Does Pushrod Rigidity Affect Engine Performance? | Stroker 6.0 LS3 Dyno Session 

Gloves to protect you hands, but no shoes on your feet?! lol MOre Powa baby...

I like these Richard Holdener style testing videos. I don't have any suggestions at the moment but I'm here for it all. Please do more testing, I love seeing these, thank you

Good point you make about customers talking to thier engine builder and listening. The builder nearly always has way more experience than the customers 6 months of Google or Facebook research without any really world experience. Yet so many customers go off on thier own tangent becoming Google & Facebook researchers without real world experience.

I just read Billy Godbold’s valvetrain book and I’m no valvetrain engineer, but, my bet is that the 5/16” .080” wall pushrods are lofting the valve. That’s why it makes more power than a stiffer/bigger pushrod. Weight is much less a factor on that side of the rocker arm than you might think. Truly though, without a Spintron or a valve lift comparison between your PAC springs and some checking springs, we’ll never know the truth.

A saying we have in the engineering world is that one good test outweighs a thousand expert opinions. Your videos are very well done, objective, and very timely for me as I am in final planning stages for an important build. Bravo.

We are proud of you! Keep up the good work!

The fact the heavy 3/8" .135" wall made the same/near same power tells me all the others were deflecting and the pwr savings from light weight parts equaled out to the power saving from the more rigid rod. So its a trade off like most everything else.

Harmonics are going to change as per the length of the push rod . so engines with longer push rods or engines with flat tappet cams are going to be prone to more harmonics at higher RPMS

i love seeing these results as i always talk shit on people putting in too much valve spring pushrod rocker etc and there just adding ass loads of weight to the whole thing for no reason and introducing lots of parts that haven't had a good work history like un damaged stock but used parts.

All due respect, but what you are seeing in these tests is Valve Loft, and has nothing to do with over all weight differences of the pushrod. It DOES however have everything to do with the rigidity of the pushrods, or lack there of, when compared to the other valvetrain parts and why the sizing effects the rest of the valvetrain. Do the tests with a Solid roller lifter and remove the plunger/oil viscosity from the equation, Add/Remove spring rate and pressure, go Higher/Lower in rocker ratio, switch to Aluminum from Steel, run a softer intensity ramp on the opening lobes, etc... Then throw 30-40lbs of boost at it and watch what happens. Each change has the same effect on what you are seeing. We've done all of these over the years, you would be amazed at just how much it is all affected by one small change, but more importantly, why it is affected. A LOT more to it than just weight.. There are other, more important instances where weight would be the cause of change in valvtrain stability. What you are seeing isn't one of them. Which pushrod someone needs is application specific, so to say the Lighter one makes more power than a heavier, more rigid one isn't entirely accurate unless you know WHY and HOW it is going to affect the rest of the valvetrain dynamics. There IS power to be had in the correct valve train for each application, and it is NOT as simple as just swapping to a "Lighter" pushrod. That said, i do like your videos for the most part, so don't take any of this as an insult. Hope this helps.

I've always wondered about this subject and am quite surprised with the results 🤔 👏🏻

I noticed the bare feet too 🤣. I really enjoy watching your videos.. very informative!! Keep on creating excellent content!

Guessing what you are seeing is the thinnest pushrod is lofting the valve giving you more lift under the curve.

I don't know... one series of pushrod tests with one valve train combo and you concluded that Grumpy Jenkins and Smokey Yunick didn't know what they were talking about? I appreciate the testing and seeing you young guys carrying the torch, but coming to that conclusion from that inconsistent and incomplete data is just wild.

@ 8000 and above and real spring pressure and large valves is where you will see a big differences. Race car stuff is what Bill and Smokey were talking about. Solid roller stuff sees more deflection at the begining of ramp and it has no give thus pushrod flexes a a pole vault effect starts and harmonics resulting from that...

Awesome! Engine comparison data is one of my favorite things. Had just been clearancing my heads on a new build to use a larger pushrod since i keep hearing of the supposed benefits of using the largest pushrod possible so definitely clears up some very interesting points. Thanks for sharing!

Great Video!!! Wanna see more different HP Vids like this!!!

barefoot in the engine room for that extra cozy feeling

Good information and very timely for me. SBF build, only engine component remaining to purchase are the Push Rods. 1211x Spring, lighter valves than in your test engine... .080 wall- check.

I'd guess that if you had a boosted engine on the dyno, we'd see more of a difference, especially from the cylinder pressure that the exhaust pushrod has to fight.

