s]... I hear he's a good guy in fairness.... but if the cam is timed up wrong, it has insufficiant C.R or a poor set up, it can soon loose a chunk of power.
     
  19. mr hillclimber Club GTI Supporter and Sponsor

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    Though I have re-ported heads that "look" great... and gained both flow and power... they were ex slick 50 too...
     
  20. madasafish100

    madasafish100 Forum Member

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    Im guessing the CR is was a bit too low, or the "custom profile" cam wasnt so good.
     

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