Don't understand cams

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I didn't see anything in this whole thread that I would say was wrong or off the mark, just different ways of looking at the same things, ...and/or different intentions in terms of outcomes. Thanks to all for the advice and information offered guys! (and, uh, I might add I noticed maybe just a bit of, shall we say, ...different personality styles) :)
 
If post get away from what the OP asked I generally blame that on the OP'er it's their thread they need to keep adding input and direct the conversation.

Problem is to many ask vague questions and then sit back and don't contribute.
Of course it will go on a tangent but I think that's good cause I think as things are discussed even if not directly related adds to our understanding.

I generally like to give people information so they can make there own informed decisions.

As for the Yellow Rose vs Frosty debated I side with Yellow Rose he could be a little more diplomatic at times but I find him informative and offen see things the same way.

I feel engines builders looking for maximum performance would look at valve events and overlap and let that dedicated lsa and duration.

But for us average enthusiasts I look at cams overlap lsa lift and duration in that order.

I do disagree with Yellow Rose in one way is for the average guy you kind of build your combo around a vague idea of what cam your gonna run mainly cause of how people gear their combo and seem to pick cr at random.

Too many on here ask for a cam recommendation on a mismatched combo in hopes that it will pull it altogether. eg 318 with stock heads 12.5:1 stock stall 3.23:1 gears and want to run on pump gas. So you need to a big cam cause of pumping gas and CR but a smaller cam cause of engine size heads gear and stall.
 
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273 you are correct, in that I start thinking about what I need as far as HP to achieve the goal. If I need 450 HP in a 3400 pound car to get, say, 11.50's then I have a starting place. Then I look at displacement. Am I going to do it on a 3.313 stroke, or 4.000 stoke? How much bore do I have to work with? The bigga the bedda I always say. Sooooo, if I can get a 4.125 bore, I can take some stroke out, make the rod a bit longer, spin it a bit higher, gear it a bit lower etc.

Once I get that sorted out in my head, I decide how much RPM I need, and can I get enough port to feed the displacement I have and the RPM I need, without a cam that need 300* at .050 and that will at least will idle at 1800 RPM or lower (I threw that in there for the 500 RPM idle in park guys with a shift speed of 7500 RPM lol). Then I start looking at compression ratio. What fuel. Then it's works on the heads and flow them to see if I'm even close to what I think I need. All the time everything except the hard parts are in flux. Things like induction, actual cam timing, final CR and such. Once the valve job is sorted out, and the ports produce enough GOOD air to make power, then I finalize all the other stuff.

It makes sense in my head.

It would be interesting to see how others think their way through a build.
 
273 said:
If post get away from what the OP asked I generally blame that on the OP'er it's their thread they need to keep adding input and direct the conversation.

Problem is to many ask vague questions and then sit back and don't contribute.
Of course it will go on a tangent but I think that's good cause I think as things are discussed even if not directly related adds to our understanding.

I generally like to give people information so they can make there own informed decisions.

As for the Yellow Rose vs Frosty debated I side with Yellow Rose he could be a little more diplomatic at times but I find him informative and offen see things the same way.

I feel engines builders looking for maximum performance would look at valve events and overlap and let that dedicated lsa and duration.

But for us average enthusiasts I look at cams overlap lsa lift and duration in that order.

I do disagree with Yellow Rose in one way is for the average guy you kind of build your combo around a vague idea of what cam your gonna run mainly cause of how people gear their combo and seem to pick cr at random.

Too many on here ask for a cam recommendation on a mismatched combo in hopes that it will pull it altogether. eg 318 with stock heads 12.5:1 stock stall 3.23:1 gears and want to run on pump gas. So you need to a big cam cause of pumping gas and CR but a smaller cam cause of engine size heads gear and stall.
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Please don't make assumptions. As far as I'm concerned, my question wasn't vague at all. I have nothing to contribute, because I'm more lost now then when I asked for the advice in the first place. Because I know nothing about cams I asked a simple question. Would the cam that I have work in a stock engine, Hell I, even posted a picture of the specs. if not what should I look for that either stock or close to it. But like most threads here, things started going south real fast. I do thank those of you that took the time to steer me in the direction, that I wanted to go. For the rest of you, keep the pissing match up, I'm not learning anything but it's good entertainment just the same. But don't expect me to contribute to something that I know nothing about.
 
norton said:
Please don't make assumptions. As far as I'm concerned, my question wasn't vague at all. I have nothing to contribute, because I'm more lost now then when I asked for the advice in the first place. Because I know nothing about cams I asked a simple question. Would the cam that I have work in a stock engine, Hell I, even posted a picture of the specs. if not what should I look for that either stock or close to it. But like most threads here, things started going south real fast. I do thank those of you that took the time to steer me in the direction, that I wanted to go. For the rest of you, keep the pissing match up, I'm not learning anything but it's good entertainment just the same. But don't expect me to contribute to something that I know nothing about.
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That's not exactly true. Somewhere in the thread several people, myself included, said that cam would NOT work with what you have and want. That's not a stock compression ratio, stock rocker, stock converter, stock gear type of cam.

