hey welcome back everybody today I'm gonna do something that I wanted to do for a long time I actually did a video on this subject I don't know four or five years ago but it wasn't as extensive as I wanted it to be and the video quality wasn't really the greatest so I want to redo this and the topic today is gonna be mm-hmm how to select the proper camshaft for your engine so I got on the internet and YouTube and I thought you know there's got to be somebody out there that has you know a video or an explanation of how to select the proper camshaft for your engine and I sifted through a whole bunch of YouTube videos on that topic and to be honest with you there's really nothing out there I mean youyou get there's a lot of videos where the guys are talking about well you know you got three you got stages of camshafts you know if you want a street car you need a mild cam with you know lower duration and lower lift and if you want you know something middle-of-the-road you need a more radical cam but if you're gonna race you need a really big cam and basically they split the camshaft categories up into four or five different categories of cams that you can choose from but the reality is when it comes to your particular engine those videos are really basically useless they don't really tell you you know so for my specific engine my cylinder heads my compression ratio my you know engine that I'm putting in my car what camshaft should I choose what cam should I actually pick for that car now there is some truth to the fact that you have to you have to decide what you want do you want high rpm power are you gonna be you know pounding this thing all the time at the drag strip or whatever or is it a daily driver I get I get a kick out of people to say oh well you know man I got a street strip car no you know I Got News for you there's no such thing as a street strip car it's either a strip car or it's a street car well you know I call a street strip car because I Drive it on the street but I like to take it to the drag strip - okay that's a street car that's not a street strip car that's a street car that you like to take out and drag race once in a while a true strip car is not something that's really very drivable on the street it's not friendly to stop and go driving or driving in traffic or it's just not it's not streetable at least it's if you do try to drive it on the street it's kind of a miserable experience but is it because it's designed basically for drag racing and then of course we have the endurance class of racing like road racing and off-road racing and I understand you know the big the big issue with those valve trains and cams is really durability and longevity and good power at the same time so there are those categories out there but again what about my engine you know I look in the in the catalog for camshafts and there's pages and pages and pages of camshafts for my particular engine and and of course I'm really we're talking about the bigger v8s here that's kind of what we specialize in that's kind of what I work on there are other factors out there when you get into the imports and stuff but we're not going to deal with that we're gonna we're gonna deal with basically you're building a domestic v8 engine with two vowels and push rods and overhead valve engine so there are several things that you need to think about so the first question that we get a lot is hey man what lift cams should I be running in my engine what lift should I get well there is a very specific way to pinpoint the lift of your cam the lift of your cam depends on how well your heads flow okay so let me explain that so the cylinder and has a valve that opens and closes we understand that right we'll put this valve in here right and the valve is gonna lift to a certain point so when I talk about the camshafts lift what I'm talking about is how far does that valve open when that rocker arm pushes that bow down how far does it open different camshaft low profiles have different lips you can get a bigger lift cam that actually opens that valve further or you can get a smaller lift cam that doesn't open a valve as far so there are just a myriad of cams available in different lifts for your specific engine whether it's a small-block Chevy big-block Chevy Ford whatever but how do I know what lift cam I should have well there's a very easy way to know that and what we have to do is we have to look at the head flow in other words how does your cylinder head flow if I put that cylinder head on a flow bench how much air or how many CFM's of air flow through that port at a specific lift point okay so what I've done here is I have put some flow numbers on this on this board behind me now now here's the thing this is basically how we do it we put the cylinder head on the flow bench and I have other videos where we're flowing heads and we're gonna flow air through that port and the flow bench has a flow comp computer and what it does is it tells me how many CFM's or cubic feet of air per minute flow through that pore now we have we can do some simple math and basically calculate the horsepower potential of any cylinder head based on air flow because the bottom line is you guys an engine