Do Longer Camshaft Splits Affect Performance? | Engine Masters

[@MotorTrendWatch]

What type of cam do you prefer using?

[@vintagesavoiur]

Didn't the olds 442 have 308 duration cams?

[@Dr_Xyzt]

The one that suits the application and combination. I'm not gonna use a cam that's 260@.050 in an LS3 with a stock intake. I also won't use an RV cam in a 540 big block that uses GM RS-X heads.

[@JukkaVaan]

The one that has no lobe wiped flat

[@mrfunky8843]

The one I can afford 😅

[@brian6029]

The 1 that has more bottom end power.

[@drewhh6821]

I'm just happy to see you guys out here still making videos

[@gordocarbo]

Me too!! Info available through this channel being free is priceless. Before it was just in magazines. Cant believe so many demand more and more of these vids but complain if they gotta pay $5.

[@adaycj]

One thing is clear to me. If i had any one of these cams, Im glad i didn't pay for an upgrade to any of the other two. The percentage difference is tiny. That is how it goes sometimes when you try science instead of just marketing. Awesome video.

[@harrywalker968]

theres less fuel exhaust, than fuel inlet. as its burnt up. this is why the exhaust valve is smaller, so a cam with same or smaller duration, is fine. bigger makes no difference..

[@gordocarbo]

Agree..Second guess myslef about not choosing my first cam choice. Would be single pattern instead of an 8 deg split and 106 vs 108lsa. If I lost a touch of torque so be it

[@ik04]

I'd like to see the effects of increasing/decreasing the lobe separation angle and even bigger exhaust duration! Also, exhaust tube length will have an effect...

[@shvrdavid]

The problem with that is the cost of the blanks to do so. There is a reason you can rarely find a 102 lobe separation camshafts for high flow heads, and that is because the vast majority of blanks don't support grinding it there due to pre grinding and hardening the lobes prior to final grinding, and that can't be ground there afterwards.... That is also why good camshafts for serious hp can cost north of 2k. The blanks are all custom made..... This video is comparing off the shelf cams, that get left in the dust when put up against anything with a well thought out camshaft. Case in point, 1000+hp NA small blocks, you are not ordering that cam from Summit...... Summit doesn't stock anything like that, because you cant grind it on a 10 dollar blank......

[@alertgasper]

@@shvrdavid agree with you, but at 2:03 David says they are custom made camshafts, so not off the shelf.a DOHC engine design could have also been used for this test.

[@shvrdavid]

@@alertgasper Custom ground is a bit different than custom made.

[@alertgasper]

@@shvrdavid naw, "Custom" means "not off the shelf". Competition Cams got busted in the 1980's by their competitors for not even making their own camshafts--they bought and reboxed 'em. Whoever makes the stick, however it's the grinding of the profile that makes it worth anything. so, custom is custom because its custom.

[@shvrdavid]

@@alertgasper I have ordered hundreds of custom cams, and that is not how it works..... You can not make a 100 degree centerline cam on a normal blank, it isn't possible.... Comp Cams will only make you profiles that they have in the catalog, because that is all you can grind on the blanks they don't even make..... They write a check for the blanks, from CMC Camshafts.... Ask me how I know that........ If you want a true custom cam, it is usually made from a tool steel rod, and you have to know what grind, lift, centerline, ramp rates, firing order, etc, etc, just to do the first rough in step to the core before it is re hardened, then the final grind can be done.... Nothing they use on this show is made that way, and comes out of a Summit catalog...... It is a "custom grind", that comes in a box that anyone can buy, on a CMC camshaft core, and nothing about it is custom at all... The lobe profiles are in the catalog, in the back, look for yourself... That is how it works..... But, it is not a custom core or even a custom cam.

[@markmonroe7330]

Excellent presentation. Thank you. This one was especially good.

[@mustangstuff7213]

This

[@logancarter2134]

I would really like to HEAR the engine idle with the different cams.

[@Kris-mx6ju]

Agreed. How did this affect idle quality? Not important to all I would think, but to some, idle quality is a consideration

[@GroovesAndLands]

And minimum steady idle RPM, and vacuum readings at minimum idle, min idle + 500rpm, min idle +1000rpm.

[@The_sinner_Jim_Whitney]

Yeah, and maybe what they did to vacuum? I'm a stickshift/fun car kinda guy (not a serious racer), so it's less important to me than to some, but I would think that off-idle response, idle quality, and drivability might be what makes this decision for most folks. As always (well, at least the good ones), this episode provided me with more questions than answers.