The short answer was nope, don't use it. Then the long answers filled in the gaps.



Since about 1988 I stopped picking my own cams. When I call a cam grinder, I have a pretty damn good idea of what I want, and they have to work hard to convince me hard to do it different. I'm still not a fan of big exhaust timing splits and wide LSA's to cover them up. Unless you KNOW you NEED all that exhaust duration. It's things like that I question, and th cam grinder needs to explain to me in terms I understand, why he is right. If we can't agree, I call someone else. If all the cam guys agree, I have to stop and consider my thinking and math.


That's why I say a relationship with a cam grinder is the BEST thing an engine builder can do. A regular, consistent relationship with flow bench numbers and dyno numbers going back and forth will always result in more power, better driveablity and less hassles.

For someone like the OP, you need to WRITE DOWN all your specs and have them in hand and get on the phone. Talk to the cam grinder. Take notes. Get as much info as you can, including the @.200 duration numbers of the lobes. Ask questions. Call 6-7-8 different companies and look at their numbers. Look for patterns. Look for the one oddball. Figure out why the oddball wants what he wants. It's all a process and it's all about the combination. You can't learn this stuff in a day or a week or a year. Most of us have been doing this **** for DECADES and we don't agree on things. You have to work with someone you get along with. Learn all you can about fluids. Learn all you can about heat and what it does. It's a lifetime process.

If your not willing to put that much skin in the game, you can buy a shelf cam. Or, you can self educate. Learn by doing and try to pass it on to help shorten someone else's learning curve.

So no, don't use that cam. Search the thread for custom cam grinders. Don't fib about what you have. In the mean time, keep learning. Develop a broad, wide, deep knowledge of internal combustion engines. Even if it's just a hobby. You can't have too much knowledge.
 
Didn't mean you in particular just in general.
But it is up to you to steer us in the right direction or we'll just go on and on lol

When it comes to cams the further away you go from stock you the more you got change and not just with the engine but also drive line.

That cam you picked would need deep gears high stall. Engine would need better valve train exhaust and CR and to make the most of it also the heads intake and carb.

Something at 220-230 and around .480 lift
Would be better depends on the rest of your combo.

As for cam specs it's kind of a black art there no hard and fast rules you can go by.
The easiest thing is to look at what cam manufacturer recommend for mods for the cam and don't go bigger than the mods your willing to do like cr intake gears stall heads headers etc...

The most important aspects of a cam we mostly don't discuss like the intake and exhaust opening and closing points and overlap. But basically you need the lift to be high enough to take advantage of all the port has to offer and generally lift gives you power with less side effects like duration would. But going way over what a port has to offer gives you little to nothing more. Depending on heads for average guy build something in the .450-.550 range. As for duration you have so little time to fill the cylinders even at a low peak rpm of 5000 rpm the cylinders would need to be filled 20 times a second not very much time. For a street car you spend 90% of your time under 3000 rpm so you don't want cams that mess too much with that. Look at the cams recommend powerband not that it's dead on either side but the further your goes outside the powerband (sweet spot) the less happy you'll be with its performance and the powerband is based on that average engine in the family so for LA it would be 360 so you build something smaller the powerband will be at higher rpm and larger will be lower. So 215-235 @ 0.050.
As for lsa you don't have many choices for off the shelf cams so it becomes somewhat irrelevant.
 
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I didn't pick this cam, it was offered to me and I told the guy that I needed to come here and see if it would work for me in my stock engine. He insisted that it was what I needed and I told him the same thing that I said here. I know nothing about cams. Thanks to the information that I got here, I didn't purchase it.
 
273 said:
Didn't mean you in particular just in general.
But it is up to you to steer us in the right direction or we'll just go on and on lol

When it comes to cams the further away you go from stock you the more you got change and not just with the engine but also drive line.

That cam you picked would need deep gears high stall. Engine would need better valve train exhaust and CR and to make the most of it also the heads intake and carb.

Something at 220-230 and around .480 lift
Would be better depends on the rest of your combo.

