Modified 8v project head

Discussion in '8-valve' started by mr hillclimber, Nov 5, 2007.

  1. Mike_H Forum Addict

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    Hydraulic and Solid lifter heads are different castings... it wouldn't be bad as a rough guide, but not 100% accurate.
     
  2. mr hillclimber Club GTI Supporter and Sponsor

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    Yeah could be worth a look, thanks.. though I aways think it's a shame to cut up a good casting, unless it's badly damaged.

    Castings of the same type do vary.. I've seen 8v heads with 42mm inlets and big throats/ports that have not had any break-through problems, yet I've seen others break through when very little has been taken out... some do, some dont. Though it's not really a problem if you know a compitant alloy welder.

    Valve prices look ok though. Now price them in the UK from R.E.C and G&S.
     
    Last edited: Dec 28, 2007
  3. badger5

    badger5 Club GTI Sponsor and Supporter Trader

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    G&S prices when I spoke to them regarding making 1.8T items were 25+ a piece (plus vat).
     
  4. mr hillclimber Club GTI Supporter and Sponsor

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    Blimey thats a bit steap.. did you try REC Bill ?
     
  5. Tristan

    Tristan Paid Member Paid Member

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    any updates?
     
  6. A.N. Other Banned after significant club disruption Dec 5th 2

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    Just to add in three pics from Jon Olds, to add to the discussion - I'm sure Jon will be along to elaborate.

    Combustion chamber view of 8v semi-downdraft:

    [​IMG]

    Inlet port view of 8v semi-downdraft:

    [​IMG]

    Second inlet port view of 8v semi-downdraft:

    [​IMG]
     
    Last edited by a moderator: Jan 23, 2018
  7. Tristan

    Tristan Paid Member Paid Member

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    Chris.... may I ask what you mean by Semi downdraught?
     
  8. A.N. Other Banned after significant club disruption Dec 5th 2

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    Hopefully Jon will be along to help us on that one..
     
  9. Jon Olds Forum Junkie

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    I should have sent chris one showing the intake manifold face. The port and intake manifold has been modified a lot more from the top face (ie away from the head gasket side, if that makes sense) so as to make the gas flow in an angle of 80 degree (say) rather than 90 degrees. Theres hardly any flange left for a gasket. (3mm ish) and the inlet manifold (other end to match 48's) weighs next to nothing.
    I thought this would be of interest as the head (although old) is a professional one that must be at a 'full race plus' level. Without name dropping who's done it(not important anyway) I guess the questions im asking myself are;
    Can a diy job get to this level?
    Is it cost effective (time=money, in some form)?
    Do the photos give any clues to you diy'ers?
    Regardless, this will soon be up and running again on a screaming 1600. I have no expectations about power outputs, I just hope it runs properly, if you know what i mean.
     
  10. Jon Olds Forum Junkie

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    When I say 80 degrees, I mean from 180 ie >90 degrees.
     
  11. mr hillclimber Club GTI Supporter and Sponsor

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    It's difficult to say looking at the pics, and certainly without knocking others work... but it all looks a bit inconsistant (again, it could just be the photo's). It's fairly standard practice when modding ports to only remove material from the top and sides and leave the port floor alone, it's how I did the project head. There looks to be a bit of a ramp at the manifold face Jon, or again is that just an illusion from the photo?

    What's happened to the chamber on the right... looks like an odd shape has been ground after a repair.. blow-up or det damage maybe ?

    There's also something odd about the shape of the short side turn in the right hand port in the close up pic, the same port shown in the manifold face pic which is then on the right hand side with the head turned around ?

    The throat directly below the seat in the right hand chamber looks like it has'nt been opened back on one side.. again, could just be the angle in the pic.

    The valve seats look a little wide compaired to what is used these days, especially for comp use.. maybe it was originally a road head though.

    In answer to you question, it most certainly can be matched or even exceeded, it looks like the ideas are right (like in the throat bowl area) but the detailing is inconsistant. What size valves are they Jon ?

