J/X Head exhaust flow?

Small Block Mopar Engine

  1. Bronze Barracuda

    Bronze Barracuda Well-Known Member

    Messages:
    278
    Likes Received:
    86
    Joined:
    Aug 17, 2019
    Location:
    Vancouver
    Local Time:
    3:22 AM
    Question of curiosity.
    So Tony on Uncle Tony's Garage, made a video about a year back on the virtues of the exhaust ports on the small block Chryslers. Basically stating that because of the angle it is a very straight shot out the head which does make sense that, that is a better design.
    He used his finger and a torch for demonstration purposes. :lol:
    I also watched an awesome video on my vintage iron about camshaft selection, he does an excellent job at explaining percentage of flow, how intake and exhaust work together, (if your intake is flowing 197 @ 500 and exhaust is flowing 128 so divide 197 into 128 you get 64%).
    A basic idea if you are pulling in 197 cfm but only dumping 128 64% of flow not so good. (these are just generic numbers not tied to any head in particular).
    So getting back to UTG and the small block mopar head, 360/340 heads in particular agood exhaust would be very beneficial?

    So today I was researching different heads and I come across this website "darkside.ca" where they are briefly explaining different heads, both aftermarket and stock type heads.
    In the stock 340/360 j head type they say.

    "The exhaust port is probably the Iron head greatest weakness. You can make the intake port flow ungodly #'s if you want, but if you can't expel all the burnt Hydrocarbons, the guy in the other lane is goanna WIN. This is why guys resort to WELDING up the exhaust on factory iron heads for better exhaust flow".

    So who is correct Uncle Tony or this darkside.ca website? Or is the truth somewhere in the middle?

    Also what the heck is, "WELDING" up the exhaust?

    Here are some links to UTG and my vintage iron.
    Honestly M Vintage Iron I think is a great channel, IMO.



     
    • Like Like x 1
    • B3422w5

      B3422w5 Well-Known Member

      Messages:
      2,185
      Likes Received:
      2451
      Joined:
      Feb 9, 2017
      Location:
      Portage michigan
      Local Time:
      6:22 AM
      Excellent article …very informative


      By David Reher, Reher-Morrison Racing Engines

      Our era is often referred to as the Information Age, but not all of the available information is necessarily useful. I am beginning to think that flow benches should be labeled with a government warning: “Caution! Excessive reliance on flow numbers may be harmful to your engine!”

      I’m kidding, of course. Used wisely, a flow bench can be a useful tool in engine development, just like a timing light or a dynamometer. Unfortunately, some racers believe that a flow bench is the ultimate answer machine.

      When the subject is cylinder heads, the four words I dread to hear are, “What do they flow?” Novice racers and magazine writers share a fixation about airflow. The mistaken belief that “more is better” is often the false assumption that produces an underperforming engine.

      I learned this lesson myself when my partners Buddy Morrison and Lee Shepherd built our first flow bench in the mid-’70s. It was a great contraption that could just about suck the windows out of our rented shop on Arkansas Lane. While this homebuilt test bench boosted our racing program, it certainly didn’t make us engine experts overnight – even though we initially thought we had found the key to the vault of knowledge.

      We had been racing 287-cubic-inch small-blocks in various Modified and Comp classes before we decided to make the move to Pro Stock with a 331ci engine. (Students of Pro Stock history will recall that the ’70s was the era of weight breaks for various engine and chassis combinations.) We were determined to be “scientific” in our approach, and reasoned that a 15 percent increase in engine displacement demanded a 15 percent increase in airflow. We dutifully enlarged the ports, increased the valve diameters, and hit our airflow targets. We set off to conquer the world of Pro Stock – but our pride and joy was a dog.

      After struggling to even qualify in our initial outings, we pulled an old pair of Modified heads off the shelf. Lee worked on the ports for an afternoon, we bolted them on our Pro Stock short-block, and we qualified fifth at Englishtown in our next race.