[@jedpratte]

Generally more overlap/longer duration the less vacuum and lumpier the idle

[@GroovesAndLands]

@@jedpratte Yes. Which is why 3000-7000rpm dyno pulls on a Superflow as performed by Engine Masters etc can be *very* misleading to the weekend warrior guys out there. What the engine does between 500-1500rpm is super important to most people and it's 99% ignored by these tests. Not to say I don't love Engine Masters! I was just suggesting that any testing involving big cams should include: 1. Minimum steady idle RPM and vacuum reading 2. Vac reading @ min idle + 500rpm 3. Vac reading @ min idle + 1000rpm

[@racerd9669]

I would have liked to seen the cranking compression on all 3 camshafts?

[@danieldimitri6133]

They would have the same intake valve closing time. The difference wouldn't show up on cranking. The differences would be how much reversion of exhaust into the combustion chamber during overlap and how much combustion pressure is lost on the power stroke do to an early exhaust opening.

[@racerd9669]

@@danieldimitri6133 You are talking theory , I want to see real world.

[@davidphillips3953]

He's right it would not affect cranking compression. At cranking speed theory and reality match up, it's when explosions start happening that theory gets a lot more complicated and harder to predict.

[@trailerparkcryptoking5213]

@@danieldimitri6133 opening the exhaust valve early causes some loss of combustion pressure, but it decreases pumping losses after BDC, which increases higher rpm HP. In my head it seems that opening the exhaust valve earlier in the power stroke would make the exhaust louder, what is your thought on that? My thoughts on this is if I install a cam in my Harley that opens exhaust earlier, the bike will be louder and sound nastier. I have noticed that a ProStock bike racer that has his own cam line has a very early exhaust opening on all his cams....

[@williamglass7806]

you need a big bang to do that so early exhaust needs more compression from either the intake lobe or the piston or both, but it's got to come from somewhere. earlier exhaust usually means more rpm and probably more duration. the word is momentum.

[@DavidBergquistfiero]

Has Engine Masters actually been canceled? If its true, I am going to be so sad. I loved my MTOD account and Engine Masters was my primary reason for keeping my subscription. (Well that and all the Roadkill versions plus Hotrod Garage)

[@corystansbury]

I assume you already watch Richard Holdener?

[@DavidBergquistfiero]

Yep

[@Stainlessslayer]

Bought up by discovery. No new episodes yet. I was bummed when I had to get discovery+ to keep watching.

[@JLC87420]

@@Stainlessslayerwhy would you purchase a peterphile network unless you are a peterphile.

[@LarryWalker-xd7sj]

You mentioned that all cams had the same lobe separation angle (lsa) but what was the lsa, and what was the intake lobe centerline?

[@AB-80X]

Considering that it is Comp and looking at the numbers, that's a basic 110 LSA and probably an a 106 CL.

[@markstopkey4085]

Digging the Brulee mullet! But, wondering what would be the difference between cam 1 and cam 3 if using nitrous? I think cam 3 would make a much bigger difference due to cylinder pressure

[@kyliejm2]

Or maybe more to the point, greater exhaust volume due to more oxygen/fuel

[@andrewmontgomery1763]

The cam that makes more power NA will then make more power with nitrous.

[@____MC____]

Id like to see the difference in dynamic compression. I really thought that would be a factor. My only guess on why hp went up is it might've gained some minor scavaging?

[@davidphillips3953]

No difference. Dynamic compression does not change with exhaust opening and closing only intake because the exhaust timing doesn't happen on the compression stroke, only intake valve timing.

[@alertgasper]

@@davidphillips3953 if it increases overlap, then it can affect scavenging and let out some of the mechanical compression available. but once the exhaust closes, then you've got a final compression ratio.

[@williamglass7806]

i believe peak cylinder pressure was about the same only at a higher rmp so the exhaust probably made the difference.

[@leewaddell8561]

Love you guys and show..keep it up.

[@mindblownwatcher8536]

Why wouldn’t u base line this with a single pattern to start and demonstrate the full effect of longer exhaust duration?

[@85bigGMC]

That’s a test he stated they’ve already done before.

[@cedricwilson2055]

You can see the trend. A single pattern is going to be lower on the top end and a tad bigger or the same through the middle. No single pattern won an emc challenge

[@TheFogLakeshore]

@@cedricwilson2055it’s still completely dependent on valve size porting and intake config.

