Advice on Cylinder Head cfm for 340 stroker

Discussion in 'Small Block Mopar Engine' started by moparodbuster, Nov 10, 2018 at 3:19 AM.

  1. moparodbuster

    moparodbuster moparodbuster

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    Looking for advice on approximate cylinder head intake/exhaust flow reccomendations for my build:
    340 block .40 over, 4.00 crank, 11:1@65cc pistons, 260@.50 solid flat tappet, victor 340 intake, worked 950 Holley.
    Going into factory weight '71 Demon w/ss leafs, 4:30 gears, reverse manual auto.
    Considering...
    1. Promaxx cnc: 285/195
    2. Brodix cnc: 300/204
    but some experienced advice before buying anything would be great.
    Thanks
     
  2. rumblefish360

    rumblefish360 so close yet so far away

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    Check deeply into the Brodix heads.

    Generally speaking, more cfm the merry. Best to have a fat curve. The best earliest flow possible.

    Who is doing the CNC work on the Pro Maxx heads?
    Can you list there flow spec sheet?
     
  3. rumblefish360

    rumblefish360 so close yet so far away

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    B1BA ..lift........200 300 400 500 600 650
    2.080 Intake ...145 203 250 286 300 302
    1.600 Exhaust .121 169 195 208 214 216
     
  4. dodgedifferent2

    dodgedifferent2 Well-Known Member

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    Trick flow heads sounds promising.
    Stay with stock heads until they hit the market?
    Brodix heads seem to be a big unknown
    Promaxx heads must be newer as I never saw anything about them when I did my stroker.

    I honestly would look towards w2, indy, w8 or w9's
    There were some 59 degree w9s posted somewhere that I wanted to get but I dont have the finances for that.


    I currently have indy *sigh* that I got used and had reworked.
    I also had w2s on this engine.
    4.30 gears
    Passon hemi od 4 speed
    tti exhaust
    Fitech carby
    Lunati Solid roller 40200734
    • Duration @ .050 (Int/Exh): 255/263
    • Gross Valve Lift (Int/Exh): .600/.600
    • LSA/ICL: 110/106
     
  5. MOPAROFFICIAL

    MOPAROFFICIAL Well-Known Member

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    If the promax is real, that's the head you want.
    Those flow numbers will keep you happy for years to come. You can make 550hp with the cam and everything that follows with those heads.
    Any head flowing 140,200,250,275 from .200-.500 is a winner in my book, port volume dependent of course, 185cc is in the zone.imo
     
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    • rumblefish360

      rumblefish360 so close yet so far away

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      Nice, I’m set up for the one size smaller cam with 1.6 rockers. It outta be a scream.
      • Advertised Duration (Int/Exh): 279/285
      • Duration @ .050 (Int/Exh): 249/255
      • Gross Valve Lift (Int/Exh): .585/.600
      • LSA/ICL: 110/106
      • Valve Lash (Int/Exh): 016/016
      • RPM Range: 3000-7000
       
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      • rumblefish360

        rumblefish360 so close yet so far away

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        How do you feel about more port volume?
        Where would you yield?
        225 to much?
         
      • 67autocross

        67autocross A new iron curtain drawn across the 49th parallel

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        I had a look at the promax heads last week, casting looks good and they claim 285 flow. Local shop will have a 360 with a 4 inch arm on the dyno in the next few months with them. The builder said it will make 550hp...
         
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        • moparodbuster

          moparodbuster moparodbuster

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          The Promaxx CNC heads are an in house option of theirs. Flow specs on their website. I'll see if I can get em posted here.
           
        • MOPAROFFICIAL

          MOPAROFFICIAL Well-Known Member

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          Relative to street strip...
          It's easy to forget... But go back to what you know, the basics, then use your math and find the smallest "usable" port volume 'for your cubic inch vs rpm' that flows the target.
          Anything under 180cc is gonna leave top end power on the table, even in a street build.imo
          Anything above 195cc is not the head i would choose for a street/strip deal. That's just me, I like velocity and as much as I can get away with. Just enough is just right.

          Honestly, I dont build cookie cut engines. Everything I build is one off. I use custom grinds for everything, even warmed up stock gets a tad diff this n that. There really is no set in stone port volume, only a range. You as the builder need to know the sweet spot.
           
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          • rumblefish360

            rumblefish360 so close yet so far away

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            Cool thought pattern. Likewise I would say.
             
          • Bobzilla

            Bobzilla Well-Known Member

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            No mention was made on intended use, so I say go for well prepped Edelbrock Victors, or second choice would be Indy 360-1.
            The Promaxx heads are sometimes said to be good castings and just need to be filled with quality parts as well, not the Chinese valves they come with.
            All that said, I see you are in Australia so I would say go with whatever has the best local support. If you have good local head shops that use one of your original considerations, that is your best bet.
             
