8v cylinder head porting with flow test results

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

  1. drunkenalan Paid Member Paid Member

    Joined:
    Jun 11, 2004
    Likes Received:
    35
    Location:
    Leicester
    it will be working soon. xmas week is transplant time
     
  2. Tristan

    Tristan Paid Member Paid Member

    Joined:
    Apr 25, 2006
    Likes Received:
    1,205
    Location:
    Southern IRELAND
    Must be something to do with the shape of the valve , even with the backcut...? I'd love to see some "penny on a stick" valves in there!
     
  3. mr hillclimber Club GTI Supporter and Sponsor

    Joined:
    Nov 24, 2005
    Likes Received:
    148
    Location:
    Southwest
    Ah good... look forward to that.

    In that case Alan this one's for you...... the slick 50 big valve head flow test....

    First, a little history to give you a bit of a picture...

    This head originally came with the engine I re-build last year. It was an ex Slick 50 unit as fitted in a former championship car. A lot of parts were supplied by TSR over the years including the engine. The original unit made 135hp at the wheels on TSR's rollers some years back, which would be an honest 160hp, though in this format, a 4-1 manifold was also fitted, not legal for the Slick 50 series but the car was then destined for hillclimb/sprint use so that was fine.

    The car passed through a couple of owners before reaching it's current pedaller who brought the engine to me as a tired unit. I re-built it into another block with custom forged pistons I had made to keep it at 1800 for the class (1799cc is close enough I think), Carrillo rods and a replacement crank due to an oval journal.

    The head remained as it was, along with the Schrick 304 cam it came with. The key change was binning the K-jet and fitting a pair of 45 DCOE's on a Mangolcr*psi (sorry Mangoletsi) inlet manifold. The combination of K-jet injection & the 304 cam, as always, made for a poor low end power delivery and even worse idle. I assured my man I could make it run much better on a pair of carbs with the same cam which it did, giving much better idle, throttle response and power.

    Apart from the carbs and new bottom end, I opened out the main port runners in the head to what I felt was a size better suited to the valve size used, and opened out the inlet manifold to suit, along with the exhaust manifold port matched (it was'nt even close previously). In this form, the engine made a strong, steady 144hp @ 7,200rpm at the wheels on a warm day. After a couple of events I changed the trumpets from 40 to 60mm, did some fine jet tuning on the road with a lambda and tweeked up the ignition timing 3degrees. In that form it was noticably quicker, and I'm more than confident it was a good 150 at the wheels, though we never had chance to get back to the rollers... so a fair 177hp. Going by the fact it'll beat 170hp Lotus Elise's I doubt it's far off that.

    The engine has now come back to me for a check over (all fine) and in particular a cam change (not as simple as just that!), so I had the chance to get the head on the flow bench (you knew this was leading somewhere!).

    The head spec is allegedly a Pack "E" or D+, as described to me by a previous owner, due to it having a 41mm inlet insted of the regular 40.5mm in the normal Pack D, along with the regular 35mm exhaust valve. It was originaly supplied by TSR so I'd imagine it came from their regular source, but cant confirm that... though I understand some were indeed supplied with 41mm inlets.

    So, (at last!) here are the numbers you want to see...

    .050 15.1
    .100 27.2
    .150 41.6
    .200 55.8
    .250 66.9
    .300 76.5
    .350 81.0
    .400 85.1
    .450 87.8
    .500 86.3

    I must admit, I was expecting around mid 90's to 100CFM as throat and seat work all looked very good, though there were some detail work I could see, and felt, could do with a little fettling.

    [​IMG]

    Not a bad looking throat/bowl area at all, and below is the opened out port runner to suit the manifold. Bare in mind the head is upside down, the odd "egg" shape at the top of the port is due to the angle of approach of the carb inlet manifold, of which nothing can be done due to the narrow ports spacing of the head, and the wider spacing of the DCOE carb.

    [​IMG]

    So all looked like it should have done better than it did. After a measure up and calculation, I figured more should be possible whilst retaining the same (41mm) valve size, and should bring the flow capability up to what the new cam spec would ideally need.

    Mike, if you wanna start a new chart and put the best standard valve flow test in for comparrison that'd be good... there's more to follow so you'll need 7 collums in total.... stay tuned.
     
    Last edited: Nov 18, 2009
  4. chrismc Forum Junkie

    Joined:
    Oct 22, 2003
    Likes Received:
    0
    More interesting results Jason...keep `em coming!!

    It will be good to see the proportional gain on the exhaust side with flow work/bigger valve in comparison. :thumbup:
     
  5. VR6T

    VR6T Forum Member

    Joined:
    Oct 23, 2003
    Likes Received:
    12
    Location:
    Aberdeenshire
    Jason looking forward to seeing the 8V against the 16V.

    From a hill/sprint point of view, it will be interesting to see how a class A2 MK1 8V matches up against an A2 MK2 16v, on power to weight ratio. Will the MK1 be the more competitive car? You can see where I am heading with this.... ;)

    Keep up the good work.....
     
  6. Mike_H Forum Addict

    Joined:
    Oct 16, 2004
    Likes Received:
    17
    Location:
    iQuit
    Chart showing new head figures vs std, vs home ported.

    [​IMG]
     
  7. mr hillclimber Club GTI Supporter and Sponsor

    Joined:
    Nov 24, 2005
    Likes Received:
    148
    Location:
    Southwest
    I've tested standard exhaust flow and 3 different porter's 35mm exhaust ports, no ported standard exhaust yet.... but I'll work on that in a couple of weeks.
     
