MOTOR MYTH BUSTING-BLOWER CAMS!

DYNO RESULTS-TESTED-NA VS BLOWER CAMS (NA & UNDER BOOST). DO BLOWER CAMS WORK NA? DO NA CAMS WORK UNDER BOOST? Does a wild NA cam with overlap allow boost to escape? Does a blower cam make more power? Does on cam lower boost pressure? Is boost really just a multiplier? We compared a wild NA cam to a dedicated blower cam both NA and with a Vortech supercharger on a healthy, high-compression 400 SBC.

[@BREW2LFOXBODY]

My man is out her dropping knowledge! Thanks for sharing all this info

[@wakjob961]

"Every cam is a boost cam"...my man.

[@addmoreboostOG]

Effin aye!

[@williamkillingsworth2619]

isn’t the blower cam more drive able out of boost? Giving it better street manners than an engine with a lot of overlap. I wonder if/how the longevity would be effected? Is the Blower cam the safer option? Or does the added overlap cause other unwanted gases into the cylinder that will rare its head at higher power levels?

[@captnjoe40]

@@williamkillingsworth2619 Look at the torque curves, the answer is no.

[@Joshie2256]

@@williamkillingsworth2619 If the overlap is less it will idle better and probably behave better just off idle. But the LSA on both cams is too wide and the duration is too long. If the overlap is correct then the duration and lobe separation can both be reduced and the mid-range will come in much stronger.

[@williamkillingsworth2619]

But its only at 6 psi. When you start raising the pressure especially in the exhaust manifold it’s gonna change things a lot. What I’m saying is an extreme elevated power levels you guys don’t think the blower Cam will allow higher power and higher boost pressures? This isn’t gonna matter so much at 6 pounds. But at 30-35??? And I’m not staunch supporting this I’m just kind of throwing it out there to she wants to discuss it I appreciate the answers thus far.

[@jaredlutz787]

I love that you’ve been using real evidence and testing to dispel “common knowledge” and misconceptions. Great job! Keep it up.

[@hu3.789]

Boost is a measure of restriction. Anytime you reduce restriction, you have a reduction of boost. With the more aggressive cam, air flow increases which reduces restriction.

[@TractorTech]

That is exactly what I was going to say.

[@Isaihernandez777]

You don’t say ? :D

[@watsisbuttndo829]

Last time i was this early, you ruled the streets with a 3/4 race!.

[@19jody72]

AND hooker headers!

[@michaelwilson5851]

I love your videos. All the data I’ve craved from similar videos in the past that lacked it. Plus, you use so many different combinations along the way, instead of just a typical “here’s what happens on an ls1” video. My opinion, the boost pressure dropped because the engine used more volume. I’ve had the same experience with my motor through the years. Lower boost means less stress, even with more power.

[@bethanyhaskiell9116]

Finally some 400 sbc testing

[@superduty4556]

Hardly any to go around these days

[@fabricationnation8052]

@@superduty4556 they're around...... I've had 3 in the last 6 or 8 years

[@JimBronson]

Aftermarket block, in fact aftermarket everything. So not cheap. But if you have the dough, it's definitely cool.

[@bevinsracing]

Sorry man..lol i have 8...yes 8 400s..all im good usable mag checked condition my buddys all joke me that i will never let a 400 go...4 fully built 500-650 range 1 concrete filled on c&s methanol carb blow thru turbo big single over 1000hp

[@wilsonfamily4922]

The best content for gearheads on KZbin. Thank You!

[@dramaface]

You. You are my hero. THANK YOU. Your genius and expertise literally get me through life easier.

[@mikef-gi2dg]

Watched this again, I still liked this test. All that power on less than 7psi manifold pressure, sing me up....that would work very nicely in any car I got. Way to bust myths!!!!!

[@DSRE535]

With ANY Engine Part its ALWAYS combination specific, everything is the perfect part for something but as also the worst part in something else, this is why every pro builder pounds it in your head that every part needs to match to get the most for a given combination

[@RealSprooseMoose]

Same as in hydraulics, pressure (boost) is the resistance to flow. Lower boost=more flow. (Assuming the air volume is the same, also the supercharger in this test will draw less power at the same time due to lower boost) I believe i am also correct in saying when you look at the boost of a positive displacement supercharger, the point of lowest boost would be the engines most effecient rpm.

[@200mphgt40]

True, when the bigger camshaft kicks in in my engine (2ZZ Yamaha-Toyota) the boost drops a little due to the greater VE of the engine. It then goes on to keep increasing as the RPM rises, but that's due to the increase in VE of the roots blower with increasing RPM. That's one thing I didn't know about or expect coming from a turbo background. A roots blower increases in VE the faster you spin it. Makes sense, as there is less time for the air to escape past the lobe tip clearance. The adiabatic efficiency however certainly does decrease the harder you push it! But that's another story - heat management.

