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  1. #1
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    Default cylinder head maths /// Make selection easier

    Hi
    Valuable info i found eventually about head selection
    Brodix have a good head selector chart

    Info will lead to better than most selections in relation to MCSA /pinch point / min cross section area
    Have a big influence on how head functions taking into account rpm and engine size

    Port velocity is nice to now as many head makers overstate there flow numbers . Port velocity depends on port design as to how much is ideal .

    Yes these formulas canbe questioned but at the moment its all I have .

    PORT VELOCITY
    Piston Speed Calculator - Universal Entry
    PISTON SP constant bore x bore MCSA
    4062.5 divide 60 multiply 4.125 x 4.125 divide 2.18 = 528.46 ft per sec

    Use above as a guide from a known combo that works !!

    PORT AREA
    bore x bore x stroke x rpm divide by 190,000
    4.125 x 4.125 x 3.75 x 6500 divide 190,000 = 2.18

    H/POWER INLET TRACT manifold and cyl head combined [from super flow info]
    Tested at 28inches = coefficient of .26
    250cfm x .26 x cyl 8 = 520hp

    ESTIMATED ENGINE SPEED
    From super flow
    VE [volumetric effic. street /strip ] divide [cu.in. divide cyl] x CFM = target rpm
    1256 divide 50 x 250cfm = 6280 rpm

    I found these helpful ,hope u do ..

    Reasonably accurate considering the dyno sheets I have looked at

    Interesting
    chev 400 195cc head 5700--5800 peak ,1.93 mcsa ===532.6 ft/ sec cam about 236/242 .050
    chev 400 210 head 2.1 mcsa cam in the 240/250 range
    chev 400 220cc head 6500 peak , 2.18 mcsa === 528.46 ft/sec

    The 195 combo on dyno sheets is happiest peaking in the very late 5000`s
    Seen a lot 210cc heads peaking about 6200-6300
    Seen no 220cc head examples
    The dyno sheets are from people that no, so there matching cam with heads.

    These heads canbe over cammed but ideally more than 500--700rpm would be a waste . A bigger head would be better solution .


    The only thing that remains is the ideal airspeed for a given cylinder head design . Eg AFR claim 310cfm from the comp 195 but if u flow cfm thru the pinch the airspeed goes vertical very high . IS it to high to be a benefit ??/ Is it all advertising bullsh.t ???
    Last edited by swampy; 06-02-2019 at 09:36 PM.

  2. #2
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    People will always purchase CFM
    Those formulae inadvertently keep many of us chained for years
    Enjoy

  3. #3
    Do you ever leave? paulzig's Avatar
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    You can get flow and airspeed on a bench at 28"H20 static.. A 355 cubic inch engine at 6500RPM is around 55-58" H20 dynamic.. The higher the depression the worse a hi speed area in the port becomes..

  4. #4
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    Quote Originally Posted by swampy View Post
    IS it to high to be a benefit ??/ Is it all advertising bullsh.t ???
    Too high and your engine stops revving up, and now people go putting on dual plane manifolds with longer runners that twist and turn, can you guess what that does to the airspeed?

    Now, when you have killed your airspeed with a slower cam which has a lot of seat duration and low lift, these dual planes are great for getting the airspeed back..

    The engine doesnt run with just heads, they need an intake and a carb or efi TB to run, so the manifold is now part of the head ..

  5. #5
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    HI
    Yes the small port high flow numbers would be a challenge all by itself compared to conventional thinking . The port might flow good numbers but at light speed . The change of direction in a dual plane will be a compromise . The air is flowing very fast for the port design .
    There are 2 different schools of thought on air speed for port design and the appropriate MCSA

    Even the manifolds u get are typicaly are designed for 350 not 400 and certainly never dyno tested on a 400 re Elderbrok info .