is nothing but an air pump that's what it does so we're gonna flow the head now these are the flow numbers that we got off of a stock small-block Chevy crate engine this is just a low performance stock type valve Stockport head this is not a good perform it's designed for like a 230 240 horsepower crate Miller okay so we're not talking about you know earth-shattering numbers here but this is a good example of just a stock type head so what we do is we open the valve to a hundred thousandths lift here we just open it slightly to a hundred thousands and we let air flow through there right and we document how much air flow then we open it to 200 then we go 300 then we go to 400 then we go to 500 we open this valve and as we're opening it to these lift points we're measuring how much air is flowing through that port into the engine right so that's pretty easy to understand so now we have to look at these flow numbers because the flow numbers are very revealing as to the characteristics of the head and also as to what lift cam I should have so if we take a look at these numbers we started a hundred thousands we got on the intake we got 56 CFM's okay we go from one to two and we just about double the amount of air going in by moving that valve a hundred thousandths that's good flow increase so that port has really good flow characteristics at that lift point we go to three hundred and instead of doubling we go up about half that much go to from two to three again we have a really good game we gain we almost go 50 CFM's up right so from one to three hundred thousandths this had it has really good flow characteristics really high velocity air we're getting a good increase by moving that valve when we go to four hundred thousandths lift that's where things start to go downhill with this particular head so we go from 158 to 172 that is only about fourteen CFM's increase in flow and I'm pushing the bow of 100,000 here I'm pushing the bomb 100 thousands and I got like 50 CFM game from here to here and here to here from 3 to 4 we gained about 14 ish or so CF outs yeah so what's happening is the further that I open that valve the port starts to get maxed out the amount of air that that port is capable of flowing starts to diminish because it's it's only because of the size and the shape of the port and the amount of air that's able to flow through a given space is going to diminish the further I open the valve we go from 4 to 500 right and we gain about 9 CF ounce not really very much gain now when we go to 5 from 5 to 600 that's where things go south really fast so a cylinder-head port gets to a point in the flow or in the amount of lift range where it becomes what we call saturated with air when a cork becomes saturated that means that it is maxed out it can't no matter how far I continue to open that valve it cannot flow any more air in fact if I continue to open the valve what happens is you'll see the numbers reverse like we have here and the port goes into what we call reversion saturation is when the port is maxed out and if I continue to open the valve my flow numbers are actually going to reverse they're gonna go into reversion and I'm gonna start losing flow well here's the problem with that you guys a lot of times what will happen is somebody will have a set of heads like this and they'll go down you know to the local hotrod shop and they'll see all these cans right and the cams have flames on the box and it says high-performance you know and another thing you hear a lot you know you talk to customers or about hey man what kind of you know what do you what are you thinking about for camshaft and their only response to that is oh I just something I just want something that sounds cool I like that old-school rough idle and then you start talking to them about well you know we kind of need to match the cam to the engine if you want it to perform well no they don't even what you talking about right because there's so much like misconception and disinformation around camshafts right and the whole idea is like well you know I got this big lift cam you know all the bigger little better right well the reality is is that bigger is definitely not better especially if you have a low performance head it's actually going to hurt your performance one of the things that we have to take into consideration is the valve springs now this is just an inner spring from a dual set most of our Springs are bigger than this but you get the idea this is a valve spring so the rocker is actuated that valve spring so I want you to think about this for a second because this is where we really start to think about why lift is important and why the lift needs to match our heads the valve springs exert pressure on the valve train or in other words camshafts don't make their own power they are driven by the crank shaft with a chain or belt or a set of gears or whatever right so the camshaft is driven by the crank the crank shaft has to overcome the resistance that the cam is putting on it so in other words the cam is a parasitic draw it takes horsepower to actuate the cams it also takes horsepower to compress these Springs now if I have a spring pressure right up here in this range about four