[pastry_chef]

Originally Posted by pmd400

What do you mean by offset?

The opening flank and closing flank are not the same.

[pmd400]

Originally Posted by pastry_chef

The opening flank and closing flank are not the same.

So how is offset different from asymmetric?

[gtofreek]

No, I'll explain later.

[gtofreek]

Originally Posted by pmd400

What do you mean by offset?

When Harold was alive, I wasn't supposed to talk about this as it was his little secret. But I suppose now that he is dead, it's OK.

Lobe offset is not the same as asymmetric. Asymmetric is when the opening ramp is different from the closing ramp.

Lobe offset is when the base circle of the lobe is offset from the center of the cam core. This moves the lobe over in relation to the cam centerline, which totally repositions the lobe and how it opens and closes the valves. It changes it a fair amount, which is why his tighter lobe sep cams have powerbands that are broader than other cams on wider lobe seps. This is also why these cams need to be advanced. Running them straight up is like retarding them. Advancing them gets the intake to exhaust valve realationship at TDC during overlap where they need to be to make these cams run right.

[pmd400]

Originally Posted by gtofreek

When Harold was alive, I wasn't supposed to talk about this as it was his little secret. But I suppose now that he is dead, it's OK.

Lobe offset is not the same as asymmetric. Asymmetric is when the opening ramp is different from the closing ramp.

Lobe offset is when the base circle of the lobe is offset from the center of the cam core. This moves the lobe over in relation to the cam centerline, which totally repositions the lobe and how it opens and closes the valves. It changes it a fair amount, which is why his tighter lobe sep cams have powerbands that are broader than other cams on wider lobe seps. This is also why these cams need to be advanced. Running them straight up is like retarding them. Advancing them gets the intake to exhaust valve realationship at TDC during overlap where they need to be to make these cams run right.

Iv got a jig on vee blocks for measuring cams. Ur saying if I put a voodoo cam on my jig(on the cam journals), place the dial indicator on the base circle, and rotate the cam on say 200* of base circle then the dial will move because the lobe is offset to the journals?

[pmd400]

Originally Posted by pmd400

Iv got a jig on vee blocks for measuring cams. Ur saying if I put a voodoo cam on my jig(on the cam journals), place the dial indicator on the base circle, and rotate the cam on say 200* of base circle then the dial will move because the lobe is offset to the journals?

In fact if the cam lobe was offset and the base circle round, then the lifter and thus the valves would move when the lifter was on the base circle.

[gtofreek]

No, you're thinking about it wrong. If you run a dial indicator on the base circle, it will still show a half round with no runout because it was ground round. It would have too, otherwise the lifter would play hell with that. You would have to find a way to indicate the lobe in relation to the core center. IIRC, Harold said it's only about a .020" offset, but it's enough to make some big changes in the way the cam works.

[Formulajones]

I remember you were explaining this to me a couple years ago Paul while I was at your shop. Harold was a genius and a real innovator.

[Formulas]

So prior Harold you would only reduce base circle to obtain a certain lobe lift but Harold reduced base circle first then constucted the lobe for desired lift?

Another way to look at it old cams keept the lobe tip stationary while adjusting base for lift and Harold would reduce base considerably first then adjust lobe tip for desired lift which changes the ramps considerably

Perhaps over simplified explaination but i think i get the jist of it

[Formulajones]

It's easier to explain in person. I understood right away when watching Paul explain it using his hands to demonstrate. I never mentioned this here for reasons Paul mentioned.

The way I understand it (Paul correct me here) If you are staring straight down the center of the camshaft, and have the lobe facing straight up, the lobe is offset sideways from the center of the camshaft.

[Steve C.]

"My designs are also unsymmetrical, meaning that the opening side and the closing side are different equations, although they match perfectly at the nose.
This is why so many cams are confusing, the engine sees them as different designs, even though the advertised numbers look the same."

Harold Brookshire
UltraDyne

Source: http://www.chevelles.com/forums/13-p...here-book.html


Here UDHarold tries his hand at C&P....