[@gollumthewicked]

This assumes perfectly flat efficiency for the blower, and that's never the case. While you'll see a drop in boost for a rise in VE, the efficiency of anything else before the last compressor stage (the engine) will have an effect. Changes in charge cooling efficiency (like from the carb), supercharger efficiency (which isn't flat let alone linear), and so on will all have an impact on realized boost levels. On most roots style blowers they're most efficient at low RPM and low boost. As you increase pressure ratio efficiency goes down and thus charge temps go up (faster than relationship of compression related heat increase). As RPMs go up, they'll also eventually start rolling off on efficiency. A twin screw will perform significantly better, but generally exhibit similar traits. The nice thing about twin screw is that the RPM at which efficiency rolls off can often be far beyond the requirements of the build. The twin screw will still have efficiency roll off with pressure ratio increase, but has more range than the roots. Also don't forget that directly attached superchargers require drive power, and that goes up with RPM. I say all this because if you look at NA vs blown dynos for the same motor, like here on Richard's channel you'll see many cases where peak TQ moves. This shows how blowers will create a second layer of efficiencies that work on top of the primary efficiencies of the engine, and of course there's also the obvious intake efficiency changes if we're looking at a roots style with a dedicated integral manifold.

[@mikef-gi2dg]

Exactly!!!

[@Rocky-cg9nl]

Hell yeah! Every cam is a boost cam! So happy to see a 400 build!

[@fastlanez3000]

Would love to see the BTR centifugal camshaft in this test. He has some specific beliefs (says he tested) regarding overlap, lift (especially exhaust), and duration for centrifugal superchargers. Would be awesome to see if that holds true. His basic premise is that his centrifugal cam will still supply the top end power, but will help bolster the low end torque that is missing from centrifugal's. Love to see that test!

[@TheProchargedmopar]

Oh, and still waiting on a 5.9 magnum sbe Chinese headed big bang episode. 🔥

[@angelovasilikos7980]

So build the motor to what you want (rpms idle quality etc) and add boost later. That great and Helps a lot with the build recipe vs building it for future boost. Thank you Another awesome video!

[@bigkellyg5947]

You totally verified my long time belief that the cams don't have to changed because you put a blower on. Thanks.

[@Peter-cn4os]

I wish I had a friend like you. The $130hr labour rate is killing me. lol Great video Richard.

[@Wolf462]

Amazing test! Thank you! I’m not sure where I got the idea that an optimized na cam wouldn’t work well with boost but I’ve been told about the sc blow by from valve overlap like you said for years and yet the test proves completely otherwise!👍🏻

[@stevenargo2802]

*TEST IDEA* I would love to see you test a double power adder like a turbo blowing into a roots style blower, and individually to compare the power curve between the two, then combined. Keep up the good work!!!

[@Hitman-ds1ei]

Yes I wonder at this too, would it enable exhaust energy to be put back to crankshaft thrust blower drive by trying to drive the rotors and lessening parasitic loses usually seen at higher rpms from blower

[@200mphgt40]

@@Hitman-ds1ei Keep an eye on the Street Machine youtube channel. Hopefully they will be doing this with their roots supercharged (Eaton M90) buick 3.8 V6. But I think with modern low inertia turbos, antilag (or just use good old fashion nitrous as anti lag for 1/4 mile racing) then the days of compound boost of turbo into roots is not worth it. Lancia did it very will of course back in 85-86 in group B rally, where no turbo lag is a distinct advantage, but then those days have long past.

[@SpecialEDy]

@@Hitman-ds1ei The turbocharger has parasitic loses too. NA is very inefficient using pistons for compression, positive displacement superchargers are more efficient using screws instead of pistons for pumping/compression. Centrifugal Superchargers and Turbochargers are the same, theyre the highest efficiency because of a turbine compressor instead of screws. The turbocharger could spool up the supercharger, or vice-verse, depending on which one is downstream. If the upstream device is supplying more air volume than the downstream device, it will windmill the downstream device up and effectively negate the parasitic loses. More likely, though, they will multiply exponentially in series. Nuether turbos now superchargers boost by pressure units, they boost by ratio. So, a supercharger with a 2:1 ratio will supply 14.7(1atm) of boost. But if that same supercharger is being fed by a turbocharger twice the size and also at a 2:1 ratio, they multiply. Lets say the engine in NA is 1000cfm, the supercharger is 2000cfm (2:1 ratio), and the turbo is 4000cfm at a 2:1 ratio. The turbo pumps 4000 cfm of atmosphere (14.7psi absolute) out at 2000cfm of 14.7lbs of boost (29.4psi absolute), then the supercharger will double it again from 2000cfm at 29.4psi absolute on the inlet to 1000cfm of 58.8 psi (44.1lbs of boost). Or, you could daisy chain turbos together. Say theyre all the same size turbos, you would have one turbo feeding the intake manifold, and you'd need two turbos feeding that turbo, and youd need 4 turbos feeding the two turbos. This is assuming turbos that are sized to provide a 2:1 (14.7psi of boost), and a volumetric efficiency of 100% (which doesnt exist).

