just curious, see so many online with cams, dual carbs etc, yet no one ever mentions if they had done anything in the valve department
There is a mathematical formula to enable you to decide if you need bigger valves. Hmmmm.. was it the Stan Weis website? I remember at one time, 4 seconds flat had info on this too... If you don't find the information, let me know, and I will search deeper after I get off of work. Sent from my XT1585 using The H.A.M.B. mobile app
Bigger valves are not the issue, theses engine have 6 exhaust ports but only 3 intake ports. being siamese intake ports, a tri carb intake with the right cam profile will wake this engine up. Bigger valves are not the concern.
There is a guy on the P15-D24 forum, Don Coatney who has installed a 25" engine in his 1948 Plymouth and installed Chev valves when he rebuilt the 25" engine before installation...........they have a more gas flow friendly tulip shape and are a cheaper buy apparently.........andyd
I cant let that one go Andy... " a more gas flow friendly tulip shape".. according to who ? The -"you should put chevy valves in your flathead Mopar" wives tail has been around a long time and there is no engineering or testing that supports the claim that they improve fuel mileage which would be the obvious result if they had better gas flow, or performance. There is lots of experience in putting bigger valves into Flathead Chryslers. I do have 1st hand documentation on multiple engines and yes both my family and the co-owner of AoK racing George Asche has built performance flatheads using chevy valves. The idea being bigger valves would allow for more fuel. The short version of the answer is, time after time the results show much more fuel usage, but a very distinct plateau in RPM. Im sure there are those that will come up with some argument on how they work well for their buddies, friend 2 times removed or maybe even themselves, but they will not have any actual documentation to prove it I would bet. On the angle of they are cheaper, that is a fools road to go down, so I will pass. But on pure performance, either HP, Torque or better fuel mileage, putting in huge Chevy valves is well proven not to be the way to go. You can get better fuel economy by moving too 3 smaller carbs each over the 3 intake ports and dual exhaust than going for huge valves, and you can get better HP, Torque and RPM with cam lift and cam duration and yes, I am very happy to have some one over to see it 1st hand. Wasn't trying to jump on you Andy, but for me too often people confuse someone who he and his buddy who have literally posted more times than there are number of topics on the forum, and between them and limited attempts at performance builds with real expertise. Tim Kingsbury
Well I have no idea who Stan Weis is and he maybe a leading expert for all I know. In the area of the math to figure out valves in general engineering terms, well the science has a number of directions. Here is a decent one. Intake valve diameter, intake valve duration and intake valve lift factor in together to determine air velocity in the intake system. Large valve diameter, long duration and high lift all cause the engine to breath better at high rpms, but also cause the air to move slower at lower rpms, which reduces power at lower rpms. Small valve diameter, short duration and low lift all cause the air in the intake system to go faster, which increases power at lower rpms, but chokes air flow when the air velocity reaches the speed of sound. The speed of sound is 767.58 mph (miles per hour) or 67547.4 fpm (feet per minute). Since the cam rotates 1 time for every 2 times the crank rotates and cam duration is measured in crank degrees, the HiPerMath equation for intake cam degrees is: intake cam degrees = intake valve duration 2 Next, we calculate the angle from the x-axis to the point at which lift begins. We call this angle "theta". theta = 90 - intake cam degrees 2 Next, we calculate the x and y values of the point at which lift begins, using the angle we just calculated: x = 0.5cos(3.14/(180 / theta)) y = 0.5sin(3.14/(180 / theta)) Next, we calculate the b-value for the equation y = ax2 + b, which is the equation for a parabola you have probably seen in your high school math classes. We use a parabola because it closely represents the shape of a cam lobe: b = intake valve lift + 0.5 The 0.5 in the equation above is the radius of what is called the cam base circle. The cam base circle is the minimum radius the lifter will rest on. Now that we have values for x, y and b, we can calculate the a-value for the equation y = ax2 + b : a = -(y - b) / x2 Now that we have the a and b values for the equation, we plug in -0.4, -0.3, -0.2, -0.1, 0, 0.1, 0.2, 0.3, 0.4 for the x values (since the x values for our parabola will range from -0.5 to 0.5, to get values for y: yn4 = -a(-0.42) + b yn3 = -a(-0.32) + b yn2 = -a(-0.42) + b yn1 = -a(-0.12) + b y0 = -a(0.12) + b y1 = -a(0.12) + b y2 = -a(0.22) + b y3 = -a(0.32) + b y4 = -a(0.42) + b We calculated values for y above because we are going to use them in the distance equations below where we calculate the distance from (0,0) to (x,y) and subtract the radius of the cam base circle: d1 = &radic (-0.42 + yn42) - 0.5 d2 = &radic (-0.32 + yn32) - 0.5 d3 = &radic (-0.22 + yn22) - 0.5 d4 = &radic (-0.12 + yn12) - 0.5 d5 = &radic (02 + y02) - 0.5 d6 = &radic (0.12 + y12) - 0.5 d7 = &radic (0.22 + y22) - 0.5 d8 = &radic (0.32 + y32) - 0.5 d9 = &radic (0.42 + y42) - 0.5 Now we calculate the average lift: average intake lift = d1 + d2 + d3 + d4 + d5 + d6 + d7 + d8 + d9 9 Next we calculate average open intake valve area: average open intake valve area = average intake lift x intake valve size x 3.14 Now we can calculate the air velocity, in fpm (feet per minute) through the intake valve, during the time it is open, at any rpm we want: air velocity through intake valve in fpm = 0.327 x number of cylinders x 2 x stroke x rpm x 3.14 x (bore / 2)2 average open intake valve area x 12 Finally, we can put 67547.4, which