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Old 06-17-2004, 04:30 AM   #1
Inygknok
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camshafts

aight, i know wat they do n such, and about the lobes n how they get driven by the cam gears which get driven by the crankshaft pulley, blah blah blah blah blah.

wat my doubt is, wat do all the numbers of duration and lift and degrees mean? i was guessing that the whole 250 degree duration thing meant something like.... the valve doesnt get opened for a 250 rotation of the camshaft, then get opened..... something like that.

anybody who understands the whole concept willing to explain to me?

thanks
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Old 06-17-2004, 06:47 AM   #2
Sick88Tbird
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Lift....example .500"/.500"=both intake and exhaust valves open(move off the valve seat) 1/2 of an inch

Duration...example 262/278=the intake valve will be open 262 degrees of rotation, exhaust valve will be open 278 degrees of rotation.

Some cam manufacturers list either "Advertised" duration or duration @ .050" lift. Advertised duration is the total time the valve is off the seat, obviously measured in degrees. Duration @ .050" lift is the time that the valve is .050" off the seat while opening and again while closing...

This can make choosing a cam a little tricky if you don't know what to look for because apparently, duration @ .050" lift will be much less than advertised duration.

hope this helps!
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Old 06-17-2004, 07:58 AM   #3
Wally
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Do you really want to know? I can give you the drum, but I don't know if it appropriate in an open forum.
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Old 06-17-2004, 11:36 AM   #4
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Two major specs looked at when selecting a camshaft are lift and duration. Lift is the height the valve is lifted off its seat, and in the United States is usually expressed in inches. Duration is the length of time the valve is held open, and is always listed in degrees of rotation. Since the cam orchestrates intake, combustion and exhaust events, and the crankshaft is what makes these motions happen, camshaft duration is expressed in crankshaft degrees and not degrees of camshaft rotation. (Remember here that the camshaft rotates at exactly half the RPM of the crankshaft.)
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Old 06-17-2004, 01:11 PM   #5
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Quote:
Originally Posted by DSMer
Two major specs looked at when selecting a camshaft are lift and duration. Lift is the height the valve is lifted off its seat, and in the United States is usually expressed in inches. Duration is the length of time the valve is held open, and is always listed in degrees of rotation. Since the cam orchestrates intake, combustion and exhaust events, and the crankshaft is what makes these motions happen, camshaft duration is expressed in crankshaft degrees and not degrees of camshaft rotation. (Remember here that the camshaft rotates at exactly half the RPM of the crankshaft.)


Lift is not in the top two of specs. LSA and duration are.
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Old 06-17-2004, 01:50 PM   #6
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Quote:
Originally Posted by Wally
Lift is not in the top two of specs. LSA and duration are.

Who said anything about "top two"? I believe I posted "two major"(BIG difference), maybe if you spent time trying to actually help the guy with his question instead of trying to correct me(wich is'nt even what I stated in the first place) You would'nt be getting flamed right now nor would you be looking stupid.... I'd suggest you read more carefully next time .
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Old 06-17-2004, 08:32 PM   #7
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ok guys..... geez DSMer, u just cant get past a day without an argument huh?

anyhow, i meant to reply last night that i had already understood everything when i read sick88tbird's reply..... just that i fell asleep talking to my gf on the phone so i didnt

thx

btw, i already knew wat the camshafts did and how they were moved and such, just needed a brief explanation like sick88's on the whole lift and duration thing.
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Old 06-17-2004, 11:24 PM   #8
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For crying out loud, will you guys get over the self actualisation chip on your shoulders. I will openly admit you all have bigger cods than me, are more manly, more knowledgable, more handsome, more of everything God intended.

I was trying to steer a member in the right direction. Nothing more nothing less.
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Old 06-17-2004, 11:31 PM   #9
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Quote:
Originally Posted by Inygknok
ok guys..... geez DSMer, u just cant get past a day without an argument huh?

anyhow, i meant to reply last night that i had already understood everything when i read sick88tbird's reply..... just that i fell asleep talking to my gf on the phone so i didnt

thx

btw, i already knew wat the camshafts did and how they were moved and such, just needed a brief explanation like sick88's on the whole lift and duration thing.

Alright chill out supra guy, but if somone steps to me claiming I said something I did'nt I think I'm going to defend myself. He "claims" to be trying to steer you in the right direction yet he has not posted any relevant information to your question yet... well I'm through with this...
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Old 06-17-2004, 11:47 PM   #10
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But I did post info, out of the gaze of people like yourself, just knowing you and others couldn't help, but get all huffy. When you post two items from a myriad of camshaft conditions and label them as "major", playing word games with sentence structure will not negate the implicit order ranking you listed.

I suggest you take some time to find out just waht increasing lift does to a car and then decide if its major in comparison to a few other more important variables.

Don't bother responding. I resign. Bye bye.
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Old 06-17-2004, 11:54 PM   #11
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umm why dont we just point you in the direction of a good book, as you could write several thesis on the subject.
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Old 06-18-2004, 12:05 AM   #12
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It's kind of funny watching ya'll play the "I'm not wrong, you are" game. Well guess what? Your both wrong. All specifications are extremely important when choosing a camshaft. Are ya'll like 13 or what?
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Old 06-18-2004, 12:08 AM   #13
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Quote:
Originally Posted by DodgeRida67
It's kind of funny watching ya'll play the "I'm not wrong, you are" game. Well guess what? Your both wrong. All specifications are extremely important when choosing a camshaft. Are ya'll like 13 or what?
I was just getting to that... but MR. Thesis and his "myriad" of ideas on camshafts ... ah wahtever...
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