Why Can't Pushrod Engines Rev High?

Why Don't Pushrod V8 Engines Have High Redlines?
How Do Engines Rev To 9,000 RPM? • How Do Some Engines Re...
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The pushrod V8 engine is an icon in the world of American muscle. It still powers the torque monsters inside Chevy Camaros and Corvettes, as well as Dodge Chargers and Challengers. And while it's not to say that the engines aren't performance bargains, one might be curious why the redline on these engines tends to be fairly lower than their European counterparts.
Again, this isn't to say that one technology is superior in every way, there are pros and cons of most engine styles. But from a curiosity standpoint, it does make one wonder why pushrod V8 engines aren't hitting 9,000 RPM in production cars, like DOHC V8's and flat-sixes. Of course, high RPM is all about engines that are tuned to breathe well at high RPM, and as the video demonstrates, that's just not what pushrod OHV engines are all about.
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[@EngineeringExplained]

Here are a few other videos you may find interesting! How Do Engines Hit 9,000 RPM? - kzbin.info/www/bejne/q2SofIt9nsyYirM Why Engines Lose Power Over Time - kzbin.info/www/bejne/q5ubmZ13n65qppY How V8 Engines Work - kzbin.info/www/bejne/gYuvqpqapcxmgrc Boxer-4 vs Inline-4 Engine - kzbin.info/www/bejne/o5jTdYeMd8p7hdk 10 Facts On The Hellcat Widebody - kzbin.info/www/bejne/laOzpICKnc2bg5o I'll also be making a video very soon on the benefits of pushrod engines, because they're actually pretty brilliant designs, despite the banter often surrounding them. Hope everyone's having a solid day!

[@michaelblacktree]

My project car has a solid day every day, because it has solid lifters. 😎 BTW, that 3D printed engine is really cool!

[@sidneyisais8862]

Engineering Explained what I want to know is where do you get those 3D printed engine models?

[@TalladegaTom]

And that small engine cam has a compression relief device. When at cranking speed, that uses spring force to move that little doohickey that changes the valve timing just enough to reduce compression which makes it easier to crank. Once running, it uses centrifugal force to return the cam to its original configuration. These are on many Briggs and Stratton engines and some others too. When that breaks it can easily trick people into thinking they have a bad battery or starter.

[@calholli]

You forgot piston speed... The reason why diesel engines have such low red line is because there is a much longer stroke. and the speed of the piston moving up and down is much greater because it has a farther distance to travel in the same time window as a normal gas engine.

[@Luck21st]

Engineering Explained AMAZING DUDE ! YOUR MY FAVOURITE !!

[@JamesMiller-jh7wg]

The 3d printed v8 is easily the coolest thing I’ve seen on KZbin in a while.

[@caribbeangtr8077]

Fast Forward to November 2019, and EFI University and Comp Cams have a LS7 revving to 11,300 rpm successfully. Quite an interesting development.

[@wrighty338]

for 1 power run of a few seconds....

[@nvl2691]

wrighty338 Still impressive honestly.

[@tomeverett2212]

My 1992 Honda VFR750 would run at 11,000 all day long achieving 42mpg on RON 84! DOHC V4.

[@analog.shootty]

Tom Everett but then again that’s not a pushrod is it?

[@tomeverett2212]

@@analog.shootty nope! Gear drive dohc.

[@marcellobittencourt1836]

I just can't believe how much I'm learning with this channel. Not to mention how easy it is to learn these stuff. You're getting better everyday, dude. Keep it up!

[@EngineeringExplained]

Very happy to hear it, thanks for watching!!

[@vishnusai469]

same review here too . u make it extremely easy to understand from a foreman level. i wished i were to learn automobile engineering supported by Ur videos

[@vishnusai469]

master blaster of engines watching Ur videos i have changed my concept of engines i now take good care for my engine hope u make some maintenance videos too for Indian passenger cars.

[@konaguzzi1]

I had previously thought your videos to be quite well thought out and very well researched alas not on this occasion cbr250rr 19500 red line 410 chev motors used in jet boats regularly rev to 10,000 rpm the old f5000 race cars of the 70s regularly 8,000-8,500 and the cross plain chev from that era 10,000 most production cars do little over 7,000 rpm (yes some will and can go higher but most do not) and pneumatics has little to do with high revs in f1 cars either it makes it easier to eliminate cams and/or have better valve timing variation

[@DENicholsAutoBravado]

konaguzzi1 I figured the pneumatic valves gave more control as you say. Just because he only mentioned one aspect and reason for them doesn't mean he doesn't understand them. I appreciate your comment however as I was only guessing at the other reasons and you have confirmed it.

[@ChristopherGaul]

Nicely done video, as usual. I think it's important to point out that OHC engines aren't necessarily better (or worse) than pushrod engines, they're just different and each excels in different applications. RPM kills and manufacturers improve reliability by designing the engine to optimize power at the lowest RPM possible. Most pushrod engines are larger displacement engines that make more power at lower RPM's which is especially good in larger North American market sedans and trucks, but even in performance applications cars like the Corvette continue to prove that pushrod engines are still able to compete with and even dominate any OHC engine in street applications. For small, lightweight European cars, lightweight, high revving, OHC engines make more sense and work well. It comes down to weight, where torque rules. Motorcycles being the extreme example on the lightweight, high revving, OHC side. Low revving, big block, pushrod, truck engines being the other end. Right tool for the right job kind of thing.

[@anthonynicholich9654]

There's a reason why Asians and Europeans quit building pushrods 70 years ago. Yes OHC and DOHC 4 and 5 valve engines are superior. Need bottom torque? Diesel! More efficient than pushrod dinosaur gas longer lasting and still more torque. In the 70's Mercedes build SOHC OM616 and 617 engines that rev to 5500 RPM last million miles and still on the road today.

[@Shade_tree_garage01]

*stares at a Chevy small block that revs to the 10k rpm range*

[@downloadingutubes]

@Zo Fryer or u do nothing and buy german that revs almost as high. Plus i bet 9k is past peak hp and lbft

[@codysides7683]

@Zo Fryer This is the reason GM has stuck with this style of motor. If you mod any other V motor from any other company, your buying 4 cams, that right there is the most expensive part of that build. I can rebuild an entire LS motor with hotter parts for the price of a set of stock 5.0 coyote cams.