[@cedricwilson2055]

@@TheFogLakeshore in the emc challenge all they used was dual pattern cams. And all the heads were killer. That pumping loss must be more detrimental to hp with single pattern cams. Those few numbers through the middle, they can accept that

[@ToxicConfusionZ]

They already did that test, they started this video saying that

[@jaykanor9613]

Love the idea of the test, but it'd be nice to see it done on a mediocre or crappy cylinder head to see how the split helps. Like on a 799 or LS3 head where the exhaust side is known to struggle

[@andrewmontgomery1763]

Those are excellent heads haha I think you mean, like a stock Windsor 302 head lol

[@dreece2000]

You go back in the days of old to find a crappy head like in the 70s excluding the 454

[@andretorben9995]

Would have been good to see the results with a full dual 2.5" exhaust system. Something like you would see on a typical muscle car. I think the exhaust duration would have more effect.

[@duanebiesterfeld4719]

Somebody said there's not very many 16° split cams out there. All Mopar 440 hp's have the 268 on the intake and 284 degrees duration on the exhaust with a .450 lift. Even the 440-6 pack which was a low taper had the same duration and lift and overlap as the regular 4bbl.

[@AB-80X]

There's a ton of cams with large splits. Just look at all the factory LS and LT stuff. Some have over 20 degrees. 14-18 degrees is very normal in LS stuff.

[@dhag72]

I love the door analogy for explaining duration. I may steal that one. Thank you for another great video Engine Masters crew. I do wish you laid a baseline for each with a single vs split for each cam. I want to know the difference at each level!

[@Iowa599]

What if you make a system that lets you use both duration lobes in one engine, with a way to switch back&forth while the engine is running?

[@markg7030]

@@Iowa599 VVT.

[@nerd1000ify]

What's missing from the analogy is that the room gets kinda crowded, so if you leave the door open too long some people will walk back out. And the exhaust is a door to a nasty back alley, leave it open too long and some people who should have left will walk back in.

[@reubenmorris487]

@@Iowa599 There is such a "system." Got V-TEC yo?

[@Iowa599]

@@reubenmorris487 I have VTECs!

[@george1la]

Great investigative true work you all are doing. Only facts matter. This is the way to approach most things.

[@lollipop84858]

Lol, I see what you done here. Nice and sarcastic. Hilarious

[@TomSmith-cv8hk]

Now you have to do it again with the LSA's changed to maintain overlap for the three different exhaust durations.

[@williamglass7806]

that would be an interesting test

[@rickgehring7507]

it would interesting to see the results with the Exhaust being the constant and the Intake growing in duration.

[@unavailable8681]

A test like this would be interresting on a 4 cam engine like a ford or toyota v8, so you could see what the cams behave like with similar overlap. or timed at similar opening times.

[@FABRIC8TIONUNLIMITE1]

The Camshaft is the Brain of an Engine, it tells the Engine when to breathe, how much to breathe. How long to hold it's breath and when to exhale. The Oil Pump is the ''Heart'', it pumps the Oil through the Engine.

[@HighrSelf]

I always believed the "ENGINE BUILDER" is the heart ❤ of any build! No?

[@aaronliddell4280]

Guess heads are the lungs then 🤷🏻‍♂️

[@OxBlitzkriegxO]

Thank you AI chat bot. We would've never figured that out for ourselves.

[@P71ScrewHead]

@@aaronliddell4280 Yes..

[@ralekriver]

@@HighrSelf No. The Engine Builder is "God" :D :D :D

[@drcolster]

And then they can play with cam timing and lashes to get more results... great stuff guys.

[@ryandeweese363]

Thanks for making this video!

[@johnbehneman1546]

THANK YOU SO MUCH!!!! GREAT VIDEO DAVID!!!! I LEARNED A LOT ABOUT CAM LOBE SEPARATION!!!!

[@mikestraley7201]

Are you that desperate for attention that you have to use all caps?

[@BustedWalletGarage]

FYI. The producers of this show have left. Don’t expect Discovery Channel to keep these shows on.

[@KingEdwardA]

Wonder why, motor trend gunna get bought out or something?

[@BustedWalletGarage]

@@KingEdwardA discovery channel has already cancelled several Motor Trend shows.

[@KingEdwardA]

@@BustedWalletGarage ahhh I see, unfortunate. Thank you sir

[@rileylindley295]

Such a bummer…..

