Solid Roller Cam ??

[bobcowan]

I was reading the other thread, and didn't want it to get too far off track.

A solid lifter valve train - roller or flat - has lash/slack built in. That prevents the valve from being held open as things change. But too much lash will cause it's own problems. This, I understand.

I thought the specified lash was to allow parts to grow as they got warm. What is valve lash on a hot engine? Isn't it nearly 0"? You wouldn't want it to be zero, I suppose. But wouldn't you want it to be nearly zero? I mean, perfect adjustment would mean that while the engine is at it's hottest - like near the end of a race - it is actually 0". But that would be darned near impossible to achieve in actual practice.

Secondly, concerning spring pressures. Lighter is better. Enough to control the valve train during it's expected use, and no more (theoretically). Any more pressure than is actually needed just wastes energy and wears out parts. Correct? So, how much is enough? Do you just go by what the cam maker recommends? Or is there a magic formula some where?

The bee hive springs intrigue me. I like the idea, and the testing seems to bear out the theory. But I'v only seen them for applications slightly above stock performance levels. I don't see that they're recommended for "big" cams and high rpms. I'v not seen them for a solid roller cam, either.

[blykins]

Lash grows when hot.

It seems counter-intuitive, but that's the way it works.

You have a cold lash setting and a hot lash setting. On a first fire-up with an engine that has an iron block and aluminum heads, I'll set the lash about .006" tighter when it's cold. For instance, if your cam card reads .016/.018" hot lash, I'll try about .010/.012" cold. It's usually pretty stinkin close.

You can manipulate lash a little bit to change the operating characteristics of an engine. Tighter lash will make the engine think it (effectively) has a larger cam. This can raise the peaks a little higher and shifter the curve to the right. Conversely, if you loosen the lash, the cam "gets" smaller.

On spring pressures, you want enough to control the valvetrain. If you use a lot more than that, horsepower can be used up in compressing the spring and you cause unnecessary valvetrain wear. You wouldn't use 750lb open pressure on a Comp Cams street roller grind that never sees anything above 6200.

Spring pressures are based on rpm and the weight of the valvetrain components. If you're running titanium valves, retainers, and locks, then you can get away with less pressure.

No real magic formulas. If I have a GOOD relationship with the cam grinder (we're not talking about Comp Cam's tech line), then I will go with their recommendations. Otherwise, it's experience, logic, and a little salt thrown across the shoulder.

The idea behind the beehives is that they are small and light, the equivilent spring pressure needed for a set valvetrain is a lot less. They are great for hydraulic roller camshafts and flat tappet stuff. I wouldn't feel comfortable with a set on solid roller stuff.

Hope that answers your questions.

[madmaxx]

Just for giggles if you required 465 open with double springs, what spring pressures would a behive get you too? 300lb?

[blykins]

Probably less than that. I can't say for sure since I don't use them.

[Hotfingrs]

It's been a long time since I used iron heads, but if I remember it's the opposite of aluminum heads. Lash gets smaller with iron heads when they heat up. In either case you don't want zero lash when hot.

[blykins]

Iron/iron combos don't change much at all.

But the point is, on a solid cam, you don't want the operating lash at zero. Keep in mind that I said operating lash, because there are some special conditions (all aluminum stuff with tight lash cams, or hydraulic roller cams running solid roller lifters , etc.) where you have to set the cold lash at zero or near zero. When you get to that point, sometimes you have to preheat the engine before firing.

[bobcowan]

Originally Posted by blykins

Lash grows when hot.

It seems counter-intuitive, but that's the way it works.

Thatis counter-intuitive. And exactly the opposite of what I was thinking. That makes the cam "smaller" as the engine warms up. Since that's the case, why not set lash near zero when cold, knowing that it will grow as the engine heats up?

Originally Posted by blykins

Probably less than that. I can't say for sure since I don't use them.

Why not? I was cruising through the Lunati web site, and they have beehive springs specifically for the solid roller cams; 425# open pressure.

Everything I'v read about the beehives say that they're the next step in spring technology. But not many racers are willing to step up and give them a try. If they're all they say they are, seems like that would be some easy power.

[madmaxx]

425open, use a hydraulic roller with same aggressive profile as solid and have the best of both worlds.

Originally Posted by bobcowan

Thatis counter-intuitive. And exactly the opposite of what I was thinking. That makes the cam "smaller" as the engine warms up. Since that's the case, why not set lash near zero when cold, knowing that it will grow as the engine heats up?



Why not? I was cruising through the Lunati web site, and they have beehive springs specifically for the solid roller cams; 425# open pressure.

Everything I'v read about the beehives say that they're the next step in spring technology. But not many racers are willing to step up and give them a try. If they're all they say they are, seems like that would be some easy power.