[@seancolfack8708]

*shrugs* revs 526 blown hemi to 12.5k

[@rcatkin1]

Still not high revs though. Would be high for a production car but nothing compared to race engines.

[@0hjaa3.06]

@@downloadingutubes Or buy Sweden and rev to 7000 with more reliable engine

[@tomkoessler4764]

This channel is a MUST for every car-enthusiast :)

[@EngineeringExplained]

Thanks for the kind words, and of course for watching!! :)

[@fakhrizzaarrifi9375]

and every automotives teacher in the world. great videos, love from indonesia

[@lorenreece1665]

@@EngineeringExplained very informative video for everyone.

[@fluffigverbimmelt]

More really more like "Combustion Engine Explained"

[@brandonlittlejohn8055]

Sadly not enough "car" people care about how a car works. Just want it to look good

[@IhateYoutube]

Piston Return Springs would fix all of these issues! :D

[@Xx1SailorScoutxX]

Brett DiMichele Studios Hey guys; Chrisfix here!

[@shabutir1820]

Except air flow. Even if you get valve float under control your cam profile, valve area, and lack of the ability to have a proper VVL system means that power at high rpms would require you to sacrifice your power at the low end.

[@IhateYoutube]

You just have to use High Flow Piston Return Springs.

[@chrisschristov475]

Chris fix the best

[@IhateYoutube]

*Hey Guuuuuyz!*

[@machinist7230]

Two valve hemi heads are pretty much the ultimate in airflow, because of cylinder head & valvetrain geometry - its basically a strait shot into the cylinder, combined with massive valves - Alan Johnsons billet hemi heads, intended for top fuel, flow in the mid 500 cfm range at max lift.

[@Prestiged_peck]

Ask any top fuel engine builder why they don't use overhead cam and see what they say

[@aklip]

A while back Hot Rod and Super Chevy magazine built high revving LS3s. Hot Rods was more budget oriented and used a forged 4.8 truck crank to destroke the LS3 to about 5.5 Liters. They used off-the-shelf AFR heads and Brian Tooley cam/valvetrain. It made 600 HP at 8000RPM and was supposedly able to spin up to 9k safely.

[@aklip]

LS7s have been built to hit 10,000 RPM as well.

[@t1ny7ank]

Finally someone that did some research. 👍🏻 NHRA Pro Stock used to go to 13k rpm. Btw.

[@aklip]

Luke Z actually the shorter stroke/ big bore reduces the piston speeds/travel distances. This results in a reduction in friction and reciprocating mass. I'm not saying longer strokes can't rev high, just that it would typically require more maintenance and 'exotic" materials

[@eb110americana]

Of note, the LS7 used titanium connecting rods from the factory to reach those RPMs. Impressive nonetheless.

[@EtxSmokeshow]

I built a small block 350 for land speed racing. Forged steel internals, solid roller cam. Shift light came on at 9200 RPM. Only thing semi-exotic was the shaft mount rockets. 4 in bore, 3.48 stroke. It can be done.

[@fullofhopkins1322]

These videos with the 3D-printed engines are *so* helpful to me. I cannot learn unless I put my hands on something or see every component of how it works. Thank you for making these, seriously. Keep it up.

[@jmurphy1973]

Gotta admit, though, that a 5.8L NASCAR engine revving to 9500+ RPM and not grenading is impressive.

[@brrebrresen1367]

fun fact, some places in Europe you are required to drive with bulletproof dragrace with motorcycles since some have been killed by the valves going straight up... so engines literally going "grenade" is a thing.... not so easy to finish a race again even if the engine is rebuilt if your body is full of holes...

[@ABArsenal]

on top of hours at max rev

[@danielanderson2030]

About 17k per motor from roush. They're actually pleased for x amount of races. They're a hell of a motor though. Once I win the lottery I'll buy myself one or two and build some bucket list rigs.

[@hooyabaaa2]

Another thing to consider isnt only the type of engine (OHV) but the mass of the system is a thing too... Formula 1 engine has tiny pistons moving up and down. Nascar have imense pistons moving probally even faster than an Formula 1 engine. Top Alcohol Dragsters are the ''miracle'' of the OHV engines. They rev as high as 11K RPM being 9,5 to 10K their peak power. This in an massive engine... 8.2 to 8.7L You can talk about endurance, but still.. More than 3K HP reving a LOT in an jurassic engine lol

[@roguepathfinder2477]

Zeh Doce Top dragsters use nitromethane and alcohol, not gasoline.

[@nunyadambinnes8723]

Why don't pushrod engines rev very high? Reason 1) Valvetrain mass. Reason 2) They generally don't NEED to rev high in order to make power... because their displacement relative to external dimensions tends to be higher than OHC engines.

[@markusgarvey]

Higher revs= more wear.

[@ltsjoke5443]

Mark Estrada well said

[@gotjuice7160]

and more pumping losses

[@jdrok5026]

Technically a dohc engine has more valvetrain mass. Just they don't need to be force up and down.

[@nunyadambinnes8723]

True, and a fair point. Amended Reason 1) *Reciprocating* valvetrain mass.

[@Mountain-Man-3000]

Title should say "Why It's Harder for Pushrod Engines to Rev". It's not that they can't rev, it's that its much more difficult and expensive to engineer them to be able to.

[@fredl.c8029]

MoutainMan3000 or you can get a rotary...sounds cooler too!

[@markoz673bajen8]

VTec braaaaaap. Not fast enough.

[@johndessire399]

Fred Larsen C. Rotary engine give twice the revs but three time the unreliability.

[@acmadniturner1668]

You dont need a rotary when you have huge cams:) they almost sound the same at idle. check my channel to see what im talking about.

[@5tarstriker78.]

Fred Larsen C. APEX SEALS!!!!!

[@johnpapa8681]

I had a streer rod with 302 with factory stock long block. Never had any problem accelerating to 6000 rpm. Never had a problem, and never needed more rpms than that. Very nice, simple, low maintenance affordable engine.

