Camshaft Specs. What they Mean

hey folks welcome back I haven't really seen a good video on camshaft specifications so I had a couple of requests I thought I'd do one this is probably going to be a lot of information so you may want to pause the video if you need to and go back and get some of the information the first of all when you buy a camshaft and I've got a got a camshaft here we're going to put in a customer's big-block Ford this is a billet camshaft it's a solid roller for a Ford a pretty typical cam for a high-performance engine but you may have that some time in your past have had somebody rattle off cam specs to you and you had no idea what they were talking about so you just looked at him and kind of smiled and said oh wow sounds awesome but you really didn't fully grasp what the things they were saying meant to you I'm going to break those things down every camshaft comes with specifications a can card if you will and the cam card for this particular camshaft I'm I've got it here and it's got a lot of specs on it so I kind of wanted to walk you through the specifications on this cam and just kind of give you a rundown of what each one of these things mean so the next time somebody rattles off cam specs or the next time you're looking for a cam or if you're looking for a camera now what you should actually be looking for you know one of the reasons that there's not a really one good video that explains everything about camshafts is because it's a huge subject I mean there's so many variables that you need to consider when you purchase a cam or when you look at cam profiles and things and so it's it's actually a huge subject but I'm going to just attempt to give you some basic ideas of what these numbers and specifications actually mean when you're looking at them because I found that a lot of people when you start talking about camshaft specs like this they don't know what you're talking about they really don't understand this a lot of the times people's responses I just want something that sounds cool right well it's possible to put any cam that sounds very cool but it doesn't run worth a darn because it's not matched to your engine so these numbers are actually pretty important if you actually want to make some power ok so first of all we need to define one of the first camshaft specs you're going to run into is you're going to run into a spec called lift okay so lift and I've made some diagrams here so hopefully this will help clear up some of the confusion lift is actually the distance that the valve opens so when the valve is closed the rocker arm your rocker arm is up here so we've got our our roller rocker arm your rocker arm is up here and when the camshaft is on the base circle or in other words you are not on the cam lobe I've got a cam lobe here when your lifter is over here on the base circle of the cam and every cam lobe got to understand is ground on a base circle so when the cam is in the position where the lifter is anywhere on this base circle that means that the valve in the engine is closed it's seated as the lifter rides the profile of this low the lifters going to come up this lobe is rotating and the lifter is going to ride the profile of a low what that does is that's going to push on your push rod so you have a a lifter riding the profile the lobe you have a push rod here the push rod is connected to the rocker arm bone now so the push rod so as we ride the profile of that lobe the push rod is going to push on this rocker arm and this rocker arm turn is going to push that valve over the distance that that valve is pushed open by this rocker arm from the time it leaves the seat till it is fully extended that distance measured in inches or thousands of an inch is your camshafts lift now the lift of the cam can vary greatly depending on what camshaft you pick so so literally what determines lift on your cam is how far off of the base circle this lobe is machined and so the taller the lobe here the more it's going to push the lifter and rocker arm and the more it's going to open that valve so the lift is actually determined by how far the lobe is above or how far this lobe protrudes above the base circle that's what lift is pretty simple to understand you've heard the term high lift cam no doubt well that means that this has a big lobe it's bigger than the normal camshaft or a stock type camshaft it's going to open the valve more now that may or may not be something that you want to have going on in your engine too much lift with the wrong kind of cylinder heads in the wrong kind of induction system is not good the lift of your valve has to actually be mated or paired up if you will with the correct type of cylinder heads so here's what happens so let's say this is an intake valve okay this is actually an exhaust valve but hypothetically let's say it's an intake valve so your valve is closed so normally let's say you just have like a cam that has 450,000 some lift in other words that's how far the valve is going to open 450,000 and you decide you're going to go out and buy a cam well you know I want a big camshaft so you go buy something you find a camshaft has flames on the box and it always got 600 left whoo okay so you put that camshaft in and you discover that your engine actually doesn't make more power it makes less the reason for that is you can't just take a high-performance cam and slap it in a motor now there are camshafts you can put in your engine that will greatly improve its output but it is also possible to go too large so you don't want to just go find the biggest camshaft you can find and stick it in a stock type engine because it's going to hurt your performance and let me explain to you why it's going to hurt your performance it's going to hurt your performance because your cylinder head so say this is an intake valve there's an intake port coming up here and air