As for cam specs it's kind of a black art there no hard and fast rules you can go by.
The easiest thing is to look at what cam manufacturer recommend for mods for the cam and don't go bigger than the mods your willing to do like cr intake gears stall heads headers etc...

The most important aspects of a cam we mostly don't discuss like the intake and exhaust opening and closing points and overlap. But basically you need the lift to be high enough to take advantage of all the port has to offer and generally lift gives you power with less side effects like duration would. But going way over what a port has to offer gives you little to nothing more. Depending on heads for average guy build something in the .450-.550 range. As for duration you have so little time to fill the cylinders even at a low peak rpm of 5000 rpm the cylinders would need to be filled 20 times a second not very much time. For a street car you spend 90% of your time under 3000 rpm so you don't want cams that mess too much with that. Look at the cams recommend powerband not that it's dead on either side but the further your goes outside the powerband (sweet spot) the less happy you'll be with its performance and the powerband is based on that average engine in the family so for LA it would be 360 so you build something smaller the powerband will be at higher rpm and larger will be lower. So 215-235 @ 0.050.
As for lsa you don't have many choices for off the shelf cams so it becomes somewhat irrelevant.
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I would like to add to this post that you can only fit so much lift on a lobe of a given duration. You also have to consider valve train stability. I ran into this on my W-5 stuff. I worked my guts out to get the heads to have a stable flow curve up to 1 inch. I did. Reverse flow was, as a percentage, very low. Then I had to pick a lobe. I'm thinking I want to NET .875-.900 lift. What I found was...if I kept the lift where I wanted, the duration would be way too much for what I needed. Otherwise, I was looking at top level Comp Eliminator lobes. Even with a Jesel rocker, I could only get a 1.65 ratio and make it fit.

The gist of all this is this: everything has to be considered. If you are limited to stock rockers, you are going to have an issue with lift. Pushrods matter. I was using 3/8-7/16 double tapered PR's and would have went bigger if I could.

It's all in the combo. And it has to match.
 
norton said:
I didn't pick this cam, it was offered to me and I told the guy that I needed to come here and see if it would work for me in my stock engine. He insisted that it was what I needed and I told him the same thing that I said here. I know nothing about cams. Thanks to the information that I got here, I didn't purchase it.
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You made a good decision.
Sounds like the seller was trying to find a happy home for the cam in your pooter.
Glad you opted to not buy it.
 
norton said:
Please don't make assumptions. As far as I'm concerned, my question wasn't vague at all. I have nothing to contribute, because I'm more lost now then when I asked for the advice in the first place. Because I know nothing about cams I asked a simple question. Would the cam that I have work in a stock engine, Hell I, even posted a picture of the specs. if not what should I look for that either stock or close to it. But like most threads here, things started going south real fast. I do thank those of you that took the time to steer me in the direction, that I wanted to go. For the rest of you, keep the pissing match up, I'm not learning anything but it's good entertainment just the same. But don't expect me to contribute to something that I know nothing about.
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Did you even read any of those links I sent? Read them over and over if you need to. I'm not bein a smartass when I say this.....but it's not our job to educate you on camshafts. It's a very complex subject and has so many different opinions, it's pathetic.

YOU gotta have some skin in this game. You have a brain. You know how to read. You have the internet. Don't get caught up in a pissing match where everybody is trying to show you.....and the world how much they know. Use your OWN mind. Read the articles I sent. Search for some similar yourself. YOU are your best teacher. You know what it takes for YOU to understand something. Don't let someone else be responsible for you learning something. You learn the way THEY want. Learn it yourself and you'll be miles ahead.
 
RustyRatRod said:
Did you even read any of those links I sent? Read them over and over if you need to. I'm not bein a smartass when I say this.....but it's not our job to educate you on camshafts. It's a very complex subject and has so many different opinions, it's pathetic.

YOU gotta have some skin in this game. You have a brain. You know how to read. You have the internet. Don't get caught up in a pissing match where everybody is trying to show you.....and the world how much they know. Use your OWN mind. Read the articles I sent. Search for some similar yourself. YOU are your best teacher. You know what it takes for YOU to understand something. Don't let someone else be responsible for you learning something. You learn the way THEY want. Learn it yourself and you'll be miles ahead.
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Hey, don't be a bogart. Send me the links. Hell I'll read them. You can never learn too much.
 
yellow rose said:
Hey, don't be a bogart. Send me the links. Hell I'll read them. You can never learn too much.
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See if norton still has them. Post um up norton if you do. I would have to dig like heck and I'm just too lazy for all that. lol
 
I wouldn't mind a read of them also.......Well........:D
 
I'll see if I can find them.
 