THE CAMSHAFT AND ITS PROFILE


The camshaft and its profile is the single most influential part of a car’s engine. Changing a cam can affect the overall performance more than a new carb or set of headers, or even more than boring and stroking. Why? All cams kind of look alike, don’t they?
Horsepower is made by burning an air/gas mixture and applying the force generated If a rod/stroke leverage to the crank. All other things being equal, the more air/gas mixture you have trapped in the cylinder, the more horsepower you’ll make. After all, superchargers work in this exact manner. They mechanically force air and gas into the cylinders.
Most forms of racing today ban superchargers and therefore the engine must depend upon atmospheric pressure to force the air/gas mixture into the cylinders. The internal geometry of the engine(the bore, the stroke, the rod-to-stroke ratio) govern the volume and therefore the rate-of-change-of-volume at any rpm. The rate-of-change-of-volume governs the capability for atmospheric air to fill the cylinder, and the port flow capability (cubic fps per valve lift) regulates the ability to fill that volume. Where’s the cam?
The cam is the critical element that ties all these factors together. It acts as a regulator or controller to match together the rate-of-change-of-volume to the ability of the port to flow air. Whatever change the cam makes in airflow at any one point in the cycle affects the air flow for all the remaining duration. The sooner we start air flow into the cylinder, and the more we flow, the more air and gas will enter. Sounds simple, doesn’t it?
If it is so simple, why are there so many different cams? And are they really different? UltraDyne, as do a small number of other cam companies, uses a computer to design all our cams. The computer allows a large number of variables to be tried, letting different profiles be evaluated within seconds. We use polynomials, and other “Un-Polynomial” equations to perform the math. All of UltraDyne’s designs are composed of 4 to 6 (or more) sections carefully designed by computer, allowing us to govern the exact duration, lift, and dynamics your engine wants to perform to its maximum.
Juggling all the conditions together at the top of the ramp and at the nose, as well as the exponents that govern the shape of the flank between ramp and nose, we find that in excess of 10 million different cams can be designed at any given lift and duration. Many of these designs won’t work (either too gentle or too rough), some can’t be physically made, and many are too close to one another. Engines react to different families of cam curves, but don’t notice differences of 10 millions of an inch.
Computer analysis allows us to simulate the valve train as 5 vibrating masses (lifter, pushrod, rocker arm, valve and retainer, and springs) and to optimize any profile for a desired rpm and range of power. Shades of the old “Polydyne” cam! Almost 30 years have gone by since the polydyne was invented by Stoddard to explain, and conquer, bad valve train dynamics. In the 1980s UltraDyne not only controls dampening and dynamic deflection of the valve train, but other derivatives of the valve lift curve also.
The UltraDyne cam has the opening contact velocity, peak positive acceleration, closing acceleration, and closing seat velocity chosen with care to produce the power, rpm, and valve train longevity you expect from us. Test facilities such as the spin fixture and the Optron test help sort out new cam acceleration curves, while dyno testing and running at the track help match intake and exhaust lobes, and lobe separations.

*NOTE: Some companies state they do not use polynomials in designing cams. However, mathematicians tell us there are only 2 ways of describing any curve, polynomials (the X & Y of algebra) or Fourier series (the sine and cosine of trig). Please note—either type will describe the exact same curve as the other.


