In this episode of Steve Tech, Steve Morris of Steve Morris Engines talks about pushrods and what attributes you want to see in pushrods and what the effect of pushrods are in the valvetrain.
Thanks Steve! I've been a professional mechanic for 30 years. I Thought I knew quite a bit about race engines until I ran into you! I realized real quick I'm just a hack. Thank you for sharing SIR!! We run a 11.5:1 psi d rotor @ 116-126% OD on a BBC. The more I watch the more I understand all of the issues we've had over the years.
Great info!!! It is truly a shame that your videos don't get more views but total garbage videos get millions of views!! I guess few people know the difference between right and wrong and who they learn from.
Damn, that was thr deepest dive into any one subject that took only 15 minutes.....and at 14 minutes I was almost out of air and the lesson was over .... then WHAM BAM !! He hits me with a baseball bat. I mean .... Dang-O Man I have to ditch some worthless childhood memories so I can retain this for later when I need it. Thanks Steve Oh, and good to see ya over at Garrett's shop.
Steve, I think what you really mean is; for equal total weight(mass) pushrods, the tubular one will be stronger in bending than a solid pushrod. Material close to the pushrod centerline contributes very little to bending strength. Having the pushrod material concentrated away from the centerline(as in a tube) maximizes bending strength for any given total pushrod weight. It's my mechanical engineering Strength of Materials class training bubbling back up 40+ years later....
That is a correct explanation and I agree 100%, however pushrods are constrained on their outer diameter. Only increasing the outer diameter brings further strength when comparing solid rods and tubes of same mass and length, so this argument here is invalid and the opposite is actually true, the hole weakens the pushrod by a small amount. Bending is not the only load a pushrod sees, it is primarily loaded in compression, where all that matters is cross sectional area and the shape is irrelevant.
@@stefanpariyski3709 You are incorrect. Look up Euler's buckling formula- the moment of inertia of the push rod is the single most important variable in defining the stiffness of a tube. By concentrating the bulk of the material away from the centre the stiffness (for a given mass) is greatly increased. Don't bother arguing with me, tell Steve Morris that his learned knowledge and years of experience and success is wrong.
@@johncrowley5612 This is physics basics logic learned in higher edu I have a long time ago. Yes the crush values of tubular design are increased by OD-Diameters increased, given some limitations of wall gauge.
Would be great to have static deflection data comparing 5/16 .080" and .105", 11/32 and 3/8 .080" and .135" since that's what most folks would likely run. Using a typical 500psi open spring pressure and 1.7 rocker. This would prove your point. Better yet, if Spintron deflection data was available up to 8500rpm and compare to static. Just a thought. I know... one can dream!
I've taken a deep dive into SBC valve-train tech recently, but I still had questions concerning pushrods and their tendency to bend / flex. You spelled it out very clearly with: "You can never have too much pushrod" (sounds sort of... dirty), which confirmed the findings of my thought-experiments on the matter. Thanks, Steve! L/S
Wanna bet on the too much ignition? The resistance between the ignition rotor and the distributor cap button increases current and will burn up a cap in no time and I’ve seen rotors short out to the distributor shaft as well.
Not sure if you guys will see this. BUT...Im working on a weird engine. Its a diesel flat 6. Im reading the manual (its poorly written, and diagrams are xeroxed three times over from the original German ones). Im not seeing hollow pushrods. The say that oil comes up to the rocker arm shaft through the heads, then through the rod, then squirts out, goes AROUND the pushrod, down to the lifters, and back into the pan. Also, not much on the lifters themselves, if they are solid or hydraulic. I havent opened up the engine yet (mostly for fear of lack of parts, and because its huge..10.35 liter). Im just writing this manual in case I will have to, and rather than chase things down with a dismantled engine, I can have all the date at the ready. Also, changes are, it might be an engine shop doing this work (since Im already disabled and getting old). So I want somebody else to have all the info possible and this ancient Romanian engine. So, am I getting this right, that the lifters get their oil from AROUND the pushrod, and that the pushrods are hollow? Thanks. Also, great visualization of loft. An often forgotten metric when it comes to valve trains. (Hey, I know SOME stuff lol)
Given certain dynamic loads a tube is stronger than a solid. This is due to total amount of surface area. Has nothing to do with heat treatment although that will significantly change the material properties.