[@anan0moose]

You could check by measuring the difference in the amount of un-burnt gas in the exhaust.

[@dalesince5957]

Thanks Richard. This is what i have thought all along. Some guys just overthink stuff without trial and error. Your channel and hard work is much appreciated. Thanks.

[@stuartcookie133]

I learn something new with EVERY video...Thanks Richard!

[@lsxtuner6126]

My experience with a centrifugal super charger is that they aren't as "picky" about cams as a turbo. The bigger issue I've found is at lower boost the centrifugal doesn't mind an aggressive NA cam at all which your dyno just proved. At higher boost and closer to maxing the blower out it starts liking that blower cam more and more especially if you like a full exhaust and reasonably quiet mufflers. The reason is at higher boost you can still have overlap with a centri, but it will really like having a lot more duration on the exhaust side.

[@patonbike]

This is interesting as I have a relatively big Vortech (Si) on a little 4 banger. I have found that with more aggressive pulley combos, at low engine speed the Vortech surges which basically stops the car dead. I have thought about putting on a large NA cam with long duration and some overlap to allow the engine to breath more so I can pour the boost on sooner without surging the blower. Do you think it would work? new cam 234 intake/235 exhaust @ .040 with 15 degrees of overlap @.040 existing cam 204 intake/198 exhaust @ .040 with -24.8 degrees of overlap @.040 The new cam does have slightly less lift than the existing cam. So... the Supercharger is oversized, I don't think I care about "blowing out" some of that air.

[@littledeel]

Turbos aren’t picky in any way.

[@i.d.1228]

Well it makes sense because boost is typically measured as pressure in the manifold. And while the valve overlap may allow some leakage of positive pressure in the manifold, that doesn't tell you how much pressure is in the combustion chamber.

[@chrismichael5016]

I love this video it kills so many bs "rules to fallow before you use a power adder"

[@chrismichael5016]

You have to have low compression and a cam with super wide lsa....WRONG! LOL

[@mikef-gi2dg]

A very smart guy told me something a very long time ago. An engine doesn't know what brand it is, what size it is, what marketing says it should do, what it is going to be installed in, if it has power adders, or what planet it is on. It knows at this instant, I see this fuel and air, at these atmospheric conditions, and with these parts, I can do THIS, at this instant in time. Jim KInsler, KInsler Fuel Injection,....1984. More fuel, better atmospheric conditions, less restrictions, more power. I bet the bsfc, went up with the n/a cam, but hey, we want more power, and this is not an emissions controlled engine. I like this test, hope to be building something under boost soon, and this showed me something. The engine saw 14.7 at sea level, then it saw appx 21.5 at seal level, or whatever, and liked it!

[@calvinevans8305]

I remember some guru from ATI Procharger explaining this engine theory. Boost being a measurement of air flow resistance, and that you should pay more attention to the volume of air going through the engine. Very interesting.

[@h.p.solutions1750]

I don't understand how you don't have more subscribers, real tests and facts no BS. Keep up the good work Richard 👍👍👍

[@richardholdener1727]

its growing-the channel is still new

[@timoneal9654]

I once heard a guy say "every cam is a blower cam!" Oh yeah, it was you.

[@andrewtreloar7389]

Best test yet Richard. You can see how the N/A cam made the engine breath better and increase volumetric efficiency, especially under boost.

[@peterlyons4389]

Great job Richard !!! You know that your not making friends with the $400 special BLOWER cam makers ••••••••• Right. You make learning fun my man. Keep up the great 👍🏻 work. Can’t wait for the next comparison.

[@dsm4959]

Yes, it would be nice to see Richard have some more content on Hemi’s. Especially 6.4L

[@cuzz63]

I didnt know a blow through carb acts like an intercooler. Thanks for teaching me something...lol

[@timothybayliss6680]

You should see what happens to a gm style roots blower when there is no fuel going through it...aluminum expands quite a bit at 400°f.

[@bevinsracing]

Man..i love that in 2020 you still show me a real...sbc 400 with boost..great video I have a sbc 408 with a 94mm turbo.

[@richardholdener1727]

that's a big boy

[@bevinsracing]

Hey Richard whats you opening on a 439" BBC all forged dome piston around 12-1..with a vortech v7 ysi with either a c&s 900 methanol carb dual needle seat or a gas 850 single needle. 10psi or so is fine looking for advice has a 714 714 ..262 268 108lsa. Im i creating a 💣

[@deanstevenson6527]

Non Rootes blower, non turbo, any NA cam is a plus. Word, RH! ( The key is that on a turbo or sequential injection turbo, the wrong cam can still cause surging or power bumps. I got told to either reduce boost or Put In a Bigger Cam! Everything in context. In a 1988 publication on SOHC Ford Pinto small bore center 2 liter engines before the later 2.3 liter 1975s Lima, Ive seen a dyno sheet showing a tiny little 255 hp gross at 6500 rpm 121 cubic inch OHC engine loosing 51 hp flywheel with too little cam duration. Moving up from the Stage 2 Ford cam with 286 degrees from degrees at lash to a 322B Crane 300 degree cam with the same V trim Garret T4 turbo in an EOA Ford engine made 306 hp, 51 more hp power without surge, and still with a 2.35 boost ratio. Those wide LSA, reduced exhaust over lap "Myths" are and are just that.. )

[@caseym3118]

It’s using the airflow . Boost is the resistance of flow .