[@pauljoe780]

I had a BSA A65 Lightning production-race M/C, which was red-lined at 8750rpm. Standard is 6000rpm. It was raced in the 1973 Production TT by Peter Bates, a 114 mile race, and finished 13th. Beating several works machines which DNFed! Std points ignition so no rev-limiter! It had a 740cc barrel kit, making it oversquare, slipper or reduced skirt pistons to handle the higher piston speed, which are common now but not then, lightened and balanced crank, ported head, std valves and springs but quite drastically lightened rockers, the top and bottom edges of the std cast-iron rocker arms were knife-edged, and the screw-adjustment bosses were greatly thinned. So very light rockers, a very long and careful job, the main reason it revved so well I think. The rockers were quite beautifully sculpted, and were not the first try I suspect. A top-half fairing was fitted, but std frame, wheels and mudguards, to comply with race-regs. It was raced in the 1973 Production TT, a 114 mile race, and finished 13th. Beating several works machines which DNF. Including the Monocoque Factory Nortons of Peter Williams and Dave Croxford. I used it as daily transport for 2yrs or so, after a rebuild as it was on Castrol "R", which I was told sludges badly if left in. It had bog standard transmission. I was never late for work! It was very torquey off the line, wheelie-ing easily, and a wickedly fast top-end! Timed at 147 mph at Snetterton. So over 150 on a good day. Probably 160 mph downhill if pushed. I still miss it.

[@AeroPR]

Your videos are gold! So much knowledge clearly explained.

[@EngineeringExplained]

Thank you so much, happy to hear you enjoy them. That’s the goal! :)

[@SuperCookieGaming_]

Pushrods can rev high but they require a little more work because there is just more reciprocating mass to control.

[@ristekostadinov2820]

ls3 with 4.8L crank you got around 600hp and 7800-8000rpm revving, write on youtube search "SHORT STROKE-AN LS MONSTER MYTH? " the channel name is Richard Holdener he is doing lot of videos with junkyard ls engines.

[@bicyclist2]

I've been telling people DOHC is better for many years. Their reputation speaks for itself. All the Ferrari's, Lamborghini's, Maserati's, Porsche's, Mercedes, Audi's, BMW's, and Jaguar's have DOHC. Nascar was dragged kicking and screaming into the modern times. Thank you.

[@ryans413]

They are not better with the long timing chains and belts.

[@AndrewSmith-wo4tu]

I'm really enjoying this channel, sure I've read about most of these discussions in numerous magazines over the years but it's really useful to see it explained in video with working models.

[@LawrenceMarkFearon]

Why can’t Chevy and Dodge push rods rev high? With variable valve timing now they all rev past 6000 rpm. But these engines are so big, they really don’t have to. Put DOHC on a Viper V10 and it’s gained 100 lbs, which definitely isn’t worth it. Increasing compression or running a longer stroke [9.0 liter] crank adds 100hp without weight.

[@josechirimoya]

Well put. We all drive on the street. Why put the peak of your power band up around 8000, when you are driving away from a stop light at 1500?

[@Bartonovich52]

Josechirimoya. So you can get good fuel economy going around town but you can hold gears while passing or accelerating.

[@Ricky-tp2qj]

if it had DOHC it wouldnt need to be 9 litre in the first place

[@DENicholsAutoBravado]

Bartonovich52 exactly. Plus variable valve timing decreases pollution.

[@edism]

LOL! @Ricky

[@harrisonvc9175]

thank you! you explain this stuff in a way that anyone can understand it :) thanks to you I'm able to accurately answer all the questions my younger brothers ask me about engines

[@EngineeringExplained]

Very welcome, thanks for watching!

[@wedge4hire]

With every revolution of the crankshaft, an internal combustion engine is trying to tear itself apart. And high RPMs are the enemy of your motor's durability, so low rpms usually leads to long engine life. Focusing on making good power at lower revs means less time under the hood with a socket and ratchet!

[@JosephArata]

That's an idiotic statement. It doesn't work like that with the laws of physics. Heavy Duty Turbo diesel engines run 1,500 RPM up and down the road all day every day, producing 1,600-2,000 ft-lbs of torque in that RPM range under full load. The reason they last long is keeping the engine lubricated, filtered, and combustion temperature from becoming too hot. Something unobtainable by gasoline spark ignition engines without a massive cost to fuel economy to keep the engine temperatures down. RPM has nothing to do with engine durability, combustion temperature, lubrication, filtration, do.

[@finharms9439]

@@JosephArata are you high? Lol i mean you're both right.. hes right in saying that is most definitely a factor and comparing gas to diesel is apples n oranges... But why do you think that as soon as overdrive transmissions became a norm engines began running alot longer because of less rotations and stress... Same with oil quality, the oil now blows away the stuff they had in the 70s or even 80s

[@waysideme]

Race car. Dont care about long term durability. Just need to finish the race.

[@wedge4hire]

@@waysideme True. But even owners of race cars want the bottom ends of their very pricey engines lasting as long as possible.

[@waysideme]

@@wedge4hire Not necessarily. At most for racing an engine is needed to finish a season. My team is done with an engine after a single race

[@EvilThing3154]

Bro, I'd watch a channel where you just take different motors apart. Love your videos. Thanks!

[@garymanis6305]

If you used a captured follower design with the followers, push rods and rockers linked together, it would allow the camshaft to pull those linked components down as well as push them up. That would eliminate the issue and allow a push rod engine to rev freely up to 12k or even 13k rpm. Provided the rest of the components are strong enough.

[@mikesawyer1336]

Great information. I love your manual demonstration of the push rod and rocker pieces.. that was a great way to illustrate.

[@ghost-jesus]

Seems to me that everyone in the comment section is forgetting the most important equation. HP = (($ x in^3)^2)/5252

[@nathanhiggins1438]

Funny

[@IvelLeCog]

Where does the 5252 come from?

[@nathanhiggins1438]

@@IvelLeCog horsepower is somewhat but not totally arbitrarily defined as 33000 ft. Lbs of work per minute (had something to do with a horse and a bucket and a well) so horsepower is ft. Lbs per minute ÷ 33000, or POWER÷33000. At some point in deriving an equation for the horsepower at a given rpm of a car you get HP= torque x RPM x 6.28 ÷ 33000. For some reason the fact that 33000 ÷ 6.28 = 5252 means HP = TORQUE x RPM /5252. I realize my explanation is incomplete but I can't totally remember and I'm hoping someone finishes the explanation to remind me.