Material, wall thickness and taper, ends, rocker cups, lash caps, lifter weights, and a host of others things determine specifically whats desired in a pushrod. They found out a long time ago with lifter mounting rev kits. The pushrod plays just as much too valve train weight at a heavy lifter
Steve, The reason that a hollow tube is stronger is that a hollow column's ultimate bearing capacity and lateral rigidity are inherently greater than a solid column's. Compared to solid shafts, hollow shafts of the same weight are superior at withstanding torsional and compressive forces. Multiple factors make tubes intrinsically stronger than solid bars of the same size. This indicates that steel tubes perform better in applications requiring durability and strength overall. Oh, and by the way, it is a common misconception that the weight of the pushrods does not matter; simple physics suggests otherwise (as you will see when you test our AWA pushrods).
Cant see how pushrod deflection causes loft. When there is clearance between the lifter and cam lobe at full lift, doesn't this give a chance for the pushrod to straighten rather than deflect? I can see agressive lobes and wrong springs cause this issue. Can someone explain what i'm missing
Real engineer here. A lot of things wrong with this video. I won't address them all but I want to make a couple of points. First. Tubes arent "stronger" than solid rod. For a given shape (round, square, etc) a structure with a hollow cross section will be more resistant to bending in compression forces when compared "pound for pound" This is due in part to the fact that a solid round bar has a “neutral axis” that, when the bar is bent, is not in compression or tension and so does not contribute to the resistance to bending. The material in the rod that is further from the center of the solid rod contributes exponentially more to the rigidity (not so much strength) of the rod increasing its bending moment. So why not remove the material from the center of that rod that contributes the least structurally to reduce weight? Well now you have a tube. If you had a 3/8" solid rod and a 3/8" .080 wall tube made from the same material Between the two the solid rod would be stronger and more rigid. However the tube will have it beat by weight. Which brings me to my next point. While I agree that Pushrod rigidity is of utmost importance for the stability of a valve train... ever hear the phrase bigger is not always better? Well here it is actually true. What you said is very misleading, a larger pushrod is not always better. There is a point of diminishing returns where once you have met the rigidity requirements for your system for a given rpm range (cam, lifters, pushrods, rockers, springs, retainers and valves make up your valve train system) and the entire system needs to work together to obtain the performance an longevity. Any real engine builder knows and will tell you that valve train design is a careful ballance of weight and strength, granted on the lifter side of the rocker "strength" ends up being of more importance than weight, but engineers still understand the concept of comprise and diminishing return. Serious engine builders are putting their engines on spintrons and spinning their engines to 10k before pistons are ever fitted, just to pinpoint valvetrain issues and solve them before the engine ever goes on a dyno. Haphazardly throwing bigger more expensive parts at the problem might have "Worked" in the past but with today's competitiveness in the racing sports that just doesnt work like it used to. We are going faster and getting there quicker, and the tenth second you used to be able to shave by removing the spare tire and adjusting your carb is costing many thousands of dollars today.
Just a little information. This is the most common mistake that almost everyone that is not a trained engineer makes. You said that the tube is stronger than a solid rod, but this is not accurate. A tube is stronger than a solid rod of the SAME WEIGHT. That means the solid rod would be much smaller in diameter than the tube. A tube with the same outside diameter of a rod would be much weaker than the solid rod. This is why top fuel dragsters have all moved to solid pushrods. Since they have a different path for the oil, they can now go to a much stronger pushrod that is solid.
@@FrescoyMembrillo The surface area for heat treatment won't change the overall strength enough to make a tube that is the same outside diameter of a solid rod somehow stronger than the rod. There us never a case where a tube that is the same O.D. as a solid rod of the same material will be stronger than the solid rod.
@@andrigtmiller I believe we're close to agreeing: I'm not saying tube is stronger than solid. I'm trying to convey that tube can be made way stronger than same mass solid rod through hardening thanks to having close to double the surface available for treatment and can go well deep into the material cross section.
@@FrescoyMembrillo Yes, a tube of the same mass will be stronger than a solid rod if the same mass. That's what I said in my original comment. A solid rod that is the same mass will be much smaller in diameter. The heat treatment is not the reason though.