is the speed of sound in fpm, in place of "air velocity through intake valve in fpm", solve the equation for rpm and find out what the maximum rpm is from that result! The HiPerMath equation is below: maximum rpm = 67547.4 x average open intake valve area x 12 0.327 x number of cylinders x 2 x stroke x 3.14 x (bore / 2)2 We just found out how much this cam allows the engine to breath! If you know the cubic inches of your engine, a simpler equation would be: maximum rpm = 67547.4 x average open intake valve area x 12 0.327 x cubic inches x 2 If you know the liters of your engine, a simpler equation would be: maximum rpm = 67547.4 x average open intake valve area x 12 0.327 x liters x 61.02 x 2 Definitions: fpm = feet per minute rpm = revolutions per minute Now after you go through the math, here is the next thing you should know. This is for overhead valve engines with modern intake chambering. It doesn't help you one bit with a flathead mopar and as "Flat Head Six" so accurately points out, your dealing with an engine with 3 Siamese intake ports, each port feeding a pair of cylinders. So I completely agree with him. Now depending on what flathead mopar were talking there have definitely been different valve sizes over the years, but as evidence to his point, I believe one of the highest reving highest HP flathead ever built is using stock size Dodge Truck valves. That engine is in our Rear Engine Dragster and while I don't know if anything ever built that revs higher, maybe there is, but what I do know for a fact is Bigger Valves in it, did not improve its performance in any way shape or form. Here is some videos of its initial start up https://www.youtube.com/channel/UC8y7yB5J7YNWI2Rnnvn8rig/videos?sort=dd&view=0&shelf_id=0 and to those who may want video evidence of it well north of 7000 rpm, we will take some and put it up sometime, but we have lots of witnesses to what it does. Ill even go further, and I am not sure we have ever disclosed the cam specs for that engine publically but in the interest in putting out actual Tech info here it is. The intake opens 30 degrees and closes at 70 degrees, and exhaust opens at 70 and closes at 30 degrees, the cam has 280 degrees of duration and 446 lift Not sure any of that helps, and if you haven't fallen asleep yet and want me to start digging out engineering books, let me know.. I have them rolling back into the 1920s and what I know for a fact is the math may be the math, but often there is as much art as science in building a performance engine and that goes for todays top fuel dragsters as it does my special order VW diesel as it does for a flathead mopar. Tim Kingsbury
You should also keep in mind that they use exhaust valve seat inserts. This limits the amount you can open up the port. So larger valves become a major hassle to install.
Tim..........I wasn't trying to upset anyone here, just relaying what I had been told by Don Coatney who I have no knowledge of apart from replies on the P15-D24 Forum.....a few years ago when I was collecting parts etc for my intended rebuild of a 230 engine I asked about valves on that forum as it seemed like some guys had a bit more knowledge than me........Don replied that he had used chev valves in his 25" engine rebuild and that their shape and cost were the determining factor...........being here in country Oz I was in no postion to contradict his info and intended to follow this idea up, however financial constraints eventually resulted in me having to sell both the car and engine..........one thing that I have found strange in getting info regarding hotting up mopar sidevalve sixes is the almost pathological desire for those in the know to restrict any and all knowledge of what actually works..........resulting in various myths, legends, half and quarter truths being passed around.................it seems a shame actually...............anyway, I'll still keep my eyes, ears and other orifices open hoping to glean info when and where I can................again apologies if I've upset anyone...............Andy Douglas
Thank you Tim. From my experience, most Chrysler engines have great engineering applied to them and seldom need any modifications other than camshaft changes to suit your desires. And you brought up a valid point that I oversaw.... The formula that I mentioned "did" apply to overhead valve engines. I looked into it and realized that fact tonight. I value your explanation involving the flathead technology. The math really intrigued me, I eager to learn as much as I can about these engines. Thank you for taking the time to point these things out. As always, your knowledge is invaluable and priceless. Every discussion we have had, has been exciting learning from you. I honestly believe that you will forget more than I will ever know on this subject. But I am going to always do my best to have fun while I begin building these engines for my projects. And I will never hesitate to reach out to you to bounce my ideas off of you. Thank you again Tim. I will read what you wrote again after I am rested up and can absorb it better. Sent from my XT1585 using The H.A.M.B. mobile app
Hi Andydodge, he is just stating facts. Nothing wrong with that. I think it's important to have whistle blowers out there to call the kettle black. If someone dumps time, effort, and money into a build, and based it on bad information, it would be devastating. I am a decent engine builder, but I have gone back in time and now want to get into these flatheads. It's a new world to me and anything Tim says on this subject is going to be second to none. His family history created these engines. When Tim is kind enough to share some cold hard facts, I am going to shut up, sit my butt down and take notes.... He wasn't causing any waves in my opinion. He just wanted to set things right. Thank you Andydodge for bring up this topic. Sent from my XT1585 using The H.A.M.B. mobile app
Ok I have to ask what is a huge chevy valve? I cannot see some one trying to put a 2.02 or larger valve in a flate head.