[@chickenfixn4439]

@@IvelLeCog all you need to know is 5252 is a constant. Every number will change when finding horsepower other than 5252. Hp= Torque x RPM / 5252. Torque and RPM can be variable. 5252 never changes

[@xriex]

@@chickenfixn4439 It depends on units being used (as Nathan explained) - you would use a different constant if calculating in Nm.

[@S.Perek1337]

You've explained to me more mechanics and physics than teachers at university :P

[@GUYANESEGT]

you'll soon hit 2 million subs. thats awesome

[@EngineeringExplained]

Very cool indeed!!! :) Thanks for subscribing folks!

[@Major-Kong]

I have an LS1, I have the rev limiter set to 8300RPM............. been like that for 8 years, it has 180000kms on it, no issues found. Valve float is solved by heavier rate valve springs and titanium valves, valve spring retainers and retainer locks. Also never had issues eating any of these hi tech rubber band motor powered cars with it.

[@Hamza-or7jm]

Right a stiffer spring and lighter valve train components are what most people do to achieve higher rpm as well as the addition of flat plane cranks which also helps with the high rpm harmonics and balance of the engine.

[@Major-Kong]

@@Hamza-or7jm I never bothered with flat plane cranks, I just get the full rotating assembly balanced and have all the pistons and rods weight matched so they are all the same weight. A good blueprinted engine lasts forever.

[@tylergauthun2707]

I appreciate all the videos you do, I’m a gear head myself and love the 3d models you use and technical logic you introduce, thank you

[@uwekonnigsstaddt524]

Beautiful explanation of an apparently difficult operating mechanism, even for those/us not “mechanically inclined”. I am convinced that certain people are gifted to become engineers, but to be able to explain it in a fast, easy way to grasp, making the complex understandable, sure adds an extra notch to that gift. I’ve watched many videos on different subjects, but this series has become my favorite, “forcing” me to look forward on more future installations. Perhaps you may tackle turbine engines in the future, like the M-1 tank or jets engines in general, even rocket engines and how they work. As always, a pleasure!! Keep up the great work!!!

[@EngineeringExplained]

Thanks for the very kind words, glad you’re enjoying the content!

[@samkwant4050]

Could you do a video on ducati's desmodromic valve system? Does having no valve springs at all automatically mean that you could (theoretically) rev them higher than a regular dohc engine?

[@EngineeringExplained]

Yes, with a purely mechanical opening and closing, you wouldn't have to worry about valve float at all. There are of course other limitations in revving high, but that's one box you could check.

[@abepowers4379]

no "valve float" has been a high selling point of Desmodronics.

[@generalrodcocker1018]

it has springs

[@williamwagner8017]

foo bar The springs in desmo engines are only there to hold the valve closed during the very short time when neither cam is in contact with the valve. The closer rocker is what actually closes the valve.

[@1barnet1]

yes it means Ducati didn't have to go pneumatic in moto gp compared to their japanese counterparts. Obviously you'd also need an oversquare design in order to keep the piston speeds manageable. However there is problem. Ducati's need frequent valve adjustments.

[@thiscrazytangerine8954]

Best explanation ever. Well done sir 👍

[@NewportGeek]

Like all your video this one is super informative. Just one comment. Stiffer valve springs don't usually result in power loss due to the "regenerative" properties of valvetrains. When one spring is compressing another spring is decompressing somewhere in the valvetrain. So set springs as stiff as is needed to not float for your given cam profile.

[@rswstudios]

Always wondered why these engines are called "pushrod" but never exectly understood why, this is by far the most clear AND simple explanation I got, thank you!!

[@24lunaticasylum]

Ok before watching, i'm gonna guess something along the lines of valve floating?

[@watchandjewelryloft4713]

Simple answer: Because they don’t need to.

[@jamest.5001]

Exactly!

[@ronalddaub7965]

Exactly

[@LITTLE1994]

Yeah, because it is possible to actually make them rev super high, but it's not a must.

[@terry1427]

Gets to show how such a small detail can have a large effect on performance!

[@mixhael6609]

I like your video clips explaining the mechanics of car engines. I am an electrical engineer and a car lover too. Thanks for the great job

[@jimmy_olds]

Nice video! A little off topic but one of my favorite engines of all time was the Ilmor Mercedes pushrod V8 used in the Penske PC23 chassis that decimated its competitors during the 1994 Indy 500. Those pushrods fit perfectly through a rule book loophole.

[@glovedcop69]

where can we buy one of those 3d printed engines? 😃

[@OzarksWildman]

The fastest race cars use push rod engines. Top fuel uses push rods and redline around 9500 rpm and make 11,000 hp. A 5000 hp 481X can spin 9000 rpms with push rods.

[@Duskconqueror]

While that is true, those are purpose-built engines. High revving daily driver pushrods are possible, but used to be inefficient and expensive to manufacture and maintain. Nowadays, with lighter materials, pushrods start to become interesting again because of their small package, relatively low weight, plus they are less top-heavy compared to OHC/DOHC engines.

[@Benedocta]

They are rebuild after every race. You could probably spin a truck engine 9000 rpm for 5 seconds as well.

[@calebnation7797]

I don’t think it’s fair to cite top fuel.... those engines get rebuilt every pass pretty much, and replace a crankshaft every 5 passes...

[@AmericanLocomotive1]

Yeah, but those valve springs on a top fuel engine are only good for one pass. That 481X engine might get a season on a set of springs at best. A Honda S2000 engine can turn up to 9,000 RPM reliably for 200,000 miles.

[@OzarksWildman]

I do agree with Jason though, OHC has many advantages.

[@jamesmonahan1819]

When it floats: Those little keeper things fall out and the valve gets sucked into the cylinder.

[@luisa.espinoza48]

I don't know ANYTHING about mechanics and stuff.. but you are so good explaining that i completely understood everything

[@Leo-lr4eq]

Yeah my dads grand Cherokee with an i6 red lines at 5k rpm.. Great explanation!

[@tri601]

Valve float is just the poor man's VTEC.