@@andrigtmiller perhaps you feel I was trying to correct you or to antagonize. I was not. I tried to expand on what you said. I'm sure there's a good reason why top fuel pushrods are solid but that doesn't change the fact that an alloy tube benefits much more from most? hardening treatments outside of those impractical to the inner surface because of size... Laser hardening in small section tubes comes to mind. Anyway, thanks for taking the time to reply. Be well!
FILLING A TUBE WITH PRESSURIZED FLUID OF ANY KIND MAKES IT STRONGER. A PVC PIPE IS WEAK BY ITSELF. ADD 100PSI OF AIR PRESSURE OR OIL PRESSURE INSIDE IT AND IT INCREASES IN STRENGTH GREATLY. THE SAME THING CAN BE APPLIED TO PUSH RODS. ADDING 100+ PSI OF HYDRAULIC OIL PRESSURE WILL MAKE IT WAY STRONGER THAN A SOLID PUSH ROD.
To follow the cam on the closing ramp the valve spring has to overcome and accelerate the total of the Valve, Valve cap and collets, Half the spring mass, the second moment of the rocker, PUSHROD and cam follower. So the valve spring is not sized for the opening ramp of the cam it's sized for the closing as it has to overcome alot more mass, actually the spring could be deleted if the valve only had to open. So yes, a Big Pushrod can be detrimental and incur more cost for heavier springs, limit top RPM, poor VE when the valve float starts and excessive wear due to increased loading.
weight of push rods does matter. the closer your valve train gets to floating, the more energy is lost to inertia; and the less of the energy, that goes into the valve spring, gets re-directed back into the engine. ( like a car going fast over a hill pushes down less on the other side ) and yeah, the rocker ratio plays into the mass x velocity^2, but it is still the mass creating the loss at whatever velocity. something to be said for overhead cams when you figure how much energy your valve train is chewing up.
🔔😎🇺🇲 Doesnt the pushrod weight affect the total valve train weight that must be controlled by the spring? Heavier prods mean stronger springs. Guess it doesnt matter much on a short 5.7 pushrod 5.0 at 6,000 rpm. Thanks for the information.👍👍
My non-expert opinion: Larger pushrods will deflect less and limit loft for that exact reason. But, a heavier pushrod will slow the spring's ability to quickly return the pushrod, causing loft for another reason. That is, for the same spring. Using a larger/heavier pushrod would then require a stronger spring to reduce the delay (loft). I also suspect (for a given pushrod/spring combination), loft begins at a particular rpm and amplifies as engine rpm increases.
Tanx Stevo, great info. I love that explanation on loft. I think you need a spintron with stacks of valve springs to get that variable valve timing feature in your pro stock lol. Such an awesome idea for increased duration at high rpm. Do the springs have to be frequently tested to maintain the perfect open pressure for loft?
Nice. I'm way back in the shallow end looking at 380ish horse at around 6k. Is that even enough to deflect the stock pushrods? (Mopar Magnum small block)
Missed one. Number 4, you can't have too much money. I have had people.wanting 5 figure engines, but they only had 4 figure money. In the circle jerk world, that the difference between a claimer engine VS. The engine that ran off way out front.
i dont think you emphasized enough that you should REDESIGN the cam profile to better follow the loft/float... you shouldnt operate with float because youre not going to prevent bouncing at all speeds. LOFT/FLOAT IS NOT a great thing... its a phenomenon caused by high inertia caused by beefier pushrods (in your example). So i understand what youre getting at, but you only once mentioned the fact that you should redesign to match the loft (if you made a power gain) or otherwise change something to rid the loft (if its detrimental), but you shouldn't leave that feature in place just because you increased the mass of your system. Its not different than float.
Hey Steve what cubic inch on the BB Chevy do you think is best suited for boosted application using Conventional Style profiler or CNC ported type Cly heads ?