five hundred lifts of about three hundred pounds per spring which is pretty average for like us a flat tappet cam with like a z28 spring or something the big rollers have much more pressure but the point is let's just say hypothetically I have 300 pounds of pressure on this spring in this area right here right and I go out and I say well you know I bought like a 620 kamme for this motor right so my left is 620 I'm way down here here's the point that you have to get when it comes to lift I need to look at my flow numbers and say gosh where does my head flow the best with this cam right here if this was me I would be putting about a 450 lift cam in this engine and here's why if I use horsepower to actuate the spring right I'm actuated that spring with the horsepower all of the rocker motion from about 450 all the way to 620 here which is where you your new lift is I'm using engine horsepower to actuate those Springs but my airflow is reversing so I have this big parasitic draw on the crank I'm using all this horsepower to actuate these but I'm getting no flow into the head and what happens is when you take a cylinder head that flows like this like a stop type head and you put a big giant big lift cam in it what happens is you actually end up with an engine that's kind of sluggish you will actually lose power so when you when they say Oh bigger is always better that is absolutely not true with camshafts the camshaft lift actually needs to be matched to the flow characteristics of your head now if you have a cylinder head like an aftermarket dart or AFR or something that flows to six 2700 lifts or whatever no problem put that big radical cam in there right and you will have right a lift that matches the flow of your head what's crazy about these heads here this is a stock crate motor head GM puts a cam in this engine from the manufacturer that's about 420 lifts so the lift is about right there right you could probably get away with 500 on this if you really wanted to and you're probably okay but even at that you're going from 400 to 500 and you're only game you're gaining you known eight or nine CFM's so you're actuated all of the force on that spring if you multiply let's say you have three hundred pounds of spring pressure and you have 16 Springs if you multiply 300 times 16 that ends up being a lot of spring pressure let's just do it 300 times 16 you got 4,800 pounds of pressure resisting the rotation of that crank between all of those Springs and you actually have more than that because we know that we know what rocker arm ratio is right so let's say you have a 1.5 rocker ratio on top of there right the rocker ratio multiplies the lifts of the cam okay we understand that if you don't ask me below and we'll talk about rocker ratio but here's the thing the rocker arm ratio is an offset from Chevrolet has a 1.5 ratio and the ratio of that rocker not only multiplies the lift of the cam at the valve but it also multiplies the spring pressure on the cam lobe so if we have a 1.5 ratio here which is a stock ratio if I have 4,800 pounds of pressure between all of those Springs being exerted on the cam it's actually 4,800 pounds at the valve spring because of the rocker ratio it's multiplied by 1 point 5 so it's 4,800 times 1.5 actually have 7,200 pounds of resistance on that cam if I have a Springs that are exerting around 300 pounds of pressure here that's 7000 pounds of pressure that your crankshaft has to overcome or that it is being put on the crank which is taking engine horsepower and I'm coming up here and I'm getting no airflow into the engine my airflow has diminished but my pressure that is being exerted on the crank is increasing because of my lift and my valve spring tension so for optimal power when it comes to lift you have to know what the flow of your heads is you have to know where they flow now if you want to run a bigger cam and you want it to the lift to be optimal you need better heads that's all there is to it you just need to get a better flowing head that flows up here stock type heads don't do well with big camshafts they just don't run good because of this issue so lift hopefully you get this lift is dependent on your heads if you call Comp Cams tech line and you say hey what lift cam should I run one of the first I got to hand it to those guys at Comp Cams the first question I'm going to ask you is what heads are you running and what are the flow numbers I've had them ask me to I call them out of curiosity and they asked me that unfortunately they haven't put out a good video that tells anybody about this ok so I don't know why is this all big secret you know it shouldn't be so you should be able to you know the average guy out there this building this motor you shouldn't be able to get online look at camshafts understanding your flow numbers and kind of figure out in the ballpark where your lift should be okay so that's lift in a nutshell that's really the factor is flow now the next duration neurons are the next spec that we always look at is duration now duration is a different spec and the determining factor in duration is going to be what RPM range do you want to make your power in now there's a lot of factors that go along with