[@JoseLikesCars-ln9qc]

This video is kinda misleading. With modern pushrod engines, the valvetrain components have gotten to a point where they can easily rev past 9000 rpm. The use of light weight metals in the valvetrain such as titanium allows this. Also the 2 valve per cylinder fow is bunk since if you look at the LS3 head flow characteristics vs the Ford coyote head, they are comparable and this is due to the runner design and large valve diameter that the LS3 head has. The limiting factor for an engine like the LSX is not the valvetrain or head flow but rather the stroke of the engine. The piston is a large reciprocating mass and with a longer stroke, at a given rpm, the change in velocity is immense compared to an engine with short stroke, hence most high revving engines, especially f1 engines, have shorter stroke. In fact, a common failure point in older LS1 engines was rod bolts, which would stretch with sustained high rpm or mechanical over rev and cause the rod bearings to spin. This was remedied by using stronger rod bolts but its still a limiting factor.

[@devil0373]

4 smaller circles in a given area will cover more area than 2 large circles. The advantage of the LS is that its had around 60 years of development and aftermarket support in the cylinder head, whereas DOHC has only recently come into the mainstream. A 4v head should theoretically flow more air than a 2v head with identical port characteristics. The issue with pushrods is they are ALWAYS heavier as a valvetrain than OHC due to the inclusion of pushrods, so will not rev as hard. For an apples to apples comparison rather than this coyote vs ls war, look at a Jack Knight BMC a series head vs the regular pushrod configuration. There is a night and day difference.

[@AmericanLocomotive1]

Those engines cannot rev to 9,000 RPM reliably, for 200,000 miles. The valve springs simply will not last revving that high. The spring pressures also start getting outrageously silly. My Honda CRF450 has a 3.75" bore, and a 4-valve SOHC head design. The max-lift spring pressure on the intake valves is just 175 pounds. It will reliably turn 12,500 RPM all day. To get an LS engine to turn 10,000 RPM requires open valve spring pressures approaching 1,000 pounds. At those pressures, the spring, rocker, pushrod and lifter life are extremely short.

[@eaglefat9398]

dude you can't compare bike engines to car engines, how many Honda street car engines rev to 12k...none and theres a good reason for that it makes zero torque thats why car engines don't go over 100hp/liter unless it weighs sub 2,500lbs and even then people complain its slow like a honda S2000/240hp@9,000rpm 0-60 in 5.7sec/14.2 which is slower then a 1985 corvette/230hp@4,800rpm 0-60 in 5.5sec /13.9sec and the corvette weighs around 1,000lbs more but is faster with less power . and bike engines don't last 200,000miles more like 20k miles.

[@AmericanLocomotive1]

No one is talking about power, acceleration, or anything here. We're strictly talking about valvetrains. The facts are that a pushrod engine with a 10,000 RPM capable valve train will not hold up. You will get extreme wear on the rockers and lifters, and the valve springs typically can only take 5-10 hours of sustained high RPM operation before they need replacing. On the other hand a DOHC engine can utilize lightweight valve train components that can easily deal with those sustained high RPM operation. Bike engines, and engines like the S2000 engine are perfect examples of this. The S2000 engine can last for hundreds of thousands of miles. I'm not sure where you figure bike engines only last 20,000 miles. Many people put tens of thousands of miles on bikes - there are many Yamaha R1s with over 50,000 miles, including some over 100,000. Like I said, on my Honda 450 (single cylinder), the valve-springs only have about 60 pounds of seat pressure with the valve closed. Pushrod engines that turn similar RPM require closed seat pressures of over 400 pounds, and open valve pressures that exceed 1000 pounds. In comparison, the open seat pressure on this Honda 450 is only around 175 pounds. That results in far less stress on every component of the valvetrain, allowing it to last longer at high RPM operation. NASCAR valve springs are typically only good for a single race, top-fuel valve springs only last a single pass. A Yamaha R1 valve spring can be expected to last 50,000 miles without issue.

[@JoseLikesCars-ln9qc]

Dude where are you getting your figures from? You don't know what you are talking about. First off, even the S2000 has valvetrain control issues. its a common problem they experience at track days where they have valve float and this causes piston to valve contact and may even drop a valve. Check out ZentRose channel, its what happened to his. Also the 1000lbs valve spring force your talking about is nonsense. PSI1511ML springs, which I run on my z06, which are probably the best beehive style spring you could run on a LSX, are rated at 370lbs at 1.175" and 130lbs at 1.800". You do realize that spring force depends on how compressed they are right? its not a constant "1000 lbs" like you are implying. Finally the fact that you are bringing up motorcycle engines shows me that you are missing the point of my comment. Motorcycle engines have short piston strokes, therefore the velocity of the piston is lower at a given rpm compared to an engine with longer stroke and there is less force on the rods.

[@PapaFowler7]

What are the advantages to using a push rod engine? Also, thanks for these videos. I'm a civil engineer but have always had an interest in cars and up until recently all my knowledge was on small engines. I've learned a lot from you and I plan on watching all the videos you put out.

[@redmanaaron97]

Simpler and more power at low engine speeds

[@YouNeedToCalmDown76]

Power and cheap/easy power

[@Conservator.]

Push rod V8’s are far less complex to build and maintain, so the are cheaper. Also there package is much smaller than a V8’s with DOHC’s. When the volumes are the same a push rod engine will have less power than a DOHC because the latter will be able to rev faster. But I think it will make more sense to compare a push rod V8 with a smaller inline 6 with DOHC, twin turbo and direct injection. That would give a comparable amount of power in a comparable package size. (But no doubt at much higher costs)

[@efcodpalama]

Packaging and weight are much better for a pushrod. They are also often more fuel efficient because you don't need crazy cams for high revs. This only holds for v engines, though.

[@Hrithik_Jayanth]

iam just like you greg

[@alejmc]

Wow man, wow. Never have had such a clear view of innards of a pushrod engine. Thanks for it.

[@thedefenestrator2994]

I love this channel, I've learned so much about my vehicles. This just explained so much about my truck. It's my first RWD V8 vehicle and I love it so damn much. It just grunts at 2k rpm and I rarely have to go higher to get up to speed.

[@ELJEFEEEE]

I beg to differ the title. I have a 525ci bbc wich is a big block with push rods and still revs to 8500rpms

[@inanismailov]

blanky blank i think he means stock ones, if you use much stiffer springs itll still rev high

[@ELJEFEEEE]

Inan Ismailov ya i didnt watch the vid yet hHahah. $18k just for the forged rotating assembly. Iron block. Aluminum heads. 805 hp 800 lbs

[@ELJEFEEEE]

GlassTopRX7 sorry lad it was a typo i edited it

[@philtripe]

a 525 cubic inch SMALL BLOCK?? i would have posted a video of that before my RC car...ive never seen a sbc clear more than 455 ci, which is amazing but 525? psssht! i wouldnt believe you if you showed me in person until i saw it draw that much air in one gulp

[@ELJEFEEEE]

stickloaf it was a typo...

