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  #16 (permalink)  
Old 02-02-2007, 01:14 PM
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Quote:
Originally Posted by RippinRon
Okay well we're on the topic of camshafts and LSA. I don't mean to hijack this thread

Any comments or suggestions??
Ron, Thanks for asking.

You are wanting us to pick a cam for you.
I am trying to help people learn how to pick a cam for the correct reasons.

Few of us understand what happens and why (I didn't for years), that is why the cam companies have tech lines to make recommendations. Most people believe that they are smarter than the techies, or they think techies are stupid, so they ask somebody else.

Choosing cams is a lot like choosing a wife.

You have not given near enough information to even consider making a cam recommendation.

I need to know how heavy is your ONE TON TRUCK at running weight, and are you just drag racing it every weekend or only pulling that 8000 pound horse trailer through the mountains? Also how much boost are you putting in with that twin turbo setup?

Please make a new thread with more information and let's help you there. OK?

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Last edited by xntrik; 02-02-2007 at 01:26 PM.
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  #17 (permalink)  
Old 02-02-2007, 02:04 PM
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xntrik,

Hope I'm not changing direction here either, but is it possible to have the vacuum (and low-end performance for cruising) of a wide LSA with that rump, rump sound we all want? Or, is it wishful thinking?
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  #18 (permalink)  
Old 02-02-2007, 02:25 PM
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Rippin,
Just make your own post. It is just as easy to make your our post as to reply to someone elses.

But it does sound you are using way too much exhaust duration for no reason. The only reason to use that much exhaust duration is if the heads flow terrible on exhaust side, or used with stock exhaust manifolds, or on super-charger and n20 engines.
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  #19 (permalink)  
Old 02-02-2007, 03:21 PM
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For our bracket race engines we keep the LSA very tight. You end
up with an engine with a narrow RPM range ~1500. Torque converter
stall speeds are very high.


Example:
13.5:1 compression 355

Dart Pro1 head

cam 271/278 @ 0.050 / 640 lift 106 LSA / 102 ICL

6000 stall; 7500 RPM at the traps

60ft 1.299
330 3.997
1/8 6.258
mph 108.63
1000 8.221
1/4 9.895
mph 134.22
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  #20 (permalink)  
Old 02-02-2007, 04:37 PM
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Quote:
Originally Posted by xntrik
Please make a new thread with more information and let's help you there. OK?
Quote:
Originally Posted by 454C10
Rippin,
Just make your own post. It is just as easy to make your our post as to reply to someone elses.
Duly noted. I should have just started a new thread.
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  #21 (permalink)  
Old 02-02-2007, 06:30 PM
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Last edited by 71C10; 02-03-2007 at 04:24 PM. Reason: More detailed info.
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  #22 (permalink)  
Old 02-02-2007, 06:40 PM
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Quote:
Originally Posted by automotive breath
For our bracket race engines we keep the LSA very tight. You end
up with an engine with a narrow RPM range ~1500.
Short circle track engines use a very tight LSA as well. They generally run in the 102-106į range. Engines with LSA's this close make outstanding mid range torque for coming off the corners.

Barry
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  #23 (permalink)  
Old 02-02-2007, 07:45 PM
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Could you make the intake closing angle less (75 to 70) by advancing or retarding the cam?? and what would this do to the other specs?? This cam stuff tough to understand.
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  #24 (permalink)  
Old 02-03-2007, 08:22 AM
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More Cam Tech,close LSA

Something I havent seen mentioned is that all things being equal,both cams installed straight up,same lift & duration,same pistons,is that the cam with the wider LSA will allow for more piston to valve clearance.
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Old 02-03-2007, 02:41 PM
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What is stupid about this thread is that two cams with different LSA are DIFFERENT.

When designing a camshaft you look at IO, IC, EO and EC events, at .050 typically. What the combination will want, depending on a variety of factors such as compression, HEAD DESIGN, intake style, peak RPM, among others, is what it wants. Where the LSA falls is where it falls. You can not take those same 4 factors and say well crap, what the engine wants works out to a 114 LSA and I want to run 108 and simply change the LSA, it doesn't work that way.

As for an EFI application needing wide LSA, that's not true. Design the camshaft to what the engine needs, with the above 4 factors, and let the LSA fall where it may.
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  #26 (permalink)  
Old 02-03-2007, 05:54 PM
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"What is stupid about this thread is that two cams with different LSA are DIFFERENT."

ahem, that is kinda like the point that is being made here, wish you had something useful to add, you just use differant parameters.

Larry
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  #27 (permalink)  
Old 02-03-2007, 06:15 PM
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From a priority standpoint in selecting a camshaft it is a stupid thing to think about. That is the point and that is a very useful piece of information to add to this thread. You can not say a 114 camshaft is a blower camshaft, you can not say a 112 camshaft is a street camshaft, you can not say a 106 is a circle track or drag camshaft. Otherwise there would be a whole lot of camshafts in winning motors that were winning in the wrong class of competition.

