camshaft theory

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1930

1930

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What specific numbers do I need to be looking at when looking at camshaft specs, there are sometimes alot of numbers the cam manufacturers post online and I know they are all important and Id like to understand what they all mean but for a beginner that can be difficult.

I plan to pick a few cams, get the most relevant numbers and post them here in hopes that people can tell how these cams differ from one another.
 
IQ52 said:
Read these first...........

COMP Cams® - Effect of Changes In Cam Timing and Lobe Separation Angle

COMP Cams® - COMP Cams® Valve Timing Tutorial
Click to expand...
Thanks I guess i could show you via an image of the piles of papers I have printed out from online and have read, its very complicated to understand but I am doing my best.

Im pretty sure Ive seen these but maybe Im wrong, Ill check them out tonight when I get home and have decent internet speed and let you know if they did help.
65wgn440 said:
You are probably best off to explain your exact combination to the different cam manufacturers you're interested in, and ask for their recommendations.
Click to expand...
Respectfully I have to disagree, I think that the only guy that gonna look for whats best for my goal is myself and I can only do that by understanding all the theories behind it all which again Im working on. I have called several cam manufaturers and more often than not they are very knowledgeable and informative but at the the end of the day they have a job to do and thats sell me a cam without spending a whole bunch of time helping me decide what would be best.

rumblefish360 said:
Also, do tell of "The goal."
Click to expand...
Respectfully thats not something I want to get into here, I want to understand cams a little better or refresh myself cause at one point a few years back I did spend quite a bit of time learning about all of this but its not like riding a bicycle.

Im hoping that some of the things like what numbers are really important will jog my memory and I can get a better understand of what these numbers mean in the end as far as sound, torque, peak H.P

Maybe I asked the wrong ? in my first post but I dont think so.
 
Lift is how far off the seat that the valve is opened...

Duration is the most important spec, as it determines the power band the cam pulls strong in...

Some people look at "advertised duration" others look at duration at .050"...

Advertised duration is supposed to be how many degrees the valve is opened total... Some manufacturers rate it at .001", others at .002", etc... You have to look at how they determine it on an individual basis...

Duration at .050" is how many degrees that the valve is open between .050" up and .050" down... Some people look at this number at .050" more, but I like to consider both... That way you can get an idea of how fast the valve is opened...

You like more "ramp speed" which how fast the valve opens... It's good to have fast opening valves, but not as good to close them fast, as the faster the valve closes, the harder it bangs the seat and the more it will wear...

Then you have the timing, of when the valves open... There is the intake center line and exhaust center line.... Then there is how far apart the intake lobe and exhaust lobe are "spaced" which is the lobe center line which is how many degrees apart the intake center line is compared to the exhaust center line...

the lobe center determines the amount of overlap where the intake and exhaust valves are both open at the same time... The longer the overlap, the rougher/choppier the idle... A smaller lobe center number has more overlap than a larger lobe center... This affects cylinder pressure...

That's quick and dirty camshaft 101....
 
1st of all, the same cam will behave differently in a variety of differently built motors and different cubic inch motors. It will also behave differently with the differences in the rest of the car, such as gears, weight, and converter.

So you ask what the numbers mean, and what numbers you should be looking at?? Well, if you have been reading the articles you have claimed to have been reading, then you already know the basics of lift, duration, duration at 50, and lobe separation. Here is the point, and you've already stated above it's not the info you are looking for:
  • The numbers on a cam card are to help you decide if the cam will behave in the manner you are hoping to achieve to the engine/car specific. Unless you know the engine and car specifics, the numbers on the cam card are pretty much useless.
 
Guys spend a lifetime learning camshaft science, and it isn't all about cam shafts.


The best way to spend your money once, and spend it right, is not to listen to a bunch of online keyboard heroes. You can't possibly learn in a short time what some have spent a life time doing, and doing it every day.

I would call Jim at Racer Brown, tell him exactly what you want to do, give him all your info and let him tell you what you need.