this with a big duration cam the bigger the duration now now let's define what duration is duration is so if I say hey what's the duration of this video today you know it'd be like you know 30 minutes so duration is a period of time duration is how long the valve stays open from the time it opens leaves the seat fully extends and encloses again during that event from open to closed how much time transpire now we can't use time on the clock like seconds or minutes or milliseconds because the engine runs into varying rpm so we have to use something that's going to be constant so what we use to time the duration is we use crankshaft degrees so in other words duration is this you guys how many degrees did my crankshaft rotate while the valve was open from this point opening to closing how many degrees went by how many degrees is the crankshaft turned now the more degrees the crankshaft turns the bigger you duration obviously so the bigger the low profile it's gonna open the valve sooner it's gonna hold it open longer and it's going to open it later big durations cam cams will do that now the bigger your duration or the longer the valve stays open the bigger effect it has on our p.m. range or power output so big duration cams as a general rule are gonna move the power band up slightly so what you'll see in the book is you'll see you'll see durations around 250 260 first cam that that that means and this is advertised duration we also have actual duration which is actually a better judge of power up but we're just gonna for intents and purposes I'm going to use the big advertised numbers right this is what the cam manufacturer says this is our advertised duration and they like it because it's a bigger number so with an advertiser ranging around 250 or 260 that's pretty much a stock cam that's gonna have and and what they'll tell you is this camshaft has an RPM operating range with this duration of 1500 to 5500 right and they'll say it as a smooth idle it's for a good low end torque right so from 1500 up it's got real good power all the way through that range but when you get to 5055 it's done you're not gonna make any power above that then we bump up and add it the book will say well this camshaft has a duration of you know to 72 to 80 somewhere in there advertised duration and it'll say this has an RPM operating range from about you know 2300 up to 6500 and again these are these are hypothetical numbers but they're pretty close to what you'll see then you get into the real radical kamsa and also where it says idle it'll say fair right it has a little bit of a low be idle but it's you know still streetable then you get up into 290 300 durations somewhere in there advertiser ratio and it'll say this has an operating range from 3500 to 8500 right and it has a very rough idle so and there's a bunch of cams in between all those but those are just three like averages or extremes well you have to figure out what operating rpm operating range you want your engine to be in now there's a couple of factors that you got to think about number one do you want to be running around town you know at 7,000 rpms everywhere you go you know maybe you do I don't know maybe that's what you're building but for the most part on the street most your power is gonna be in the mid to low rpm range you know if you build in the race car then that changes everything so the duration really just depends on what RPM range you plan on making your power in now when you get into big duration cams there's a lot of stuff that you have to consider number one if you have an automatic transmission you have to put a higher stall speed converter in in fact they'll even tell you in the cam book you know you get to a certain level and they say this is the biggest cam you can run with a stock converter and then they go to the next cam up with bigger durations say you have to have a high stall speed converter because what happens with a stock tight torque converter and automatic if you get the duration too big you get that rough idle when you get to two to the stoplight in traffic the car will start to surge right so you'll come up on the converter and the car you'll see the car I'll just be hood they'll be surging you know if a card is surging at a stoplight your cam is too big for the stall speed of your converter you need to step up to a bigger converter so there's a lot of stuff to consider when it comes to duration but but really what now you may say oh man I want to turn 8,000 rpms so the big question is is your engine capable of turning 8,000 rpms right and so we have something called piston speed right we calculate how fast the piston is moving now here's the thing the longer the stroke of the crank the faster the piston speed is going to be at a given rpm if you have a big cubic inch motor with a big long stroke you're actually limited on how much RPMs you can turn and be safe right because the piston comes up to TDC it stops changes direction goes down at BDC in US and it stops and changes direct so it's reciprocating it's going back and forth well the longer the stroke if I have a three inch stroke like in a 302 that's gonna be a much slower spittin speed at 8,000 rpms than a four and a half inch stroke like a big-block stroker so you have to understand the longer the stroke of the engine the faster the piston speeds gonna be now at a certain piston speed if I exceed a certain speed right the Pistons gonna go to bottom dead center where it's supposed to top stop and change directions it's not gonna stop it's gonna keep going right out through your bow so you have to consider you know the stroke of your engine we have to consider piston speed there's actually a really simple formula for figuring this out and I'm gonna give it to you because I want to put the power in your hands I want you guys to be able to build something and make educated guesses right as to what camshafts you you should have and if you if you do this right you should be able to get this pretty close okay so here's the formula guys for piston speed it's really simple it's stroke the stroke of your piston whatever that is multiplied by the RPM you want to run whatever our RPM you want to target rpm you pick that right and we're going to do a couple here and then we divide that by six and that gives us piston speed or the average piston speed and feet per minute now the piston doesn't travel the same speed all the way up and down the bore it depends on the rod ratio the length of the stroke the length of the rod longer rods and shorter rods will change where that piston accelerates and slows down in the bore there's a whole other issue with with rod length and rod ratio and you know a lot of guys used to make a big deal about the length of the rod you know long rods are the best you know well I like long connecting rods mainly because it's easier on the piston you don't have as much angularity and you got less sight loading but the reality is when it comes to power output we've done a lot of tests with long rods and short rod motors and honestly the dyno results there's really not a lot of difference we don't see much difference there's guys that swear by long rods and say they make the engine makes way more torque and stuff the reality is on the dyno we haven't seen that that hasn't actually played out in in our experience I like the longer rods because they're easier on the pistons and the rod bearings but as far as power output goes your rod ratio yeah it's the difference is nominal it doesn't really matter that much so the stroke of the engine though and the RPM has a ton effect on piston speed so let's do a couple years so let's say we have like a 302 Ford like I said earlier it has a three inch stroke my target horsepower it's like hey man I want to turn eight thousand rpms okay so I take my stroke and I multiply it by the RPM that I want eight thousand that gives me 24,000 if I divide that by six it's gonna give me my piston speed and feet per minute how many feet per minute is that piston traveling now with a modified engine a street rod type motor the general rule is you can go to about 4,500 feet per minute and be really safe I back that off because I want my engines to be safe I don't want to blow nothing up I want to be and I want longevity I want this thing to live for a long time so I say the maximum that I want to see with anything I'm building is I want my rpm range to be around 4,000 feet per minute right that's really safe even for like a stock type engine so if we look at the 302 we get at 8,000 rpms my piston speed is 4,000 feet per minute which is really safe so suffice it to say you can put a duration a cam that runs to 8,000 rpms in a mildly built 302 or 3 inch stroke motor and be really safe at that rpm if the things a screamer 327 s were the same way 327 Chevy was a screamers because the piston speed wasn't crazy high because of the short stroke now let's go to the other extreme let's do like a big 500 Plus cubic inch stroker that has a four and a half inch stroke okay let's do a big stroker we want to twist that to 8,000 so four and a half inch stroke times 8,000 rpms is 36,000 divided by six that's 6,000 feet per minute Wow okay so there are engines that turn 6,000 feet per minute but we're talking about really high-end super tricked-out motors and they usually have a pretty short life this is like a high-end race motor that gets rebuilt a lot torn down a lot for a street car or street rod or something you're building it you want to live you don't want to go to 6,000 feet per minute trust me so if you have this big stroker and you go out and you buy a camshaft that has you know 290 300 duration or whatever and it's oh yeah the RPM are greater ranges from 35 to 8000 well that's not really there smart to do that because if you're twisting this thing up to 8,000 most likely that thing's gonna have a real short life right yes it'll do it but you are compromising the integrity of that engine by singing those Pistons that fast that's going to shorten the life of the Pistons so these are things that you have to consider so when I'm picking a duration for a cam I want a camshaft that is gonna put me around the 4,000 feet per minute I want my camshaft duration to max out I want my max rpm so in this case I don't want to turn this motor to 6,000 I'd probably turn it like 258 I want a camshaft that's gonna max out around 6,000 rpms because above that I'm just gonna