[@GlassTopRX7]

The pressure dropped because the volume has effectively increased with the bigger cam. More of the available flow is going into the engine. It's like taking small gulp of air from a balloon vs a longer bigger gulf. The reason for "boost" cam is to retain the refinement. There is something to be said for how docile the modern factory boosted V8 are until you put your foot into them. Making big power these days is easy, harnessing effectively isn't as easy.

[@matthewdupuis232]

How about both? A little "leakage", a little more air consumption from the healthier engine. Even with less boost, the added overlap improves the scavenging which ensures a high VE, which only adds to the power.

[@darrenrich3492]

The boost is lower cuz the engine/ cam setup isn’t backing up the flow through the intake! But l would Like to see what the NA cam at 114 to 117 las would do!

[@Evildaddy911]

I think that there is also some intake air passing out the exhaust. But that can be a good thing - the point of overlap is to flush leftover exhaust gases, allowing more intake charge into the cylinders by the time the valve closes. More pressure and airflow during that period just increases the effect

[@bartpang]

@@Evildaddy911 The only thing about the intake air passing out the exhaust is shouldn't the low rpm boost pressure be a lot lower with the extra overlap? Darren why would you want such a wide LSA on a 400? A 107 LSA would probably be optimum for this combination.

[@5533851]

Richard, you're a bloody legend mate.

[@DWBmotorsports]

Because boost is a measure of restriction and the NA cam is more efficient boost pressure dropped. Now if you were to change pulley size to match the previous runs boost pressure the difference would have been even greater between the two cams.

[@dilsher12]

An equivalent supercharger cam to the N/A cam would be similar intake duration wider LSA and more exhaust duration . If you put in a cam with more duration over all ofcourse it's going to make more power with or without boost .

[@roknroy1]

the best place to learn how to build power!!!! thanks, rich!!!

[@MikeSmith-px7ec]

Awesome comparison. Before I watched your video I just picked a camshaft that's supposed to be an aggressive N/A on a 110LSA but I had them grind it on a 113LSA. I had the idea that since I wasn't going to run more than 10psi I'd rather have my engine making good power before I add the blower. So I guess that theory holds true after watching your video.

[@richardholdener1727]

it would make more na and boosted power with a 110

[@MikeSmith-px7ec]

@@richardholdener1727 good to know for next time. It seems like the amount of a fraction of a second that the overlap is happening doesn't really have an effect on boost. This cam still has 4 degrees of overlap vs negative overlap that a lot of blower cams have so I think it'll still make good power. I didn't go too crazy with the LSA I only went to 113

[@richardholdener1727]

we have run cams with 37 degrees of overlap with turbos-don't worry about overlap

[@ryanhubble9157]

I would like to see fuel usage... i believe the over lap is making more power due to better cylinder evaluating. Just like the old 2 stroke Detroit diesels

[@donellmuniz590]

A 2 stroke (and a diesel!) engine is a completely different animal.

[@fabricationnation8052]

Thank you so much for the 400 video.....I'll never complain about one of those

[@rickohlson3962]

I believe it’s losing boost threw the lsa but at the same time pushing the heat out and making more hp with cooler air temps .thanks for the share

[@echadmiyodea]

The answer is both. The engine is using more air due to increase in VE, especially at the higher RPM. It was also bleeding out a little more through the exhaust, especially at the lower RPM where there is more time per event, and around the range where the header scavenging is strongest. The primary cause is increased overall VE though. One other small factor is the drag on the crank pulley is a little less with the increased VE. I think, at least in the past, people were picking blower cams in order to keep them mild but get more from the boost. With EFI it used to be more desirable to run milder cams to keep vacuum more steady. Also the lobes were not quite as intense decades ago. A blower cam may also prove a little more beneficial on a vehicle with a full exhaust system, where a tight lope-sep cam may have a little disadvantage with the muffled exhaust.

[@fildavis2024]

Awesome video!! So cool to see real results instead of theories. Thanks for providing all this GREAT information!!

[@199412valve]

I believe the boost drop and extra power came just from the extra 14 degrees of intake duration. I think if both cams were the same other than the LSA boost would have been the same, but the blower cam would have made a little more power up top while the NA cam would have made a little more torque down low.

[@detrickv]

I wish I would’ve seen this earlier before swapping my na cam out

[@benhowe2087]

With the larger cam the cylinders have more time to fill. They flow more air through them. The engine capacity is increased. The supercharger airflow is a constant. Engine capacity goes up. Supercharger airflow remains the same. Supercharger power draw goes down. Power is increased from less power draw, lower charge temp and more dense air charge at the lower boost pressure.

