[aaron9252]

The only thing I know, is that my motor has a CAM. (But doesnt all motors have a CAM??)

Could someone please help me understand what exactly a CAM is and what it does? Why would someone "upgrade" their CAM?

Can a CAM even make a car idle differently?

Any help on this subject would be great. I'm learning.

Thanks!
-Aaron

 

[brandonc707]

a camshaft decides when and how far your valves open and close.
A cam will decide the whole attitude of your motor. But dont get too aggressive with this selection. If you are going to replace yours call the tech line from one of the major manufacturers, Comp, Crane,Isky ect.
Cam selection is dependant on things like compression and RPM's that the motor will be operating with. The biggest mistake that can be made IMO is to go too big because you end up with a motor that is wont make any power until 4000 RPM. Most catalogs have a guideline for each cam, with mainly compression ratio and RPM being the two deciding factors. In my own experience, use these guides to get you in the ballpark for duration @.050 (dont even pay attention to advertised duration) and go for the biggest lift you can find within the duration you come up with.
Duration is what gives you the different idle sound. BE CAREFUL dont go too big because the more duration you have,the more compression you will need to make it run good, and the further up the RPM range goes.

 

[dnult]

All four cycle motors have cam shafts. The latest Chevy High Performance magazine has a pretty good 101 on cams you might be interested in. Just beware there is a whacky table in the article that summarizes the differences between cams with wide and narrow load separation angles. The table has a couple of typos in it, but the article is a good overview with pictures.

 

[aaron9252]

Does the motor have to be out in order to replace/change a CAM?

How can one tell what kind/size/type of CAM a motor has?

Thanks for your help!

 

[fatblock]

The only thing I know, is that my motor has a CAM. (But doesnt all motors have a CAM??)

Could someone please help me understand what exactly a CAM is and what it does? Why would someone "upgrade" their CAM?

Can a CAM even make a car idle differently?

Any help on this subject would be great. I'm learning.

Thanks!
-Aaron

There is tons of reading material available online and in bookstores that will help you understand the camshaft in an internal combustion engine.You should really try to understand why the cam is reqd..and then the questions you have will be easier for you to understand.Simply stated..the camshaft selection can assist or undermine any engine combo that put together.Think of it as the brains of the engine.

 

[brandonc707]

I have done it with the motor in. not easy but can be done.
have to remove radiator,intake manifold (to change the lifters)damper, water pump, timing chain cover and drop the front of the oil pan (to allow removal of timing chain cover)
To see for sure what cam you now have you will need to look at the part # stamped on the front of the cam. so ,unless you have a two piece timing chain cover, you will need to drop the front of the pan and remove timing chain cover.
I would not even mess with looking at what I have now. I would call the cam mfg. hotline, tell them what you have got and what you will be doing with the motor, and order a cam and lifters.
Do you know what copmpression ratio of your motor is? you will need to know this.
this was actually my first project too, a great place to learn. I have always been a visual learner, so if I see how something goes together and how it works then I understand a lot better!!
DIVE IN HEAD FIRST DUDE YOU CAN DO IT!!!!:thumbsup:

Where are you from?
If I am close by maybe I can help if you need it???:beers:

 

[brandonc707]

never mind the "where are you from??" I just saw, cant be further away!

 

[fatblock]

Does the motor have to be out in order to replace/change a CAM?

How can one tell what kind/size/type of CAM a motor has?

Thanks for your help!

No..the cam can be changed in the car.
You can spec out a cam with a degree wheel and a dial indicator in the car but it is tedious and crossmember issues will dictate the size of the degree wheel for accuracy.
It would be safe to say that if you have valve lash clearance..you have a mechanical cam vs hydraulic.You will need to view the lifters to determine flat tappet or roller.

 

[aaron9252]

I know right! But thanks for your help.

So, there is quite a bit when dealing with a CAM.

Your right FATBLOCK, I will be doing some homework.

Thanks guys

 

[pdq67]

aaron,

Pull up Isky's site and get into their old tech articles and read them...

Ron's Dad, Ed is called the "Cam-Father" b/c of his vast early knowledge that promoted cams to what they are now!!

And if you want to learn more, then go over to Team Chevelle and READ every post by UDHarold, the owner of the now defunct Ultradyne Cam Company!!