[blykins]

Originally Posted by bobcowan

Thatis counter-intuitive. And exactly the opposite of what I was thinking. That makes the cam "smaller" as the engine warms up. Since that's the case, why not set lash near zero when cold, knowing that it will grow as the engine heats up?

Why not? I was cruising through the Lunati web site, and they have beehive springs specifically for the solid roller cams; 425# open pressure.

Everything I'v read about the beehives say that they're the next step in spring technology. But not many racers are willing to step up and give them a try. If they're all they say they are, seems like that would be some easy power.

That's right....the effective duration of the cam gets smaller as the engine heats up.

The reason you don't set it near zero is because it only grows so much. In the case of iron block/aluminum heads, you get around .006" growth. If you set cold lash to near zero, then you'd only have a little lash when hot. Due to the lobe design, camshafts are designed with lash in mind. That's why your cam card for your solid cam will give you hot lash specs. Most are in the .016-.022 range. Some a little more, some a little less.

I wouldn't trust a beehive in a solid roller application. You have a small single spring there, taking the brunt of everything. If that single spring fails, then you've dropped a valve.

There's been some OEM LS beehive spring issues in the past. No trust here.

[Snakebit]

My solid lifter cam with AFR aluminum heads is set at .019 cold to yield .022 hot.

[dorramide7]

Originally Posted by Hotfingrs

It's been a long time since I used iron heads, but if I remember it's the opposite of aluminum heads. Lash gets smaller with iron heads when they heat up. In either case you don't want zero lash when hot.

Iron/iron combos don't change much at all.

But the point is, on a solid cam, you don't want the operating lash at zero. Keep in mind that I said operating lash, because there are some special conditions (all aluminum stuff with tight lash cams, or hydraulic roller cams running solid roller lifters , etc.) where you have to set the cold lash at zero or near zero. When you get to that point, sometimes you have to preheat the engine before firing.

[Barry_R]

I have not signed in on the whole beehive thing yet. In agreement with Keith on a lot of this stuff. Between the two of us I bet we've installed a thousand cams or more.

Reducing the mass of the retainer is nice - but no way is it enough to compensate for a 30% reduction in spring rate. They were probably oversprung in the first place and playing with fire afterward. Might be lofting the valve over the top of the lobe to gain some "cheater lift" knowing that durability was not going to be a factor in testing.

You CANNOT directly compare the opening and closing specifications of roller and non-roller, solid or hydraulic cams at any point unless you do all the measurement at the valve. Making assumptions about the entire lobe profile based on what happens at a small and arbitrary lift point - such as .050 - is also way overly simplistic. These days a sophisticated lobe is entirely non-linear in design. An awful lot happens at .100, .200, .300, .400 etc and none of it is similar from lobe to lobe.

Cams are best expressed as lift curves plotted at the valve over the entire range of action. You never see this data provided by any cam suppliers. You can have two cams with similar duration measurements at .006 (SAE), ..050 lift, and peak lift that will be completely different in terms of lobe area if you measure them this way.

Lash is a very modest tuning tool. You need to keep the valves closed when cold. And they need to remain in control over the full lift curve. Once the lobe designer has decided upon a lash ramp and built that into the lobe profile you should not move too far away from it. A bit tighter rarely seems to hurt things, but looser can play havoc if the lifter tags the lobe beyond the ramp.

As much as I hate to say it, there is no "keyboard" way to select the perfect cam. I wish there was. Because the perfect cam does not exist. All we can do is try one we know will meet the individual customer's expectations and run with it based on EXPERIENCE. Some guys want more of a rumpity idle, the next guy will want more top end, the next guy will want smoother driving. I've had the same cam described as too smooth and too wild within a week in comparable builds.

With the Engine Masters Challenge FE entries I have installed lots of cams into the same engine to see what happens. It rarely follows common predictions - we've had great results with way too big a cam installed insanely advanced. You need to TRY things. The engine cannot read.

[bobcowan]

I remember when CC first came wout with beehive springs for the SBC. And I remember reading about some failures. I used them for a while, but didn't see any real differance. I'v also heard the argument that dual springs can support the valve if one of them breaks.

That's something I'll be watching as the years go by. I'm tempted to be bold and try them again. But that can get expensive real fast.

Not trying to beat a dead horse, but trying to understand a little better. I have no experiance with solid lifters at all.

Lash is - essentially - a bad thing. It makes the cam "smaller" when you really want it to be bigger, and causes parts to bash together. Which is why solid lifters and cams don't last 100K miles. Launching the lifter off the back side of the cam lobe can't be a good thing. Wasn't that the reason hydraulic lifters were invented - to prevent the bashing, and therefore make things last longer?