rip my motor to shreds again if you build a hardcore all-out race motor you can do it buddy but if you want longevity I wouldn't go there so the duration really is a factor in what RPM range you want your engine to run in and you really need to think about piston speed okay so hopefully I'm access so we've covered lift and we've covered duration now there's a couple other things that you have to consider with the camshaft one of them is lobe separation now you'll see that on the kit on a canvas shows LSA or lobe separation angle lobe separation angle is not as big of a factor as it would be as lift and duration but it is a thing here's what it is lobe separation you have your cam shaft here it's the number of degrees between the centerline of the intake lobe and the centerline of the exhaust lobe so this number of degrees here is your lobe separation tighter lobe separation is going to increase overlap move your rpm range up higher into the RPM range and it's going to make your idle rougher right wider lobe separation the lobes are going to separate right in here and it's going to diminish the overlap smooth out the idle and lower powerband slightly one of the one of the recommendations are one of the issues with lobe separation is when we get into computer controlled cars like obd ii stuff that s fuel injection and computer control when you see computer control cams what you'll notice is let's say i want a to eighty duration cam right i want to cam that has 280 duration because that fits my my RPM range needs but i have a computer an obd2 computer and the problem with that is when I get into a 280 duration cam with tighter lobe separation right like most street rod or hot rod cams that kind of have that rough idle what's going to happen is your obd ii computer is going to go uh uh boom check engine the computer is gonna go i don't know what's wrong but the NOC sensors are going nuts misfire misfire misfire so it's going to tell you you got a misfire because it's going to interpret that rough idle as a knock this is a problem that sometimes is very difficult to tune out so what they do with computer controlled cans they cheat a little bit I have a two eighty duration cam but if I take the lobe separation and I widen that out that diminishes where these two cams these lobes intersect and it diminishes the overlap so I could literally have a two eighty duration cam with say a hundred and fourteen degrees of lobe separation and it's going to smooth out the idle if that was around 106 or 104 lobe separation right like you can buy it's gonna have a very rough idle so when it comes to manipulating the the idle quality we can kind of play with that with lobe separation and that really comes into play when we talk about like LS motors with obd2 computers and stuff so so that that is also a big deal so hopefully this helps you this hopefully this will give you some direction because you know there there's just nothing out there okay guys so stay with me here this this is gonna get a little bit involved here and that's why I have my calculator so let's go back to these flow numbers again and we need to talk about the different types of camshafts so you'll see what they call single profile and dual profile cams a single profile cam is defined as a camshaft that has exactly the same lift and duration on the intake lobe as it does on the exhaust lobe they both have you know 520 lifts and they both have you know 282 duration the intake and exhaust are identical then we have dual profile cams dual profile cams our cam shafts that have a different intake and exhaust profile the intake has a different lift than the exhaust on the same cylinder and the exhaust has a the intake has a different duration right they have their they're not the same so how do I pick single or dual profile this is another issue that we have to look at the flow numbers and we also have to look not only at the flow of the intake but we have to look at the exhaust we have something called percentage of flow so I put a couple of heads up here that we've actually float on the bench and these are the max flow numbers the first tab is a stock Chevrolet head it's actually a Vortech right which is they're they're pretty decent right there okay the second one is the 427 big-block Chevy heads that I put on my s10 427 okay so the first example we have here is we have a a maximum intake lift of 197 CFM or flow I should say have 500 lifts and we have at 500 lifts we have 128 CFM's of flow on the exhaust okay this is typical of a stock more tech head now in order to get the percentage of flow now this let me say this when it comes to dual or single profile cams we have two what's the determining factor whether or not I buy a buy a dual or a single profile is actually the percentage of or in other words percent of flow is this what percentage of my in tank flow is my exhaust flowing now if we do the math on this so what we're going to do is we're going to take and we're going to divide 197 into 128 or we're dividing backwards from what we normally do we're going to divide the larger number into the smaller because we want a percentage well if we divide 197 into 128 or in taken or exhaust flow we get 64 percent of