Harold designed CC's old EXCELLENT 268HE and later Lunati's VooDoo Line as well as all of his old Ultradyne cam's that Lunati sells too!!

Harold is a real stand up guy and flat KNOW's his stuff, great guy too!!!!!!!!!!

And if you ever talk to him, please say hello from old pdq67!!!

pdq67

 

[novaderrik]

go to howstuffworks.com and check out the section on the internal combustion engine, and read the stuff that pdq pointed out. but be careful- it's easy to get in over your head when thinking about camshafts, which usually leads to getting a cam that's too big for what you have and you will have a car that you hate to drive because you can't get it to run right.

 

[dnult]

novaderrik brings up a good point. The best cam match for your engine will depend on several factors. Examples are the compression ratio, heads (newer high flowing heads can take advantage of higher lift and lift profiles), type of transmission, and most of all -- your intended use. It's best to get all those details together and then call your cam supplier(s) for a recommendation.

 

[pdq67]

A standard old engine like ours are that are generally right at 10 to 1 CR. will run just about their best w/ no more than a 268 to 272 cam!!! 268 a bit more grunt and 272 a bit more topend sorta deal.......

I go by this for starters...

8 to 1 CR = 250 duration;

9 to 1 CR = 260 duration;

10 to 1 = 270 duration;

10.5 to 1 CR = 280 duration;

11 to 1 CR = 290 duration; and

12 to 1 CR = 300 duration...

pdq67

 

[68zproject]

11 to 1 CR = 290 duration;
pdq67

What was duration for the stock 302 cam?

 

[pdq67]

GM said, -346, W/B/R said 314 and Pat K. say's like 304 and after all is said and done, probably somewhere between Pat and W/B/R...

Now to really open up a can of WORM's, factor in that it is a solid and turn it into a hy-cam and it's probably right at 290, imho...

pdq67

 

[kustomwerker]

the fact is that even the best cam will work poorly with a crappy set of heads...not to sound dicky at all, but this is a really loaded question!!!you really need to know a little about the fundamentals of an engine before you can unbderstand the design of a cam...its lobe seperation angle, lift, duration, ramp profile, roller or non, mechanical or hydraulic...lol...there is a lot of info here to digest...basically, a cam in simplest form is a series of steel "ramps" that push open valves...all 4 stroke engines have cams...cams will completely change the way an engine performs...a shorter duration (like a 250)with mild lift will produce torque, and at low rpm...a longer duration( like a 292 duration) with a bigger lift will give torque at a later time and hp in a higher rpm.torque is a mathmatical function of horsepower and rpm...and after all of this, a piss poor cam with a fantastic sety of heads is gonna outperform a fantastic cam with piss poor heads...cams rely on compression ratio, intake runner length and volume, valve size, and many other things in order to function correctly, so your homework unfortunately just gained a few more subjects...lol...take everything i`ve just said lightly, as this isnt meant to hurt feelings, but just to inform...hope it helps...

 

[77wolf10.85]

Couldn't agree more about good heads.
Yah, you need to go study the suck- squish -bang - blow- theory of 4 cycle engines. AKA intake- compression- power- exhaust.
The CAM is what allows all these things to happen effectively, by actuating the valvetrain.
Then, go get you a Briggs engine and strew it, and finger everything, and then put it back together and start the damthing.
And keep askin questions.
Later
Tim

 

[speedshifter]

Interesting discussion. I'd never seen anything like that list comapring CR to advertised duration. Looks like a good rule of thumb. There's so much to understanding camshaft events and their impact on how an engine runs it's a good thing we have cam companies to call when it comes time to choose, like brandonc707 points out. Of course, none of this would ever come up if it weren't for us hot rod nuts trying to make our toys sing a different tune. You, Aaron, sound like a true hot rodder.

 

[CurtiSS 69]

Hello Aaron,
Read this article -http://www.elgincams.com/campaper.html- the cam part is a little ways down, but it goes through the details and outlines the importance of each valve event.

Regards

CurtiSS 69

 

[DROPTOPtimes2]

Buy this book:

http://www.amazon.com/How-Rebuild-Your-Small-Block-Chevy/dp/1557880298

I always have it open when I'm doing engine work.