In real world testing, is there any REAL difference in these cams? Textbook cam stuff would lead me to believe that the voodoo would have a wider power band and more idle vacuum being on a 112 LSA. I would think the XE262 would run a little harder in the 2000-4000 range, being on a tighter LSA.

Let's forget about lobe design rocket science, brand loyalties, quality problems, etc. I cannot believe that there is really a HUGE difference in lift curve area between the two lobe designs. With similar seat durations, 0.050" durations, and total lift, there is only so much you can do with the lobe based on physics. Let's assume that no XE cams ever went flat, and let's forget about noise.

Does the XE262 make more peak torque in the mid-range than the Voodoo (at the expense of vaccum and top rpm power)? If not, why?

I believe UD Harold posted his Voodoo 262 made about 10 more hp up top. I really like my XE262!

I ran the XE262H in a 350 for a couple of years, it is a sweet cam.

The testing was done in the summer/fall of 2004, I left all data behind when I was fired. If Doug F. is reading this, he was in charge of the dyno-testing and may be able to supply the results. I know that we tested both the XE262H and the VooDoo 262 in the same engine, back-to-back.
Forget about all that. Let's just talk cam basics.
All cams boil down to Area-Under-The-Curve, and Reversion. Just because 2 cams have the same seat duration, .050 duration, and valve lift, it does not mean that they flow the identical amount of air, or make the identical amount of power.
I have maintained since 1980 that the power, torque, gas mileage, etc, etc, etc, depends on the SHAPE of the area under the curve, and how that is affected by the reversion produced at overlap.
Does LSA affect all this? Yes most definitely. Even in symmetrical cams, wider LSAs produce smoother idles, more vacuum, flatter torque curves. Throw in unsymmetricalness, and it gets more pronounced. Plus there are different degrees(pun possibly intended!!) of unsymmetricalness.
The engine sees all this, every revolution, every RPM.
I used to say the most important degree in your camshaft is the degree BEFORE the intake valve opened. I still do. If a measurement was made in your cylinder of the volume and pressure of burned gases existing there before the intake valve opened, that would give you a figure of merit for what the engine would flow in clean air and fuel, for whatever intake lobe is on the engine. We see this in dyno-testing the same intake and exhaust lobes, but with different LSAs, when we install the intake lobe on the same ICL for both tests.
In both tests the intake lobe is on the identical LSA, the only difference being the position of the exhaust lobe. The differing positions of the exhaust lobe produce different amounts of exhaust gas pressure and volume just before the intake valve opens, and starts airflow earlier or later, producing different torque and BHP curves in this engine.
What happens then when 2 competing cams have the same seat and .050 durations, and valve lifts? At that point the shape of the curve comes into play. Engines do not know what the final duration of a cam is, they only know what is happening at the current point of lift, and what has gone on before(the velocity and volume of the charge entering the cylinder). Small differences can make a big difference.
There is a lot more to cam design than seat duration, .050 duration, and valve lift.
A whole lot more.......

UDHarold

wow I just got a headache.............

Harold... I don't doubt that the duration at .100, .200 etc can be different for 2 cams with identical lift, seat, .050 figures. I am just wondering how much this really matters in a typical street engine.

You mention the residual exhaust volume and pressure at the moment the intake opens. Spreading LSA will open the exhaust valve sooner while intake events stay the same. This assumes both cams are installed on the same ICL. If I recall correctly, the Voodoo is to be installed on a 108 ICL, while Comp recommends a 106 ICL.

As I understand it, the earlier intake closing of the 106 ICL cam, combined with the later exhaust opening due to 110 LSA will build torque in the midrange at the expense of high end power. I think this is due to less cylinder filling at high rpms from earlier Intake closing, and less time to evacuate cylinder at higher speeds from late exh opening. Overlap is also higher on 110 LSA cam, leading to less vacuum at idle.

I think you are telling me the Voodoo makes the same (or more) midrange torque as the XE. What, specifically, happens with 'area under the curve' that can make up for differences in valve events (opening and closing) with tighter LSA cams?

Seems to me that the 112 LSA might be a compromise to maintain vaccum and off-idle performance, since enthusiasts tend to overcam engines. Nothing 'wrong' with this design philosophy, as it probably increases customer satisfaction and sells cams. Just trying to understand how lobe design can counter the age-old 'rule' that tight LSA cams make more peak torque, while wide LSA cams make a broader power curve at the expense of peak torque.

