View Full Version : Cam question

06-22-2005, 02:19 AM
ive done a bit of searching and i cant really figgure what they mean when they describe cams in terms of numbers. what do they mean by exhaust duration and all that? i read alot about it and think i get the idea but i want to make sure. does 210 duration stand for the number of degrees during the ehaust strok that the exhast valve is open? and then what is the best cam for these cars i read about coy millers his was the only one i could see that was for order. another question what is the process for regrinding a cam (just eh jist i dont need the long explanation just the basic idea)? thanks in advance guys

06-22-2005, 04:10 AM
You're on the right track. Talk to dave d. on which cam to choose, or talk to a respected engine builder. My cam is something like 276 duration w/ a .499 lift. Very lopee, but make a rediculuous amount of torque.

06-22-2005, 04:45 AM
and what does lift mean exactly hahah i know this is a push rod system so i assum it has to do with the rockers. what does the cam do for intake as well and by lopee you mean it goes seems to rev up in down.

06-22-2005, 06:47 PM
here ya go :) - http://auto.howstuffworks.com/camshaft.htm

06-23-2005, 03:52 AM
yeah i checked how stuff works first and read the whole thing it enver expleaind what a 225/210 means at what a .499 lift is thats what im trying to find out what tha means so i can understand it better when i go to buiy a cam

06-23-2005, 07:45 AM
The lift is the amount of "opening" the camshaft allows the valve to open. In the cylinder head, there are valves. These valves control the air in and out of the motor.

The "Lift" is the height that the intake and exhaust valves are opened to allow air and fuel "IN or OUT" of the motor. The higher the lift, the more air comes in usually. Lift works in conjuction with "Duration".

Duration is the amount of time; measured in degrees of camshaft rotation; that the valve is "OPEN". This means that the camshaft has 360 degrees of rotation. The intake valve allows in air and fuel. Exhaust valve allows out air/fuel (spent mixture).

The higher the lift and duration, the "larger the cam". The more duration allows for a very "Lopey" cam, meaning the car sounds like a 60's hot rod "sort of".

Getting the right cam is tricky. It takes knowledge, experience and testing, (all of which we have done here over the years through trying different ones), and knowing the engine. Some engines react to lift and duration differently.

I suggest that talking to XR7DAVE or others here that have experience with cam mods can help in your decision.

The stock cam specs can be found here in a search and regrinding a cam means they take material from the BOTTOM of the cam, to increase the lift at the top. Meaning that the lifter will fall further down at the bottom, making the cam and engine believe that when the cam comes up top of the lobe, it has higher lift .

Good luck and hope this helped.


06-23-2005, 10:59 AM
now thats what i was looking for so a 210/215 cam with a .455 lift means that the intake valve opens up .455 inches int the combustion chamber for 210 degrees of the combustion stroke and it opens again for 215 degrees of the exhaust stroke thanks for the answer that was the info i needed

06-23-2005, 11:07 AM
Glad I could help. The whole thing can be confusing and again, take a look at the "How it works" section again. Shows exactly how it works.