So, if you want lash to be at it a minimum during the worst/harshest operating range, why would you not set it at something like .001" cold, and let things grow as they may? The cam would not shrink, and things wouldn't bash so much. Why start out with such a big lash?

Again, not trying to beat a dead horse. But I like to understand things before I give them a try.

[blykins]

Solid cams are very necessary in high-rpm, high-hp engines. Hydraulic cams with their function based on oil pressure, oil flow, heavy components etc, will float the valves way before a solid cam will (generally speaking). As a general rule in the back of my mind, hp peaks up to 5500-6000 usually get hydraulic cams. Over that and I usually recommend solids.

Solid flat tappet cams will last for a long, long, long time. Solid roller cams will last for a long, long, long time, but the lifters won't. Also, the spring pressures that are required for wild lobes and high rpms will wear a spring out, which necessitates spring maintenance.

You can get away with a much wilder lobe on a solid cam. A wilder lobe introduces more power. A wilder lobe will open the valve quicker, hold it open longer, and then set it back down quicker. There are limits with hydraulic cams, as you can bleed down a lifter if you get too funky.

There is a camshaft term called "major intensity". It's basically the difference between advertised duration and .050" duration. I'm not a cam grinder, I'm an engine builder, so my definitions won't be as in depth as say Mike Jones, Harold Brookshire, etc. could get with them. But when you sit back and look at a lobe's design, with how fast it opens, how long it's open (the duration at .200"), how fast it closes, the lift, and the major intensity, you can get an idea of how wild a cam is.

A hydraulic cam (say a Comp Cams Xtreme Energy lobe) has a MI of about 50-52°. Relatively speaking, the MI of a Comp Cams TK solid roller lobe is 28°. This means the difference between advertised and .050" duration is very low. Which means that things happen in a hurry. Valve opening is instant, the valve is open long, and valve close is instant.

If you tried to design a hydraulic cam with 28° MI, it would self destruct. But wild cam lobes is what makes a race engine a race engine.

Lash may make a cam's duration effectively smaller, but as an engine builder, you know to add duration to compensate. A hydraulic cam with a 230° duration at .050" will not behave the same as a solid cam with a 230° at .050". You usually have to add around 10° for a solid cam equivilent.

Lash ramps are made into a lobe's design for a reason. Again, I'm not a cam designer, but there has to be a specific amount of take-up in a cam lobe's design for it 1. to function correctly and 2. to not be ultra-violent. The purpose is basically to avoid high velocity collisions. There are such things as tight lash cams, but essentially, you need that lash ramp there so that the clearance is taken up slowly and all the valvetrain parts don't take a severe beating.

[bobcowan]

Thanx. That is very insightfull.

I'm considering a solid roller cam for more rpm's. But the car does spend a lot of time cruising at 2200 rpm's. So I'll have to spend the bux on some of the higher quality lifters.

Since I have an 8 stack system, I'll probably have to get a custom cam for the wider LSA. All the off the shelf cams I'v found are 108-110*, I need 114-115*.

[blykins]

I think the new Comp lifters would work just fine. 2200 is way more than enough rpm to get a little oil slung up on them. But it certainly wouldn't do any harm to jump up to a Morel, Isky, or Crower lifter.

Yes, you will need a little wider LSA.

Let me know if you decide to buy a new bumpstick...I'm a Comp Cams dealer as well as a distributor for Jones Cams. I can do a completely custom cam for you.

[madmaxx]

Interesting article on beehive springs in Hot Rod this month. There testing showed behive spring with about 100lb less open pressure as a traditional spring and better top end performance. Talking about a win, taking 100lb of your spring load from 375 to 275? and getting better results and substantially reducing valve train loads. In fact they said the dual springs helped low end a little due to the valve train deflection and widening the LSA!!!

[blykins]

Anytime you reduce the weight of a valvetrain component, you're ahead. The beehives are so small and light...plus the retainers are very small in comparison to a 1.550" spring.

[bobcowan]

Thanx, Brent. Next winter I might be ready to make the leap. For now, things are running so well, I hate to make any changes.

[Keithc8]

Who the hell told someone they could deduct 100 to 150 from the open spring pressure just because they went to a BeeHive spring. The main thing about a BeeHive spring is that it is smaller at the top and you have a lighter retainer. The design of the spring is also suppose to have better harmonics for better valve control. I would not run but about 30 to 50 lbs less with a BeeHive spring depending on the application. They have there place and they are not always the best thing to use. There is way more that goes into this stuff but this cam **** has been beat to death.
This lash deal is something else that most people do not understand. There is a reason for it and it does not go anywhere close to zero when the engine gets hot. It all has to do with the design of the camshaft and the opening and closing rams. If we got into a camshaft discussion it would take to long for me to type out all of the information about them.
We can set you with anything you need and cut through the bull****, it is that simple.

Good luck, Keith