Just to be clear, I'm not saying the Comp XE262 is better than the VooDoo 262. I have not yet run a VooDoo cam. I trust Harold's experience. What I'm saying is, for a 9:1 compression street engine, the XE262 (or any similar cam) is a really, really sweet combination of street manners plus performance potential. My 3900# Chevelle with 350CI engine, 2000 stall, and 3.42 gears went easy 13's in the 1/4 mile with the 262 cam, and it was streetable enough to drive to work every day in Manhattan if you were inclined to do so. Throttle response at any RPM was excellent. Right now I'm running the XE268, and it's not appreciably quicker than the XE262 in my combination. I have purchased a VooDoo 268, but changing a cam with the engine in the car is such a pain, I just haven't been able to motivate myself to swap it out yet. Maybe later this spring :)

The power, torque, etc, of any engine is really a product of the time available to fill the cylinder(basically, the high-lift area of the cam), and the rate of filling the cylinder(the port velocity, affected by the amount of reversion).
Cams of the same basic seat duration do not necessarily have the identical opening and closing points. This means that they will have different reversion amounts, and that they will start airflow into the cylinder at different points ATDC. Less reversion means earlier airflow start, and higher port velocities, and rates of cylinder filling.
Even with cams of the same seat duration and valve lift, you do not necessarily have the same area under the curve. One easy check is how pointy the nose is. Pointy-nosed cams have less high-lift area than more rounded-nose cams, and so less time to fill the cylinder with high-velocity air.
If you're really good at cam design, you can do a lobe that is fat enough up high that when it is on a 112 LSA, it may have more area under the curve than a similarly-sized cam on 110.
Just 1* at .200 on the opening side does that.
The engine may think that the 112 LSA is a bigger cam than the 110, and the airflow is dependent on where the valve-lift curve is, at EACH DEGREE OF VALVE LIFT.
This is where all the power comes from.

UDHarold

Harold, everything you said above makes perfect sense, except for one thing:

Cams of the same basic seat duration do not necessarily have the identical opening and closing points.

How can this be true? SAE seat timing figures are used to establish durations. By definition, isn't the opening and closing described by duration and lobe centerline? I don't see how this can be a grey area.

I'll buy into your points about reversion and cylinder filling, but I can't see how there can be any varience in opening and closing points of two cams measured @ .004" tappet lift. Once you take up any defection, clearance and/or hyd lifter 'give', the valve starts opening, no? :confused:

Not challenging your statement... just trying to learn. :)

With all this being said it would be good for me to ask UD Harold how the voodoo 262 will work with my 30 over flat top 327 with 041 irons, performer EPS intake, stock exhaust manifolds, and dual exhaust. Since I plan on using this grind I would like to have your opinion on how it would run being in a 70 malibu with a tall street gear. Or maybe another grind?

I know it will not be a rocket but I am looking to at least have it be torquey. Looking to get a 331 gear at some point. Thanks!

Steve

OK, perhaps you have read here before that I design UNSYMMETRICAL cams?
Do you know that this means the 2 sides ARE NOT the same?
I will use my famous old 288R(Yes, I know you're talking about hydraulic cams, but I have these numbers memorized, and my hydraulics have always been designed unsymmetrical, also).
The 288R measures 288* at .020, 255* at .050. I install them at 100-102 ATDC.
However, at .020, the opening side is a 282* cam, with the opening side of a 282* cam on 100-102 ICL. At .050, the opening side is a 252* cam, with the numbers of a 252* cam at 100-102 ICL.
However, on the closing side at .020, the cam is a 294* cam, with the closing point of a 294* cam on a 100-102 ICL, and at .050, it is a 258* cam, again at 100-102 ICL.
What size cam is it? At .020, it measures 288*, with the reversion and port velocity of a 282* cam.
It has the high-lift area and the time to fill the cylinder of a 294* cam.
It has run this way since 1980.
The hydraulics are very similar, maybe a degree or so off, but then I have always designed all my cams, hydraulic, solid, normal lash, tight-lash, with the same computer program.
Once at UltraDyne, I designed 8 other cams that were all 288 at .020, 255 at .050, and the same lobe lift, to illustrate what I meant, to my salesmen.
They ALL have different opening and closing points, on the same ICL.

UDHarold

OK, perhaps you have read here before that I design UNSYMMETRICAL cams?
Do you know that this means the 2 sides ARE NOT the same?

So let's take a crude example: Voodoo 262 intake lobe on a 108 ICL. This would ordinarily mean 131 deg before ICL, 131 deg after ICL. At .050", we'd have 219/2, or 109.5 before ICL, 109.5 after ICL.