is rushing in when this valve opens air rushes in past the valve into your cylinder down here well your head or your cylinder head port is only going to flow a certain amount of air depending on your lifter your vowel so at some point what's going to happen is the valve head and the port are going to become saturated or they're going to reach a saturation point now let me explain what that means you guys can rewind this if you need to because I know this is a lot of information but your air is coming in at a certain point in your lift the head is going to lose its ability to put more air in in other words the air flow numbers instead of increasing the amount of air that goes in if I open this too far the air numbers are going to start to revert and you're actually going to be putting less air in because that port is only capable of flowing so much air so if I put a big lift cam in let's say I have a head and it has a 450 lift cam in it from the factory and those heads actually flow their optimum CFM at around 450 thousands of lifts about right there if I put a cam in that's going to push this valve open a lot further and I'm exaggerating there my head port was maxed out at 450 thousand spoken eval two 600 now I'm wasting all of that rocker arm motion I'm using horsepower to compress the spring even further and I'm not getting more air into the cylinder I am exerting horsepower to actuate the valve train but I'm not gaining power because the airflow in the cylinder is actually decreased so hopefully that makes sense so it is possible to put too big of a cam in the motor camshaft selection should always be based on number one the intended purpose of the vehicle and also very important is you need to really understand the flow capability or literally the flow numbers of your head if you have a set of heads you put them on the flow bench and they max out at 450 lifts you don't want to put a 600 lift cam in that motor because you're actually going to make less power you're going to be looey exerting engine horsepower and so hopefully you understand that concept so lift is actually how far the valve is going to open that's that distance above this base circle that's left okay if we look at our cam card here on this camshaft here and this is a pretty big engine it's over 500 cubic inches I have 650 thousandths of lift on my intake valve but again this is a 500 cubic inch engine so I'm filling a big cylinder and it's it's got really big well breathing heads on it so that's that's that would be considered a pretty big camshaft for a street car anyway okay so now the next thing is you may have heard the term lobe separation okay lobe separation angle lobe separation is literally the distance between the centerline of the intake lobe and the centerline of the exhaust lobe how many degrees is between the centerline of the center of mass that's lobe separation now that can be varied okay if I have wider lobe separation let's say I we ground this crank this camshaft to kick crank grounder you know manufacture this crank and grout re grounded on their grinding machine and they made these lobe setters further apart that means that you would have bigger load separation more degrees between the center lines of these two lobes now lobe separation is important because lobe separation affects overlap now overlap is the period of time that the intake valve and the exhaust valve are open at the same time so what happens in your cylinder is you have the piston here and we'll go through the fourth stroke so we go down on the intake stroke as we're going down on the intake stroke what happens is the intake valve opens right and the the piston draws in the intake charge because of negative pressure the next step is the intake valve closes the piston comes up and it compresses that mixture because the valves are closed we have a sealed chamber here compresses the mixture spark plug fires bang that ignition ignites the field of fuel forces the piston back down in the cylinder that's the third stroke then we have the exhaust stroke now on the exhaust stroke the exhaust valve opens and the piston is coming up and it's pushing all the exhaust out well before the exhaust valve closes the exhaust valve will start to close the intake valve over here is going to open and now I have my intake and exhaust valves both open at the same time this the amount or the number of degrees of crankshaft rotation that those two valves are open is called overlap overlap is very important because what it does scavenges the cylinder it helps to pull in air fuel charge in the air fuel charge coming in helps to evacuate exhaust out of the cylinder so the overlap period is actually affected by lobe separation so the overlap period on the cam is going to be right in here where these two lobes are intersecting with each other above the base circle so if I have wider lobes separation in other words I grind these and I put the centre lines further apart that is going to diminish the amount of overlap I have and it's going to change the power band of the engine it will also change how the engine idles wide lobe separation is going to have a tendency to to make a camshaft build more low end torque narrow lobe separation and also wide loops separation will make the engine the idle smooth out as well narrow solar lobe separation if I bring these center lines in real close I'm actually building up this area or putting these Lopes closer together which makes the overlap increase I have more degrees of overlap now because these are closer together what that does is it actually builds more high-end horsepower and it causes some of the low-end torque to drop off and it will also make the engine idle rough it will give you a rough ride so real tight lobe separation one hundred and 204 degrees is usually kind of a rough idling cam if I want to smooth out that idle and get a little