      If you went strictly by the flow numbers, those heads would hardly enough air to satisfy a respectable big-inch bracket racing engine – and yet they were magic on the race track. That was when I realized that cfm isn’t everything. It’s a lesson that I have seen repeated countless times in the last 25 years.

      A flow bench measures air movement in a very rudimentary way – steady-state flow at a constant depression (vacuum). Obviously the conditions that exist inside a running engine are quite different. The flow bench can’t simulate the effects of the pistons going up and down, the reversion pulses as the valves open and close, the sonic waves that resonate inside the runners, the inertia of the fuel droplets, and all of the other phenomena that influence engine performance in the real world. When you flow test a cylinder head, you are simply measuring how far you can move the liquid in a manometer.

      The bigger you make a port, the more it flows. That’s hardly shocking news. Bolt a sewer pipe onto a flow bench and it will generate terrific flow numbers. So should we use ports as big as sewer pipes on our race cars? The flow bench says we should – the time slip says something completely different.

      If airflow were everything, we would all use the longest duration camshafts we could find – after all, more duration means more flow. In fact we know that there is a finite limit to how long the valves can be open before performance suffers. That is because the valve events have to be in harmony with the rest of the engine.

      The same principle applies to cylinder heads. Simple airflow capacity should never be the first consideration in evaluating cylinder heads. Characteristics that are far more important include air speed, port cross section, port volume and shape, and the relationship between the size of the throat and the valve seat. If these attributes are wrong, you can work forever on the flow bench and not overcome the fundamental flaws.

      Here is a do-it-yourself example: Turn on a garden hose and the water will dribble out a couple of feet. Now put a nozzle on the hose and the water will spray across your backyard. The water pressure and volume haven’t changed, but the velocity has increased dramatically. Now think about the air and fuel going into your engine’s cylinders. Which would you prefer: slow and lazy or fast and responsive?

      An engineer will tell you that an engine requires a prescribed amount of air and fuel to produce “X” horsepower. In a perfect world, that may be true – but we race with imperfect engines. The shape and cross-sectional area of the runners are absolutely critical to performance. For example, I have two sets of Pro Stock cylinder heads that produce nearly identical flow numbers, yet one pair produces nearly 150 more horsepower at 9,200 rpm than the other. The flow bench can’t tell the difference between them, but the engine certainly can.

      There are software programs that claim to be able to predict an engine’s performance based on airflow numbers. Unfortunately, a critical shortcoming of many of these programs is that they are based on inaccurate information or false assumptions. A computer is an excellent calculator, but it is not an experienced engine builder. The software doesn’t know whether a port’s short-turn radius is shaped properly, whether the flow is turbulent at critical valve lifts, or whether the flame speed is fast enough. Racers have a tendency to believe that computers are infallible, so they accept the software’s solutions as gospel, when in fact they may be badly flawed.

      Textbooks would lead you to believe that an exhaust to intake flow ratio of 80 percent is ideal – yet a typical Pro Stock head has exhaust ports that flow less than 60 percent of the intake runners. You can improve the exhaust flow tremendously with about 40 minutes of work with a hand grinder – but the supposed improvements will just about kill the engine’s on-track performance. I know because I’ve been there.

      We have also learned that low-lift flow (meaning anything below .400-inch valve lift in a Pro Stock engine with a .900-inch lift camshaft) is relatively unimportant. Think about the valve events in a racing engine: From the point when the valve first moves off its seat until it reaches mid-lift, the piston is either going the wrong way (that is, it is rising in the cylinder) or it’s parked near TDC. The piston doesn’t begin to move away from the combustion chamber with enough velocity to lower the pressure in the cylinder until the valve is nearly halfway open. Consequently it is high-lift flow that really matters in a drag racing engine.

      The shape of the combustion chamber also has a significant impact on performance. A conventional chamber with deep reliefs around the valve seats and a relatively flat valve seat angle can produce terrific flow at .200 to .300-inch valve lift. Today a state-of-the-art chamber typically has 55-degree valve seats and steep walls that guide the air/fuel mixture into the cylinder to enhance high-lift flow.