[@markgiraldes4062]

Probably not green enough !!! 🤬💩🧳’s

[@johnbehneman1546]

THANK YOU TO ALL PRODUCTS INVOLVED IN THIS BUILD!!!!! SHE RUNS TOTALLYAWSOME!!!!

[@mikestraley7201]

Is your cap lock broken, or you just get that easily excited?

[@Macaziod]

Would be curious how a greater exhaust durations would effect turbo applications.

[@Mirage8v]

Love this series.

[@dhern2613]

Did you adjust ignition timing? Fuel timing? This is equivalent to putting a larger exhaust on your car but not tuning it to suit the modification, to see the best results

[@SolamenteVees]

Dave, asking the questions over-thinking gearheads (like me) need to know.

[@johnbehneman1546]

THANK YOU SO MUCH!!!! THAT MOTOR IS TOTALLY AWSOME FOR ANY APPLICATION!!!!!

[@mikestraley7201]

YOU REALLY DON'T HAVE TO USE ALL CAPS EVERY SINGLE TIME YOU REPLY!!!!! THEY CAN SEE YOU AND THEY KNOW YOU'RE STARVED FOR ATTENTION

[@davidreed6070]

We use big spreads on sbc engines when we spray them, usually on the opening side of the ex.

[@harrywalker968]

sbc needs all the help they can get.. or, buy a clevo..& a decent cam.. no other mods needed.. no speed shops.. bs machining ect.. sbc were designed in 1936, never changed.. dead horse flogging.. LS. = updated FE. from 1955.. wake up chev, your centuries behind..

[@harrywalker968]

chev even fkt up with the 454.. its just not quit a 460.. missed again..

[@TheMattC9999]

It's not that the split affects the performance it's a matter of having the right camshaft for your particular engine combination.

[@ronnieboucherthecrystalcraftsm]

Brian crower 264 - wrx sti factory spec - big raves about this factory grind - 2004 i think = mine is automatic anyway .

[@spankyham9607]

I think you would see more difference with exhaust duration if you were running manifolds and full exhaust. A relatively unrestricted exhaust isn't going to need more duration or lift on it.

[@cedricwilson2055]

You forget scavenging and wave resonance. May be down on power no matter the split or little hp gain

[@russriley3005]

it should be noted that typically, stock cam will not have the same separation as the aftermarket. even a mild aftermarket cam will give longer duration and separation.

[@user-pr1zr9yg1d]

I have a 92 Chet Astro with a 4.3. Looking to put in a larger cam for performance. Need some guidance.

[@CQBWarfighter]

Running a 277/293 227/243 on a 113 in a 398ci LS stroker with ls3 heads. Makes a ton of torque.

[@mikebrown8065]

More on camshaft lobe separation Please 🙏🏻 🙂 how about rocker arm lengths with the different lobes?

[@jgregorykline3457]

First thing I wondered like others have mentioned is how the exhaust tone changes...

[@MrIngorodrigues]

The talk with these 3 its so much interteining

[@idontcare3013]

It could be argued that the narrower duration separation is better, giving more low-end torque, allowing for similar or same ET's with longer engine life. RPMs are the enemy of longevity. The true test would trying it in a car, unfortunately adding more variables.

[@АлексейСоловьёв-ь3щ5ш]

I friend of mine got a reverse split pattern, he's got 264 on the intake and 260 on the exhaust side. I am only diving into tuning and i am curious how this reverse split pattern affects engine performance.

[@stevegross9477]

I like the Pontiac firing order sweat shirt.

[@danieldimitri6133]

That's the most common v8 firing order. Fords looked different mostly because they number their cylinders differently 1=5 2=1 3=6 4=2 5=7 6=4 7=8 8=4. But the roller can Fords do have a different order similar to an ls or 4-7 3-2 swap. All the gm v8s of the same era and the chrysler v8s had the 18436572 order.

[@fullnoyz7670]

Holden gm 304 firing order is 12784563

[@garyszewc3339]

Pontiac, Chevy, Oldsmobile, Cadillac, Buick, Chrysler, Plymouth, Dodge, pretty much everything but Ford products. Ford numbers their cylinders 1234 on the right, and 5678 on the left.

[@scottzito4797]

Even if the door is open longer, what about if the door isn't open as wide and the door is smaller? Does the exhaust require more duration due to a smaller valve and possibly less lift?

[@MrBlackbutang]

Intake open/close angles are the most important any camshaft.

[@harrywalker968]

fast open, stay open, close fast.. like most modern cams, not peaky..