Voodoo cam card only calls out valve events at .050", so I can't really see what is happening between seat and .050". When I look at valve events on cam card, I see int open 1.5 deg BTDC, and closes 37.5 ATDC. 1.5 deg + 109.5 = 108deg ATDC, which is exactly where the lobe centerline is sitting. 109.5-(180-108) = 37.5... exactly where the cam card says it should be. Looks pretty symmetrical when viewing .050" lift numbers.

Now I am sure the lift curve is probably symmetrical on opening and closing ramps, but what does that have to do with actual opening and closing events?

Is all the asymmetry happening between .050" and seat - i.e. 262-219 = 43, with 20 deg going to the opening side, and 23 deg going to the exhaust? If this is true, it really screws up the DCR calculator guys! ;)

Again... not trying to challenge you... just trying to learn! :)

I'll try to find some of my old notes I made when designing the VooDoo cams.
However, you are comparing cam cards. Neither Lunati or Comp Cams put down the opening and closing points as they actually are, or else they are all making symmetrical cams.
It is the difference between calculating timing points very simply, or looking them up in a table. Here are some numbers off a cam I designed AFTER I left Lunati:
267 at .004---64.5/69.0
259 at .006---63.4/66.2
213 at .050---53.2/53,4
126 at .200
.30296" lobe lift=.454" valve lift.
The VooDoo 256 turned 6200, where we had an ignition cut-off, with a pair of stock Vortec heads with stock Vortec springs. This one will do as good or better.
You would use the 64.5 opening side to find the intake opening point, then subtract that and 180* to find the intake closing point for DCR calculations. This cam opens as a 258, and closes as a 276.
It has 53.88* of hydraulic intensity, but the opening side has 45.3, and the closing side 62.5.
Now you see the problems.......

UDHarold

I've now run both cams in the same 350, in the same vehicle with no other changes. I had the xe262 go flat at 50k miles in my pickup. Had to pull the motor and replace all the bearings. I replaced the xe262 with the voodoo 262. I havent had the truck on the dyno yet, but seat of the pants is definately stronger. I can also slip the band in my 200-4r at 3/4 throttle now. Before the trans held the power fine with the xe262. Granted I must have been right on the edge. So I'll give the voodoo 262 the nod. I will say that for some reason it's much much noisier then the xe262, and I thought the XE was noisy. I've adjusted the valves and did an inspection finding nothing wrong. Just noisey at certain rpms. The voodoo also seems to be a bit thirstier then the XE. Seems to be costing me about 3mpg. I had a high of 21 before and best of 18 now.

Steve70Malibu,

For your application, the VooDoo 256 would be a better match. It is a healthy cam for a 327 with stock exhaust manifolds, good idle, lots of vacuum. It even works good in 350s, so it is not too small for a 327. It also turned 6200 in a 350 with stock Vortec heads and stock springs on it, so it will rev decently also.
You will like the VooDoo 256.

UDHarold

Steve70Malibu,

For your application, the VooDoo 256 would be a better match. It is a healthy cam for a 327 with stock exhaust manifolds, good idle, lots of vacuum. It even works good in 350s, so it is not too small for a 327. It also turned 6200 in a 350 with stock Vortec heads and stock springs on it, so it will rev decently also.
You will like the VooDoo 256.

UDHarold


In another thread I created everyone told me the 262 was the best choice so I ordered it. I wanted the 256 but was advised that 9.5:1 compression was too much for that cam. I felt the 256 was perfect but what do I know? I hope the 262 will work, I have Z28 springs and good retainers and will be using 1.52 rockers. Thanks UD Harold.

Steve

However, you are comparing cam cards. Neither Lunati or Comp Cams put down the opening and closing points as they actually are, or else they are all making symmetrical cams.

I guess that is the piece of the puzzle that I was missing! :)

I assumed that if a company was publishing specifications on a cam card, they would be correct. Your example of the 267 @ .004 cam makes it clear. Thanks.

In another thread I created everyone told me the 262 was the best choice so I ordered it. I wanted the 256 but was advised that 9.5:1 compression was too much for that cam. I felt the 256 was perfect but what do I know? I hope the 262 will work, I have Z28 springs and good retainers and will be using 1.52 rockers. Thanks UD Harold.

Steve

You will be VERY happy with the 262 voodoo, I use 1.6 Harlands and it runs and sounds great. Lots of power.:thumbsup:

Snap... how's that 262 work below 2500 rpm in that small engine? What is your Comp Ratio?