[@uberdriver5711]

Thank you rich for making that happen. I asked and you did it. Awesome video

[@bdugle1]

Great video, proves again that every cam is a boost cam. What about BSFC? Did it change between the two cams? That’s about the only parameter that might go down (up) with boost blowing through the cam’s overlap. If you’re running this combo on the street, you’re not too worried about fuel mileage, but it might indicate efficiency of the combo. And, of course the answer to the question you posed: more efficient pumping due to better cam timing means less resistance through the engine, thus less boost pressure. Thanks for continued awesomeness!

[@ts302]

Great vid Richard! I would be interested to see you hot lap (back to back dyno pulls) a test engine to compare the output power as the engine heats up.

[@claymerritt3116]

Looks to me like the drop in boost pressure is the result of a restriction being removed (a valve closing sooner). The engine is able to use more of the air through more duration. If power had dropped then maybe a case for bleed off could be made.

[@obbyjep7597]

Awsome! Iv always heard this, good test! Keep it up, cant get enuff👍

[@rhandbhf4ever]

Well, that was good to know! I was concerned I'd need a specific kind of cam for my E-force 5.7.

[@davidreed6070]

Overlap makes power, also we need to look at the bsfc.that will tell the story

[@michaelking1869]

I do agree that there is no reason to fear running an NA cam with boost there are some issues with the idea. Sticking to centrifugal stuff... Almost every setup you build will gain a peak of 400-600rpm when you add a centrifugal supercharger. If you had a peak of say 6400rpm NA you'll likely expect a peak of 6800-7000 rpm with that same setup likely giving you a shift point of around 7400rpm or so. Will the owner be ready to run the new setup that high? Anytime you aren't using the entire powerband you have the wrong cam whether you're NA or supercharged. If you aren't using all of the power band you are putting together a setup that has worse drivability, needs a higher stall converter than necessary, and will likely have a higher EGT than a better done setup. Taking a 400 inch motor with say a 242/248 110 cam that peaks at say 6400 and now peaks at 7000 for a shift point around 7400 or so and yet could likely be matched with a camshaft of around a 224/240 117 with a small amount of boost difference to make comparable power. I like keeping the boost numbers down for efficiency and IAT's, but the smaller cam with heavy exhaust split should keep EGT's in a better range helping with timing numbers as well as piston/ring temps. The LSA being a bit higher will help make sure to get the rpm peak still around 6600 or so which overall would put your shift point around say 7000rpm (more likely accepted by the owner). The thought process without putting a name to the cam puts the idea in the ball park of what is sold as a "blower cam". This is my thought on the idea although I do agree that there isn't anything wrong when a naturally aspirated camshaft with boost. What do you think about this thought process? Am I just being too technical or ridiculous?

[@therocketshop]

it was a fun test and i hate to be a naysayer but if the cams were basically the same, just with different LSA it may have been more informative. Is the LSA not mainly the basic difference between a blower and an NA cam ? Possibly a greater spread between intake and exhaust duration as well? Maybe the results would have been the same. Fun test none the less. Good job Richard.

[@MrOgre1110]

Here's what I think, firstly great video Richard your videos are very welcomed. So what I am thinking is that the na cam is losing air straight through. The reason why I think that is the power difference na to boosted, na 31 hp boosted 29 The thing to remember is that the supercharger is turning the same speed, same revs same pulleys so same total air intake, less back pressure/psi suggests the na cam is using more air but making less comparable hp. In summing up, the na cam used more air but didn't show in produced hp.

[@chucksgarage7165]

I would like to see what LSA does under boost and NA. Two cams with the same lift and duration on both cams. One with a “NA” LSA and the other with a “boost” LSA. Then you could see just what LSA does. Of course you’ve probably already done that. Oh yeah and IMHO the decrease in boost is probably a little of both. Probably, more due to the efficiency increase than due to the overlap. But what do I know. GREAT VID!!

[@vengeanceizmine9878]

Apples to apples, changes in LSA only, just moves the power band in a given combination..

[@patlandymore7035]

I would be very interested to see fuel consumption and exhaust temperatures at for example, peak torque for both cams. That would truly tell us which cam was more effective under boost. Awesome test!’

[@Jockebanan99]

Yeah, I was just going to ask the same questions 👍👍

[@richardholdener1727]

peak torque already tells you that

[@dazaspc]

I think the real question between these is. How easy are they to start and How well do they run when not WOT?

[@Racing11gt]

The na cam made more power everywhere so I would imagine it would drive better than the blower cam too. 🤷‍♂️

[@ReubenHorner]

@@Racing11gt I think that is a very false assumption to make

[@thereluctantgearhead4544]

Not a pleasant daily driver in either tune, but lots of fun.