[@glenb.9811]

Would be interesting to see the effect of an increased LSA with increased duration ie. open point stays the same, but close point is later.

[@amcam124]

What was the split in advertised ( AKA) total running duration? Was it the same split as the .050 number?

[@spacebutlermk2]

how would this effect turbos?

[@veleriphon]

Isn't the Atkinson cycle an earlier, longer duration intake? What about that?

[@Scubasteve22]

I always appreciate your testing and info....What might have been better would be to test a cyl. head with a bad exhaust flow, more for a street deal....

[@ChristopherHallett]

This is why you just use a modern engine with variable cam timing on both the inlet and exhaust camshafts. Mercury make a quad-cam big block Chebby motor, right? Does that have VCT?

[@gordocarbo]

Do you feel having a good exhaust port it wasnt able to benefit with more exh duration? (say compared to a GM iron)

[@bobgaudet9941]

I would love to see the 3rd cam what's the most exhaust duration receive a higher ratio rocker arm

[@RickHaile]

Yes! Everything effects performance!

[@toddclark332]

❤👍🇺🇸always a great show thanks guy's

[@rayvarnson8976]

Why not using a typical street engine 330 - 400 cid, why a 477 cid???

[@waybad]

Awesome test 🎉

[@danmallery9142]

I wonder how this test would go for an engine with a poor intake/exhaust ratio, like on some small block Fords I've seen with 2.02/1.46 valves? Would there be a benefit on a head with, say, a .72 ratio?

[@jimfryar1]

So how would this same test have worked in a supercharger situation?

[@kevinclemence4661]

Isn't it the increased overlap that contributes to the top end charge rather than, as Mr F suggested, giving a boost to mid range torque?

[@Ecosse57]

*i'd like to see a video on 4 pattern cams.*

[@mattbauckman9907]

Just a guess, but I think the difference in the cams would be more noticeable with exhaust manifolds vs headers or a more restrictive exhaust.

[@krusher74]

yes, its always be a crutch mod for a poor flowing exhaust.

[@MrBlackbutang]

Camshaft specs is for specific engine performance . Drag circle and drifting all require a different camshaft specs. You can tune a car but you can’t tuna fish!

[@WardoUSA]

Sound checks would have been cool. Great video

[@Null-h6c]

ideal ? Would be a skidoo cvt type system linking cam and crank .

[@Mohammed-m7t2u]

can you please test: -10 negative overlap vs ''zero overlap'' vs +10 positive overlap

[@donmelvin7102]

So, it seems the differences are quite small for anything but track only engines. I wonder what would change if you ran the same test, but with changing the lift instead?

[@stuartbuckley6113]

The results can be very similar by switching rocker ratios on the intake and exhaust, a tuning thing.

[@tunemymods]

Valve timing is expressed in degrees, but the actual amount of time the valve is open is what really matters (up top). Sadly it's inverse with rpm - the faster the crank spins the less time the valve is open.

[@shotamakarashvili3714]

That's where vtec is shining))

[@Marc_Wolfe]

Ehh, would have liked to see the opening point be the only thing that changes duration. Actually, yeah, stock amounts of valve overlap, change other things, for ease of EFI tuning. Closed loop O2 readings and all that. I've heard you'll get a very lean O2 reading, at least at lower RPMS, with lots of overlap.

[@rogerbennett2025]

ONLY 478 cubic inches and 12.5 compression ...LOL

[@Demoralized88]

It's insane how out of touch and lacking self awareness some people are.

[@davepalmer4125]

I'd like to see that test with a turbo engine. Starting with a single pattern and working through those 3

[@b_hall]

It depends on the intake flow vs exhaust flow ratio percentage. Anything over 75% can use a single pattern camshaft. Add 1 degree exhaust duration for every 1 percent under 75%.

[@krusher74]

Yes, these split cams are just masking poor exhaust flow.

[@b_hall]

@@krusher74 on this video there is minimal increase in power because the engine has good aftermarket heads. Most aftermarket high performance heads have 75% i/e flow or better.

[@shotamakarashvili3714]

Just changing exhaust camshaft isn't going to give much of the gain- it has to be a few other changes as well. You want to increase CR, install oversized intake valve and only then increase exhaust cam duration.

[@jeffreyschweiger7960]

This question is unrelated to camshafts or is it? What do I have to do to my 440 Charger to run E85, this car is a street cruiser and use to be my daily driver years ago.

[@joe-hp4nk]

Add more rocker ratio on the intake and you'll really see a difference.