    Manifold differences eg vic jr and rpm air gap , 2 different manifolds designed many many years apart . The A/gap performs well because of this. Picks up strong TQ early and holds Hp well .
    There are many a dyno sheet where the air gap is used on a 410 till 6500 plus . Believable dunno ??

    To take advantage of the 195 COMP heads small port/high volume / high speed single plain might work [vicjr] . The need for unobstructed flow other wise the advantage will basically be lost . This is individual to this size head .RE air speed To get the most outta the head because of its need for high speed there`s no other choice hmmm …

    There are write ups about Edelbrock manifolds cfm flows b4 and after mods . Gains were not huge at lower rpms. The air gap/vic jr were not that different. Both 240-250 cfm .
    The supa vic was only 260-270cfm

    I suspect with 210 heads and a dual plain with a 236/242 would have a flatter power curve. Probably why there popular . slower air speed . Probably use a d/plain more efficiently.

  6. #6
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    What sort of person flows a manifold on its own, its nowhere near a real world scenario.. You bolt the head, manifold even the carburetor or TB on top and then flow it if you are a CFM chaser... It will drop the CFM as opposed to flowing head alone.. exhaust ports you dont even need a number there..

    LOL, forget the dual plane for a second Use the 210 a supervictor or a Holley strip dominator assuming a 383/400 cu.in why dont you just change the cam from that 236/242 that you were going to use for the dual plane to lets say 230/244 109LSA something like that then that will use a single plane more efficiently there is your 6000-6500 peak range.. Im not saying what you are planning is right or wrong, I am asking why you are stuck in your thinking process at dual plane.

    If you had a 185-195cc head, with a single plane that 236/244 on a 108LSA would be the cam to use for 6000-6300 peak on a 383

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    Quote Originally Posted by swampy View Post
    HI
    Yes the small port high flow numbers would be a challenge all by itself compared to conventional thinking . The port might flow good numbers but at light speed . The change of direction in a dual plane will be a compromise . The air is flowing very fast for the port design .
    There are 2 different schools of thought on air speed for port design and the appropriate MCSA

    Even the manifolds u get are typicaly are designed for 350 not 400 and certainly never dyno tested on a 400 re Elderbrok info .

    Manifold differences eg vic jr and rpm air gap , 2 different manifolds designed many many years apart . The A/gap performs well because of this. Picks up strong TQ early and holds Hp well .
    There are many a dyno sheet where the air gap is used on a 410 till 6500 plus . Believable dunno ??

    To take advantage of the 195 COMP heads small port/high volume / high speed single plain might work [vicjr] . The need for unobstructed flow other wise the advantage will basically be lost . This is individual to this size head .RE air speed To get the most outta the head because of its need for high speed there`s no other choice hmmm Ö

    There are write ups about Edelbrock manifolds cfm flows b4 and after mods . Gains were not huge at lower rpms. The air gap/vic jr were not that different. Both 240-250 cfm .
    The supa vic was only 260-270cfm

    I suspect with 210 heads and a dual plain with a 236/242 would have a flatter power curve. Probably why there popular . slower air speed . Probably use a d/plain more efficiently.
    You do not know why and how a dual plane does or does not do what it does
    Most of us either donít or subscribe to popular theories
    Why donít plumbers use dual plane down pipes for low flow conditions -
    A to B directly is the go
    If a straight runner could expand and contract then that would be the closest to practically usable
    You cannot bend nature to your will
    Anyways since your pocket is driving this research continue.

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    Hi
    Not trying to rely upon peoples experiences . Much like asking Why because 1 persons impression is different to another much like every bodies impression of budget engine . Ask 10 different people 10 different answers.

    Many of these popular theories come from experienced sources eg super flow. I suggest u reread b4 commenting !
    Even thou many places offer formulas they mostly say there approximates but have been given good results over many years .

    Many places although there are formulas will not release them re Edelbrock .