      This doesn’t mean that every racer needs state-of-the-art Pro Stock cylinder heads – along with the high maintenance they require. The heads have to match the application. Conventional combustion chambers and 45-degree valve seats are just fine for a dependable, low-maintenance racing engine that will run a full season between overhauls.

      The classic Hemi combustion chamber is capable of producing impressive flow figures, but it’s not going to make impressive power. Engine technology in all forms of motorsports is converging around smaller, high-efficiency combustion chamber designs. You can see the result in lower brake specific fuel consumption (BSFC) numbers, which indicate improved engine efficiency. Twenty years ago, a racing engine with a .48 BSFC was considered very good; today’s competition engines produce BSFC numbers in the neighborhood of .35. This means that a given quantity of fuel is being atomized and burned more effectively to produce more power. A cylinder head’s combustion efficiency can’t be measured on a flow bench, yet it has a huge impact on performance.

      I am not against flow benches; in fact, we use computerized flow benches daily at Reher-Morrison Racing Engines. What I am against is over reliance on flow numbers as the primary measurement of a cylinder head’s performance. A flow bench is a valuable tool that can help a racer fine tune a combination – but it is not the ultimate authority.

      Share this:
       
      • Thanks! Thanks! x 10
      • Like Like x 3
      • Agree Agree x 1
      • Dartswinger70

        Dartswinger70 I been North I been East to the California beach

        Messages:
        3,828
        Likes Received:
        2178
        Joined:
        Sep 20, 2005
        Location:
        Southeastern Pa.
        Local Time:
        6:22 AM
        I wouldn't think Uncle Tony is 100% correct on anything...what are his credentials besides being a shade tree bullshitter? His cars are pure scrap also...facts is facts. :lol:
         
        • Like Like x 2
        • Agree Agree x 1
        • Disagree Disagree x 1
        • 66jim

          66jim Well-Known Member

          Messages:
          621
          Likes Received:
          610
          Joined:
          Dec 11, 2007
          Location:
          NE PA ie pennsyltucky
          Local Time:
          6:22 AM
          Your articulate post is going to ruffle lots of feathers here. Thanks for sharing real world experience.
           
          • Agree Agree x 1
          • MOPAROFFICIAL

            MOPAROFFICIAL FABO Gold Member FABO Gold Member

            Messages:
            10,196
            Likes Received:
            9559
            Joined:
            Jun 1, 2016
            Location:
            Oceanside ca.
            Local Time:
            3:22 AM
            Uncle Tony is an idiot. When you burn something there's not going to be 100% of it left.
            Nowadays...I dont know who to blame more , uncle phonie ... or his viewers. Quit posting UTC garbage.
            In fact if you have an article to share , post a link to the article don't copy and paste it here to take more server space.
            It's long known that the intake is more important than the exhaust. BB Fords can be a great example, 700 hp with a 60% exh flow ratio. Not to say exh flow ratio isnt important in other ways, it is , it's just not as important as you think. It can be worked around to.
             
            • Agree Agree x 2
            • Like Like x 1
            • Disagree Disagree x 1
            • PRH

              PRH Well-Known Member

              Messages:
              3,787
              Likes Received:
              5573
              Joined:
              Dec 14, 2018
              Location:
              So. Burlington, Vt
              Local Time:
              6:22 AM
              “For what most people are doing with them”........ the factory 340/360 head exhaust ports aren’t a significant enough limitation to keep one from reaching their goals.

              They aren’t great ports, with their poorly shaped floor after the SSR(aside from the 308 head), but there are other heads from the same era that are worse.

              Generally, after the valve job is done.......the first well executed 5-10 minutes of work in a J/X head exhaust port is the best bang for the buck.
              After that initial work, it takes a lot more time per/cfm.
               