  8. mr hillclimber Club GTI Supporter and Sponsor

    Joined:
    Nov 24, 2005
    Likes Received:
    148
    Location:
    Southwest
    I can indeed! :lol:

    The 16v will allways make more power, but a MK1 will always be lighter....

    A modded 16v head makes around 30CFM more, but theres more to it than that... we can have a chat about that.
     
  9. mr hillclimber Club GTI Supporter and Sponsor

    Joined:
    Nov 24, 2005
    Likes Received:
    148
    Location:
    Southwest
    Mike, thats brilliant thanks, your now my chart man! :lol:

    I'll get the "ported" ported head results up asap... in the mean time you'll all just have to sweat! [:D]
     
  10. Mike_H Forum Addict

    Joined:
    Oct 16, 2004
    Likes Received:
    17
    Location:
    iQuit
    No worries - 'tis only an Excel spreadsheet.
     
  11. mr hillclimber Club GTI Supporter and Sponsor

    Joined:
    Nov 24, 2005
    Likes Received:
    148
    Location:
    Southwest
    Well this next bit is fairly simple... I opened out the throat area & re-profiled the seat to a size i felt more conductive for the valve size being used, & tapered off the guide (I did this head before the std valve one, so may not have tapered the guide after those results). I also opened out the inlet port runner some more (I'll explain more on that later!).

    The above mods gave this result...

    .050 17.0
    .100 30.5
    .150 44.8
    .200 58.1
    .250 70.2
    .300 79.6
    .350 87.4
    .400 92.2
    .450 95.9
    .500 93.9

    We now have a fair step up from the pack D+, with a good increase right through the lift range with no penalty anywhere. I also feel we are now seeing the true worth of the bigger inlet valve.
     
  12. RobT

    RobT Forum Junkie

    Joined:
    Oct 24, 2003
    Likes Received:
    975
    Location:
    Cheshire
    top stuff - really nice to see some proper measurements going on rather than wink wink witchcraft
     
  13. drunkenalan Paid Member Paid Member

    Joined:
    Jun 11, 2004
    Likes Received:
    35
    Location:
    Leicester
    wow that was a big jump in the figures!
     
  14. 50ftdubdemon Forum Member

    Joined:
    Jan 12, 2009
    Likes Received:
    0
    nice strong curve.. bigger valves/runner/throat Ds seem to be good match for work done to bowl/bend area. hopefully youll get similar effect when you fit the bigger valves to the other head ie release benefits of work you did blendin the boss/guide area
     
  15. mr hillclimber Club GTI Supporter and Sponsor

    Joined:
    Nov 24, 2005
    Likes Received:
    148
    Location:
    Southwest
    ;) Thanks chaps.

    Being a greedy bunch that us engine tuners are, I wondered if it was possible to just detail things a little more after the proper 3-anlge seats had been cut & new guides fitted. I blend out the seats into both the chamber & the lower cut into the throat and gently dress the short side turn.

    After the above work, I tried one last flow test to see the final results... and this is an example of how changes can be made that move the flow curve around.

    .050 17.0
    .100 32.9
    .150 47.0
    .200 62.0
    .250 75.4
    .300 80.4
    .350 83.6
    .400 88.1
    .450 91.3
    .500 96.2

    [​IMG]


    As you can see (when Mike put the figure in the chart;)), a further big improvement in the lower end of the lift scale between .100-.250 thou, but with a head-scratching loss at .350-.450. A gain returned at .500 with 96.2 over the 93.9 at the same lift on the previous test, and I ran one test at .550 just to see what was happening and saw 97.8.

    The figures at .500 and above are for interest only really as not many cams lift that high, even the race stuff... which got me thinking...

    The losses at the top of the curve are a lot less than the total gains at the low end, and as the lower points are covered twice during the lift cycle (opening & closing), the whole area under the curve has improved.

    There are also arguments over cylinder filling... the sooner and faster the cylinder fills the better, and in most of the flow tests I've seen over the years where low lift flow is favoured over top end flow, more power & a better curve has been the result.

    So whilst I was a touch dissapointed to see some loss at the top, I'm more than pleased with the low end gains, particularly as the cam I'm using has very rapid valve acceleration... so for this project I'm keeping the head as is.

    Now, these heads/engines dont run without some form of fueling, which in this case is supplied by a pair of Weber DCOE's. So what effect does a carb inlet manifold have on these results...
     
    Last edited: Nov 23, 2009
  16. Mike_H Forum Addict

    Joined:
    Oct 16, 2004
    Likes Received:
    17
    Location:
    iQuit
    Apologies for the delay in your secretarial service - I'll do it when I get home tonight ;)

    Do you think some of the odd changes are maybe variability in the test equipment?

    Nice work anyway!
     
  17. drunkenalan Paid Member Paid Member

    Joined:
    Jun 11, 2004
    Likes Received:
    35
    Location:
    Leicester

    more good work mr h... :thumbup:

    does that mean you need a head sent for further tests??? :hug: I happen to have one that may need some work
     
  18. Neal H Forum Member

    Joined:
    Oct 18, 2007
    Likes Received:
    5
    Come on Mike, pull your finger out ;)
     
  19. Mike_H Forum Addict

    Joined:
    Oct 16, 2004
    Likes Received:
    17
    Location:
    iQuit
    Sorry... a lady came round for dinner... I de-prioritised your request and made paella.
     
  20. drunkenalan Paid Member Paid Member

    Joined:
    Jun 11, 2004
    Likes Received:
    35
    Location:
    Leicester
    I hope the result of the dinner was more interesting than this thread mike.......?
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice