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  1. #1
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    Default chev head sizing //to big /to small / or just right for your engine .Ahhhh choices

    hi
    How do u calculate head to engine size ?? To feed your beast !! Experiences ??
    effects choice
    focussing on pinch size [Mcsa]
    valve size
    port volume

    end use drag or street or track
    cam shaft type and duration
    efi or carby
    is throttle response important to u if so how much
    keep in mind quality of port shape
    rear gearing
    convertor stall
    economy--WTF
    head makers are favouring air speed as a priority

    Whats clear is around the 220cc port size flow slows . The only way is to go is 60/40 valve position although gains are not outstanding

    What are some good flowing 215 //220 / 227/ 230 heads preferably without 60/40 valving ???

    Thoughts ??????

  2. #2
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    CSA = (cubic inches/8) (RPM / 360) / Air Speed in FPS

    = 355/8 x 6500/360 / 330 or 300

    = 44.375 x 18.05/330

    = 2.42" This is more average CSA but the minimum would be closer to 2.2" this is using
    the 330FPS constant you can use the 300 constant and it will say bigger will work...

    I use pipemax at 285FPS which works out similar but I dont set the RPM to peak HP I set it to the over rev so if I had something peak at 6000-6200...
    I would want this to go to 7000+

    I dont care about anything silly like what it would make under 3000RPM, crap like that unless
    it was a tow truck...


    Whats clear is around the 220cc port size flow slows .
    I pray to God it does slow, put something too fast on and 1st gear of a 3speed auto around 2.5 ratio with even a street diff gear ratio you are looking at 3000RPM per second acceleration rate you will choke the port. A dyno goes 300-600RPM per second..

    Throttle response is also how quick an engine revs up, if you have a bog, stumble or its sluggish then its a tune/timing or issue with converter, or gearing... Or your cam is wrong etc Why go straight to blaming a head if it bogs down because of something else? Efi VS carb, both will work Efi wont make an engine so completely different to a carb that the carb one becomes undrivable..

    Head makers arent favouring HIGH air speed as a priority (the good ones dont even focus on flow numbers) they prioritise shape and the CORRECT air speed making sure the port can handle the speed, if they favour high CFM through a smaller hole making a head too fast then buy from somewhere else

  3. #3
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    hi
    Piston speed/ft per min = stroke x rpm divide 6
    FTper sec divide 60 = ft/min

    Ps =3.75 x 6500rpm divide 6

    ft/min
    [3750 divide 60] x [4.125bore x 4.125 divide portsq/in 1.93]
    62.5 ft/sec x 8.81638 =551 ft per sec airflow

    ***All air flow goes turbulent at 613.8 according to cyl head makers
    The above is for 400chev with 1.93 cyl head 6000rev limit [this seems to be the limit for this port area ]

    400 chev with 2.34 port area, 6500 rev limit =492 ft/sec air speed

    Using TrikHQ as an example
    400 chev with 2.34 port area , 7000 rev limit = 530 ft/sec airflow
    Would consider the limit of head considering the size of cam [approx. 260 solid hr ]

    What calculators donot take into account is how the quality of flow increases with the better head 60-40 valve split

    https://www.cartechbooks.com/techtip...e-performance/
    These calculators are a little different to pipe max which I find weird. Opinions ?

  4. #4
    Do you ever leave? paulzig's Avatar
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    Calculators dont take into account whether or not the shape of the port can handle airspeed, if it cant go bigger.

    I dont know what quality of flow is nor what you mean by it, do you mean more CFM per square inch of area?

    Like I said on a dyno that is 600RPM per second maybe a 1.93 port has a 6000 max RPM but in a car that accelerates in 1st gear with the appropriate diff gears this now becomes around 3500 RPM per second you dont think this will show up an airspeed issue sooner than at 600?

    Thats another stupid thing about the off idle torque down low people, 3500RPM per second in 1st gear you are up to 6000RPM In under 2 seconds, and if you shift at 6500 the rest of the gears you have seen low RPM for a brief instance and only once in the run... It is ridiculous lol

  5. #5
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    Yeah but it isnt the racers that bang on about low down, theyre on the line, stalled up and waiting to let fly.. its the daily driver guys who cant come to terms with it, youre either towing a trailer or youre driving a performance car.. the best bet for them is install a positive displacement supercharger.