              • Like Like x 1
              • Thanks! Thanks! x 1
              • Bronze Barracuda

                Bronze Barracuda Well-Known Member

                Messages:
                278
                Likes Received:
                86
                Joined:
                Aug 17, 2019
                Location:
                Vancouver
                Local Time:
                3:22 AM
                Not sure who yer refering to about copying and pasting, I just gave a couple links to some channels in reference to what I was talking about. That's why I'm asking questions, to hopefully learn a thing or two. I didn't copy and paste anything personally myself.
                 
              • Bronze Barracuda

                Bronze Barracuda Well-Known Member

                Messages:
                278
                Likes Received:
                86
                Joined:
                Aug 17, 2019
                Location:
                Vancouver
                Local Time:
                3:22 AM
                Thanks so nothing particularly great about the small block Mopar heads exhaust ports?
                 
              • Bronze Barracuda

                Bronze Barracuda Well-Known Member

                Messages:
                278
                Likes Received:
                86
                Joined:
                Aug 17, 2019
                Location:
                Vancouver
                Local Time:
                3:22 AM
                I haven't heard much at all on exhaust percentage flow until I watched the video about camshaft selection in the link to my vintage iron. There is a bit in there about exhaust flow percentage. Personally I think it makes a lot of sense. The more exhaust you get out the more air/fuel mixture you can get in on the intake stroke. Definitely not stating that exhaust is of greater significance than intake though.
                 
              • MOPAROFFICIAL

                MOPAROFFICIAL FABO Gold Member FABO Gold Member

                Messages:
                10,196
                Likes Received:
                9559
                Joined:
                Jun 1, 2016
                Location:
                Oceanside ca.
                Local Time:
                3:22 AM
                Uncle pot stirrer
                 
                • Like Like x 2
                • MOPAROFFICIAL

                  MOPAROFFICIAL FABO Gold Member FABO Gold Member

                  Messages:
                  10,196
                  Likes Received:
                  9559
                  Joined:
                  Jun 1, 2016
                  Location:
                  Oceanside ca.
                  Local Time:
                  3:22 AM
                  Well stop sourcing your info from a
                  crackerjack box.lol kidding

                  Engine builder has many online articles that give factual information.
                   
                  • Agree Agree x 1
                  • QuickDart360

                    QuickDart360 Well-Known Member

                    Messages:
                    1,478
                    Likes Received:
                    650
                    Joined:
                    Apr 5, 2014
                    Location:
                    San Antonio
                    Local Time:
                    5:22 AM
                    I am a fan of X heads and run a pair on my 360. They feel like they flow pretty well. No porting done. I never liked the magnum head. Many like them over la heads. I just don't care for them.
                     
                    • Agree Agree x 3
                    • Like Like x 1
                    • rumblefish360

                      rumblefish360 I have escaped the evil Empire State! FABO Gold Member

                      Messages:
                      42,311
                      Likes Received:
                      14505
                      Joined:
                      Jun 21, 2005
                      Location:
                      Florida
                      Local Time:
                      6:22 AM
                      Correct. Then again, what do some of the other brands look like and do or perform. This is where Tony is making his case. But it is still a stock head which will only perform so well, stock or ported.

                      The “%” thing you bring up is also a thing to see where the ports are in terms of there flow & balance. If the ports fall short, which in your example of 64% being low, the cam companies in the past introduced the split pattern cam. In which, if the balance is good or over the normally accepted balanced area percentages, less exhaust duration can be used. (More intake duration vs exhaust)

                      This leaves the question of “Do I need a split duration cam?”

                      Back to the head topic….

                      Aftermarket heads having better ports and metal to port address this as well as the porter. If maximum power is the goal, the head porter can have someone weld the floor or wall to create a new port floor or wall to allow a better shape by creating a new port.

                      So, literally he is welding the port smaller. Or whatever he needs to do to make what he wants. As the pro’s say, shape is everything. So if the port is to low, not high enough, to wide, whip out the welder!
                       
