Is solid roller lifter loading really the highest at idle?

[CamKing]

540Rat,
I see your point, but I don't think the loads you are talking about have anything to do with the lifter failure of roller lifters on the street.
After the lash is taken out, the loads the roller sees going up the opening side, across the nose and down the back side of the lobe are nothing compared to the hit the roller takes at the opening lash point.

[TheEngineWorks.com]

How do the axles and bearings in the OEM hyd rollers compare to the race rollers ?

Size,material,hardness,etc.

The race rollers are stronger.
It's not a material issue.

The "hammer blow" of the lobe hitting the solid roller at the lash point is 4 times harder then what the hydraulic roller sees.

I am happy you concur with my feelings. Due to resent lifter failure, I started thinking very heavy on what is the MOST destructive force on a roller.. The theory I came up with was the "impact" at the point the lash goes away, more aggressive profiles may exacerbate that, but I don't think its as much as some may think. I believe the current combo in my personal car may end up with negative lash when cold, which would be due to the expansion with aluminum block and heads.

[CamKing]

. I believe the current combo in my personal car may end up with negative lash when cold, which would be due to the expansion with aluminum block and heads.

The problem is, depending on the type of clearance ramp on the opening side of your cam, this may not help at all.

BTW, don't try and start your motor with negative lash. The valves don't seem to like it.

[Doug F]

Camking can correct me, but from what I have seen and know about lash ramps, it is possible to provide a "gentle" takeup of the lash. This will then "adversly" affect the so called intensity numbers some people look at which I don't care for personally.

Some cams basically don't hardly have a "ramp" and the lash takeup point is at a large accel rate.

People that open the lash up from the design target take the risk of entering a higher rate of accel portion on the lobe which is specific to that lobe.

I personally think roller lifter failure has a lot to do with the lobe profile.

[CamKing]

Doug,
yes you can make a gentler ramp, but the acceleration of the ramp may not be the problem.

With a clearance ramp, we're assuming the lifter is falling all the way back down on the base circle and lifter velocity becomes zero. as the lifter starts to move up the clearance ramp it accelerates to the lash point.

Now, what if the lifter never falls all the way back to the base circle??
After the lifter gets to the lash point on the closing side, the lifter no longer has the spring to force the lifter down. Spintron testing shows that the lifter can actually bounce off the base circle and come back and open the valve multiple times. If the Lifter is bouncing back to a point between the base circle and the lash point when it comes back around on the clearance ramp, it will hit hard somewhere on that ramp. What the cam designer did below that point will have no effect on how hard it hits at that point. It will only be effected by the velocity at that point.

[540 RAT]

540Rat,
I see your point, but I don't think the loads you are talking about have anything to do with the lifter failure of roller lifters on the street.
After the lash is taken out, the loads the roller sees going up the opening side, across the nose and down the back side of the lobe are nothing compared to the hit the roller takes at the opening lash point.

I'd have to agree with you about the hit the lifter takes on opening (and you may have a real good point about the lifter bouncing on the base circle, then really getting hammered at the lash point). But while the original discussion was on loading vs rpm, I never stated, that the load going up the lobe was THE cause of the failures we see. It is likely only a piece of the overall puzzle. However, radical lobes are bound to cause a greater reduction in the metal's fatigue life, due to higher loading, than milder lobes would.

Speaking of taking out the lash, I had previously asked you about running less lash than called for. Then you said it could help or else do no good at all, and you went on to say that you thought it would hurt performance in any case, due to seat to seat changes. So, are you saying then, that for a given grind, you just have to live with what you have and hope for the best? Or can you offer any recommendations for helping the situation with lash changes at all, for a given grind that is already in the motor?

[af2]

So, if that is the case, then for a given grind, you just have to live with what you have and hope for the best, I guess? Is that about it? Or can you offer any recommendations for helping the situation with lash changes at all, for a given grind that is already in the motor?

If the one you are using to has no clue on ramp design, How can Mike make decision?
All true cam grinders do ramps different. There is no one lash fits all in the conversation.
Just my .02

[540 RAT]

So, if that is the case, then for a given grind, you just have to live with what you have and hope for the best, I guess? Is that about it? Or can you offer any recommendations for helping the situation with lash changes at all, for a given grind that is already in the motor?