flow 64 percent of flow is not very good that's very typical of a stock type engine some of the small block forward hands were around 55 percent of flow okay so 64 percent of flow now here's the general rule if your head flows less than 75 percent of flow right 75 percent is the number we're looking for you need to get a dual profile cam and generally what we're gonna have is we're gonna have an exhaust lobe that has a little bigger lift and duration an exhaust lobe that has a bigger lift and duration is slightly is going to help compensate for that poor flowing exhaust port that that's the idea behind it so with this head here I would definitely want a dual profile cam I would want a camshaft it has a little bigger lift and duration on the exhaust and when you see the numbers in the book you'll see yeah you know what do I guess single profile do I want both intake and exhaust the same if it's below 64 percent of flow then no most stock heads most mild cams in fact if you look at look at a lot of the stock cams that come in the OEM engines they're almost always dual profile and they will beef up that exhaust spec a little bit to help that crappie poor flowing exhaust port especially if it's a small block forward garbage okay so now let's look at the big-block ported monster heads that are on this 427 they are flowing 338 CFM's on the intake and 307 CFM's the exhaust if we do the division there we get 91% of flow that's above 75% of flow so we would definitely want a single profile cam which is exactly what we put in there right and the camshaft that's in that engine has 650 ish lifts you see where it flows to 680 yeah well from 650 to 680 it only went up about 10 CF pounds so we're comfortable with that 650 lift cam and that thing now the other thing is let's say you want to I want a bigger cam you know I want more horsepower I want something better right there is a way to figure out how much horsepower you can get potentially from these heads let's say I have these heads and they have a percent of flows not very good I'm not very happy with the horsepower that these are putting out I want a better set of heads I have a target horsepower number and I want to hit that okay there's a real simple way to do that if you have the flow numbers which we do here SuperFlow has been really good about giving us the correct math equations so that we can figure out what the horsepower potential of the head is and we know that this math works because we do this math after we flow the head we put the heads on the engine and we take it out to the dyno and the dyno numbers are within five or six horsepower almost every time so this stuff works I'm telling you okay so what I do is I take my intake CFM now let's say we've we flowed the heads at 28 inches right now 28 inches is a flow rate that we set the bench for the bench can be set for so we have on the old analog benches we have a tube on the side of it and we turn the bench on and it will pull liquid up that tube based on how fast the the motor speed and the bench is if we turn the motor speed up it pulls liquid higher up the tube if we turn the motor speed down and pulls less liquid so the standard for the industry is we flow stuff I have lease for street rod hot rod you know non professional type drag racing stuff we flow it at 28 inches in other words when we flipped that bench on it's going to pull it with 28 inches up that too that's how fast the motor speed is 28 inches is the industry standard and the reason we use 28 inches across the board is because when I flow heads on the bench here I want to be able to compare them to a set of heads I'm looking out on the Internet where the flow numbers are posted and they will almost always say float at 28 inches that way we can compare apples to apples so we know from super flow that a head that's float at 28 inches which is the standard that's how fast my speed is that cylinder head is going to be able to produce potentially 0.26 horsepower per CFM okay so intake CFM times 0.26 horsepower it gives us what we call our total potential horsepower that's the total potential horsepower that's a number that these heads are capable of making so it's really simple if I take 197 and I multiply it by 0.26 let's see what we get here one nine seven times point two six is 51 point two two horsepower we'll just say 51 horsepower well you say well 51 horsepower that's not very good remember guys that's one cylinder right so we got 51 horsepower per cylinder and we're gonna say times 8 it's a v8 409 horsepower so these heads are capable right times a of 409 horsepower now there's more to the equation let me tell you something those heads right there with those flow numbers wouldn't make 409 horsepower if you strapped a rocket to them and drop them off a cliff right there's something missing from that that's not the final number that we're gonna get what we have to do is we have to look at the percentage of flow you guys because everything that goes into that cylinder has to come out while we're only flowing sixty-four percent of our intake here so what we do is we take our 409 and we simply multiply it we say times 64 % point 6 4 in my case I have a percentage so I say 64% equals two