    The main thing is, as you have it.. use it and see how it performs.

    I have a "slick 50 " head stripped. The work is very consistant in the throats but the inlet ports are almost standard size. When I asked a couple of seasoned pro's about it, as I was a bit concerned I may have made my ports too big for road work and may have missed a trick, they both said the ports were way too small for the valve sizes used, in fact, they both said the big valve would be doing nothing over the standard size.

    I'll be re-vamping this head during the re-build, and with the owners consent, maybe able to show some pics.
     
  12. Jon Olds Forum Junkie

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    Valves are 40:35
     
  13. mr hillclimber Club GTI Supporter and Sponsor

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    For a "big power" 1600, you'd ideally need 41mm inlet, the exhausts would be fine. If it's a known head, I'd be inclined to use it as is maybe, and if it does'nt give the results yr after start again whilst you keep it running with that head.

    Or maybe upgrade that head before you use it if you only want to do the job once.. it depends how much you like tinkering.

    What cam are you going to use with it.. what sort of power/power spread are you looking for?
     
  14. Tristan

    Tristan Paid Member Paid Member

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    I thought bigger exhausts was the "done thing"?
     
  15. Jon Olds Forum Junkie

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    Valve sizes

    I'm happy enough with the 40 inlets. They are a good shape and in fine condition. Its nice to have some 'meat' between the chambers. My earlier heron 1600 head/engine produced a nice curve from 5.5 to 8K on a gs6, also on 40:35's, but that was on 45's.
    Not sure how this one will fair on 48's as it will not have much carb signal lower down the range. Time will tell.
     
  16. Razzer Forum Member

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    Hi John,
    found bare 1600 flat head in garage, not chambered with 40/35 valves looks nicely prep'ed with reference no. T000 or could be TG00 on one end.
    I don't know the history any clues ?
    If you wanted to try/use it on any of your projects your more than welcome,just let me know
    Regards,
    Razzer
     
  17. mr hillclimber Club GTI Supporter and Sponsor

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    Just run a smaller choke Jon. You can go down to 36mm in 48's, which is big enough for 180hp. Can you not run the 45's ?
     
  18. mr hillclimber Club GTI Supporter and Sponsor

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    I've not been able to get to the bottom of this myself yet. It's an engines ability to process air and fuel that makes power, i.e, it's ability to get as much "in" as possible, making the size of the inlet valve/throat/port the most important.
     
  19. Jon Olds Forum Junkie

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    The T ref head. Not a one I have come across. I'll send you a pm about the head.
    The reason I am probably going to keep 48's is that the inlet manifold that matches the head is at 48mm.
    I had the 48's on my 2L16V and they are a better match sizewise.
    I'm sure 45's would be fine. Interestingly it used to run 38 chokes in the 48's, which seems big to me too, for a 1600.
    With a 328 schrick cam and a massive tubular 4:1 its probably not to to have enough pull to drive onto the trailer. Itll be a laugh tho.
    To get back onto the thread: Exhaust valve sizes: I used to run offset exhaust valves in my race mini to get 37:31mm, but the last engine I built I used a 37:29 head and the results were similar. The text book(s) generally confirm this, to a certain extent, although quoting a mini with a 5 port head is probably not a good example.
     
  20. mr hillclimber Club GTI Supporter and Sponsor

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    Makes sence if it's all run together in the past...

    The 38mm chokes may not be too big if the engine produces the goods with a cam that big, it'll need plenty of c.r though.

    The first time you look at the exhaust valves and throats on an 8v head, they look small compaired to the inlet, and the seat/throat/bowl area certainly has some odd shapes in there. But on a ratio of approx 0.8-0.83 between inlet and exhaust valve sizes, a 33mm exhaust is fine with a 40mm inlet. Plus I doubt VW just took a wild guess to come up with that size either.

    The same goes for the Mini example you quote.
     

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