Solid Roller Cam ??

[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.