                      • Like Like x 2
                      • Thanks! Thanks! x 1
                      • Agree Agree x 1
                      • Bronze Barracuda

                        Bronze Barracuda Well-Known Member

                        Messages:
                        278
                        Likes Received:
                        86
                        Joined:
                        Aug 17, 2019
                        Location:
                        Vancouver
                        Local Time:
                        3:22 AM
                        Excellent. Thanks great info. Still it would be nice to take my heads to get flow numbers after I've done my porting just to see where I'm at, and use this info to help buy a cam. Probably overthinking it for a street car. But I do geek out a bit on stuff like this. lol.
                         
                        • Like Like x 2
                        • Bronze Barracuda

                          Bronze Barracuda Well-Known Member

                          Messages:
                          278
                          Likes Received:
                          86
                          Joined:
                          Aug 17, 2019
                          Location:
                          Vancouver
                          Local Time:
                          3:22 AM
                          Yeah crackerjack box. I'd leave that terminology for uncle Tony. But the guy from my vintage iron is a very experienced engine builder. Check out some of his stuff if you get the time.
                           
                          • Thanks! Thanks! x 1
                          • rumblefish360

                            rumblefish360 I have escaped the evil Empire State! FABO Gold Member

                            Messages:
                            42,311
                            Likes Received:
                            14505
                            Joined:
                            Jun 21, 2005
                            Location:
                            Florida
                            Local Time:
                            6:22 AM
                            Great numbers are a catch 22. Knowing where the port peaks in flow is key to a cam.
                             
                            • Like Like x 1
                            • Agree Agree x 1
                            • Killer6

                              Killer6 Well-Known Member

                              Messages:
                              3,030
                              Likes Received:
                              1135
                              Joined:
                              Mar 9, 2015
                              Location:
                              PA
                              Local Time:
                              5:22 AM
                              Chances are, if You install hardened seats, 192-196cfm...that's what I end up with on "J"'s...the valve-job & margin/head profile + header tune is 80+% of it for You anyway....
                               
                              • Like Like x 1
                              • perfacar

                                perfacar Well-Known Member

                                Messages:
                                1,111
                                Likes Received:
                                298
                                Joined:
                                Mar 1, 2006
                                Location:
                                renton,wa
                                Local Time:
                                3:22 AM
                                I attended a seminar put on by superflow years ago. mr. betts stated, port shape and port velocity is everything, don't get hung up on flow numbers! he was and is still right. faster air / fuel mixture gets in , more cylinder pressure is developed, =more torque, = more power. simple!
                                 
                              • Bewy

                                Bewy Well-Known Member

                                Messages:
                                1,543
                                Likes Received:
                                991
                                Joined:
                                Jan 1, 2021
                                Location:
                                Australia
                                Local Time:
                                10:22 PM
                                I saw that UT video. I disagree with UT that the upward location of the exh port makes it flow well.
                                Pontiac heads have a relatively long exh port because the head is wide & the chamber is biased to the intake side. The exh port also has a 135* bend in it that forces the port to curve down, which ignorant people, stupidly, claim that it hurts flow. [ Using THAT logic, how well would upward facing SBC, SBM, BBM exh ports, fare with headers that have a 90* bend. Gas almost makes a U turn! ].
                                I have done some amateur porting on Pontiac factory heads & got as much as 200 cfm @ 0.500". A stock Edel exh port flowed 184 @ 0.500".
                                 
                              • Killer6

                                Killer6 Well-Known Member

                                Messages:
                                3,030
                                Likes Received:
                                1135
                                Joined:
                                Mar 9, 2015
                                Location:
                                PA
                                Local Time:
                                5:22 AM
                                If You want more for an example that "flow" as the primary factor in the exhaust really isn't, watch the Freiburger & Dulcich vid "Header Bash", the high energy-low density gas is most affected getting around the valve. After that, a great seal & proper tube size/length to utilize velocity is king, even with some kinks & dings. If You wanted the best flowing exhaust, You'd want a large log w/a sewer pipe off of it, one large pipe has way less surface area/frictional factor than a bundle of small-long tubes. It would handily out-flow a header set, yet We all know which one will run rings around the other........
                                 