[@thereluctantgearhead4544]

Keep another normal car around for life's bullshit, use the hotrod for entertainment.

[@chipcurrey653]

Maybe starting is an issue with carbs. I've tuned bottom of the page cams in efi LSes and never had starting trouble, but cranking timing and leanout are fully configurable.

[@19jody72]

I'll be damn!! Great info!!! So I can have the pro.stock "sounding" cam and my blower! Definitely air flow dropped the boost...I think.

[@sepg5084]

need a sensor on the exhaust side to check how much unburned fuel is getting leaked out, or to check if it is really leaking out.

[@TheProchargedmopar]

Jody Haha , good call ✅

[@rickybobby0314]

I would say a simple O2 sensor will tell you if you are running fat. Anyway the N/A cam still made more power and if was spitting out unburied fuel you would see it and smell it as well (a little smoky) lol

[@edmcguirk8603]

That certainly makes sense with a centrifugal blower that will automatically flow more air if the engine will accept it. (not as much as a turbo, but still, more) You may be wasting some of the air out the exhaust but the engine is also capturing more air. The added volumetric efficiency is more than the wasted exhaust. Will it still work the same with a positive displacement blower? The boost will go down. The efficiency will go up. But the boosted air volume will remain almost the same. The added efficiency may not be enough to make more HP.

[@gollumthewicked]

Oh no, you're bleeding out all that boost and turning it into POWAAAHHH

[@andyharman3022]

You asked if the lower boost pressure with the NA cam was due to higher airflow or more overlap. My answer is: both. Higher volumetric efficiency NA will lower boost pressure from the supercharger, and more overlap angle*area will bleed off some boost pressure. But you didn't have the required instrumentation on the engine to be able to separate the two phenomena. And the test was muddied by having an NA cam with 14 degrees more duration. It would have been a cleaner test if the NA and Blower cams had the same duration, and a large difference in displacement angle, like 106 to 116.

[@jeffschwartz5199]

Great comparison ! Love the question, it has to be making energy from the boost and it was still climbing in HP when you stopped the pull. 🤔

[@baby-sharkgto4902]

With a centrifugal supercharger the boost increases with rpm so yes the max power is most always at max RPM

[@timothybayliss6680]

I like this test but I don't like how it was done. The "blower cam" thing is usually about 10% more area under the lift curve as compared to a NA cam on the exhaust side. The LSA is usually wider only to keep the overlap triangle similar. This test there is only a relative change of 4° of exhaust cam duration as compared to the intake. The test is also done at less than 7psi, something that is barely considered "blown", there isn't the need to bias the valve timing as there is with the effective port pressures in a dedicated blown application that runs lots more boost. If I was gonna do this test to directly test blower v NA cam I would do a few things differently. BTR makes ls3 stage 3 cams for both NA and centrifugal blower and it looks like they have the same intake lobe. It's the exhaust lobe, lsa and advance that are different. I would also test it on something that has massive boost, like a 4.8 with 706 heads and an F1A blower. You could do a mass air v power test to see the effect of charge short circuit but a wide band can sometimes show it. If you notice one camshaft makes peak power when it's way more lean than the other, you can assume some fresh air charge is going right out the exhaust, even worst case total short circuit rarely gets to 5%, and your comparing two camshafts that have all else being considered, really similar overlap triangles. The difference is going to be like 1 or 2%. You maybe brought up a better point of people picking a cam that doesn't work as good as it could because some put a sticker on it "blower".

[@andrewdynes5300]

Agree 100%; my thoughts exactly. I think he should redo this test

[@kanebfr]

I think to be most accurate the cam specs duration and lift should've been the same. Just different valve timing/lsa. Longer duration = less boost psi

[@kennethwilson6869]

This video is old but oh well. If the boost was bleeding out it wouldn't make more power so best guess is the boost pressure is less because it's flowing better with the bigger cam.

[@dannycarwile1330]

The cam flows better so less resistance for the air flow so boost drops.

[@danieldimitri6133]