Snap... how's that 262 work below 2500 rpm in that small engine? What is your Comp Ratio?
novadude my 327 idles at 850rpm has a real nice lope, (check sig) and to date I have NEVER driven or been in a car with a mild street 327 that had as much torque down low in the rpm band as my currant engine. I know a solid cam/roller or not would give me more power but given how well my combo work's I have no imidiate plans to change this cam.I run 9.5cr, this engine/car from a dead stop, runs up to 2500rpm(normally accelerating) in 1st gear so fast its just a pleasure to drive. In 4th gear/ 40-50mph the responce is great when you need to pass. I am used to BB OLDS cars, I love my 455's, but I guess its just the combo that works. Lunati calls the 262 a great 4by4 cam so 4spd or auto I think it works very well. Thanks Harold.:thumbsup:

It's not that cam cards are "incorrect"; it's just that they don't tell the whole story.

Think for a minute about ICL ..... Intake Center Line. How do you define it and identify it???

You might put a dial indicator on a lobe, and look for the highest number (peak lift), and move the cam a few degrees each way looking for some specific amount of downward movement (say, .025" or .050" or something); and halfway in between would be the CL. Or, you might look at it from the lowest number (valve on the seat), and look for the lifter to rise .050" or whatever, and then halfway in between THOSE points would be the CL. That second way is pretty much the cam card method. Now, if the lobe is symmetrical - that is, if it rises and falls BOTH at the exact same rate - those 2 methods will "find" the same CL.

But what if the lobe isn't symmetrical? What if it has a STEEP rise, and a GRADUAL fall (or vice-versa)? It should be pretty obvious that under THOSE conditions, the 2 methods shown above will "find" a DIFFERENT CL. And, if the CL is DIFFERENT according to how you measure it, then where is it REALLY, and what it the RIGHT way to measure it once it's installed? For instance, if you have an exhaust that opens slow and closes fast (CL by the "peak" method is LATER than CL by "cam card" method), and an intake that's the reverse ("peak" CL ahead of "cam card" CL), what's the "lobe separation angle", and how much "overlap" is there? And, how do you determine whether the intake lobe is "advanced", "straight up", or "retarded"? It's not so easy any more. And, I haven't really heard from ANY of the cam mfrs, how they want their cams "degreed", beyond totally generic descriptions like are on their web sites.

That's what the cam companies aren't telling you. Because in order for them to do so, the only way to accurately describe where the ICL is, would be to give you the complete lobe function (lift vs degrees), which would then basically give away all that research they did (or none, as the case may be) on generating those proprietary (or not) lobes that they hope will give them some kind of advantage in the marketplace, from their making the best customer-satisfying compromise among power, idle quality, RPM capability, spring requirements, parts stress, noise, likelihood of surviving break-in, mfg cost, etc. etc. etc. that they have to take into account. I think Harold would agree that THAT isn't going to happen any time soon.

Think for a minute about ICL ..... Intake Center Line. How do you define it and identify it???

You might put a dial indicator on a lobe, and look for the highest number (peak lift), and move the cam a few degrees each way looking for some specific amount of downward movement (say, .025" or .050" or something); and halfway in between would be the CL. Or, you might look at it from the lowest number (valve on the seat), and look for the lifter to rise .050" or whatever, and then halfway in between THOSE points would be the CL. That second way is pretty much the cam card method. Now, if the lobe is symmetrical - that is, if it rises and falls BOTH at the exact same rate - those 2 methods will "find" the same CL.


Although Harold's cams assymetrical ramps, they are nearly symetrical by .200 lobe lift. By .300, all assymetry is gone. Even assymetrical cams have to match at the nose, so.............................

How do you degree in one of Harold's cams? Use method #1:thumbsup:

.025" or .05" from max lobe lift might be excessive, though.

ICL is (or should be) measured at peak lobe lift.


And, I haven't really heard from ANY of the cam mfrs, how they want their cams "degreed", beyond totally generic descriptions like are on their web sites.
We'll just have to do something about that, won't we?:beers:

Here is my recommended procedure:

1. ***Make sure TDC is actually TDC.***
2. Find max lobe lift. Zero your indicator.
3. Turn the motor backwards past .015" less lift.
4. Rotate the motor in the standard direction, taking degree measurements @ .015", .010", and .005" before and after max lift.
5. Average all 6 measurements. The result is you ICL.

This method isn't affected by the assymetry of the ramps. It also does a good job of dealing with those half and quarter degree measurements, as well as timing chain/belt slack.