Or, you can look around and end up with comp junk, or some other mass produced compromise camshaft.
 
I don't think you asked wrongly. I was asking what I did to better focus on the intended useage and goal of changing a cam out for best results since even the same cam specs on paper can have vastly different results.

But I get what your asking and I think it best to currently limit the scope of the topic to just a simple and general high performance camshaft applications.

I will generalize some points:

Advertised duration:

A general sizing of the camshaft in degrees that start and end at the same point in lobe lift at a given measurement.

The problem here is even from the same cam grinder, different cam can be measured at different lift points. A good example is if you look into a cam manufacturers catolog, Comp Cams is good, flip through the pages and take a look at all the cams with an advertised duration of 280* and notice where they start to measure the Cams duration. Sometimes it is .004, .006, .010....

Duration @ .050

The standard were all are told to compare cams. Then as above, compare this .050 value to the advertised value for a glimpse into how fast the lifter is rising & the difference between the asvertised numbers.

Total lift:

In conjunction with the duration numbers and how fast or slow the cam is lifting the tappet, the total lift also shows how fast the lifter is going up. Generally speaking, quicker is better.

This can be confusing at this point because the numbers can cross inform.

Cam lobe seperation:

(Still in the spirit of keeping things in line with the KISS method...)

The wider (or larger number) of cam, the idle will mello out, smooth out. Cams on a 112 or larger will normally have a smooth idle.
Cams on the (normally seen for hot rods/muscle cars) 110 or 108 will have a choppy idle.

Also where the cam opens and closes the valve has an effect on power. And from here, we get a little deep into cam workings and theory.
 
listen to yellow rose!
Give the cam grinder all your information and decide exactly what you want your combination to do.Too many build an engine for the quarter mile and are very disappointed when it's driven on the street.
 
I think that from this point, you can get a cam in the ball park of what you maybe trying to do. But the field is still wide open.

If your not obsessed with the perfect cam and you are exploring ideas, don't mind tinkering around, a decent choice can be made with this basic above understanding and following cam manufacturers guide lines.

And Yellow Rose is correct!

While I think I can make a decent choice for my ride and it's intended purpose, my idea may not suite your need or goal and the outcome could not be a happy or desired one.

I have also noted that the same phone call to 10 places will net 10 different choices. As well as 10 phone calls to the same company will yield 10 more cam suggestions.

I for one do not mind changing cams out. I enjoy it. Along with intakes and carbs and....
I do like to tinker around just to see what happens. That's what I did before the internet!

General cams, purple cams, Comp cams, oval track cams, drag cams.... just for fun mind you.

But I am no cam expert!
 
According to many...... yes...
And I really don't give a hoot.

It's been a bad decade plus for having fun, but there is light at the end of the tunnel. I see it coming!

I am looking forward to getting back to tinkering and the strip where I can flounder and flop about like a new guy again trying to remember what I forgot, figure out why it went wrong (probably because I assumed!!!!) and enjoy the frustration and small victories.
 
318willrun said:
1st of all, the same cam will behave differently in a variety of differently built motors and different cubic inch motors. It will also behave differently with the differences in the rest of the car, such as gears, weight, and converter.

So you ask what the numbers mean, and what numbers you should be looking at?? Well, if you have been reading the articles you have claimed to have been reading, then you already know the basics of lift, duration, duration at 50, and lobe separation. Here is the point, and you've already stated above it's not the info you are looking for:
  • The numbers on a cam card are to help you decide if the cam will behave in the manner you are hoping to achieve to the engine/car specific. Unless you know the engine and car specifics, the numbers on the cam card are pretty much useless.
Click to expand...
I have read alot, its been a while since I talked camshafts though so I do need a refresher, Im gonna check out the links tonight given above.
yellow rose said:
Guys spend a lifetime learning camshaft science, and it isn't all about cam shafts.