You are a very brave man working around stuff like that barefoot

It depends on the intended use of the motor, but I might be inclined to give up a couple HP for the stiffer pushrod....

Thank you. Id love to see this on a gen 3 hemi. I built one with customer supplied heavy pushrods with a street cam (2x weight compared to .080 wall 5/16 rods) and had an issue with it. It seemed like i was over reacting at the time but this proves my point.

This is super interesting and makes for great automotive science. Looks like I need some titanium/composite pushrods for the Viper.

Its always interesting to also weigh pushrods full of oil. Great testing 👍

One thing could be going on maybe the thinner pushrod is springboarding causeing more lift by laufting

I kinda knew what results were gonna show from similar testing before. The curve ball was the biggest heaviest push rod, I guess we could contribute that to optimum stability but interesting nonetheless.

great video

Like to see same test with solid roller

Great test!! But those short travel lifters could be hiding a lifter pump up issue. The softer pushrod will deflect up the ramp and spring back over the nose, a longer travel lifter would try to take up the slack and hold the valve off the seat.

Good info thanks for sharing

one thing ive always herd is if the engine is sitting for a long time to rotate it every so often so the valve springs arnt stationary in the various positions, what a good test would be if u can do a test on a valve spring to get its rate, then put it in a vice fully compressed for 6 months or so and then take it out and see if the rates stay the same or the spring changes

Steve Morris built the big black hemi. 906 CI. Pushrods are 9/16 diameter.

more power because of lower inertia makes sense - valves keep up with high rpm

Awesome video. Very cool info. Thanks. 🍻

No shoes....yo mah G, doing it old school👏🤙💪

Did anyone notice the clock on the wall and how little time it took for them to do the tests? What a great team!

another great content thank you for sharing your findings

Showing how far past peak hp it could hold the power would have helped a lot with the info from this test. Sometimes adding to the curve after peak is the best gains for racing.

It can, but also the extra weight will float the valves sooner

the lights ones🤞🏾

Having used 5/16 pushrods in 600 lift solid roller 7500 rpm SBC that is all that is required IF you have your geometry right. Get it wrong and those heavy 3/8 ones will still bend as well as breaking rockers. The only pushrod issues I have ever had was pushrods not compatible with Yella Terra rockers and it chewed the ends off. They supplied me some pushrods to suit and no more issues

Thats really good stuff

Very good test thanks

I am seeing more videos about this. Yes thank you every thing is application specific, some don't point this out. From what I can gather, Technology has improved with designing lobes to smoothly accelerate the valve opening and decel the landing of the valve. Back in the day off seat energy was more shocking and thus a stiffer push rod was better. My hunch is new more stable lobes are allowing less weight to shine in dyno testing. As a road racer, I'd like to see some spintron testing or something along those lines to see stability from gear changes or over revs. Yes I am sure the cam designers are testing to make things stable. The biggest advocates for larger pushrods were involved in short track motor development where cams are compromised to get around rules.

I'd say 5/16 .080 or the .105 wall. I don't feel anything stiffer is required, but we shall see.

Interesting test! The conclusion drawn - absent a spintron - was the weight difference cost hp, but what if the loss in power was not directly 'weight'? Less rigid pushrods may act as a spring and gave your valve 'x' amount more lift & duration? Perhaps when you installed a less flexible pushrod your valvetrain is now 'under control' and you get less effective lift/duration or only that which your cam lobes provide. Could the dyno results be showing the need for a slightly 'larger' or optimized cam to reclaim the extra 10+ hp and the need for more rigid pushrods resulting in a more stable valvetrain at the same rpm/peaks? A springy pushrod isn't bad nor is a stiff one, both can create problems and or break parts, like you said, it is system dependent.

Barefoot because the less amount of accessories the more hp. Cool video showing the slight differences with a surprising outcome.

thanks for the info!

To really do this you need to combine the spintron with the dyno to see what is really happening. Without a spintron with a high speed camera you do not know what is really going on. Steve Morris just broke a super top of the line valve spring by running it at the same speed for too long and that caused harmonic damage.

good test

So you did a pushrod strength test using a hydraulic lifter.......and then implied that Jenkin's and Smokey didn't know what they're doing when saying to use the strongest pushrods available for a solid lifter.(they built race engines and those don't use hydraulic lifters) Have you ever heard of a Spintron? In your test, of course the lightest pushrod is going to work best since in your test it's more about lifter plunger stability than controlling the rest of the valve train.