more low-end torque I can get a cam that has wider lobe separation 112 114 degrees okay okay so hopefully that makes sense now another very important fact is centerline okay so we talked about how lobe separation is the distance between the centerline of this slope and the centerline of this slope if we draw a line through the center of the lobe all the way down through the center of the cam shaft the number of degrees from the center line around to the center of the cam shaft here that number of degrees right there is called my load center line or in this case it would be intake lobe centerline and over here from the exhaust lobe all the way down here to the center of the base circle that however many degrees that is that is my exhaust lobe centerline now if you figure out your intake globe centerline and your exhaust slope centerline you can use those two numbers to calculate your lobe separation and that's something that's done when you degree the camp I'm going to do another video on cam degree but I want to keep that separate because that's a pretty intense video cam degreeing is not a simple process at least not when you're learning it once you learn it it's like riding a bike and it's simple but in the beginning stages when I teach cam degreeing people are like wow they don't it takes them a while to pick it up so we won't get any category in just yet but here's the thing so if I have if I degree my cam and I discover I have 104 degrees right of intake little centerline and I do the exhaust slope centerline and I discover I have 118 degrees which is those are just hypothetical numbers but there are cancer that's that's in the ballpark what I discover so let's take a look at this so we said that we have a intake loop centerline is 104 degrees that's from the base circle to the center of the lobe and my exhaust lobe centerline from the base circle to the center of the exhaust lobe was 118 degrees I add those two numbers together I add them together I get 222 degrees if I add the intake lobe centerline in the exhaust lobe center line then you take to get your lobe separation you divide 222 by 2 when you cut it in half and we get a lobe separation of 111 degrees that's how you do it so if you know if you get if you degree the cam and you get your intake lobe centerline your exhaust hold center line multiply them together and divide them by two and boom you get your lobe separation okay so let's talk about duration now you've heard we've talked about lift we've talked about lobe separation we've talked about intake and exhaust slope centerline and later we'll talk about why these are important you know some of your thinking out there well you know who cares why does it matter oh it matters a lot because these things all affect how the cam performs in the engine and just exactly what it does okay so great now we had to talk about durations so when you talk about when you say the term duration okay what we mean when we say duration if I said if I asked you hey what's the duration of this video okay let's say this video lasts 15 minutes hypothetically you'd say oh well the duration of that video is 15 minutes in other words it's um it's it's a period of time okay that is exactly what duration is on the cam it is a it is a measurement of time or literally distance but we call it duration it's the amount of time duration is the amount of time that the valve is open so from the time the valve leaves the seat fully extends and then closes again that is duration what transpired during that period of time in other words how much how many degrees did the crankshaft rotate from the time the valve went who opened up all the way and then shut again that is literally the duration of the cam now camshaft degrees for the most part are measured in in crankshaft rotation not camshaft rotation it's important that we understand this I have a I have a timing set here and you'll notice that the gear for the cam is much larger than the gear for the crank it's literally twice as many teeth here and the reason is is because the camshaft turns half the speed of the crankshaft so for every one revolution of this crankshaft the cam only turns one half of a revolution for every two full rotations of the crank the camshaft will turn one revolution so in other words when the cam is ready when the crankshaft rather is running six thousand rpms the camshaft is only turning three thousand rpms the cam chef and that's why how they do they put this big gear on their gear it down so it's important to understand that even though we're talking about the camshaft specifications on our cam card here it's important to understand that most of the camshaft specs that you look at are measured in crankshaft degrees not camshaft degrees remember the Stern's half the speed of the crank that's why when you see somebody degreeing a crankshaft the degree wheel is actually bolted to the crankshaft not the camshaft and the reason we both a degree wheel to the crankshaft and we measure crankshaft degrees is because literally what we're doing is we want to know what this valve does in relationship to where this is so basically cam degreeing as we are fine-tuning or literally adjusting when this valve opens based on where your piston is so you can advance your camshaft which means this valve is going to open sooner that means the piston will be further down the hole when it starts to open if you the camshaft timing that means that this valves going to open later the piston will be up closer to it when the valve starts to open now that makes a big difference in the way that the engine performs obviously and so we can actually tune by advancing the cam slightly which makes the valve open sooner or retarding the cam which makes the valve open later we can actually tune the power band of the engine that way so that's why cam degreeing is so important another reason can be