The best way to spend your money once, and spend it right, is not to listen to a bunch of online keyboard heroes. You can't possibly learn in a short time what some have spent a life time doing, and doing it every day.

I would call Jim at Racer Brown, tell him exactly what you want to do, give him all your info and let him tell you what you need.


Or, you can look around and end up with comp junk, or some other mass produced compromise camshaft.
Click to expand...
I hear you and that does make me feel better. Not so stupid I mean

rumblefish360 said:
I don't think you asked wrongly. I was asking what I did to better focus on the intended useage and goal of changing a cam out for best results since even the same cam specs on paper can have vastly different results.

But I get what your asking and I think it best to currently limit the scope of the topic to just a simple and general high performance camshaft applications.

I will generalize some points:

Advertised duration:

A general sizing of the camshaft in degrees that start and end at the same point in lobe lift at a given measurement.

The problem here is even from the same cam grinder, different cam can be measured at different lift points. A good example is if you look into a cam manufacturers catolog, Comp Cams is good, flip through the pages and take a look at all the cams with an advertised duration of 280* and notice where they start to measure the Cams duration. Sometimes it is .004, .006, .010....

Duration @ .050

The standard were all are told to compare cams. Then as above, compare this .050 value to the advertised value for a glimpse into how fast the lifter is rising & the difference between the asvertised numbers.

Total lift:

In conjunction with the duration numbers and how fast or slow the cam is lifting the tappet, the total lift also shows how fast the lifter is going up. Generally speaking, quicker is better.

This can be confusing at this point because the numbers can cross inform.

Cam lobe seperation:

(Still in the spirit of keeping things in line with the KISS method...)

The wider (or larger number) of cam, the idle will mello out, smooth out. Cams on a 112 or larger will normally have a smooth idle.
Cams on the (normally seen for hot rods/muscle cars) 110 or 108 will have a choppy idle.

Also where the cam opens and closes the valve has an effect on power. And from here, we get a little deep into cam workings and theory.
Click to expand...

ir3333 said:
listen to yellow rose!
Give the cam grinder all your information and decide exactly what you want your combination to do.Too many build an engine for the quarter mile and are very disappointed when it's driven on the street.
Click to expand...

I didnt want to give any more info cause this is a car site ( I find there NOT alot of people that like trucks so its tough to gain someone interest in my project ) but from what Ive seen online this site and Ramcharger Central have the most knowledgeable people willing to help that Ive run across, this site however seems to have alot more members participating than R.C and I like different opinions so I get different viewpoints and so sometimes if its a real tough subject for me I can read the same thing being said 12 different ways and more things click for me if that makes sense.

With that said Id like to find the absolute best cam choice for my vehicle which is a 6000 pound 4 wheel drive truck. Will you help me:

The criteria s :

1- Id like it to sound just plain nasty

2-Id like it to not fall flat on its face when I hit the gas, if it fell down to one knee but then got right back up than that would be Ok though.

3- Id like it to sound just plain nasty

4- Id like it to not fall flat on its face when I hit the gas, if it fell down to one knee but then got right back up than that would be Ok though. Im not gonna race the thing

I dont want to just mindlessly throw a thumper cam in it though, Id like to use my head ( or your head ) and come up with the best possible happy medium and Id like to understand why Im going the route I am going.

I dont give two hoots if it spins the tires, right now its got 33, not sure what the future holds as far as tire size, for sure no smaller. Its got an NP 435 ( 4 speed ) with granny gear and 3.55s in the axles.

Its a nice truck that Ive restored, my plan with it is too take it too shows, show off my work and thats it, I could try and care less about gas mileage but I dont think its possible.

Ive even considered bumping up the compression to have to run race fuel if thats what it takes to get that sound. The engine is a 440, .060 over.

Mistakes Ive prob. made but cant change is I bought the heavy 6 pack piston. I know now that if I would have lightened the rotating assy that it would have helped it rev faster. I should have also bought lighter rods. Im using stock

Engine has been balanced and Im gonna measure everything I can measure so I can say I blueprinted it.