                              • rumblefish360

                                rumblefish360 I have escaped the evil Empire State! FABO Gold Member

                                Messages:
                                42,311
                                Likes Received:
                                14505
                                Joined:
                                Jun 21, 2005
                                Location:
                                Florida
                                Local Time:
                                6:22 AM
                                Please expand on this. (Above)
                                It sounds like your stating an exhaust manifold with huge tubes out flow headers.
                                 
                              • K.O. SWINGER

                                K.O. SWINGER Meeting in the alley since 1976

                                Messages:
                                2,468
                                Likes Received:
                                2238
                                Joined:
                                Nov 18, 2010
                                Location:
                                oregon
                                Local Time:
                                5:22 AM
                                It has been no real secret that quickest increase was had by relief work on a x or j head , okay for you who are under 55 years old relief is another word for exhaust port work . Traditional thinking was and I probably agree clean up transition areas and stay off the floor of the port .
                                 
                                • Like Like x 1
                                • Killer6

                                  Killer6 Well-Known Member

                                  Messages:
                                  3,030
                                  Likes Received:
                                  1135
                                  Joined:
                                  Mar 9, 2015
                                  Location:
                                  PA
                                  Local Time:
                                  5:22 AM
                                  I am. NOT a factory log, but one with the equivalent area of or greater than the large exhaust pipe. If flow was the goal, 6 or 8 long tubes are easily out-flowed by 2 large ones with the same total CA......
                                   
                                • nckennyb

                                  nckennyb Well-Known Member

                                  Messages:
                                  65
                                  Likes Received:
                                  23
                                  Joined:
                                  May 8, 2014
                                  Location:
                                  NC
                                  Local Time:
                                  6:22 AM
                                  Back in 1985, I welded up a couple of J heads exhaust ports to raise the floor and make them look like my brother's W2 ports. Both heads cracked in the exhaust port across the valve seat where the crossover to the intake is so I got seats put in those two exhaust ports. I wondered if they would hold up so I never used them until around 1995 when I got the 1969 Dart and needed an engine to replace the 225 slant 6. My brother who worked at a tractor dealership and had access to valve grinding tools put 2.02 intakes in the heads and I ported them myself mostly a bowl blend and opened up the pinch at the pushrod a little. I also cut down that dog leg in the exhaust port roof some. They've worked good and made a little power but I don't know if it's much more than an unported set. The engine is a 340 with a .508 MP Performance hydraulic cam, LD 340 intake, 4.10 gears, A904 with low 1st gear and pinion snubber, it runs 86 to 88mph in the eighth dependent on the weather on street tires through the mufflers whatever that equates to in horsepower. I don't have any side by side comparison numbers though.
                                   
                                  Last edited: Oct 6, 2021
                                  • Like Like x 2
                                  • S.Rodney

                                    S.Rodney "Hang 10" owner

                                    Messages:
                                    55
                                    Likes Received:
                                    39
                                    Joined:
                                    Dec 17, 2016
                                    Location:
                                    Quebec City, Canada
                                    Local Time:
                                    6:22 AM
                                    I kind of agree with 'em... When I saw the whole video about Piston bank swapping giving you more HP... It didn't make any sense... Here's how Freiburger and Dulcich destroyed his arguement...


                                    Since that day, I've stopped giving any credit to Uncle Tony's "tips" or expertise.

                                    As far as camshaft goes, I'd give ya this tip... get a custom grind (call an engine shop) for your setup... it's the very best way to optimize your engine for your needs.
                                     
                                    • Like Like x 2
                                    • Agree Agree x 1
                                    1. This site uses cookies to help personalize content, tailor your experience and to keep you logged in if you register.
                                      By continuing to use this site, you are consenting to our use of cookies.