[@ryanbarbolt3691]

Id want to see an increase in exhaust direction without changing the lsa. Keep the ex valve opening event the same just more duration. This way is adding too much overlap as you add duration.

[@thomaskehoe2092]

Are those the advertised duration numbers or the at 0.050 duration numbers?

[@utahcountypicazospage5412]

A camshaft calculator to know overlap would help know why this is happening since overlap can lose some compression

[@AK-DIRECT907]

Flow test intake and exhaust at .500 then time the volume of air. Then set the duration of the exhaust to match intake. Then test it.

[@adamcooper7677]

Anyone know how we can get the latest roadkill in the UK? Discovery plus only has up to season 9 😢

[@jhobbs6953]

It should be all be on hbo max but you may need a vpn if you’re in the uk

[@Zedsdead83]

Seems like a stupid business model stoping people from being able to pay/see these shows. I dont get it.

[@EngineKrahnicles]

They aren't worth it anyways. Roadkill died years ago

[@nathanvillarreal7937]

More exhaust duration is kinda a ls thing ls3 head for example flow really good on intake side but suffer on exhaust side so maybe a ls3 would benefit from the longer exhaust duration making up for such small exhaust flow

[@krusher74]

or just some exhaust porting.

[@mehrshadvr4]

Why would you run a bigger lobes on exhaust and not the intake?

[@machinist7230]

Very interesting, eapecially as i have a 478 planned for my first gen Camaro,albiet at a more pump gas friendly 10.5:1.👍

[@krusher74]

this is all dependant on the exhaust to inlet flow ratios.

[@t0mn8r35]

Interesting test.

[@Driven_Dragon]

Wouldn't it be cool if two camshafts went flat?

[@drcolster]

I reckon the Oil Pump is the Heart, the Cam is the Brain of the Engine...

[@guyconnell2250]

I don't know. To me, given the torque is in the 600s and hp in the 700s, I don't think there's a statistically significant change between the first and second cams. Those curves, for all intents and purposes, are identical.

[@dustinandtarynwolfe5540]

Anybody else notice they use the same audio for every Dyno?

[@rcairforceone]

I feel like the longer exhaust duration would reduce turbo lag, perhaps?

[@blkcoupequattro]

You actually want a pretty mild cam for turbo engines unless your compression ratio is really high, and your running E84 or other high octane fuels to suppress knocking.

[@Jimmyy32]

You forgot to take into account how much cooler your car sounds sitting at a stop light

[@davidphillips3953]

Who cares if it's taking the talk? It only matters if it can walk the walk.

[@alertgasper]

@@davidphillips3953 true, but...on a busy street, or pulling out of a show with the cops sitting nearby to catch folks...a choppy idle speaks loudly. just like when you pop the hood...you could have a 7 litre aftermarket stroker small block with a single quad that looks stock, but nothing says power like some version of a blower feeding the engine.

[@danieltustison822]

That good test now yall need do same everything just changing intake.

[@MrBlackbutang]

Heads determine what camshaft you use Holman Moody heads you never use more duration on exhaust side. Stock heads have low exhaust flow rates .

[@ricepony33]

I love this show but it needs more engine variety!

[@Santor-]

Yeah, throw some kia engines in there!

[@ricepony33]

@@Santor- 30psi gate pressure seems like a good place to start ;)

[@robertwest3093]

Steve Brule and not the one from Adult Swim lol. Love that guy.

[@calibra690v2]

question . why only the exhaust valves were modified, if the volume of air entered remains the same, it is not a loss to modify only the duration of the exhaust, can you test what happens if you modify the duration of the intake and leave it unchanged on the exhaust?

[@krusher74]

The exhaust is the restriction, so letting more air in with more duration isn't going to help.

[@calibra690v2]

a ok, I understood, thanks for the info

[@igokarts4510]

I have a 318 with stock heads. The exhaust valves are small. I'm thinking that s is exactly what I need

[@jonathoncouchey7151]

Something on a 107 lobe center (lsa). 260-270 total 220@50. Duration and .450 - .470 lift.

[@joshuagarvey9362]

Can you just change the Lifters on the exhaust side to 1.6 if your running 1.5’s??If just changing exhaust side lifters to 1.6 will that change sound of the engine like a dual pattern??If going to a 1.6 rocker on exhaust side with this be to much of a split?

[@monikhushalpuri]

Just search on google "running bigger roller rockers on exhaust forum" and you'll find your answer