OK let's talk about hopping up flathead Chrysler sixes. On the good side they were a well built engine made of the best materials available at the time. They have such up to date features as insert bearings, full pressure oiling and good cooling systems (not true of their main rivals). In addition, they were very detuned from the factory and it is possible to get 25% to 50% more horsepower without too many modifications. The down side is it is a long stroke flathead, basically an early 30s design that has been obsolete for nearly 70 years. If you want large amounts of horsepower, say more than 150 - 175 HP there are a million better engines to chose from. So if you want to do a straight rebuild with a cam, dual carbs, dual exhaust, shaved head and shaved flywheel I am all for it. If you want to go beyond that I suggest you consider another engine. This is just a roundabout way of saying I doubt you can go very much larger in the valve department and it may not be worth the expense. Slightly bigger valves with slimmer stems might be worthwhile.
No problem Andy - and my apologies.. I assumed that was the source and I just wanted to put some clarity to the claim of Chevy Valves "having a more gas flow friendly tulip shape" because that is fiction when we are talking using in a flathead mopar as comparing to Chrysler Corporation Valves. It is sad and I do agree with you that a lot have always guarded their secrets and most have gone to their graves with them. There is also and you sort of hinted at it, a fringe who take their one build or the "my buddy built" syndrome and talk endlessly about how it is the only thing in the world to do. There is also another type and I call them the instant experts. They really have had little to know really experience with Flathead Mopars, and in 1 case if you check them out their experience is pulling them to put v6 and v8s into the vehicles.. But they love to be the center of attention so when some one arrives who may not know a lot, but are looking for information they are instant experts. You will almost always see them when details are needed move to "check your manual" or the "a good machine shop should...... " Mode Translation their ability ends at their ability to search on Google or Yahoo. What I know is for decades it doesn't matter at all whether you buy something or even want to buy anything, my Grandfather who was the GM of the engine plant in Windsor, to my Dad, to myself.. if we can help out were happy to do so, and if we don't know we would tell you. Sadly GrandDad and Dad are no longer with us so its just me from the Kingsbury/Bolton families.. But my partner in crime (beating Chevys) George Asche JR who was born a week from my Dad in 1932 is exactly the same. If you want to call George up and talk about flathead mopars or overdrives, he will spend all kinds of time talking to you and happy to give you ever secret he knows freely. And to be honest, I know a lot of people who are exactly the same. Most get tired of the crap on boards so they withdraw. That is too bad. I am sorry you no longer have your car or engine, and you are a distance away to invite you over for a ride or a chat, but if you are ever in the need of information let me know.. I would be happy to help. TimKingsbury [email protected]
Blush... I am not worthy.. The good news is of the 3 smartest Flathead Mopar people I have ever met, at least one is still alive and a pleasure to talk with ... George Asche Jr born in 1932 can be reached at 814-354-2621.. Around 6-8pm est is always the best. His boys Rob and George III now run the starter, alternator, and mechanical rebuild business next door and share the same number. So during the day George is usually in his office .. also known as his work shop building overdrives or engines, or carbs or linkage.. For me, while tucked away in a drawer I do have an iron ring, and I am the keeper of my Grand Father and Dad's books, journals, shop manuals etc etc oh and a substantial collection of vehicles (150 or so still) and while I have a pretty good memory and have been beside Grandfather and Dad on dozens and dozens, hell maybe a 100 engine builds and yes long ago tore down and rebuilt quite a few on my own, by true ability is knowing what I don't know or don't remember but where to get the right answer and lol... a directly line to my buddy George and a few other knowledgeable guys. But I do appreciate the note I really do.. Tim Kingsbury
Just keep the torch lit Tim.... I am now in preschool now with the flathead. I already got my bachelor's in the slant six school. And I know a couple of things about Hemi's, Small Block & Big Block Mopars.... I just hope to be a authority someday on these Flatheads. And don't sell yourself short, we all will need you when the time comes for those of us not willing to forget the past and keep the technology alive. PS- I just hope that my kids don't resent me for teaching them what I know. Sent from my XT1585 using The H.A.M.B. mobile app
The Jalopy Journal