PAGE 2 OF THE 1982/1983 UltraDyne CAM CATALOG


THE HOWS AND WHYS OF THE UNSYMMETRICAL CAM

Until the computer gained widespread use, most cams that were actually designed and not copied, were designed by using a desk calculator. This task, if done properly, would take 4 to 5 days for each side of the cam. Even so, if the design had incorrect input data, or numbers were mis-read during the calculations, mistakes would not show up until after the model was made, often a total period of 2 to 3 weeks. Obviously, the side designed would be a compromise between opening and closing requirements.
With the computer came large programs correcting all sorts of valve train dynamics, used mainly by the major car companies. The result? Almost all factory cams are unsymmetrical, although not radically so. In most cases, they softened the closing ramp of an already gentle cam, to increase longevity of the valve train.
UltraDyne designs and makes racing cams only. We are extremely concerned about valve train longevity, but of a different degree of life. Our main concerns are making the ultimate horsepower per cubic inch for your engine, and making your valve train live enough to win and win again. Any other cam than an unsymmetrical cam is a compromise between the two points. Generally, cams with long, gentle ramps are very stable in rpm, with a decrease in bottom end and mid-range power, while cams with short, rapid ramps produce excellent mid-range and top end power, but are rpm limited.
UltraDyne’s unsymmetrical cams are designed as two entirely separate profiles. The opening side is short, to minimize reversion, which is the entry of burned exhaust gases into the intake port. The actual point of opening is critical here. Yet, we still need a large cam after TDC. Therefore we open it fast. If we opened it late, but at a slow or normal rate, the cam would be either too small or be retarded too far, or else have an extremely high acceleration rate, all bad features. By using the highest possible opening rates, we are able to catch cams 6 to 10 degrees larger in duration before they get to TDC. From TDC on throughout the profile an UltraDyne cam acts as if it was 6 to 10 degrees larger than its seat duration.
Isn’t this bad? Isn’t the cam too big? No! Up to the limits set by port flow and engine geometry, engines love big cam lift and duration. What kills most big cams in engines is the early intake valve opening. The sooner an intake valve opens, the more and higher pressured exhaust gases will enter the intake port and the longer they will delay cylinder filling with a clean air/gas mixture.
Instantaneous flow in the intake port is directly related to the instantaneous flow occurring momentarily before. A port that starts flow late can never catch up. The sooner we start flow into the cylinder, the higher the port velocity the flow will have at any larger degree of crank rotation. When an engine is over-cammed, the cam lift has exceeded the port flow capability, generally very early in the downstroke, and the common cause is intake port dilution due to exhaust gases.
The original purpose of the gentle closing ramp was to prevent valve bounce and float, therefore extending valve train life. This purpose is completely met by the UltraDyne cam. Valve train longevity has increased due to the gentle closing side. There were 2 additional power making features that were not obvious in the original concept.
First, by closing the valve gently instead of letting it slam shut and bounce off the seat, the valve was effectively closing much earlier than with a conventional symmetric cam. When a intake valve closes, the piston is approaching its highest velocity. Pressures inside the cylinder rise almost instantaneous in a degree or two of crank rotation. Now let the valve bounce off the seat. The compressed air/gas mixture that should be burned is now blasted into the intake port. When the valve recovers and shuts properlyk the cylinder has lost some of its mixture and therefore power, and the post has a disturbance in it to hinder the next cycle’s filling.
UltraDynes’s later, gentler closing builds in bottom end and mid-range power by effectively closing the valve earlier, not later. The high port velocity creates a ram effect to keep filling the cylinder long after a conventional symmetrical cam has slowed down the rate of filling. Not only does the gentle ramp close sooner, but it traps more air/gas mixture in the cylinder. It’s not unusual to have to increase jet sizes 2 to 4 sizes larger to handle the increased port flow. In oval track and drag cars with automatic transmissions the bottom end power and response is tremendous, and still with the gain in mid-range and top end.
Whether oval track or superstock, modified or ProStock, the correct UltraDyne cam will give you the power to win, and the longevity of valve train to finish. Call UltraDyne today for expert advice on the proper cam to make you—and keep you—a winner.


PAGE 3 OF THE 1982/1983 ULTRADYNE CATALOG

These are pages 2 & 3 from my 2nd catalog, 1982/1983. I believe they are also pages 2 & 3 from my 1st catalog, the Summer of 1980, but I can't find one.
This information is older than some of you........

UDHarold


.

[Steve C.]

" It changes it a fair amount, which is why his tighter lobe sep cams have powerbands that are broader than other cams on wider lobe seps."

And I presume a possible factor in why Harold Brookshire recommended two cams for me used in two different engines with a 108 lobe separation. Both solid roller cams. That said, both combos made peak power above 6000 rpm and with loose converters and 3.73 gears.


.

[pastry_chef]

Comp Cams Engineer on lobe shape VS. LSA..

