Solid roller lifters, cylinder heads and more

[blykins]

"Yes, I will follow some guidelines given here and move up the LBS scale on the valve springs.

What other means, besides going to Ti valves, can be done to make the valvtrain even more reliable?"


Besides going to titanium valves, just try to make the rest of the valvetrain as light as possible. Also, a shaft mounted rocker arm setup isn't a bad idea as rocker studs/cheap rocker arms/etc will deflect at high rpms/stiff spring pressures.

"- If valves, retainers and locks are changed from steel to Ti; by how much can the sping LBS rating be lowered (everything else kept equal)?

- If locks & retainers are changed only, is there any reason to go down on spring rating? (I have not looked on the numbers, but it will be , I think, a net loss of 15 grams on each valve?)"

I don't have a good answer for that. I do know that titanium retainers (with the same valves, same springs/etc) are good for about a 200-300 rpm increase.

In your case, I would increase spring pressures, and add the lightweight valvetrain components. Just changing to titanium locks and retainers still wouldn't give me a fuzzy feeling with your setup.

[Caprimaniac]

Thank you again, Brent. Strange way to discuss engineengineering, but information might be valuable to others as well!

I have come down to some conclusions, and hopefully i will soon decide what steps will be taken....

Regards
Rs

[Keithc8]

Let me say this about lash on a solid roller camshaft, it is put in there by design. The camshaft has what is called opening and closing rams. The lifter is eased of the lobe and then is accelerated very fast, and it is the same on the closing side. The lifter is closing very fast and then it is caught by the clsoing ramp and eased on to the lobe. There is no reason for the lash to slam anything and is there by design. Most solid roller fail because of the spring rate and the lack of oil to the roller.
This why they came out with the new lifters that direct oil the roller to help the life of wheel. The smoother the lobe the less spring pressure you have to run. The lighter the valve, spring, retainer and locks the lighter the spring pressure can be as well. The advantage to the hydraulic roller is that you normally run a smoother camshaft and have less spring pressure so they last much longer normally.
If you run a street solid roller that is smooth which most are you can get away with 150 on the seat and 400lbs open in most cases with a small block because of the lighter valves. Every engine is different has a few things that will affect the valve train on that engine.
We do hydraulic rollers that will turn 7000 rpms on the street and run for 100,000 miles if you know what you are doing. The deal above about the spring pressure beating the lobe out on the closing side crazy to me. It almost sounded like it did not have enough spring pressure and the valve train is bouncing. A 3/8 pushrod should have been plenty strong with the spring pressure used. To many people getting to much advice from people that do not even know about this stuff.

Good luck, Keith

[Caprimaniac]

I think you might be correct about this, Keith.

Unfortunately I am not an valvetrain harmonics engineer, and do not know all that is to know about this. I therefore follow the advices from the cam fabricators and add some known "facts" about lighter moving parts etc.

rS

[RET_COP]

I'm not an engineer and without doing any in depth reading on valve lash, it seems to me that lash has everything to do with expansion of metals, allowing the valve to fully close, and that's it. Its there because the engine does not operate in a perfect setup, that is to say that in a perfect set up that would be no lash, just the lifter following the cam lobe, no slamming, no space to take up, no expanding metals, valve closing fully on the base circle, springs holding it all together. That would be absolutely perfect. The ramp designs have everything to do with acceleration/deceleration and how the lifter and springs coincide with each other, and stress on parts. The hydraulic would be perfect except there are more parts to it, it is heavy and it requires oil to hold the plunger up.
Lou

[olddog]

Originally Posted by RET_COP

I'm not an engineer and without doing any in depth reading on valve lash, it seems to me that lash has everything to do with expansion of metals, allowing the valve to fully close, and that's it. Its there because the engine does not operate in a perfect setup, that is to say that in a perfect set up that would be no lash, just the lifter following the cam lobe, no slamming, no space to take up, no expanding metals, valve closing fully on the base circle, springs holding it all together. That would be absolutely perfect. The ramp designs have everything to do with acceleration/deceleration and how the lifter and springs coincide with each other, and stress on parts. The hydraulic would be perfect except there are more parts to it, it is heavy and it requires oil to hold the plunger up.
Lou

So then why do the cam specs tend be in the 0.020" inch gap range when hot? A cast iron engine is generally 0.005" tighter when cold give or take. They could still be 0.010" tighter before hitting zero lash cold, and they do not do this, even though they could.

[blykins]

There are such things as "tight lash" camshafts...

However, on the general, you NEED that much lash. The lobes are designed for it as it makes a nice gentle (if you can call any of this gentle, but it's a relative term) take-off and let-down of the valve. Otherwise it would be a very violent collision. Again, it all depends on the lobe design....some of the Comp street roller cams like around .016". Some of the other lobes like .020-.022". It just depends. It is necessary though to keep from being hard on, and breaking parts.

[RET_COP]

Think about how much clearance .010 actually is.With all the different metals involved that someone could mix and match, Heads, Block, different valve stems, different gas temperatures It has to be there for some insurance that the valve will close. There selling cams for alot of different engine combination's.
Ask the question, Why is there No valve lash with hydraulics?
The above problems don't apply.
After knowing how the metals in your personal engine move at operating temps, you could then set your own lash tighter (more causes problems)than recommendations. It changes the cam profile, but if you could grind you own cams profiles to your engine you could keep tighter lashes and have the same profile as the off the shelf one that worked.
Lou

[Ant]

Titanium valves, I opted to go stainless valves with the Yates heads for several reasons my engine is 373 and doesnt need to go over 7000rpm, another was that Titanium valves have less of a life cycle than stainless valves due to the coating wearing?

[Barry_R]

It sounds like you are pulling the heads anyways. Pull and swap out/rework the lifters. At this point it needs to be done - 2-3 hard seasons is enough especially with marginal spring pressures.

When you remove them look carefully at the backside of each lobe - beyind max lift. I'm beting you se an indentation where the lifter "landed" after each opening event. If you remove the springs you'll also see signs of metal transfer around each keeper/retainer interface. All signs of valve float and loss of control. You may not hear it - but with those pressures it is happening.

[Snakebit]

I am running a Comp Cams 282 solid lifter cam. AFR 185 heads with 1.9 install height on the valves. Using 930-16 double springs rated 145# closed and 342# at .528 lift. Builder recomended 7800 redline. Engine is a 68 302 stroked to 331 Scat forged crank, crower Sportsman rods, JE forged pistons, and billet main caps on 2,3,&4 and a Canton main cap stud girdle. Valve lash .019 cold and.022 hot