  6. #6
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    Anyway im building a Dart 400 at the moment so im all ears on those numbers there

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    hi
    Paul
    Quality of flow . Port flow in general improves with 60/40 spacing 1st valve sizing 2nd valve spacing =ports shape is changed and slightly more efficient . All the head makers complain about sbc heads compared to modern standards at least the ones I have contacted . As we all no 1brand vs another the port shape canbe different for the sameport size in cc .
    Air speed
    quality of port shape = better flow and better cylinder filling
    air volume typically a result of pinch size [mcsa]
    valve size

    The summary is its no surprise why there is "LS" and 13 deg motors because the standard 23 deg head is just a poor performer . Compared also to even other brands of motor Ford ,Chrysler etc


    Hq308ute

    The calculators I have come across point to 400chev 6500rpm =2.2 pinch [mcsa ] . It would appear this is some where near the max rpm and if cammed properly would peak hp around 6400 . Spoken to Comp cams and they suggested 242/248 ground with no advance or retard [installed straight up] 110Lsa .Maybe even 242/250 ,this would stretch the top end rpm a little . This combo needs even more refining as any cam past 230/236 drops engine vacumm more than I like

    The 242/248 needs at minimum 3.6 rear gear [3000 eng rpm per 100kph ] and min 3000stall

    There is trick flow super 23 CNC 230 ,Mcsa ? good flow on paper fair cost little cheaper than afr but less flow
    Flow like port size and cnc is an indicator of potential but its not guaranteed
    AFR 220 competition 322 cfm at 650 lift MCSA 2.18
    The afr 227 only adds to the topend flow slightly but has a 2.34 mcsa
    Most 227and up require rocker shafts =much $$$

    A lot off drag go 227 every time .

    Are there better heads dunno ???
    -------------------------

    There is Chad Spier port calculators which recommend larger port sizings similar to Paulzig

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    Quote Originally Posted by swampy View Post
    There is Chad Spier port calculators which recommend larger port sizings similar to Paulzig
    Seems they target the same air speed...

    Pick your bore and stroke, pick your MAX RPM (not peak HP) where you shift which is just before you set the rev limiter... Like I said for a 6500 peak to me that equals a 7000-7200RPM shift point minimum.. If you target 6500 and thats where you shift you havent used the power that you could have, engine takes a while to take a nose dive after peak so why not use it?

  9. #9
    Do you ever leave? HQ308Ute's Avatar
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    Dart SHP 4.125" 350 mains
    Scat 3.750"
    Scat Pro series I Beam 6" rods
    Mahle Forged flat tops

    Bottom end is easy, i always stress on the top end, i was thinking Edelbrock Part # 61255 Victor Jr. 23 220 cylinder heads would be ok for the street.. and "some kind of roller"

  10. #10
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    Quote Originally Posted by HQ308Ute View Post
    i was thinking Edelbrock Part # 61255 Victor Jr. 23 220 cylinder heads would be ok for the street..
    Too expensive...

    $1390ea bare, and you buy them bare and you can get the springs and valves yourself setup for your valvetrain...

    Buy:

    https://www.summitracing.com/int/par...make/chevrolet $647 bare

    or

    https://www.summitracing.com/int/par...make/chevrolet $1087, these are Vortecs and will need a different intake If I was doing a 400 I'd buy these

    Or look at some profilers, or even the Promaxx 200cc a copy of the Brodix Ik200 which you could also look at..

    Use a Hydraulic roller 227/240 109LSA .580 lift something like that

  11. #11
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    its not the money.. no probs there just want a good head design.

  12. #12
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    Quote Originally Posted by HQ308Ute View Post
    its not the money.. no probs there just want a good head design.
    All 23 is the same really, the Vortec is a revision with the raised runner and fast burn chamber... GMPP Fastburn. They wont flow as much as an AFR most likely but who cares...

  13. #13
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    hi
    AFR 220cc competition [double cut cnc].
    400 steam holes need drilling in heads [cheapest done by AFR]
    get the right v/springs when ordering also
    3200$ in ozzy last time I checked
    flow 322 cfm at 650 lift and will flow to 700 lift at 326cfm [not much gain above 650]
    vehicle and engine setup are critical for package to work

    Cnc at least makes the gaskets match
    AFR competition is double cut cnc and also has directional vanes around v/guides at least in the 195 comp

    Trivia The 195 comp is the latest design head and performs well vs its bigger bros .

    Some manifolds are only 1205 gasket .When heads did not flow they had smaller ports . Vic jnr manifold has 1205 ports
    Good flowing heads are typically 1206 gasket Team G has 1206 ports . The 7530 fits under a bonnet as well . There are taller versions also.

    Remember the difference between the comp afr heads 195-210-220 is probably approx 30 hp and that's with a 260+ large cam.

    When u compare the flow of the sbc heads to other engines there flow is limited . U need every cfm u can get .

    Brodix sell economy and exp heads as well. AFR heads vs Brodix ,,which is better dunno .
    https://brodix.com/cylinder-head-recommendation-guide
    10.5 CR ratio min
    -BP IK 210
    -Track 1 std.
    -STS T1 215
    -STS T1 227
    no idea of pinch [mcsa]. On air flow alone 215 or 227
    Last edited by swampy; 26-06-2019 at 08:43 PM.

  14. #14
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    those Promaxx look the goods actually..

    No steam holes in dart blocks.. Their SBC blocks are designed with scalloped water jackets that add additional cooling capacity around the cylinders eliminating the need for steam holes.
    Last edited by HQ308Ute; 26-06-2019 at 08:39 PM.

  15. #15
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    Quote Originally Posted by HQ308Ute View Post
    those Promaxx look the goods actually..
    Doesnt look like a bad casting in the pictures.... You need some flow numbers lol..

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