Can a 105 LSA "act" like a 115? Listen starting at 30 minutes.

LSA or valve events?

https://www.youtube.com/watch?v=whmOxK4XDYQ

[Holeshot71]

I've been working on getting the short block assembled on the 455. Something that's been bugging me is how to secure the pick up tube into the oil pump. So I pulled out an old pump to try out some ideas. Here's what I came up with.
First I removed the pump cover an gears and popped out the pick up tube from the housing. It's amazing how easy it was to remove the pickup with just the press fit. Using a carbide burr, I made a scoop on the inside edge of the pickup tube hole (Stuffed a couple paper towels in the well to contain the chips). Then tapped the pickup tube back into the housing. The pickup wasn't exactly tight at this point.
Then used an air hammer with a rounded punch and formed the edge of the pickup into the scoop. Thought this would be easier than a hammer and punch.
I have to say the tube isn't going anywhere. I formed the tube into the scoop but seriously think one tap or "dent" is all you need.
Here's some pics...

[Holeshot71]

Is it me or does that last pic have some kind of weird illusion?

Here's another pic

[70GS455]

Originally Posted by Formulajones

It's easier to explain in person. I understood right away when watching Paul explain it using his hands to demonstrate. I never mentioned this here for reasons Paul mentioned.

The way I understand it (Paul correct me here) If you are staring straight down the center of the camshaft, and have the lobe facing straight up, the lobe is offset sideways from the center of the camshaft.

That would still mean, as stated earlier, that the base circle is no longer a perfect half round (its sometimes called runout, and usually a manufacturing or machining error) and the lifter will try to move while it is supposed to be stationary and on the base circle.

I supposed if the lifter moves downward, the lifter internals will take up the slack and be rwady to move upward once the opening flank hits.

But if it tries to move upward while on the base circle....

Sent from my SM-T817V using Tapatalk

[pmd400]

Originally Posted by 70GS455

That would still mean, as stated earlier, that the base circle is no longer a perfect half round (its sometimes called runout, and usually a manufacturing or machining error) and the lifter will try to move while it is supposed to be stationary and on the base circle.

I supposed if the lifter moves downward, the lifter internals will take up the slack and be rwady to move upward once the opening flank hits.

But if it tries to move upward while on the base circle....

Sent from my SM-T817V using Tapatalk

That's right, the base 1/2 of the lobe still needs to be concentric with the main cam journal. So if the centres are offset then the base of the lobe will have to be ovaled to be concentric with the journal. Design and manufacturing would likely be more expensive as well.

[gtofreek]

Originally Posted by 70GS455

That would still mean, as stated earlier, that the base circle is no longer a perfect half round (its sometimes called runout, and usually a manufacturing or machining error) and the lifter will try to move while it is supposed to be stationary and on the base circle.

I supposed if the lifter moves downward, the lifter internals will take up the slack and be rwady to move upward once the opening flank hits.

But if it tries to move upward while on the base circle....

Sent from my SM-T817V using Tapatalk

After re-reading my post[that I wrote while half asleep], it would sound like I was saying the base circle has runout. It will not. What I was and still trying to say[as it's hard sometimes for me to put these things into words] is the opening and closing ramps are different, which we all know as asymmetrical, but, also, by design, the lobe is offset slightly one way from center, but this would be seen at the nose, not at the base circle, as it needs to be centered. In the design software, he moved the lobe ramps over, or off center, after the base circle. So when the computer grinds the cam off the software, it still has the base circle centered but moves the offset once it's off the base circle. So basically, the offset will mostly be seen at the nose of the lobe. Harold was a very ingenious cam designer. He also manipulated the software to eliminate any areas of the lobe where the opening ramp became stagnate and did not keep increasing the rate of acceleration up the ramp. In other words, if there were areas of the opening ramp that would maintain a constant opening rate, he didn't like it, so he would eliminate those areas and make it so the opening ramp was always accelerating the opening rate of the valve faster and faster until it got up near the nose where it would have to start slowing down to go over the nose. This made for an opening ramp that would keep increasing the velocity of the intake charge. A very clever guy he was.