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Thread: VN heads

  1. #31
    Do you ever leave? HQ308Ute's Avatar
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    Quote Originally Posted by Conrod View Post
    Exhausts are to big and better of with texture in the chamber......
    There you go HPE Pete you learn something new everyday :P

  2. #32
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    26 is better then 32 no point in lead time and inefficient burn........
    Polishing looks good though

  3. #33
    Do you ever leave? HPE PETE's Avatar
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    Quote Originally Posted by HQ308Ute View Post
    There you go HPE Pete you learn something new everyday :P
    LOL....thats it mate thats the great thing about having the internet you do learn something everyday with so many experts around.

    there is a reason i wont comment on the ex ports which i dont want to do here.

    conrod maybe you should email darrin morgan and tell him hezs been doing all of his nascar SB2 heads wrong with a smooth chamber finish




  4. #34
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    conrod please enlighten us all on how a polished combustion chamber creates inefficient burn

    A polished combustion chamber will reflect combustion heat in to cooler areas of the combustion chamber further improving burn characteristics

    Heres a few quotes out of a combustion science article

    When we are speaking of Reflectability, we are looking at the ability of a surface to reflect heat. Generally this characteristic has been achieved by polishing the combustion chamber surfaces. A polished "bright" surface will reflect heat into cooler areas. This can be illustrated by considering an irregularly shaped room, lighted by a single bulb. There will be areas of the room that do not receive as much light, either because of being shrouded or simply because of being further from the light source. If you were to line the walls with mirrors the light would be reflected into the darker areas providing near equal levels of light through out the room. A combustion chamber would react the same way if the light/heat generated by ignition could be more evenly dispersed within the combustion chamber. More even and complete oxidation of fuel would occur, thus increasing the efficiency of the engine...end quote

    Polishing actually melts and seals the skin of the surface being polished thus forming a bit of a barrier to help retain heat in that area. These benefits exist even after these areas carbon up because the underlying surfaces are still sealed…end quote..there are many more quotes but I couldn’t be bothered

    It is desirable to keep heat in the combustion chamber because heat is power which is what we are after

    As for ign timing if a good efficient combustion chamber will tolerate 32 deg of timing it means the engine will tolerate more compression which will further improve burn

    As for atomization this is why we use a coarse 60 grit finish in intake ports also notice in the pics of darrins nascar head the area just under the valve seat the "off cutter" finish this will help re atomize fuel in to the air stream

    I don’t think polishing makes a LOT of difference but it certainly doesn’t hurt it at all and every little bit helps especially when we chase as much comp as possible and also considering we smooth the chamber anyway whilst blending away sharp "square" edges and the polish is just another process that takes bugger all time to achieve one you already have a smooth surface
    Last edited by HPE PETE; 01-04-2012 at 07:56 PM.

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    spewing that blows my theory away

    you do learn something everyday on the net using theory learnt from this forum this is what i have come up with for my own heads high atomisation intake port and combustion chamber



  6. #36
    Senior Member JCY 74's Avatar
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    Quote Originally Posted by bloke308 View Post
    spewing that blows my theory away

    you do learn something everyday on the net using theory learnt from this forum this is what i have come up with for my own heads high atomisation intake port and combustion chamber


    oh dear god!!!

  7. #37
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    was that done with a hammer and chisel?

  8. #38
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    Quote Originally Posted by BLOKE308 View Post
    spewing that blows my theory away

    you do learn something everyday on the net using theory learnt from this forum this is what i have come up with for my own heads high atomisation intake port and combustion chamber


    you knocking my work champ?
    rev the chev kev!

  9. #39
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    How can you compare a SB2.2 to a vn head the chambers are 20 years apart .
    Different fuel different use !

  10. #40
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    Oh and the heads from hendricks and the like are not polished.....

  11. #41
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    its a bit ruff but its just a practice head i got off my mate that works at scrap metal yard for free i tried to make it as ruff finish as i could for high atomisation

  12. #42
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    Quote Originally Posted by BLOKE308 View Post
    its a bit ruff but its just a practice head i got off my mate that works at scrap metal yard for free i tried to make it as ruff finish as i could for high atomisation
    Geeezus Bloke308 thought you were taking the piss with that one lolz

  13. #43
    Part of the furniture phtwgn's Avatar
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    Ruff would be the perfect word/ description for that port work !

    Did you get any tips off CONROD?

  14. #44
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    Quote Originally Posted by Conrod View Post
    How can you compare a SB2.2 to a vn head the chambers are 20 years apart .
    Different fuel different use !
    did i compare a sb2 chamber design to a VN chamber?
    did i mention fuel?
    did i mention anything about hendricks heads?


    do you think single every race head gets bolted on as it is received from the manufacturer, i just used darrins heads as an example of his work ( not head type ) which really is beautiful work and looks like its finished with fine scotchbrite no texture there brother


    surely bloke is taking the piss if so thats fu*ken funny, if not good on ya for trying

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    Twas posted on 1/4/12 - methinks not serious!

    Polishing chambers - meh, if someone wants em polished & will pay me to do it then yeah, otherwise just a sanding roll finish is good enough for me, we're not talking prostock here.

    A hint/note for guys on here that read a lot of stuff by top end porters (such as Darin) - the stuff they are talking about applies to top end engines with cutting edge components (like the latest & greatest head designs etc), stuff like 'pressure recovery' & 'coefficient of discharge' (just as examples) are often not particularly relevant to the sort of stuff most 'enthusiast' type guys are going to be playing with. You're not shooting for 3hp/ci, with the parts most people can afford you have no chance of even going close on that, using factory castings or aftermarket 'average joe' castings most of the high end porting tecniques are pretty much irrelevant - they cannot, for the most part, be achieved using 'normal' heads.
    That's the most challenging part of 'our' job (guys like me & Pete) - cutting through the BS & Hype & developing port profiles that will work as well as possible given the limitations of what we have to work with (both in the hardware & the customers budget). Often the port profiles will be a long way from 'ideals' used in high end stuff.

    Examples -

    An engine with X bore, Y stroke running at Z rpm will require a valve of A size to achieve proper CD (coefficient of discharge) for the engine.
    Problem is, using a valve of the 'perfect' size also required the perfect cam & valve train for it to work as it should, now a 'perfect' valve train is usually either horribly expensive, unreliable or maintenence intesive (or all of the above).
    In the real world A valve size just isn't going to work for a guy on a budget, so you sacrifice ideals to get the max performance out of what Joe can afford.
    Often you'll stick in a bigger valve so you don't have to lift it as high, if a bigger valve won't fit you'll go up on cam duration & bigger in the throat to patch it etc etc.

    In the real world there is no such thing as ideal, just a series of compromises - what is best to compromise to achieve the end goal is our job.
    There is no formula for that, experience counts for more than any simulation or ideal.

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