Cam Specs 101

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Jul 30, 2002 | 04:11 PM

L4m3r

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Cam Specs 101

224/224 581/581 112LSA cam card OK guys can you tell me and Several others on this board how to read these damn things? and what to look for? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />

Jul 30, 2002 | 04:28 PM

R U A LS1

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Re: Cam Specs 101

<blockquote>quote:<hr />Originally posted by L4m3r:
224/224 581/581 112LSA cam card OK guys can you tell me and Several others on this board how to read these damn things? and what to look for? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> <hr /></blockquote>I can COMPLETELY relate i remember 2 years or so ago when i would read mags and say WTF, ill stick to bolt ons. But its fairly simple, so ill try to keep it simple. We all had to learn this one time or another in the past...

224/224-----this is the duration of the intake and exaust valves, usually at .050 (not sure what that is, pretty sure its the degrees the cam is installed at)...the first one being the intake second the exaust. Hence this means the valve is open for 224 thousandths of a second
581/581-----this is the amount of lift fr each valve in thousandths of an inch.
112-----lobe seperation

What to look for? that all depends on what you're looking for. Bigger duration numbers usually make more power, although bigger lift is also a factor. Automatic cars dont handle tighter lobe seperations as Manuals do, but it's nothing a tune can't take care of.

[ July 30, 2002, 04:29 PM: Message edited by: R U A LS1 ]

Jul 30, 2002 | 04:37 PM

VipZ28

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Re: Cam Specs 101

<blockquote>quote:<hr />Originally posted by R U A LS1:
 <blockquote>quote:<hr />Originally posted by L4m3r:
224/224 581/581 112LSA cam card OK guys can you tell me and Several others on this board how to read these damn things? and what to look for? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> <hr /></blockquote>I can COMPLETELY relate i remember 2 years or so ago when i would read mags and say WTF, ill stick to bolt ons. But its fairly simple, so ill try to keep it simple. We all had to learn this one time or another in the past...

224/224-----this is the duration of the intake and exaust valves, usually at .050 (not sure what that is, pretty sure its the degrees the cam is installed at)...the first one being the intake second the exaust. Hence this means the valve is open for 224 thousandths of a second
581/581-----this is the amount of lift fr each valve in thousandths of an inch.
112-----lobe seperation

What to look for? that all depends on what you're looking for. Bigger duration numbers usually make more power, although bigger lift is also a factor. Automatic cars dont handle tighter lobe seperations as Manuals do, but it's nothing a tune can't take care of.<hr /></blockquote>Very close, but the 224/224 is actually measured in degrees of rotation, not time in seconds! <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Jul 30, 2002 | 08:11 PM

SSINFUL

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Re: Cam Specs 101

Mr. Garrison: "Remember, there are no stupid questions, just stupid people."

"224/224 @ 112LSA". The first "224" tells you that each intake valve is open for 224 degrees of rotation. Remember, we're talking a 4 stroke engine here, so there are really 720 degrees of rotation: 360 x 2 (4 cycles: Intake, compression, power/detonation, exhaust).

...Intake, the piston is going down, away from the spark plug, sucking in fuel/air. Compression, the fuel/air mix is being compressed by the piston moving up to whatever compression ratio yer engine is set-up for. Power, the spark ignites the mixture which forces the piston down to turn the crank, and Exhaust, where the piston comes back up forcing the spent gases out. On the Intake and Exhaust stroke, the valves are open. How long they are open and AT WHAT TIMES in relation the these events plays a great deal in determining where and how much power yer engine puts out...

Likewise, the second "224" tells you that the exhaust valves are open for 224 degrees of total rotation.

Yes, those "224" #'s are at .050 lift. Most cam makers will give an "advertised" duration #, as well. This is frequently at .006 lift (there is, duh, no duration at zero lift).

The "112" is the lobe separation angle. This means that if you were to make a chart of the valve events like at http://www.compcams.com/information/Tutorials/ , you'd see the peaks of the valves being fully opened would be 112 degrees apart. This is relatively close when combined with the long durations that both the intake and exhaust valves will be opened. This induces "valve overlap". The *more* valve overlap a cam creates or has, the higher the powerband.

The .581 is the valve lift. It is the amount the valve will fully open (using 1.7 rockers as in the stock LS1) away from being fully closed. The spec card will have a base # for lobe lift as well.

What is at least as important as the general duration and LSA #'s are the valve events themselves. When they open in relationship to the piston position is critical (TDC: Top Dead Center), especially the Intake valve opening. You can have the wildest durations in the world, but if they aren't in the correct relationship to the piston position, yer screwed.

Here is a great website. It has a downloadable guide to lots of interesting stuff on how engines work and how key components figure into the mix: http://www.motionsoftware.com/minigide.htm Follow the steps, download the minigide and print it. It's truly great reading.

Also, Chevy High Performance magazine, Super Chevy mag, GM High Tech Performance, Camaro Performers, High Performance Pontiac and several other mags frequently have excellent articles defining engine components and their characteristics and functions.

Jul 30, 2002 | 08:30 PM

StevieZ

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Re: Cam Specs 101

<blockquote>quote:<hr />Yes, those "224" #'s are at .050 lift. Most cam makers will give an "advertised" duration #, as well. This is frequently at .006 lift (there is, duh, no duration at zero lift).
<hr /></blockquote>What exactly is "advertised duration"? The cam card for my MTI-Comp Cams B1 gives 280 duration at .006 tappet lift. This is a higher # than the 273 he has maked for the TR 224??? Does this mean that the 224 is a faster ramping cam?

[ July 30, 2002, 08:33 PM: Message edited by: StevieZ ]

Jul 30, 2002 | 08:51 PM

R U A LS1

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Re: Cam Specs 101

Thanks Vip ooops. <img border="0" title="" alt="[Embarrassed]" src="gr_emb.gif" /> what can i say you learn something new every day <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Jul 30, 2002 | 09:15 PM

L4m3r

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Re: Cam Specs 101

Thanks man good info..... i knew what the intake and exhaust numbers were but not exaclty how they looked on the spec card... thanks for the great info....