I should probably go back and watch again to be sure I didn't misunderstand, but my take away at the last test was that the heavy wall 3/8" performed about the same (or better) as the heavy wall 5/16". That seems to contradict the "lighter is better" theory. That having been said, I can't make good sense of that, because the rest of the data agrees with your end point. I wonder if the heaviest version finally offered enough rigidity to overcome its added weight. If we were to rank in order, did we not see that lightest was most powerful, heaviest was second most powerful, with the two in between sizes being the worst choice? I was shocked to see you barefoot in the dyno room, but I saw your earlier response as to the reason.

next test smeding cams :) ... different typ of intakes and heads

Great video, I learned something today. Will you be testing the dual quad set up on this engine??

Building anything over stock requires a good selection of quality parts.. but dodgey advice on heavy duty parts can lead to overkill in all the wrong places if you have no idear what you need in the first place but skimping out on some bits can create equal headaches and wasted money..

just got to the end, very interesting results. i cant decide on the PAC 1207x or the 1209x but it seems either way the 5/16ths is the way to go. I would like to see data on the pTR intake with mixing the intake runners.

I'll pass this on to Richard Holdner

Great job What kind of lifters did you use?

PUT YOUR DAMN SHOES ON IN THE SHOP !!! 🤣🤣🤣

Wow that is so against what i learned online, everyone told me i needed the biggest pushrods i could run. i went with .116 5/16 with 420lbs on the nose. if i ever tear down my engine i am going to change my quench to .045 so it will be getting .080 wall pushrods then.

Better tell the NASCAR boys your findings

it could be you are having a little loft and gain some lift with the lightest push rod?

Could be that all of them are flexing except the big thick one. The stiffer rod gives more power, but also looses some with the higher weight.

Id say those results are showing there is no difference. So one can just choose what feels right. The more rigid pushrod should give better longevity one would assume.

Why wouldn’t you use a spintron?

Wonder what 7/16 carbon fiber would do if they made it. They make carbon fuel pump push rods, so why not?

The muscle mustangs magazine did this testing 10-15 years ago at the height of nmca mustang racing when they were turning 8000+ with stock 302 ho cams

i resemble the bare feet

i would think the lightest weight pushrods would make the most horsepower but i have 3/8th in pushrods so i secretly hope they make more power. okay now imma unpause and see what the data shows

But wouldn't u want strength over 2-5 hp tho

Make a video of my 383 I ordered lol

What internals you use iin this engine to spin 7500 rpm without issues?

But does the engine making most power nessesarily mean there is no deflection? Does the engine making least power mean there is deflection? Hmm. Only really says one is heavier than another.

520 pounds of open spring pressure isn’t like a ton of pressure is it? I imagine with higher spring rates on a solid roller might be different???

Interesting stuff. So now the real question is: How do we make push rods lighter and stronger? Is there a better material or design to enhance rigidity without adding weight? Would also be interesting to see a similar experiment with forced induction. Awesome content!

So, would you also recommend the 5/16 .080 wall pushrod on a gen v lt car? It seems the 3/8 .080 is the main go to size for pushrod on the gen v LT's. Going to be running the same springs you were and turning more towards the 8k rpm mark.

Are the smeding 260cc heads able to be ran with the wiseco K448x3 pistons in a 408 build? I know the pistons are a standard ls2 15* piston but I messaged 1 other shop and they said their head isn’t compatible then another stated their house brand is. Trying to shop around and find a cylinder her for my build for max performance also running a rectangle port intake.

A couple of horsepower here and there is not gonna make a hill of bens difference.

Why do you have no shoes on 🤯

Nobody uses pushrods for hp though. You want something that isn't gonna bend or break when you are racing. They are doing one 1 minute pull if that. With the 708hp he is making I'd still go with the 5/16 .108 wall.

Thank you for your knowledge and videos USA 🇺🇸 TRUMP 2024 2024 TRUMP 🇺🇸

Odd choice of footwear in the shop.

Why is that kid not wearing shoes. Just doesn't make any sense at all. Not professional at all !!!!!

The 5/16 .080 wall is lofting the valve… put a light valve spring in and the power curve will probably match the 3/8 .135 wall. Just my 2 cents

You said stiff, HA

like anything , it depends, and a heavier pushrod with the same spring with a pushrod that doesn't deflect excessively, will not return the desired results.

Great video and testing 👍🇦🇺

Awesome! 5/16 baby...