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post #1 of 13 (permalink) Old 11-29-04, 01:51 AM Thread Starter
'77 XC Wagon in progress
 
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Cams - what does it all mean?

Could someone please translate the following for me? I don't know enough about cams to translate it!

First one:

ADVERTISED DURATION (.006" lift)
Intake 282 deg
Exhaust 292 deg
VALVE LIFT
Intake .458"
Exhaust .484"
DURATION @ .050" lift
Intake 194 deg
Exhaust 204 deg
LOBE SEPARATION 110 deg

Second one:

ADVERTISED DURATION (.006" lift)
Intake 282 deg
Exhaust 292 deg
VALVE LIFT
Intake .486"
Exhaust .512"
DURATION @ .050" lift
Intake 204 deg
Exhaust 214 deg
LOBE SEPARATION 112 deg

1. What does that all mean?
2. Are they any "good"?
3. Bearing in mind that it'll be shoved into a pretty much stock 351, how much of a cam could I get away with? Heads will have tough valve springs, but otherwise, it'll be pretty much stock...
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post #2 of 13 (permalink) Old 11-29-04, 02:10 AM
74 XB Fairmont
 
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Re: Cams - what does it all mean?

112 lobe sep means power comes in gently and the power band is usually wider than most. As the lobe sep drops ie 108 or 106 the more savage the cam is.

Both those cams aren't much above stock. The second one being the bigger of the two but only just!

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post #3 of 13 (permalink) Old 11-29-04, 02:19 AM Thread Starter
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Re: Cams - what does it all mean?

So is it right that "lift" means more meat on the lobe, which means the pushrods are extended more, making the valves open deeper into the combustion chamber? And duration dictates how long the valves are open?

You see - this is how I get confused! You imply that lower lobe sep numbers mean a savage cam, to which I translate that to "rough idle" and other stuff like that. Yet the lobe sep on the first is more on the second, and yet the second is "bigger"... which i equate to being lumpy and stuff.

Am I just being thick here?
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post #4 of 13 (permalink) Old 11-29-04, 02:25 AM
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Re: Cams - what does it all mean?

Quote:
Originally Posted by Neeek
So is it right that "lift" means more meat on the lobe, which means the pushrods are extended more, making the valves open deeper into the combustion chamber? And duration dictates how long the valves are open?
Sounds like you got it Neek, correct.
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post #5 of 13 (permalink) Old 11-29-04, 02:29 AM
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Re: Cams - what does it all mean?

Other than the lobe seperation, i look at lift and the duration at 50 thou. The lift is ovious. The higher the "meat" on the lobe the more the pushrod pushes and the more the lift at the valve is.
Duration indicates how long the valve is open. The 50 thou figure measurement is taken from the instant the valve is opened 50thou off the seat, untill it opens thens shuts untill it is 50 thou from landing on the valve seat again. The 50 thou figure is listed as this is where airflow really starts. When the valve is 10 thou off the seat, there is bugger all aiflow happening, so they give the 50 thou figures. These are generally the figures to look at when comparing cam duration.

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post #6 of 13 (permalink) Old 11-29-04, 02:31 AM
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Re: Cams - what does it all mean?

More than likely the 1st one has more of an idle than the 2nd one. Depends what you want noise or power.

Brenden

XB Fairmont (street car) 11.07@123.02mph.
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post #7 of 13 (permalink) Old 11-29-04, 02:40 AM Thread Starter
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Re: Cams - what does it all mean?

Quote:
Originally Posted by falcon coupe
Correct on both counts.
So that would also mean that there's a limit for a stock engine with cams otherwise valves will hit pistons... well, seeing as I'm not after a ball-tearing cam, that shouldn't be a problem...
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post #8 of 13 (permalink) Old 11-29-04, 02:47 AM Thread Starter
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Re: Cams - what does it all mean?

Quote:
Originally Posted by brenx
More than likely the 1st one has more of an idle than the 2nd one. Depends what you want noise or power.
"More" idle? You mean lumpy?

As for what I'm after, I want an idle that sounds a little more menacing than stock, but I also want some power, although I'd prefer a big flat torque curve to masses of top end power every day of the week and twice on Sundays
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post #9 of 13 (permalink) Old 11-29-04, 03:26 AM
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Re: Cams - what does it all mean?

Yup. Topend you won't get out of either of those. They are lowend->mig range cams.

Brenden

XB Fairmont (street car) 11.07@123.02mph.
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post #10 of 13 (permalink) Old 11-29-04, 06:01 AM
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Re: Cams - what does it all mean?

Lope separation degrees dont mean much I reckon. You can have two cams with identical lobe sep, but one could have far more overlap making it much more aggresive cam.
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