If the one you are using to has no clue on ramp design, How can Mike make decision?
All true cam grinders do ramps different. There is no one lash fits all in the conversation.
Just my .02

I wasn't asking him for a specific lash to run. I know he doesn't have all the details on some unknown lobe. I was just asking for his take on a general recommendation to apply, if there is one. I thought perhaps he might say something like reducing the lash by x amount will generally always help, or by reducing the lash by y percent will generally always help. That wouldn't be giving a specific number, just a direction to go for improvement. Previously he, didn't really offer any recommendation. Maybe there is none, which takes us back to living with what you have already. But he's had some time to think about it by now. He's the cam pro, so let's see if he's had any further thoughts on the matter.

[540 RAT]

What's up with this software, it keeps duplicating instead of editing?

[540 RAT]

What's up with this software, it keeps duplicating instead of editing?

[CamKing]

I thought perhaps he might say something like reducing the lash by x amount will generally always help, or by reducing the lash by y percent will generally always help.

Without looking at the ramp on the cam, I can't make any recommendation.

If you want to send it to me, I can measure it, and make a recommendation.

[540 RAT]

If you want to send it to me, I can measure it, and make a recommendation.

Hmmm, my cam is in my just built 540, and I won't be taking it out any time soon. So, I guess I'm out of luck there, thanks anyway.

[540 RAT]

I believe the current combo in my personal car may end up with negative lash when cold, which would be due to the expansion with aluminum block and heads.

I have to agree with CamKing here, you may want to rethink this one. Do the negative lash thing, then do a leakdown test. You won't like what you see. Do a compression test and you won't like what you see there either. IF it will even start, it will run poorly (its like all the valves are leaking so badly that they don't seal at all). And the whole time you are waiting for it to warm up and achieve some lash, the valves would be getting burned. Obviously not good. An old timer once said, " I'd rather hear 'em than smell 'em". Still good advice, even today.

Even if you simply tighten up the lash to a bare minimum, but not negative, in an effort to reduce hammering at the lash point, which might sound very tempting, you may be shooting yourself in the foot. You'd be increasing your seat to seat duration, which on the surface might seem like a good thing. Also keep in mind that tighter lash will open valves sooner and close them later. And that also might sound like a good idea. And it is IF you are getting that with a larger cam, if that is what you want. But doing that without larger lobes will open the intake a bit sooner but it will be only a tiny crack open so it is without benefit of any extra flow that could be realized with larger lobes. Then closing the intake a bit later, again without benefit of the additional flow a bigger lobe would provide, will only begin building compression a bit later. All of which won't help performance any on the intake side, it will only serve to degrade performance somewhat. On the exhaust side, it will crack open sooner, bleeding off some combustion pressure earlier than normal, again without the benefit of any additional flow. And then the exhaust will close a bit later, but also without the benefit of any additional flow that a bigger lobe would provide. So, this isn't going to offer any performance on the exhaust side either, it will also only help to degrade it. It stands to reason that this is one reason why lash isn't called out as .001 or some other tiny little amount. In an earlier discussion, CamKing said that in his opinion, running lash much much less than called for would decrease performance. I assume this is what he was referring too. And Tech Author David Vizard has said that very thing in magazine articles in the past. Something else for us to consider in the pursuit of lifter longevity. We seem to be between a rock and a hard place on the lash issue...........

[CamKing]

Something else for us to consider in the pursuit of lifter longevity. We seem to be between a rock and a hard place on the lash issue...........

Not if you go with a rev-kit.
It'll make the clearance ramp do what it's supposed to do, and your lifters will live longer.
Of course, it may cause the rollers on your rocker arms to fail sooner.

[n2omike]

Mike,
Are the solid roller cams marketed as "street rollers" designed to have lower acceleration on the ramps? Is that the main difference between a street roller lobe and a race lobe?

Mike is the expert, and I'm just a 'parrot' relaying what I read in this particular post... but...

Comp's Xtreme Energy street cams are advertised to have lift ramps 'almost' as fast as their race cams, but slower closing ramps for less noise, and less pounding on the valvetrain and seats.