[@SalveMonesvol]

SOHC seems like a good compromise if you want something simpler and lighter than dohc while also delivering peak power at 6000 rpm without a sweat.

[@charliedee9276]

Mainly because they do not need to, they make sufficient power at lower rpm's. If needed they can rev, look at a NASCAR engine. Over 9000 at times with pushrods and rocker arms.

[@EngineeringExplained]

As discussed in the video! :)

[@charliedee9276]

Yes it was. Outstanding video BTW. As an Engineer also, (retired), you explain things very clearly.

[@MrCuervo22779]

charlie dee pro stock engines were turning somewhere in the neighborhood of 11k rpm or more the last time I was into it. They run huge springs and massive amounts of open and seat pressure. Seat tends to be 500lbs and open is around 1000-1200lbs. Pretty impressive in my book.

[@joeinmi8671]

500 cu. in. with over 1" lift cams and a single throttle body... Try doing that OHC and DOHC... F1 cars are unreal but they dont hold a candle to pro stock. Also NASCAR engines are flat tappet.

[@t1ny7ank]

Engineering Explained maybe the take a look at NHRA pro stock motors. Currently 10500 rpm. Used to be 12-13000. And they are 500 cubic inches.

[@ron827]

I am a slow listener so playing these videos x.75 works very well for me. Lots of good info here and easier to understand at a slower speed.

[@YouNameItGaming]

just to touch on the mention of multiple cam profiles with overhead cam, i know some companies are using it to simply adjust the lift and profile, but a few weeks ago i pondered the possibility of using such a setup to completely change the way the valvetrain operates at lower RPM. for example, at higher RPM you have modest lift on both intake valves, but at lower RPM the camshaft slides into profile 2 which disables 1 valve completely and increases lift on the other to improve intake charge velocity. i guess a possible side effect of this is slightly more restriction low down, but in saying that it would also likely create some turbulence, which might just benefit fuel atomisation

[@juzoli]

That’s why we need Koenigsegg’s FreeValve technology.

[@jdrok5026]

Zoltán Juhász so pneumatic actuators? I mean we don't need it more valve surface area displacement revs and air/fuel is all we need.

[@sleepydingo7090]

Then us Aussies have burnout cars running push rod setups revving 10000+ rpm in engines up to 7L

[@TheBunnyDeveloper]

That 7L is tearing itself apart

[@berjyacoubian6173]

Direct valve from Koenigsegg that would fix all the problems

[@wazzzappening4848]

Free Valve for all four stroke engine perfection. Agreed.

[@Kneedragon1962]

Good explanation. Another factor not mentioned, high performance pushrod engines use solid lifters, and sometimes roller lifters, but normal every day engines tend to use hydraulic lifters. A hydraulic lifter is designed to self adjust for valve lash, no manual adjustment required. But they do have a range of speeds, and at higher revs they tend to pump up, and the the valves don't shut. Stiffer valve-springs will not only help control valve float, they will also reduce pump-up, but it will happen. There is also a half-way step where you can get bleed-down lifters, which are designed for quite high performance applications. Those are usually quite resistant to pump-up, because for one thing, they're designed to bleed down, and offer lower lift & less duration at lower revs. That does tend to cancel out the pump-up but it can still happen. Another problem is the sheer strength of the pushrods. A big valve and a stiff spring, a strong roller-rocker, a solid lifter and a solid cam, and a standard pushrod can bend. If it happens slightly, you just take them out and tap them straight with a hammer, (nylon head hammer if you must) on a block of wood. But if it happens in a big way you can completely lunch the rod and maybe the lifter as well. So what is a suitable speed for a single cam pushrod engine? Depends... I seem to remember one company made a 2.85 litre IndyCar motor, with pushrods & 4 valves. I'm not sure but I think that was Mercedes. They only did it to show it could be done, to show off, but that engine ran the Indy 500 and it was still going strong...

[@mirceadimian4048]

How can someone dislike such a correctly informed and comprehensive video ?

[@zx10r6]

Chevy and Dodge use the pushrod "OHV" design instead of the dual overhead cam "DOHC" design for two reasons. 1st, OHV engines have less moving parts which makes them far more mechanically efficient = more power. 2nd, OHV engines by design are much smaller dimensionally than DHOC engines thus saving weight and allowing a lower center of gravity= better handling. Also, to the best of my knowledge there has never been a DOHC motor that put out anywhere near the horsepower of a Top Fuel Dragster 500 cubic-inch OHV engine, "8000 to 9000 hp". Lastly, anyone who actually turns wrench for a living knows that working on a OHV is far easier than working on a DOHC. Long live OHV engines. It's just one of the rare times when an eairler design is better than a newer one.

[@BC08]

Lol, less moving parts makes OHV more mechanically efficient? Why do you guys make these statements when it obvious you don’t have a clue? Your statement is dead wrong, BTW.

[@j.adamwegs2882]

You know, in all my years of turning wrenches on everything from forklifts to semis, i can tell you OHV motors are pretty much universally more reliable and easier to work on with a couple exceptions.

[@godaboss]

What is that spike thing on the crank shaft?

[@ΑΡΗΣΚΟΡΝΑΡΑΚΗΣ]

godaboss oil splasher

[@CODMarioWarfare]

Why don't those racing engines use OHC's?

[@mycubehead]

Probably pushrod engines have lover centre of gravitiy compared to OHC engines. Lower CG is better especially in racing.

[@efcodpalama]

Also weight, packaging and, often, efficiency.

[@efcodpalama]

ZERO94AIC Like Can Am and Top Fuel?

[@jothain]

mycubehead That's not a reason. Pushrod design is always heavier than other more modern designs. Reason seems to be always the rules of racing class

[@markusgarvey]

Aston Martin, Ferrari, Lamborghini,Peugeot,Audi, Mercedes and most of the Japanese cars do In WEC, IMSA, GT racing. They use SOCH and OHC engines against push rod engines. Corvettes running LS engines would beat ALL of them every time if not for BOP (Balance Of Performance) restrictions in GTLM and GTD classes.