Ive got an edelbrock RPM performer intake
Ive got an edelbrock 750 carb
Ive got Edelbrock RPM aluminum heads
Ive got 1.6 roller rockers
This is where I may lose you ( I hope not ) Ive got a NOS un-used P.J gear drive
Ive got some really nice aluminum valve covers that I may modify with a piece of lexan so you can see my roller rockers :)

I can tell you anything else you need to know, can you take some time to tell me what is the BEST cam choice?
 
This is the cam I have right now for it, it wouldnt hurt my feelings if I didnt use it right now, Id save it for another build.

Ik now they say that sound and performance dont go together so much when it come to a street vehicle but I beg to differ, Ive got a 67 Falcon with a professionally built little 289 in it that sounds like one of the nastiest cars you see at the track and I still drive it on the street and it will still pass my daily driver all day long and thats what Im after. A happy medium and again to learn some things and find that medium.
Picture 467.jpg
 
Last edited:
318willrun said:
That is the PERFECT cam !!!!!!!!......... for somebodies application. Unless you know the rest of your build, car, and intended use, then you just have a "cam" :)
Click to expand...
Does all the info I gave above not suffice. I can give whatever is needed
 
1930 said:
Does all the info I gave above not suffice. I can give whatever is needed
Click to expand...
sorry, I didn't read all of your post 15.
I don't think this is the cam that will give you the "nasty" sound you are looking for. You may need to go the way of Whiplash cam.
Cams that idle "nasty" are usually upper RPM cams. IF you want the sound and still keep low end grunt, a Hughes whiplash cam may be your best bet.
 
That Lunati 220/226 should work for what you are doing. A 6000 lb truck with 3.55 gears would be easy to over cam so I'd start on the small side. If you want to use a solid flat tappet cam then something like the Mopar Performance .528 flat tappet might work. It would have a bit of a rough idle but probably not too bad in a 440. Should pull hard with the low first gear in your trans. I don't think you would want anything larger than the 528.
 
AndyF said:
That Lunati 220/226 should work for what you are doing. A 6000 lb truck with 3.55 gears would be easy to over cam so I'd start on the small side. If you want to use a solid flat tappet cam then something like the Mopar Performance .528 flat tappet might work. It would have a bit of a rough idle but probably not too bad in a 440. Should pull hard with the low first gear in your trans. I don't think you would want anything larger than the 528.
Click to expand...
I agree the cam he has would be a nice fit for his truck, but he wants a nasty sound (I'm assuming this means a "rough idle" sound), and he won't get that with the cam he listed.
 
if that cam were 108 instead of 112 lsa i bet it would sound to his liking.

that said, i would run that cam because it seems like it would work great.
 

1930 said:
I have read alot, its been a while since I talked camshafts though so I do need a refresher, Im gonna check out the links tonight given above.
I hear you and that does make me feel better. Not so stupid I mean





I didnt want to give any more info cause this is a car site ( I find there NOT alot of people that like trucks so its tough to gain someone interest in my project ) but from what Ive seen online this site and Ramcharger Central have the most knowledgeable people willing to help that Ive run across, this site however seems to have alot more members participating than R.C and I like different opinions so I get different viewpoints and so sometimes if its a real tough subject for me I can read the same thing being said 12 different ways and more things click for me if that makes sense.

With that said Id like to find the absolute best cam choice for my vehicle which is a 6000 pound 4 wheel drive truck. Will you help me:

The criteria s :

1- Id like it to sound just plain nasty

2-Id like it to not fall flat on its face when I hit the gas, if it fell down to one knee but then got right back up than that would be Ok though.

3- Id like it to sound just plain nasty

4- Id like it to not fall flat on its face when I hit the gas, if it fell down to one knee but then got right back up than that would be Ok though. Im not gonna race the thing

I dont want to just mindlessly throw a thumper cam in it though, Id like to use my head ( or your head ) and come up with the best possible happy medium and Id like to understand why Im going the route I am going.