What you can say is after designing a camshaft for X application the LDA ended up at Y. In a drag nitrous application that could be 110, 113, 108 who knows? In the end it will depend on the application, not some rule of thumb.
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  #28 (permalink)  
Old 02-03-2007, 06:28 PM
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same thing, differant parameters used to come up with the same conclusion

Larry
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  #29 (permalink)  
Old 02-03-2007, 07:10 PM
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Actually there's nothing stupid at all about learning about camshaft
design. Is LSA important, you bet, that's why the put it on the cam card.

Quote Popularhotrodding.com

LOBE SEPARATION ANGLE (LSA)
A camshaft consists of intake and exhaust lobes, and a key consideration when designing a cam is the lobe separation angle, sometimes also called the lobe displacement angle, or lobe spread. The definition here is simply the distance in degrees, as measured on the cam, between the point of peak lift on the intake lobe and the peak lift on the exhaust lobe. There are several measurements found in a camís specs, which give clues to the performance characteristics of a given grind. Some, such as lift and duration, are easy enough for even the neophyte camshaft connoisseur to understand. These are often the only specs considered when selecting a cam. Really, for any given lobe, thatís all there is, lift and duration, and the two can be related to map the profile of a lobe throughout its lift cycle. Though lift and duration alone can fully describe an individual lobe, each cylinder of an engine has intake and exhaust lobes, and the timing of these events relative to each other have a significant influence on engine performance. Neither lift nor duration gives any clue as to this aspect of a camís design. Lobe separation angle does.

Simply put, the lobe separation angle (LSA) is a measurement of how the intake and exhaust lobes are phased with each other. To establish the position of each lobe, the traditional reference point is where the lobes reach max lift. Picturing the end-view of a cam as a circle with 360 degrees; the lobe separation is a measurement in degrees of the distance between the max lift on the exhaust and intake lobes, respectively. Note that degrees of lobe separation angle are given in a simple degree measurement at the cam, in contrast to how duration is measured as degrees of rotation of the crank, which turns at twice the camís speed. With this in mind, lobe separation angle is said to be in cam degrees, while duration is quoted as crank degrees. Itís not astonishing to us that lobe separation will have a big impact on performance. After all, the valve timing events have to occur at the most advantageous moments to glean the desired results from an engine combo. Obviously a LSA of zero would have the intake and exhaust valves open and close at the same time and even we know this wonít work. Cam grinders are pretty sharp on this subject, and have found the sweet range for LSAs in the range of 104-115 degrees for most applications. Typical off-the-self aftermarket cams will have a lobe spread between these values, with the greatest number of offerings falling toward the middle of this range. Coincidence? We think itís a pretty safe bet that theyíve got a handle on what works, and grind their cams accordingly.

Even within this relatively narrow range, the lobe separation angles will affect engine performance. The following chart gives some of the general haracteristics youíll see with two otherwise identical cams ground on narrow or wide lobe separation angles, assuming they are installed with the same amount of advance.

EFFECTS OF LOBE SEPARATION ANGLE

LSA--------------NARROW-----WIDE
Intake Open------Earlier--------Later
Intake Close------Earlier--------Later
Exhaust Open-----Later---------Earlier
Overlap-----------More---------Less
Cylinder Pressure--Gain----------Lose
Idle Quality-------Worse--------Better
Idle Vacuum------Less----------More
Torque Curve-----Peakier-------Flatter
Peak Torque------More---------Less
High RPM---------Drops Off-----Hangs On

Last edited by automotive breath; 02-03-2007 at 08:07 PM.
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  #30 (permalink)  
Old 02-03-2007, 09:51 PM
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Here are some conclusions I see that are not true

Circle track engines run very narrow LSA's - Some do some don't. You don't on 10:1 IE 39cc headed circle track motors, they test out liking 110 MUCH better than 108 or 106.

EFI needs wide LSA's - Nope, and I do a lot of EFI tuning. EFI motors like the same LSA's as if they were carbed. Tuning is not an issue. Plenty of ability to adapt the VE table resolution on EFI systems for very adequate resolution.

Narrow up the LSA and get more mid and top end - what if it over scavanges?

Nitrous likes wide LSA's, not always and far from a golden rule in my opinion.

When looking at camshafts why not look at the lobe in relationship to the lifter and spec out a lobe that utilizes MORE of the lifter? Put a cam on a Cam Doctor with Audie software and see what I mean. When looking at a camshaft why not look at the lobe and specify a lobe that moves the valve into the area of the timing cylce ATDC where peak flow velocity occurs more effectively?

If it was as easy as reading a PHR article we'd all be designing camshafts and building championship winning engines. After spending a few years playing around with combinations on the dyno, track, with the flow bench, cam doctor it's not quite as easy as picking up a $5.00 magazine to look up the answer. I am sure you know that AB

My point is don't take a perfectly fine 110 LSA camshaft out of your car and install a 106 LSA camshaft just because you think you'll go faster. Don't take a perfectly fine 110 LSA camshaft out of your car and install a 114 LSA camshaft just because your going to blow 100 HP of nitrous into it. I don't think that's the correct approach for making a change.
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