[@PAVANZYL]

Very informative channel. I had a Honda CX500 that revved happily to 10 500 day in and day out. Four valves per cylinder and pushrods. That was in the early 80s. In the 1930s the desmodromic valve system was developed to overcome valve float. I can't find much on the history but I believe that the Auto Union and Mercedes racers of the pre-war era used it - with overhead cams. That eliminated the valve springs with the associated energy consumption of compressing very stiff valve springs 10 000 times a minute. It was not very effective at lower rpm though. I wish somebody would build a production engine with pneumatic springs.

[@gcvcodis6982]

7:45 That cam gear glows every so often

[@james10739]

I'm going to stick with my ls pushrod motors less to go wrong and cheaper not really any less efficient and can easily make plenty of power

[@michaelkuzmadutton7879]

James Holbrook yeah, as long as you don't scream it and you run it normally it will hold up fine.

[@Clobercow1]

What always blows my mind, is that a costly i4 engine with DOHC barely revs to 8 or 9k RPM, but these LS pushrod engines do 6500 to 7k RPM reliably. IMO: I don't think DOHC is THAT huge of an advantage when we can get considerably more displacement in the same package.

[@ryanj4423]

corvette also had a dohc in the 90s

[@markusgarvey]

They might be using one for a mid engine C8.

[@Gcrilla]

ryan janki yeah in the original zr1 it was actually a lotus or Yamaha built engine I believe.

[@eaglefat9398]

The original LT5 had lotus designed heads and was assembled by mercury marine boat engine builders, it was a very trick engine with 18 throttle bodies and half the throttle bodies closed off at low rpm for a vtec like effect , it was super expensive and it was all aluminum but weighed more then the iron push rod 5.7L and the ZR1 weighed 200lbs more then the iron block Z51 , and didn't really make that much more power then the push rod LT4 , 405hp vs 330hp but keep in mind the weight disadvantage which also kill the 50/50 balance the base model had. But it was fast for a 3,550lbs car with 405hp to go 0-60 in 4.3sec and 12.7sec 1/4 mile. GM plained to use it in the C5 corvette but it was way to heavy and didn't fit under the hood and the LS6 made just as much power but cheaper and 150lbs lighter and lower

[@jdrok5026]

I'll be Frank I'm Leary about using my name it was a lotus design from ground up when gm bought them lotus loved the time with their engine they offered Chevy a lt5.2 for the c5 Chevy turned them down. Sad that we aren't seeing lotus and Chevy have another love child together.

[@eaglefat9398]

that LT5.2 was a beast, it had variable cam lift and made over 530hp @7,800rpm which for 1997 would have been unheard of. Oh the glory it could have brought to this nation, to bad it weighed like 600lbs compared to a 425lbs LS1 and was to way big to fit under the c5s tiny hood.

[@RealSprooseMoose]

GM used cam phasing on the L99 before the LT1. It was the 6.2 in the automatic camaro's (manual trans got the LS3)

[@chopstickstotheclouds]

Why did I only find your channel today? This is the best thing on KZbin. Awesome content, applause!

[@AnonYmous-qg4ph]

An over square engine with solid roller lifters, roller rockers, and stiff valve springs will rev pretty high...

[@EM6285]

Can beehive style sprongs help push-rod engines to rev higjer?

[@kubanskiloewe]

if only have 1 camshaft no other 3 can make problems ;-) not to mention aabout all these huge long chains and all the stuff to hold them in place ! In a chevy LS or LT you have only 1 short chain !

[@ErrtuZarathos]

40years ago Honda made CX500 pushrod V twin bike that had 4 valves in cylinder and reved up to 10000 rpm.. also it had 50hp in that 500cc engine..

[@eaglefat9398]

bike engines can not be compared to car engines

[@ErrtuZarathos]

I'll be Frank I'm Leary about using my name yeah, you can. It is really easy. Just take two engines and compare their specs against each other.

[@jdrok5026]

Errtu Zarathos they aren't comparable Tho. A car is under more stress for weight a bike is under more stress from it's own engine.

[@sethh8892]

They can rev high, just no need to. With plenty of displacement and well manufactured components, you have a beautiful torque curve that allows great hp potential.

[@ryans413]

In my push rod car I barley ever rev higher then 3000 rpms there no need to at 2500 rpms im already doing highway speed the torque is amazing i love it.

[@TheLeonmafioso]

Hello Jason, i've been asking you about the Fiat/Lancia TriFlux engine. I also have to tell that you can have high revs in a pushrod engine, but the problem is you need a very short stroke and a big bore, with light pistons and rotary assembly. Also you need to improve all the pushrod assembly, solid roller lifters, lighter rocker arms, stiffer springs, a good oil. You needto do a expensive inversion

[@tbones55]

Combustion! How primitive! You humans crack me up. Getting back on my gravity wave warp cruiser. See you last year.

[@cancermonkey7334]

~4:29 Jason says “A fish in sea lost”? Does he mean Nemo? Not sure what that has to do with pushrods.

[@terryalbritton915]

Cancer Monkey he said efficiency loss lol but i get how you heard that

[@ThaRealGecko]

7:31 Your timing is off ... Way off lol

[@GarageProfessor]

Don't know if I missed it in the video (they are great BTW) here are a couple of things that are often why that may have been overlooked Large valve size which are heavy Hydraulic lifter limits before they pump up. Mechanical lifters require maintenance, so not often used in production except on high perf engines. Also valve train weight on the lifter side of the fulcrum is much less important than on the valve side. Overall another great video!

[@zacharymartin4861]

I was wondering about this the other day, but couldn't find anything on it. Thanks!

[@partymanau]

Built properly , pushrod engines can rev just as high as OHC engines. Remember the valves run at half crank speed.

[@angelgjr1999]

I have a Ford 4.0 v6 engine. Now I know why it doesn’t like to go above 6,000 rpm :(

[@BigRedtheGinger]

Angel Gutierrez at least you can hit 6k, my Jeep's 5.2 V8 is limited to 5200.

[@derriklee287]

Angel Gutierrez thats a sohc so no, you're wrong again.

[@electric6877]

Derrik Lee Some of them are Pushrod.