I dont give two hoots if it spins the tires, right now its got 33, not sure what the future holds as far as tire size, for sure no smaller. Its got an NP 435 ( 4 speed ) with granny gear and 3.55s in the axles.

Its a nice truck that Ive restored, my plan with it is too take it too shows, show off my work and thats it, I could try and care less about gas mileage but I dont think its possible.

Ive even considered bumping up the compression to have to run race fuel if thats what it takes to get that sound. The engine is a 440, .060 over.

Mistakes Ive prob. made but cant change is I bought the heavy 6 pack piston. I know now that if I would have lightened the rotating assy that it would have helped it rev faster. I should have also bought lighter rods. Im using stock

Engine has been balanced and Im gonna measure everything I can measure so I can say I blueprinted it.

Ive got an edelbrock RPM performer intake
Ive got an edelbrock 750 carb
Ive got Edelbrock RPM aluminum heads
Ive got 1.6 roller rockers
This is where I may lose you ( I hope not ) Ive got a NOS un-used P.J gear drive
Ive got some really nice aluminum valve covers that I may modify with a piece of lexan so you can see my roller rockers :)

I can tell you anything else you need to know, can you take some time to tell me what is the BEST cam choice?
Click to expand...




Numbers 1, 3 and vehicle weight are going to kill you. I'd sell the Jackson GD and either buy a QUALITY 3 gear drive like a Milodon or buy a timing chain. That floating idler gear thing is a timing nightmare, in that every time the engine speed changes, or the load, the floater slides back and forth in there. Since one gear is smaller than the other, the cam moves around.

If you have a stumble when you mash the throttle, that is a tune up issue.

Lightweight bob weight is highly over rated so don't fret over that.

At your weight and gear 9:1 CR is about it unless you get a cam specific for more compression. Even at 9:1 you have to be careful or you will run it into detonation, especially at low speed high throttle opening.

Measuring everything doesn't blueprint anything. Blueprinting is probably one of the most misused words in engine building vernacular. If you are going to "blueprint" an engine, you have to machine everything to the factory blueprint. I can say I've never done that.

There is a difference between building something to a blueprint, and actually building an engine that runs. As an example, if the blueprint calls out a 9.560 deck height and you cut the decks to exactly that number, but the piston is down the hole .060 what good did it do you to set it to the print? Are the rods too short? Stroke too short? Compression height too short? All of that? Some of it?

Most of us are stuck with the Pistons we get. Most shops don't have the tooling to make all the rods the same length so you get what you get with those. Most cranks aren't indexed very close when ground, although aftermarket cranks are almost always spot on.

To me, blue printing is nothing more than making everything the same, not machining to a blueprint. You correct what you can.

After all that, your best money spent, especially looking at your application is a custom ground cam. Yes, it's a few dollars more than a cam out of a catalog, but unless you like to tinker like rumble fish, and you don't mind changing cams in a truck your best bet is to call Jim at RB and tell him exactly what you want and let him grind it.


Jim Dowell
Racer Brown cams
410-866-7660

He prefers phone calls be AFTER 5pm eastern time. He answers the phones. He grinds the cams.

There is also Cam Motion. And Jones cams. Bullet cams.

You have choices other than a catalog guess.
 
Did not know that on the blueprint deal, very interesting and Im sure every bit of it is true but Im gonna keep calling it blueprinting cause everyone recognizes that.

Here is where Im gonna sound super ignorant, years ago you rarely ever saw me on the weekends cause I was spectating at the track, I seen time after time big heavy trucks ( usually Chevy or Ford ) pull up to the line and launch like a bat out of hell. Huge cam, big tires and it still took off like a rocket, if I can find a cam that sounds big and makes my truck take off like a Honda Accord than Id be happy.
 
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