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            • 67autocross

              67autocross A new iron curtain drawn across the 49th parallel

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              The Victors are at a whole other price level, I was at the local machine shop yesterday when I found out the trick flow heads would be delayed again.... the owner of the shop said let’s price some Victors out... he stop himself when it passed the $5000 Canadian mark ... looked at me and said you would have to be nuts to even think about them...
               
            • rumblefish360

              rumblefish360 so close yet so far away

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              Or a serious chashing the money racer.

              Or so rich there is no care or consideration for what falls out of your pocket.
               
            • mbaird

              mbaird mbaird FABO Gold Member

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              I have less than 4k in my W2s... that includes new HS rockers, Ferrea Valves , Shady Dell port job , Moly retainers , Smith Bros pushrods , Custom Roller cam , Crower Severe Duty Hippo roller lifters , NOS Victor intake.... 297 cfm @ .650
               
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              • mbaird

                mbaird mbaird FABO Gold Member

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                and those heads were new and unused.
                 
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                • 67autocross

                  67autocross A new iron curtain drawn across the 49th parallel

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                  I’m not operating out of the poor house by any means... but if I’m going do spend that kind of cash on heads I will be changing directions... like doing a turbo build.
                   
                • moparodbuster

                  moparodbuster moparodbuster

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                  Yeah really. Victors, w2's, all high priced options on their own not to mention scrapping all my existing valve train, intake manifold, tti headers, etc. Not worth the cost and hassle when similar flow numbers are available from less expensive, standard valve train, standard intake, exhaust port heads. This all makes the Promaxx look like the best bet as long as I'm not restricting the engines potential by a huge amount. I'm just in the dark about what the noticable difference on my build would be between 285 and 300 cfm/intake... are those last 15 cfm only usable approaching my 7k rev limit or do they affect the entire rev range?
                   
                • rumblefish360

                  rumblefish360 so close yet so far away

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                  You are
                  Correct to a degree. The standard port aftermarket heads are still considered a stock replacement head and as such, they only obtain so much power. And a good bit of it they make. But only so fast you can go. Now you enter the Indy, W series heads.

                  Your wondering if you’ll feel or notice they extra 15 cfm?

                  Are you lifting the valve that high?

                  If not, then don’t bother.

                  Are you racing the car or is it still mostly street?

                  If it is not a light weight race ride, then don’t bother.

                  Are you going to take full advantage of the upper level head?

                  Of not, then don’t bother.

                  FWIW, your cam is listed at 260*’s @ .050.
                  I call that a small big cam.
                  You also never mentioned the cams lift or the rocker ratio along with the current head flow specs. Without this information, were kind of shooting in the dark to get you out of the dark. You want out of the dark, you need to turn on some more light onto the situation with complete information on your set up.

                  Also, (not breaking balls, but) your car is really heavy to realize any gains from more advantageous parts. Bust that heavy girls gut down to sub 3K.
                  Less weight is faster and less broken parts.
                   
                • 67autocross

                  67autocross A new iron curtain drawn across the 49th parallel

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                  I’m lucky because my local shop is building a 360 with 4 inch arm and the CNC ported promaxx heads as we speak, it will be running a 600 lift roller cam. I could wait until it’s off the dyno and I could make some adjustments to my 340 stroker build based on how it works.
                  I was thinking of ordering the promax heads bare and putting a 205 valve in them and doing a bit of porting... I would like to see close to 300cfm flow out of them and try make 575hp with a solid lifter cam. If I can do that with the promax heads I will forget all about the trick flows.
                   
                • MOPAROFFICIAL

                  MOPAROFFICIAL Well-Known Member

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                  Too much for what?
                   
                • rumblefish360

                  rumblefish360 so close yet so far away

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                  And that was sort of the question to you, sorry if it was to vague. But, Oh! I don’t know, 408 - 436 - small block drag car low street useage?

                  Dialing it back some, I have found the as cast Edelbrock head very good on a mild engine. Ported does well on bopped up mills and mild strokers, not that you couldnt race with them.....
                   
                • MOPAROFFICIAL

                  MOPAROFFICIAL Well-Known Member

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                  180-200cc how's that for vague, right?
                  Starting from 177-179cc "ported" would take them to at least 180cc + right?
                   
                • MHEAD

                  MHEAD Member

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                  I bought the promaxx heads bare and sent them to modern.2.08 manley valves,pac springs all good stuff. I believe they flowed 312 @ .600 and 220 exhaust.The best way to get ahold of them is email.
                   
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                  • moparodbuster

                    moparodbuster moparodbuster

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                    That's amazing, are they the Promaxx cnc bare heads that you got?