[@bestmillimeter1858]

My DOHC 3.5 V6 F150 revs to 7000 🤣

[@SparxMusik]

My 3.0 ohv has a rev limiter at 5900

[@MrBAJACOUNTRY]

Lmao. So Nascar engines, which are push rod... Don't Rev high? Hmmmm

[@AmericanLocomotive1]

They can't rev high for very long, and require frequent valve spring replacements because of the forces the valve train experiences. A modern DOHC engine can turn 9,000 RPM for decades.

[@MrBAJACOUNTRY]

No. Nascar engines Rev to 9 grand for hours. Go back to sleep.

[@MrBAJACOUNTRY]

bigpigslapper Oink I work for Nascar so.... Yes I do know how long they last. It's for hours. Especially the long tracks. Please stop it.

[@MrBAJACOUNTRY]

bigpigslapper Oink sorry my messages are going to the wrong peeps.

[@Kepe]

Nascar engines are racing engines. They are serviced between each race, so they only need to last a few hours of usage between changing parts. Compare that to racing DOHC engines. They rev to 15000 and more. So yes, when comparing pushrod engines to equivalent DOHC engines, pushrod engines can't rev very high at all. In normal day to day cars, pushrod engines can't rev as high as DOHC engines because they need to last a long time. Which they won't if they are revved high.

[@JoeIsCrazyWillman]

Dang, that was more things than I even knew of. I knew about mass and therefore limitations of the springs (also probably doesn't help that with rocker arms changing the direction of the action of the valves 130-160 degrees probably reduces the overall effective effort of the spring as well, regardless of RPM, yes?). Love it.

[@TheRealBmanswan]

From personal experience owning a car that weighs 2,500 pounds and has a dodge caravan 3.3 v6 I can definitely say with the power it puts out it has a lot of torque for a low rev engine. Usually have the upper hand at the 1/4 mile because of it.

[@erikhadinger7655]

Grossly mistitled! There are many pushrod engines that rev 7 + 8000 RPM a simple LS engine for example. If you do not have the springs that are strong enough to return the valve I don't care if it is an overhead cam or a push rod you will get valve float at a certain RPM plain and simple. This is a very misleading title and does not describe the true things that make an engine able to turn high RPMs push rod or overhead cam valve springs and engine stroke are very limiting factors of RPM

[@francoisd6942]

This is what happen when young boys try to explain something they know nothing about.

[@devinwilliams3489]

8000 rpm is high for a pushrod motor, not for an ohc design with the same work put into it and design intentions. OHC also needs less spring pressure than ohv

[@alexleonard1852]

this video was made by OHC gang

[@Theophilus138]

I'd love to see a video about 4 valve pushrod motors and why they exist. Another comment mentioned a Honda V-twin 500cc motorcycle engine in the CX500, the new Harley-Davidson Milwaukee-Eight engine has a four-valve layout with pushrods, and the Cummins B-series engines in the Ram HD trucks are also have 4 valve pushrod valvetrains.

[@nunyabizness7013]

Puerto Ricans love the Toyota 3tc engine it's a 1.8 L I4 pushrod with hemispherical heads, yes a pushrod hemi from Toyota 😀 and as you know those guys get crazy performance outta them at the drag strip.

[@cosmicbluevox1001]

For your next video idea, Can you make a video explaining the most difficult task of any manufacturer? >>how do auto manufacturer engineers so good at perfecting the Stock feel and drivability of a car? even sports cars stock feel have that stockness to it. Even the best aftermarket performance companies cannot increase performance without destroying the stock feel, drivability, and longevity...and they use even higher quality materials. Here's an idea for another great video.

[@roadrunner681]

i still like ohv, there lower in height and i like that even though im working a truck for off roading i can fit more stuff under the hood like alternators and air compressors easier and its easier at least in the us to find parts suited for what i need which isnt rpm its low rpm power turn big heavy tires

[@johnwgw9842]

I have learned more from your channel, than the 4 years of shop in highschool i took! Thanks!

[@sachellebabbar9005]

The original Camaro Z28 302 revved well into the high 7000 range. The fact that we have superchargers across the board now means we can have a smaller stroke V8 that will rev super high, with the supercharger mitigating what people would see as HP loss (due to marketing in the Horsepower Wars). Naturally, the supercharger then has to be tuned for what rpm range it will operate optimally at.

[@keithwalton]

Independent variable valve timing exists for pushrod engines. The old viper engine had a duocam/duophase camshaft (manufactured under license) this special camshaft combined with a special camphaser allows fully independent continuously variable valve timing of both intake and exhaust valves. The engine with this system was so potent it had to be significantly de-tuned for the rest of the drive train to be able to cope and was only fully unleashed in the drag pack edition cars. With ever tightening emissions regulations I wouldn't be surprised to see more pushrod engines using VVT/VVL valve trains, both are possible

[@KartRacer9516]

I know I'll sound like a broken record, but you really do make the videos easy to understand, keep up the great work!

[@Flydevice1]

I have to say your video explanations have gotten a lot better.

[@richardmogel2186]

Nhra prostock I'm sure has been over 11,500 rpm. 500" 90° v8. There has been LS engines over 10,000. Camshaft technology has come a long way from what you are describing. Solid roller keyed lifters, asymmetrical cam lobes, DLC, etc. Watch a spintron video or search for comp cams. Billy Godbold has done so much work on the spintron and made us pushrod knuckle draggers competitive with the Dohc engines.

[@matthewstorm5188]

Another issue with pushrod engines that is very important but seldom mentioned is intake porting. In a pushrod engine, the intake ports compete with the pushrods for the same real estate in the head casting. Therefore, intake port geometry is generally compromised in pushrod engines vs OHC engines. Intake ports typically must take on a tall, skinny cross section as they pass through the pushrod wells. This, along with the need to transition to this shape in the intake manifold and then transition to a round valve, hurts flow compared to the more optimal intake porting that OHC heads allow. Newer pushrod heads (such as GM LS and Chrysler Hemi) do MUCH better in this respect than older designs, but are still behind contemporary OHC heads. This compromised flow is another factor that limits the rev capacity of pushrod engines.

[@Vizion1998]

This is great as an educational video for those who dont understand valve trains yet, or are just curious, however, my question is why we care that push rod engines cant rev high, high rpm does not nessacerily mean high power, look at scooters, more important than high rpm is a good transmission and rear end (on rear wheel drive cars) gear those right and you can get a lot of speed on low rpm