    Getting ideal air speed recommendations outa the cyl head companies is like pulling teeth .[each port design will have its limits]


    Tony Mamo former AFR designer agrees with the thought to feed high to very high air speed to the 195cc head in a high demand situation . With its small MCSA when restricting feed to this head severly reduces performance eg very small dual plane . The 195 performance is dependant on very high air speed way higher than even the next larger head in similar situation .

    What is good news is there are new AFR manifolds coming to market . Currently just released a high rise single plain . There will be a CNC ported low rise later this year. The low rise should outperform a victor jr and fit under the bonnet .
    Last edited by swampy; 07-02-2019 at 03:39 PM.

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    Quote Originally Posted by swampy View Post
    Hi
    Not trying to rely upon peoples experiences . Much like asking Why because 1 persons impression is different to another much like every bodies impression of budget engine . Ask 10 different people 10 different answers.

    Many of these popular theories come from experienced sources eg super flow. I suggest u reread b4 commenting !
    Even thou many places offer formulas they mostly say there approximates but have been given good results over many years .

    Many places although there are formulas will not release them re Edelbrock .

    Getting ideal air speed recommendations outa the cyl head companies is like pulling teeth .[each port design will have its limits]


    Tony Mamo former AFR designer agrees with the thought to feed high to very high air speed to the 195cc head in a high demand situation . With its small MCSA when restricting feed to this head severly reduces performance eg very small dual plane . The 195 performance is dependant on very high air speed way higher than even the next larger head in similar situation .

    What is good news is there are new AFR manifolds coming to market . Currently just released a high rise single plain . There will be a CNC ported low rise later this year. The low rise should outperform a victor jr and fit under the bonnet .
    I will give you a reply that you may comprehend -
    Then again your not too bright
    Enjoy

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    HI
    Actrol
    Your lack of fact based constructive comments and being unable to participate positively in community forum suggests u may well be not so bright yourself .
    Last edited by swampy; 07-02-2019 at 07:01 PM.

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    So are you going to purchase a set of 195cc AFRs, an Edelbrock dual plane air-gap and a 236/242 hydraulic roller... Is that what you are leaning towards currently?

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    Daniel Bernoulli...

  13. #13
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    Quote Originally Posted by EH179 View Post
    Daniel Bernoulli...
    A fan of the single plane

  14. #14
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    Swampy,
    David Vizard's Port & Flow test book [ S-A books #215 ] is good reading. Especially his thoughts on why the established 28" pressure drop figure is misleading.

    Out of the big three, Chrysler got it right the first time more than the other two, IMO. They tried a single plane manifold with the 273 V8 for one year only, in 1968 [ VE Valiants here ]. The years before & after were dual plane. Since a SP manifold is cheaper/easier to make, but they still dropped it after only one year.....tells a story.

    A dual plane manifold is simply two SP manifolds in one casting. Each plenum feeds 4 cyl. The runners are typically longer & more restrictive & so are rpm limited. You need to look at the expected rpm range & decide which is best. A SP might add 20 hp for the final 500 rpm but give up 30 ft/lbs in the low mid/range over a DP. If it was a street car, I know which one I would use...

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    Quote Originally Posted by Actrol View Post
    I will give you a reply that you may comprehend -
    Then again your not too bright
    Enjoy
    Quote Originally Posted by swampy View Post
    HI
    Actrol
    Your lack of fact based constructive comments and being unable to participate positively in community forum suggests u may well be not so bright yourself .

    ... to BOTH members going the man and NOT the message,
    I would suggest if you continue, a nice holiday is coming your way

    free too ! ... as we will be from the tripe and personal comments
    you are subjecting the rest of us to.


    ps
    Actrol, you should really get the Queen's English correct
    before using it for barbs at another member...

    "again your not too bright" ..... is not quite right!
    My Grade 3 English teacher would have laid the ruler on
    if I said/spoke that. "again, you're not too bright"
    gets 100% for spelling , zero for courtesy though

    Please keep it nice ....
    Last edited by Smitty2; 07-02-2019 at 07:07 PM.
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