Oh the myth of the boost cam. Sometimes that overlap is good and overcomes a restricted exhaust. 90's emmissions cars often had single exhaust with a poor y pipe design and the legal headers of the day weren't exactly long tube with 3" collectors. People confuse the issue of exhaust backpressure. It's not just a parasitic loss. It's also exhaust stuck in the combustion chamber effectively reducing ve and possibly causing detonation. Normally on an ideal performance built the velocity of the exhaust system can keep the flow during the overlap period and evacuate the combination chamber. But on some of those single exhaust catalyst cars even the legal headers and high flow cats were only able to do this for maybe 300hp. But in those days centrifugal superchargers were pretty damn awesome and the rising boost curve could help it exceed the rising exhaust pressure curve. They can even work well with stock manifolds. While many thought blowers need open exhaust they may actually deal with backpressure better than NA because the ve isn't negatively affected. I think the worry about over cammed blown applications is more that the exhaust Temps could run away. Or that the bsfc could go down because. But the boost pressure would still be a good representation of what the cylinder density will be. Like the mass flow might go up more than the boost pressure would indicate but you're not really reducing cylinder pressure any more than you're reducing boost pressure.. The other thing that makes it a myth is the idea that adding 4 or 10 degrees of lsa is going to help the overlap much when you have added 30 or more degrees of duration over stock. Sure maybe a little tweak to the lsa might be a good thing for a setup that helps keep the flow one directional but the idea that the right amount is always 112-118 degrees or that this exclusively related to getting rid of overlap is a little bit silly. But it seems this trend was around even when roots aka "Jimmy" blowers were popular. I can see shorter duration being used on centrifugal setups 1 because the Era that popularized them had to deal with smog laws and 2 because the rising boost curve extends the Rev range so it's easy to get Into a situation where hp is rising but you have to shift to keep from valve damage and you aren't taking advantage of all the power the induction setup has to offer because the rest of your parts aren't matched for that kind of rpm. As far as turbo cams, low overlap might be good for small responsive turbos but for well flowing turbos you might find that you get much better response from a cam that is torque centric. I believe Ken duttweiler (perhaps it was someone else) was talking Buick cams, and yes a Buick is an rpm restricted engine because of the oil system but the ball park numbers he threw out there were like 215 or 218 degrees @0.050 intake duration, 109lsa and I forget exactly what he said about the exhaust but these numbers sound a lot like mild chevy small block cams with that narrow for the street lsa. His explanation was that the turbos he was using were very efficient and maybe didn't suffer from the issues of exhaust pressure that exceeds intake pressure. Sure even with a narrow lsa the cam probably wasn't too heavy on overlap because of the short lobe durations but it was still a departure from the boost cams of the time. As much as I agree that on the Dyno a boosted engine does what it does without boost just more of it. I have to say that there may be a little logic behind the aftermarket targeting certain offerings. 1- just plain marketing. 2- in the world of professional racing you might find certain limits. A race engine that detonates may limit your tuning range, and a less powerful cam that overcomes detonation may allow more boost. Or maybe it's an exhaust temperature limit. It sucks to burn valves. 3- a supercharger may make a milder engine more appealing. Everyone like high end hp untill they drive something that can blow the tires off on the slightest tip in. The high end engine might be fun to go racing on a back road but the mild engine can tickle you're hp obsession driving to work in city traffic with the ac running. So all cams may be blower cams and turbo cams and turbo and supercharger cams work fine NA . But maybe it's less about a number and more about a total package. And sometimes you have to consider the exhaust, the car, the torque converter, the gear, and not just what the cam says on the box.

[@silkysixx]

Longer duration = more air breathed in by the engine = lower restriction to flow and lower intake manifold pressure. For certain.

[@markstopkey4085]

It's a combination of both. Engine using more of the boosted air and some cam overlap bleed

[@postmortemspasm]

My man, when youre mentioning duration you gotta specify whether its at advertised or 0.050"

[@Owens_Racing]

In his level of building. It’s a given it’s numbers at .050” when one speaks of a cams duration. One could say he needs specify if Advertised or not . ;)

[@dsm4959]

Appreciate your videos. It would be nice to see a video with the NA vs Boosted Cam on a Centrifugal Supercharger, like a ProCharger. Also, a video showing the results of a Supercharged Engine with stock exhaust manifolds vs headers(being a more efficient engine). Keep the videos coming!

[@richardholdener1727]

I HAVE CAM TESTS ON CENTRFUGAL BLOWER VIDS UP

[@raycaraway3230]

@richardholdener1727 would this also apply to a Gen3 Hemi? Most in the Hemi world say what works on a Chevy doesn't work on a Hemi.

[@oldschoolbudgetracing1458]

What I was interested to see was which gained the most power from the addition of the blower and it is interesting to see the gains were pretty much the same. The N/A cam gained 149hp and 102tq where the boost cam gained 148hp and 108tq. Virtually the same gains from each. I had heard this about nitrous cams as well many years ago and it is nice to see it playing out with blowers and turbos so naturally you would assume it's the same with nitrous.

[@MrADVANCEDTEK]

I've had many talks about this with friends and racers doing their own builds to no avail. I would say there's really no difference with most setups. I could see the thought of maybe a blower not having enough volume but not turbo's. I can't say I was the "engine guru" of my crowd back then. I never had the money to try everything but I was definitely the wrench for some. I just loved my lope a little rowdy!

[@awhitness]

It isn’t so much leaked boost as it is hotter temps with the overlap. So with the wider lobe separation you can ad more boost. The N/A cam had a 25% increase in power boosted. The boost cam had a 26% increase. Gave a big advantage to the NA cam with 265 duration and only 6psi. But I bet at 12psi that NA cam is going to get hot!

[@raimondhyperburia3855]

What are you saying, na cams made more power

[@markymark6108]

I think the value of running a less radical cam under boost is drivability when not playing.

