Im swapping in my second set of springs after break-in, and it looks like the valve stem faces are being stressed a bit by the roller rocker tips. I think this is due to the small radius of the roller compared to a stock rocker tip putting a lot of pressure on the valve stem face. The pic below shows what the faces look like. These are machined sort of rough from the factory, so the wear areas have a more of a mirror finish to them. The thin bottom wear stripe is where the rocker tip is for most of the valve lift as I have the rockers set up for min travel at max lift. It looks like an indentation is forming there from the roller tip. Should I consider running lash caps? I didn't think to initially as my springs only have around 275 lbs of pressure at the max cam lift.

Edit: this was only after a couple hours of running and some driving. Just wondering if they'll hold up over the long haul or not without caps.

 

Although it's close, your rocker tip isn't centered over the valve stem. You should have different length pushrods. If you do use lash caps, you'll change the height of the tip then will definitely need different length pushrods.

My heads have 11/32" exhaust and 5/16" intake valve stems. I use lash caps on the intakes just to give the rocker a larger surface plus with the huge 2.300" valve head and triple valve springs with over 800 pounds open pressure, the lash caps will help protect the tip of the stem.

For your application, you don't need lash caps but you should recheck your valve train geometry and probably get different length pushrods. Like I said, it's close but not perfectly centered.

 

The centering thing is something thats out of my control, unfortunately. Im still sort of tempted to err on the side of caution and run them, anyway. The wear there, along with the slight indentation in the stem is just from around 200 lbs at max lift. With the dual springs in, there will probably be close to 60,000 PSI of peak contact pressure between the roller and stem face by my estimates. But, if they where centered, they probably would not be making a small indentation in the first place as the contact area would be larger. Maybe play a wait and see approach? Thoughts?

FWIW, in order to center the tips on the stems, it requires a much shorter pushrod that results in basically the rocker sitting very low, having an odd sweep patern, and basically the slot of the rocker ends up resting on the base of the rocker stud. If I set them up per the smallest wear pattern as commonly recommended by the aftermarket companies actually makes it even worse. The tip is right next to the edge of the valve stem face. I have a feeling it has more to do with the dimensions of the parts themselves not quite adding up.

 

A small sweep is more important than being centered. Wide is bad, even if centered.

IMO, caps are just one more thing to get loose and cause other trouble.

 

The wide sweep takes place in the first 30% or so of the valve travel. After that, the valve tip dwells in the narrow stripe at the bottom of the wear pattern. This is how they are set up stock, as to minimize travel when the spring pressure is high. The small contact pattern has all the travel after mid-lift when the pressure is higher (see illustration). Further, it moves the contact point even farther out. This would just make the pressure on the valve tip even greater, causing mushrooming. I played around with this a bit when I set up the motor, and decided to stick with the stock geometry.

Now that thats out of the way, what to do about the wear issue?

With only 200 lb break-in springs, the roller tip is still literally sinking into the valve stem face, leaving a very small rut after only a short ammount of run time. My concern is that it will cause pitting and surface fatigue in the long term. I dont know if its just due to soft metal, or more likely, the very small contact point that results from a roller as opposed to a large loading surface of a standard stock rocker tip.

Whats the best solution? See if I can find valves with pressed-on hardened stem faces like those used in some stock GM apps.? Go with the lash caps?

 

If you decide to go with the caps, make absolutely certain that they are not going to come into contact with any of the locks or retainers. They're hardened and somewhat brittle, and any gap between the valve tip and cap and it'll snap in two.

I'm a little surprised to see that with a relatively low spring pressure IMHO. What heads and valves are these?

 

Thanks. I am aware that they do require additional clearance. I know comp has the super locks that Im using with the grooves cut into them for the lash caps.

These are trickflow 195s that I bought as complete heads and basically swapped out the valve springs with comp cams 986 dual coils. I dont remember who makes the valves (theyre sold under the house brand), but they are stainless steel.

Its hard to say if its actually the valve, or just the valve faces being overloaded by the small radius of teh roller tip (theyre comp magnums). I calculated the average stress that the tip puts across the face under the roller using teh indentation left on that valve. With 200 lbs springs, it comes to a peak of 60,000 PSI. With the full 275 lbs. of open spring pressure, that could be as high as 90,000 PSI! These are the types of pressures that you would typically start to encounter in a transmission between the gear teeth. And unlike valves, typical gears are heat treated and case hardened.

I think this is a case of the aftermarket companies not appreciating the forces and stresses involved when they come up with these parts. I know my vortecs had hardened faces pressed onto the exhaust valve stems for extra durability, and that was just for the weenie little stock springs.

 

I've run higher spring pressures than that on 113's and some AFR's with roller tips with no issues. Keep in mind even the factory rockers have a small contact patch.

 

I agree that its not a lot of spring pressure. I had planned to run 340 lbs of open pressure for my original roller setup. I get the feeling that the trick flow house brand valves dont have all teh treatments that would normally be given to a stock valve to prevent wear from the high point loading. If I where still using my vortecs with the stock valves, I probably wouldn't have any issues.

I also wonder if this says anything about the valves in general, like maybe they are not properly heat treated.

 

That would make more sense than anything else, if they really are getting damaged and thats not just a shiny spot. I guess if valve replacement isnt a viable option the lash caps would be the best alternative at this point.

 

Well, I installed the lashcaps and pushrods. I went to check the valve stem material with a magnet to see what its made of. Using a very powerful rare earth magnet, the stems are somewhat magnetic. Not fully magnetic like striaght iron or steel, but magnetic. Im not quite sure what to make of that. If they were full EV8 SS, then it would explain why they wore as it can't be hardened, but its non-magnetic as far as I know. Although, Ive heard that some austenitic metals can be permeable when worked, depending on the structure and nickel content.

If they are full EV8, then screw Summit for being cheap and not making them a two-piece design.