Thanks again RRR for the links.........but as alway, reading and learning, cause desire for even more understanding.
Ok here is my question. It has to do with overlap. I had this all figured out long ago but, NO.

My 340 had a MPP cam .474/280* cam with a 60* of overlap. My new cam to match my new 408 motor has a Hyd Roller Cam that is much larger.562/.550 lift 243/247 duration @.050". Gross(@.006") duration of 294/297)
So this cam by Comp, does not have a Overlap spec but by using the cam card i see that the intake close and exhaust open spec's it can be figured out. or so i though...........
so Intake opens at 19* btdc and exh close at 13 atdc. so my math says that i only have 32* of overlap. Now these ## are a @.050"
I realise that i'm comparing apples to oranges here but, that is only half of the overlap, of my smaller cam.
Now i'm sure that they differ because of the gross and @.050" But over 30+ degrees.....less???
 
yellow rose said:
It would be interesting to see how others think their way through a build.
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FWIW: For me, it all starts with the application. I'm not intending to be critical, but I'm just thinking that the process YR outlined above seems to be drag race oriented (X ET with Y weight = Z HP). There are a lot more apps out there: street and rally (and road race to a lesser extent) dictate considerably wider RPM ranges for good torque, especially with just 3 or 4 gears. For NA carbed engines, that puts a cap on the duration and overlap to avoid dropping the low RPM torque into the toilet, and drives to higher lift to make up for smaller durations, and then higher SCR to help the lower end RPM torque.

If it was drag racing or circle track, then the operating RPM ranges can be smaller and that opens up the the duration you can use for NA carbed.

All this is driven by NA carbed and 3 or 4 speeds. Put in a 6 speed like a modern rally car, and all of a sudden, the need for a wide RPM range diminishes.
 
Sure, comparing advertised numbers to .050" can be that far off. That's why most all camshaft manufacturers went to the .050" standard........AND why we should use MORE info than just the .050" standard when choosing a camshaft.

Cudafever said:
Thanks again RRR for the links.........but as alway, reading and learning, cause desire for even more understanding.
Ok here is my question. It has to do with overlap. I had this all figured out long ago but, NO.

My 340 had a MPP cam .474/280* cam with a 60* of overlap. My new cam to match my new 408 motor has a Hyd Roller Cam that is much larger.562/.550 lift 243/247 duration @.050". Gross(@.006") duration of 294/297)
So this cam by Comp, does not have a Overlap spec but by using the cam card i see that the intake close and exhaust open spec's it can be figured out. or so i though...........
so Intake opens at 19* btdc and exh close at 13 atdc. so my math says that i only have 32* of overlap. Now these ## are a @.050"
I realise that i'm comparing apples to oranges here but, that is only half of the overlap, of my smaller cam.
Now i'm sure that they differ because of the gross and @.050" But over 30+ degrees.....less???
Click to expand...
 
Cudafever said:
so Intake opens at 19* btdc and exh close at 13 atdc. so my math says that i only have 32* of overlap. Now these ## are a @.050"
I realise that i'm comparing apples to oranges here but, that is only half of the overlap, of my smaller cam.
Now i'm sure that they differ because of the gross and @.050" But over 30+ degrees.....less???
Click to expand...
Your math is right but overlap has to computed at advertised durations, not .050" durations. I'd expect the overlap to typically compute out to 40-50* higher (or 50+* with a slower ramp cam) using advertised valve timing versus .050" valve timing, which reflects almost directly into the overlap numbers. So, yes, that's not comparing the 2 cams properly; don't do that LOL.

Go to some data sheets like the Crane or Lunati catalog pages, where they show numerous cams in a page listing format, and you will see the 40-50 degree difference in advertised versus .050" durations. For the Lunati catalog, you'll see the general overlap numbers vary to some degree by family of cams.
 
Yeah i wish it showed advertised open and close but only @.050". Adding 50* to that would make it be close to what i would have expected.
Only cams i have use were MPP cams before now, So they were ease to compare. all were at advertised. trying to compare to other cam manufacturer is just about impossible. I think i read somewheres that chry figure there cams duration and overlap at .002 lift not 0. them you have comp that will give some advertised spec's. But they do them at .006"
I realize that chry is the only one that give spec's strictly by advertise and the standard has become @.050.
It just make it hard to shift gears, so to speak. i had a smaller cam with 280*duration. Now i have a larger cam with 240 esh duration and less overlap (@.050) This and a million other reasons why most, can not pic out a cam without leaving a lot on the table. Just by picking a slow lobe ramp compared to a much faster/ aggressive lobe ramp can make to cams with the same exact spec, perform differently.
That's why i let them figure out what cam will work best for me. " I want a came that make power down low to stretch my 2800 converter, bla bla bla live/race at 6600 feet, don't want to buy expensive valve train part. (don't want to rev over 6500)" Got the cam i posted above and vary happy with it.
 