[@baby-sharkgto4902]

That exact principle applies to any cam

[@HiShBL2]

Great vid , we need more LS blower vs NA cam comparison , the last one hurt some feelings and people are still denying over the forums . Good job Richard .

[@jeremypike9153]

Not all of the boost escapes just a measurable portion.

[@philofab]

I wish I had watched this before I put a LS9 cam in my Caprice.

[@richardholdener1727]

Those R cheap and they make good top end

[@philofab]

@@richardholdener1727 Yea, but I had a big LS3 Texas Speed cam on the shelf I could have put in. I didn't because I plan on putting a LSA on it later.

[@gmstudent93]

Time to sell a "boost cam" and get a tsp!!

[@bartpang]

One thing about that cam that is good i it will soften the lower rpm power because positive displacement blowers make a lot more boost at lower rpms than centrifugal blowers.

[@alexalanis8077]

I hope what guys take away also is that putting the right cam for your application is still ideal. There's that one guy putting a sprint car cam in a Street car with a 3.5:1 gear and low stall automatic adding boost.

[@zmanphx]

An NA motor is still boosted but only at 1 bar. So if run 7lbs of boost the absolute pressure is 1 bar + 7lbs.

[@vengeanceizmine9878]

Exactly! Way too many people over think this without realizing what boost actually is.

[@stephanM5]

This was a great video, very informative and very interesting dispelling the myth of bleeding out boost due to valve overlap from using an NA cam. Question; can you explain what is "LSA" (Lobe Separation Angle) and what impact that figure has on the performance of a cam? Is this the overlap of the valves? Thanks!

[@richardholdener1727]

take a look at the lsa test video

[@bermanss350]

Lsa is the measurement in degrees that the valve events occur in relation to each other, or how close they are are to each other, let's assume a stock cam has an lsa of 116, the valves aren't open together very much going from the exhaust stroke to the intake stroke, now a more performance minded cam with an lsa of say 108, the valves are opened more at the same time between said stroke, the basic object is to get exhaust to scavenge or pull the exhaust from the cylinder while drawing in fuel and air mix, this event is what causes a tighter lsa cam to also what more "lope" along with duration measured at .050", I hate advertised duration its misleading

[@bradmaas6875]

Was anyone following fuel consumption? My thoughts would be with a healthy NA cam, you might find more of the fuel air pushing through the cylinder into the exhaust unburned. O2 sensor might show that also.

[@delamin8r]

We know the NA cam was burning more air and fuel than the blower cam, because the NA cam was making more power. Maybe some of the charge was also escaping out the exhaust during overlap, but even if that was happening, it would still be a fair tradeoff - because more air was ALSO staying in the cylinder for combustion, and that's what matters because that's what turns into horesepower.

[@johnparrish9215]

I see your running a set of the Speedmaster Race I Beam connecting rods, I was just wondering about those. I think I'll order a set for an experiment I have in mind. Thank You.

[@jaydubb71]

The boost dropped for BOTH REASONS. The overlap (lobe separation) and the fact that the motor is using the airflow better. So I will keep my NA cam in my G8 and slap the LSA on. Lol

[@slapnutzracing2152]

Did u monitor the exhaust temps with the different cams. I seen a blower 406 sbc with a n/a cam turn the headers red just a few min of drive time and it was not running rich nor lean. A dedicated forced induction cam fixed that problem. Just saying a few seconds of dyno pulls may not show that problem.

[@PhillipBridges-cr1ns]

If you spin that blower hard and compare the two for max power the blower will higher , i have tried several cams was sponsored by comp and the wider lob separation will help .something that was never mentioned was how was they installed, straight up advanced 4*. Also regardless of how much boost you have 5 spinning the guts out of the blower will eat more power than one making 5 psi at say half the speed will make more power . The amount it takes to turn the blower is not affected by boost , it is mostly affected by blower speed . . Do a test and turning the blower at max speed and swap cams and you will see the NA cam eat the dust . Fact

[@richardholdener1727]

the amount of parasitic loss associated with spinning the blower is absolutely affected by the boost

[@jdcarguy1242]

The VE is self-adjusting. Cool comparo.

[@chasewebber4316]

About to drop a 400 .60 over sbc in my 89 short bed chevy. Gonna be lots of fun Also, more SBC videos.

[@donwalsh7521]

Hello sir I also have a .060 over 400 as well thats a 4.185 bore and head gasket is 4.190 bore is this the same on yours and does it work or need a different gasket.

[@chasewebber4316]

@@donwalsh7521 we used a 4.225 gasket I think. I can check. We blew that motor up. Building another 400 now .020 over. Last one had a bad tune on a 200shot. Just got greedy I suppose.

[@rmdhndwi]

Boost cam sales : not stonks 📉

[@austincrider20]

Man my s10 has a blower cam and a single turbo and it works great. Everybody said it wouldn’t work. Man I wish I would have seen this video back then I wouldn’t have worried so much haha

[@justinwright54]

Love the content man!!