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Old 11-05-2005, 14:59   #1 (permalink)
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Solid cam confusion

I was flicking through the comp cams web site just having look.
I found a cam that says .022 hot lash in/ex ,3000-7000rpm range, 280/284 adv , 242/246@.050, 541/522lift in/exh , 106 lobe sep , 10.1 comp req. cam number 31-639-5

On the same page another cam, 10.5comp 250/260@.050, 106 lobes, 568/592 lift,285/295adv with the same 3000-7000rpms.


My old cam was a 294s which had more lift .560, 248@.050 more duration, wider lobe 110's but only had an rpm range of 2500-6500.


Can someone explain how the first two cams can have different spec's but the same rpm range?

How does a cam with 106 lobes effect an engine?


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Old 11-05-2005, 15:21   #2 (permalink)
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Re: Solid cam confusion

They have the same rpm range spec'd due to the spacing on the in/ex lobes and the duration split.
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Old 11-05-2005, 16:51   #3 (permalink)
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Re: Solid cam confusion

wider lobe sep. generally means more grunt down low. Conversely, an angle like 106 deg. means less low mid range and more up top... roughly speaking.
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Old 11-05-2005, 23:16   #4 (permalink)
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Re: Solid cam confusion

Would the following solid cam have a mild ,rough or very rough idle ?

.022 hot lash in/ex ,3000-7000rpm range, 280/284 adv , 242/246@.050, 541/522lift in/exh , 106 lobe sep
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Old 11-05-2005, 23:17   #5 (permalink)
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Re: Solid cam confusion

yup without a doubt it'll have a rough idle. It won't shake the car to bits but it'll sound nice @ the lights.
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Old 11-06-2005, 16:15   #6 (permalink)
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Re: Solid cam confusion

Quote:
Originally Posted by 347
Would the following solid cam have a mild ,rough or very rough idle ?

.022 hot lash in/ex ,3000-7000rpm range, 280/284 adv , 242/246@.050, 541/522lift in/exh , 106 lobe sep
Tuned well I would say more of a lopey idle rather than rough - somewhere between mild and rough.
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Old 11-06-2005, 19:04   #7 (permalink)
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Re: Solid cam confusion

Quote:
Originally Posted by 347
I was flicking through the comp cams web site just having look.
I found a cam that says .022 hot lash in/ex ,3000-7000rpm range, 280/284 adv , 242/246@.050, 541/522lift in/exh , 106 lobe sep , 10.1 comp req. cam number 31-639-5

On the same page another cam, 10.5comp 250/260@.050, 106 lobes, 568/592 lift,285/295adv with the same 3000-7000rpms.


My old cam was a 294s which had more lift .560, 248@.050 more duration, wider lobe 110's but only had an rpm range of 2500-6500.


Can someone explain how the first two cams can have different spec's but the same rpm range?

How does a cam with 106 lobes effect an engine?


IP:
1) Forget this cam and get the solid roller conversion that is advertised on here for sale.
2) as above
3) flat tappet power band is only approx 3,000 - do the maths!
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Old 11-06-2005, 19:53   #8 (permalink)
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Re: Solid cam confusion

I found this on the subject,

Overlap and LCA (LSA)
There is more to cam selection than lift and duration contrary to popular belief. The most critical aspect that is almost always overlooked is valve overlap. Another important aspect is intake valve closing point; which is directly related to duration but can also be manipulated a slight amount. These two factors will effect the engine's performance more than a person might think.
Overlap is the amount of time that both the intake and exhaust valves are open when the piston is around TDC. If there is too much overlap, vacuum is adversely affected, reversion will occur, a lean and damaging combustion process will occur, idle quality will suffer, pore low and midrange torque will result, reduced peak engine output and poor gas mileage will occur as well. If too little valve overlap is ground into the cam for a particular build, inadequate cylinder filling, reduced cylinder scavenging/filling and inadequate exhaust gas evacuation will occur; which will all hinder performance.
Valve overlap is directly affected by Duration, Lift and Lobe Center Angle. A cam for 350 CID with a somewhat wide LCA of 114 but long duration and high lift could very well have more overlap than a cam with a tighter 110 LCA that has a short duration and low lift.
The following are overlap's broken into groups that seem to be routinely followed that I find handy to reference. The shorter side of each group works for smaller CID while the longer side of each group is for larger CID.
10*-35*: trucks and RV's that require low-end torque and where gas mileage is a concern.
30*-55*: cars and trucks where idle quality, low-rpm performance, good street manners and strong off-idle throttle response are desired.
50*-75*: high performance cars where performance is the primary goal with reasonable street manners.
70*-95*: roundy round, open road race and strip engines that consistently operate at high rpm's
90*-115*: all-out drag-race engines.
If I'm building street/strip engine and the cam card shows 80* overlap, then I know I should be looking at another grind.
As mentioned earlier, valve overlap is directly affected by duration, lift and LCA. This is where cam selection starts to get difficult. When looking at grinds, all four have to be scrutinized. If the cam is ground on a 110 LCA and the overlap is 30, valve lift will be more during the overlap phase with .600" lift than 500" lift. Although the duration of overlap remained the same, the amount of overlap is increased. When lobe duration is added and the LCA remains the same, the duration of overlap and also the amount of overlap is increased. Keeping this in mind, a grind with an overlap of 30 and lift of .500" might be just right, but increasing lift to .600" might increase the amount of overlap to a point where it is excessive for the build and targeted performance will be lost. All of these considerations can become quite confusing very fast.
LCA is often referred as a reference to valve overlap. While a cam with a LCA of 106 will have more overlap than the same cam with a wider LCA of 114, the amount of overlap will vary greatly with differing lobe duration and lifts. For this reason, I don't rely on LCA alone. I look at the valve events and calculate the overlap if it is not provided with the cam specs.
Performance grinds will usually be ground on a LCA between 106 and 114. When I'm looking at grinds, I like to start out with a 110 LCA and fudge this number in either direction depending on the overlap and duration. If I know that the build will require a duration of 234 @ .050" to target peak power at 6000 rpm, I look at different grinds at this duration. I then compare their respective LCA's and overlaps to find a grind with the most appealing combination. I don't believe that there is a "perfect" LCA for any particular engine and the amount of overlap should be the primary concern.
The following are LCA's that are commonly associated with high performance engines in regards to carbureted SBC CID. These are only guidelines and should not be a primary bases for cam selection. They get me "in the ballpark" only and should be used with discretion.
112-114 302
110-112 327
108-110 350
106-108 383
104-106 406
102-104 420
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Old 11-06-2005, 22:30   #9 (permalink)
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Re: Solid cam confusion

Quote:
Originally Posted by Racer
1) Forget this cam and get the solid roller conversion that is advertised on here for sale.
2) as above
3) flat tappet power band is only approx 3,000 - do the maths!
I dont see one for sale?
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Old 11-06-2005, 22:35   #10 (permalink)
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Re: Solid cam confusion

Quote:
Originally Posted by 347
I dont see one for sale?
Quote:
Originally Posted by XD408
Im selling my old camshaft which is a solid roller camshaft, roller lifters and triple valve springs, collets and retainers for sale pitty though you cant use windsor stuff in a clevo im only asking $900 all up. Was going to put it together in my old block (with Stud girdle) with ARIAS forged flat top pistons, HV pump, new bearings rings etc... for $2200 if anyones interested and ive also got a BG 1000cfm Demon with regulater and 3/8 braided line and earls fittings all in good cond carby and reg. is like brand new for $1000 all up. Aswell as a BG 220 Pump cost me $650 again like new $300.
PM XD408 for details
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