Cudafever said:
I think i read somewheres that chry figure there cams duration and overlap at .002 lift not 0. them you have comp that will give some advertised spec's. But they do them at .006"
I realize that chry is the only one that give spec's strictly by advertise and the standard has become @.050.
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I don't think anyone every gave advertised at .000" lift; it is too vague to find on the cam lobe in the measurement process. It is common to give advertised duration as well as .050" duration from just about everyone. Now, there are quite a variety of lifts at which advertised durations are measured; I've seen .004" and .006" and some larger numbers for some solids.

The .050" lift standard is just one standard point of measurement; it surely does not tell the whole story, as you and others have pointed out. I'd want to know both; it gives some idea on the ramp shapes.

BTW, so your cam card does NOT have the advertised valve timing events? With the .050" and advertised durations, one thing you could do is:
- figure the difference between the 2 numbers for intake and exhaust
- divide those numbers in half
- add those to the .050" exhaust closure angle and subtract from the .050" intake opening angle to get some 'advertised' valve event angles
- figure overlap from that.
That process does not account for asymmetrical lobe shapes, but will get you close.
 
nm9stheham said:
I don't think anyone every gave advertised at .000" lift; it is too vague to find on the cam lobe in the measurement process. It is common to give advertised duration as well as .050" duration from just about everyone. Now, there are quite a variety of lifts at which advertised durations are measured; I've seen .004" and .006" and some larger numbers for some solids.

The .050" lift standard is just one standard point of measurement; it surely does not tell the whole story, as you and others have pointed out. I'd want to know both; it gives some idea on the ramp shapes.

BTW, so your cam card does NOT have the advertised valve timing events? With the .050" and advertised durations, one thing you could do is:
- figure the difference between the 2 numbers for intake and exhaust
- divide those numbers in half
- add those to the .050" exhaust closure angle and subtract from the .050" intake opening angle to get some 'advertised' valve event angles
- figure overlap from that.
That process does not account for asymmetrical lobe shapes, but will get you close.
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What 2 numbers? not quite getting this.
 
yellow rose said:
It would be interesting to see how others think their way through a build.
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For a street or street and strip engine I feel you got to design it differently than race car. Cause if got to fill so many different roles and with full racing engine there's rule you usually have to follow which dictates the build.

On a street engine you got to decide how far your willing to go with redesigning the drive line and what manners your willing to put up with.

One of the problems I see when people want advice on what to do is they pick a random power level out of a hat. Eg. I got a 360 and want 400 hp what do I need to do ?
The problem with that is there's a big dollar difference between a 360 hp or so and 400 hp.
A fairly stock long block and gearing will work with 360 hp. Going 400 hp start to take things to the next level engine and driveline requiring a lot more $$$ for hp that you will rarely use and make the engine more dogish where you do.

I go with SB since that's what most build.
Since most street cars are gonna be 550 hp or less. 273/318/360/340 all can handle that power and for the most part they all have the bore size to support the flow needed. Realistically the 273 would have a hard time doing it flow and rpm wise and would be a stone under 5000 rpm but in the right hands probably doable.


So when coming up for a recipe for your driveline. After deciding what you'll live with gearing stall idle mileage durability etc...
And if engines size is open It's time to decide the power to weight ratio your after.
After you decide that it time to decide on power to cid ratio. 0.8:1 or so is basically equal to stock muscle car specs. 1:1 is just a basic carb intake cam and headers up grade.
And up to 1.2:1 ish you move more into street strip territory needing deep gears stall heads etc.. Basically complete driveline upgrade. Above that is starting to get into race car territory.

Next I'd decide what heads do I need to reach that power level. The two hp per cfm rule of thumb wont work on moderate cr and cammed engine your more likely make 1.8 hp or less per cfm.

So if you wanted 8:1 weight to power ratio on a 3400 lbs car = 425 hp and 1.2:1 power to cid ratio = 354 so 360 and around 235 cfm heads.
Which gives you a ballpark frame work to decide on the parts needed.

Next it's time to call up the cam companies and figure out what cam and CR you need.

Then I'd put the basic info into my software dyno and play with heads and cams until I got the longest flatest torque curve that don't give up too much down low and with a hp curve that extends way past the peak.

But this gives you a frame work to base your decision to tweak out all the parts for your combo.
 
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