hundred and sixty two horsepower okay what's crazy is the 350 with the Vortech heads if you put a good camshaft and a set of flattop Pistons in it you end up with about 260 horsepower doing you you can you can really beat them up you can you can put bigger valves in you can you can do a lot of work to those heads and make them much more than that but that's that's a good baseline that's really what they're capable over that flow and another thing we're gonna increase the flow here a lot right so when we modify these heads we put bigger valves in them we do a little porting on the exhaust we might get that up to 80% and that's gonna make this number way over 325 330 horsepower and for tech half so we do it all the time but in stock form ya die right so now let's look at a real set of heads so if we take our 338 note now keep in mind my goal with this s10 motor this 427 with these heads was 500 horsepower at the wheels that's what I wanted right that was my target horsepower number so if we take 338 times point two six right that's our intake flow so three three eight times point two six equals eighty seven point eight or eighty eight horsepower okay so we're gonna say we have 88 horsepower per cylinder times a eighty eight times eight 703 horsepower but again we got our work our percentage of flow now we have a high percentage of flow here so if we take our total potential horsepower which is 703 703 times 91 percent times 91% we get 639 horsepower that's our realistic horsepower these heads olmec 639 right 6:39 at the crankshaft we're gonna lose about 20% in the drivetrain so if we take 639 and we multiply it by 20% 639 that's 127 horsepower now we're gonna lose so 639 minus 127 512 horsepower there's what I realistically would get the wheels my goal was 500 now this wasn't an accident it's not like I said well guy won 500 the wheels I'm just gonna grab all these parts and throw them together and see if it works we ran all the numbers we knew what we needed as far as head flow and camshaft selection and all that to go together to make this horsepower so the thing is if you want to target horsepower number right it's the bottom line you guys it's all based on head flow it really is the camshaft selection it depends on on what head you have it also depends on the RPM range of the engine and so forth but these are really basic fundamental things that you need to know when you're looking for a camshaft it's not it's not just you know I want the most radical cam I can get because I like the cool sound yeah well I mean I'm not against a cool radical sounding cam I like the way they sound too but the reality is is that may not be the best choice for what you're doing so hopefully this makes sense I've I've I've just been you know really perplexed lately I've had a lot of people they they get on social media and they say hey man I got XYZ motor what cam should I run well and then you say well you know what heads are you run and what's the flow numbers they have no idea right asking somebody what cam you should put in your motor based on the fact that you have a 350 or a 400 or whatever that's like going to the doctor and say hey doc I got a pain here what's wrong right tell them come on come on what what's wrong with me you know well he's gonna say well you know you're got a pulled muscle or cancer I'm not sure right so you know what's he have to do to tell you what's wrong with you he's got to do a bunch of investigation right he's gotta do what Jess he's gonna examine blob all he's got all these tests you know and at the end of the day he's like yeah you got a pulled muscle or whatever here's some here's some muscle relaxers you know so you know there's some vet it's the same thing with an engine and and the thing is the thing that makes this so so right difficult is every engine is different right depending on the compression ratio the size of the engine the cylinder head design the you know the vehicle that it's in there's all kinds of issues that go along with this that you have to consider so hopefully this makes sense if you have any questions I hope I didn't make you even more confused than you were before you watch this video but these are really some basic things that you have to kind of put into practice if you're gonna pick a camshaft that actually works so I appreciate you watching please support this channel subscribe like and if you have any questions make sure you ask them below and I will talk to you very soon I promise I got a bunch more videos coming up got a Pontiac stroker got an ls1 coming yes finally so thanks for watching and stay tuned I will see you soon
How to select a cam-
Step 1: have flow bench
Well fuck.
Great info though, I enjoyed the video.
This guy is pretty awesome. I am building a 383 stroker using his videos as a guide. Talk about a wealth of knowledge. He definitely hasn’t heard of K.I.S.S., but that is probably a good thing when building race motors.
This is a great video. I feel like I took a class. I guess I kind of did.
Probably the best video on explaining camshafts - I build engines as a hobby and worked for years in a shop doing the same -- this guy explains it better than I ever could and seems to hit all the points.