agreeing is so important is because you may have a cam card that looks like this and you go to degree the cam and you find out that the cam chef that's in that box doesn't match this because it's miss boxed I've had that happen to me several times if I hadn't agreed it the engine would not have performed like it was supposed to because they actually had the wrong camshaft in the Box people do make mistakes another thing is I've had camshafts out of the box that didn't match this cam card when I'd agreed the cam and come to find out that the camp I actually was i defective it had some kind of a defect from the manufacturer if you don't degree the cam you're never going to find this out plus you're not going to be able to fine tune your power band unless you you know degree this camp so hopefully all that stuff makes sense now duration duration is literally so remember we're going to bolt our degree wheel to the cam gear here so we have it our cameras up to our cranky or rather we have a degree wheel bolted to the crankshaft so we're checking crankshaft degrees duration is literally how many degrees the crankshaft down here rotates our degree wheel system to the how many degrees did this crankshaft rotate while the valve was open and we check that with a dial indicator obviously so duration of the cam let's say that you have a two hundred and sixty degrees of advertised duration okay and we'll talk about duration at 50 thousandths and advertised duration let's look at our camp card here our cam card here for this cam uh says that we have what we got here we have two hundred and thirty six degrees of duration at 50 thousandths so what that means is we're going to open the cam we're going to we're going to rotate our degree wheel and we're going to bring it up until the valve opens 50 thousandths of an inch so we're going to come off the base circle with our lifter up to 50 thousands once we get up to 50 thousands on here then we're going to start reading our degree wheel so from 50 let's say there was 50,000 s here we're going to go all the way around and open the cam we're going to stop at 50,000 for the valve closes and we're going to look at how many degrees the crankshaft rotate it so literally duration is how many degrees did this crankshaft rotate and crankshaft rotating under how many degrees did this crankshaft rotate while the valve was open from the time it left the seat to the time it closed but we have to have a reference point that's why it says duration at 50 thousandths so what we do is we rotate our wheel we have a dial indicator up here on the cam and the rocker and we rotate the degree wheel until the valve comes off of the seat 50 thousands at 50 thousand right there we look at our degree wheel and we make a mark on it and then we continue to rotate and we rotate till the valve opens and then and when we get to 50 thousands before the valve closes we stop we look at our degree wheel so literally how many degrees did this crankshaft rotate while the valve opened from 50 thousandths all the way open and back to 50,000 for closed that's duration at 50 thousands advertised duration is basically the same thing only we only come off the seat a small amount maybe five thousands maybe six we just barely come off the valve and the manufacturer will tell you how many degrees to come off of the C with your valve I hope this is making sense I know this is complex stuff but it's important to know and you can rewind this if you want and go over this material again duration of the cam is how many degrees does the crankshaft rotate while the valve is open hopefully that makes sense to you okay so we talked about duration we talked about lobe separation we talked about intake lobe centerline and here's another one this is duration at 50 thousandths so literally we're going to rotate this to the valve comes up to 50 right our lifters coming up here or lifter our valve starts open right here our lifters coming around boom we look at our indicator the valves open 50 thousandths and from this point all the way over to this point as we're rotating the engine we're looking at the degree wheel how many degrees does the crankshaft rotate from 50 thousands on the opening side to 50 thousand on the closing side that's all right so hopefully that helps you we're going to do more on this I'm going to probably add to this we're going to have a cam degreeing video we actually degree a cam but you need to watch these camshaft specifications and degree in videos in sequence because they kind of build on each other and if I just did a cam degreeing video right now it wouldn't make sense at all to you I don't I I know that the cam specs and all the degree and everything doesn't make total sense to you now I understand that but at least what you have some idea of you know what these cam specs mean so what you're looking at here is a degree wheel it has we have a pointer and then like we talked about there's a dial indicator set up on the lifter itself this is a shaft that goes down to the lifter we also have a dial indicator on the piston itself to find top dead center on the piston and if you look at the degree wheel here you can see that the degree wheel is actually bolted to the crankshaft so make sure you subscribe below and stay tuned we're going to have more cam degree videos coming up and we'll get into this cam degree stuff soon

Channel: Myvintageiron7512

Views: 332,727

Keywords: Acura, Toyota, Cars, Drag Racing (Sport), Comp Cams, Camshaft, Chevy, Camaro, Race, Drag Race, Muscle, Civic, Cobra, Honda Civic, Corvette, Mile, Buick, Street, Chevrolet (Brand), Mustang, HotRod, Shelby, Drag, Supra, Z28, Burnout, Nitrous, Boost, Dodge, Stock, Burnout Paradise, New, Turbo, Run, Pontiac, Holden, Exhaust, YouTube, Ford, Oldsmobile, Honda, Ls1, Mazda, Vtec

Id: zUnJXSOSRU4

Length: 27min 46sec (1666 seconds)

Published: Mon Dec 23 2013