That loft thing.....not good for roller lifers...at least on bbc. We run springs...lots of pressure...better way to much than just exactly what you think you need.. A vid about pushrods and no instructions on how the establish the correct length?? You sound like you have worked on some "stuff" What you think of the valve guides in these heads? NO, they dont have the wrong size stems for the guides....They are worn that bad and yes the motor ran fine...it did idle a little rough...Motor is a closed chamber 427 in a v-drive hydro With a .710 x 260 *.050 cam, 300 on the seat, 650 open. I would spin it 7800 and spin it 7k several miles at a time...i did not pull the heads off to fix the guides, motor spun a main after fram oil filter shit the bed...No damage to the seats, the cleaned up with a minor kiss on my bosses sunnen...one of those single angle deals...reused the exhaust valves, could have reused the intakes but i found a set of 2.310 valves and we cut the seats to match....Cause of the bad guides? Bad springs...sitting on the bench the ends were kinda crooked. People think guide wear is all about getting the roller down the middle of the stem. it aint so. Dont believe me? Get a head with a loose guide, figure out a way to open the valve with a pushrod...open the valve..the valve does not get pushed to one side...it just hangs there...if it goes to one side the spring is crooked. If the roller had any kind off a chance to push the stem sideways and wear out the guide the stock rockers would wreck guides faster than you could replace them ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-11eXlFkZekM.html
to much fuel pump = too much heat in the fuel... if we are talking about street cars, not to mention noise rather run 4 smaller pumps than a A1000... cant carry on a conversation in the car with one of those going... BAAAAAAAAAAAAAAAHHHHHHHHHHHHHHHHHHHHHHHHHHHHH
Actually you can have to big/to heavy pushrod. Especislly in top fuel where The inertia from The pushrod actually makes cracks in the billet block and top. Thats why they are smaller and from Titanium. And its common in higher reving engines. Thats why its mostly eliminated in higher reving engines to eliminate vibration and overall complexity by using overhead cam design instead. But its common for alot of american engine builders to be biased.
2:04 Tubes are not inherently stronger than solid rods of same outer diameter, I have no idea where this false notion is coming from, but I have heard it other places as well and it perplexed me then as well. The pushrods you are showing are all limited in their outer diameter, so there is no benefit to strength of them being hollow, on the contrary, the hole makes them weaker. Not by a lot, so it's not a problem and the obvious problem of needing to deliver oil to the top end outweighs the small loss of ultimate strength.
Funny how people who have absolutely no clue about what he’s talking about love to make stupid comments about what he’s doing. Gfys. Steve keep up to good work.
@@Crawlerworkz2023 oh I don't think we have to resort to swearing already? Or is your vocabulary already exhausted after one sentence? I actually don't speak internet lingo so had to look up what "gfys" means. And I don't think you're portraying a very friendly attitude. Your apprehensiveness in the way you communicate suggests that "good for your soul" is not what you meant. To you sir I say goodbye. Gfys.
You do realize this guy makes his own engine, as in designs, and builds it, sells it in varying power levels from 1000 through 3500 horsepower. As well as builds Chevys, Ford's etc. To say "he doesn't know" is laughable at best. He is quite literally one of the best high performance engine designer/builders in the world, at least when it comes to a conventional ohv v8 90° crank engines.
@@b.c4066 then he clearly still has much to learn! As in his comment about how pushrod weight doesent matter. Top fuel dragsters used to have problems with their tops cracking then they shifted to lighter titanium rods and presto no more cracked tops. Designing an engine isn't that hard nowadays btw. Lots of the new cad programs even design the part if you just put in the strength parameters and some initial design.
@@joachimsingh2929 got 100's of drag week style 2500 plus horsepower engines out there running? Scratch that, even one v8 engine that you did a clean sheet design of and have successfully ran it thousands of miles and clicked off 6 second passes in? Cause if you don't you really should shut up. Your arrogance and cynical comments are not welcome. I'm sure him saying "I don't know" in this context means it's not a super big deal and what he has to offer is good, reliable etc (more than adequate for the combination he builds for each customer). But maybe I'm wrong, perhaps you are an engineer versus a keyboard warrior. For another point of reference he has done Lamborghini engines making in excess of 2500 hp and rev to 10,000 rpm. We can all agree the man knows more about high performance valve trains than most of us would learn in a lifetime.. but as I said, maybe you are among the 1% that do actually know and design/build this stuff for a living and have customers on an 18 month waiting list to get one of YOUR engines? Enquiring minds want to know. If you have indepth knowledge please expound on it and share it with us all, but to slam a respected engine builder that makes a world class product that sets records, wins consistently just makes your comments appear infantile and downright ignorant sir. The man is an innovator and right up there with the likes of Dan Jesel, and so many more. Good day to you.
