63mako

If your taking it down to replace shims, resetting up installed height, new pushrods and the capacity of your rocker arms are at max I would spend $108 now to make sure I didn't have to go back in. It might seem fine but still have the harmonic issue. Looking at the spring shims it could possibly take out the flat tappet lobes.
http://www.race-mart.com/Lunati-LTI-73100-16.html

REELAV8R

I was just going to replace the .015 shims. No plans on changing the installed height. So it will remain 1.8".
Not sure what you mean by it taking out the flat tappet lobes. Roller cam here. Do you mean the cam lobes could be now or later get damaged by the situation should it persist.
Looking at the pushrods, rockers, and roller tips I don't see any evidence of them loosing contact with their mating surfaces, at least not to the point of creating any flat spots or unusual wear. But point taken on potential for damage.
Thanks for the link on the springs. Good price. Suspiciously cheap springs compared to what is installed now.

63mako

Roller, right. The thing is if the harmonics are such that the spring surge is causing the spring to jump off the shim as is apparent from your picture that same motion is imparted through the spring, retainer, locks to the rocker in constant contact and transferred through the pushrod to the cam/lifter contact point. The damage you see on the shim will eventually be the same at the cam or other contact points in the valvetrain. The shim is a large contact area. The roller rocker tip to valve, pushrod to rocker, pushrod to lifter and roller/cam contact points are all considerably smaller. I wouldn't think of taking the chance vs the cost of the springs. Pushrods might fix it, but how do you know for sure the harmonics are gone? Since you see no damage to the other components you likely caught it before further damage was done. This is why when I had the same issue I could see it as erratic timing. The harmonics were transferring from the spring, through the valvetrain to the dist gear and maybe the timing chain and crank gear causing that harmonic vibration that accelerates as RPM increases and showed up with the timing light as erratic timing.
Edit: Think install height is 1.850 on these. Might need spring cups and or retainers. Nothing is easy!
http://www.lunatipower.com/Tech/Valv...pringTech.aspx

cardo0

REEL, sorry i know its not funny to u but the rocker tip or its pattern on the vlv tip didnt do that. Ok enough, i dont want to ruin your thread as your efforts sharing this is going to help a lot of us here.

So i took a look at your dyno thread and your dyno sheet only goes to 5200rpm. Up to that speed the curve looks mostly smooth but seemed to die down a little early for your cam.

Also i see your cam lift is 0.549" and spring installed height is 1.80" with 1.251" full open but what is that springs solid height? U really need 0.060" safety margin which would put your solid height needed at 1.191". I bet your not even close to having safe margin.

Only quick fix i can think of (if your springs solid height is > 1.191") is replace your shims (correct the installed height) and install 1.5 ratio rockers. Yea, still an experiment so the fix is really up to you with what u can afford.

Good night everybody.

63mako

Install height is 1.800. Full open is 1.251. Coil bind height is 1.100. .149 is plenty of safety margin.

REELAV8R

Right 1.251 would be the max compressed height of the spring under running conditions with .549" lift. Coil bind on this spring with 1.8" installed height is 1.080". So no way coil bind is an issue. That is .171" from coil bind.

Your right the rocker tip or it's sweep did not eat out that shim. The spring did. But you got to ask yourself why did the spring do that?
In order to eat up that shim the spring had to be jack hammering the shim. Which means at times it was not in contact with the shim.
In a properly operating hydraulic valve train nothing should loose contact with anything else, unless your lofting valves.
So then why would the spring loose contact with the shim? That's the question. Seat and open pressures are adequate for the application so that's not it.
Spring surge cause by resonance is believed to be the reason. spring surge that violent has to be induced by resonance.
Pushrod length, wall thickness, diameter and rigidity can all change the resonance frequency of the valve train due to how the pushrod "rings" when it pushes the rocker because it flexes. Not only that but any vibrations from the cam shaft, crank shaft, and the block, heck the whole engine, are also transmitted through the pushrod to the rocker to the spring.

Obviously numerous other factors also effect the frequency. But here it assumed the pushrod length could be the answer...for now. It will of course still resonate just hopefully not destructively.
Mako63 is also speculating that it could be the springs and how they resonate with the rest of the engine and valve train.

I'm not stressing over it. It's kinda interesting to me, and a great learning experience. Just like to get it under control, that's all.

scott foxwell

.149, IMO, is too much clearance from CB. IF POSSIBLE, given all the factors, I like to run under .100 from CB. As a rule, the closer you can run to CB the more settled the spring will be although some springs seem to run a little better a little further off CB. In this case the rocker is the limiting factor since it will take only so much pressure. I would install this spring where the open pressure was 10-15# below the max recommended of the rocker which is 350#, so I would be shooting for an installed height that, with the spring's measured rate combined with my net lift, would give me somewhere around 335-340 open pressure. The cam will love the added seat pressure and the closer this gets you to CB the better. Since the open pressure is the limiting factor you kinda have to back into the best installed height.

63mako

Spring recommended by Lunati for his specific cam has an install height of 1.850, lift is .549, Spring height at max lift is 1.301 Coil bind is 1.110. Difference between max lift height and coil bind is .191 if you use the recommended spring with the recommended install height from the cam manufacturer.

scott foxwell

How many other cams do you think they recommend that spring for?
Perfect example of why I like to think these things through instead of just go off a catalog. Quite often I'll have two different springs on a set of heads, one for intake, one for ex. The devil is in the details.

REELAV8R

From what I'm seeing on the guide wear on the intake valves vs the exhaust valves, this statement seems logical. The intakes are wearing faster than the exhaust.
It appears that perhaps the difference in the mass to control or maybe that combined with the temps that they run at is having some effect on the guide wear. So the two valves are not responding/acting the same despite having the same spring and installed height.

cardo0

Cant see much of the vlv guide from any of your pics REEL but while u have some of the springs off u should measure the distance from the installed vlv retainer (no spring) to the top of the guide with the seal installed also. U need your max lift of 0.549" + 0.060" safety margin for 0.609" clearance under the retainer. Thats all i can think of right now as your not running a huge cam but something is hammering the shim under the spring.

Also checking your rocker clearances is something needed to be done for the full travel of the rocker arm.
Check the rocker arm to retainer clearance (0.40").
Check the rocker slot ends from the underside - 0.060" each end of travel (vlv open and vlv closed).
Thick unbent paper clips work pretty good for this.

Wow coil bind at 1.100" - thats huge from what im used to. But an extra 0.080" more than needed is another topic no one here can say is too much. Though your spings seem to have a short life and are declining fast your dyno chart doesnt reflect bad harmonics. Thats why im think'n somethings not fit up quite right.

63mako

Good luck! Hope you get it sorted out.

REELAV8R

Couple of thoughts here.
I don't know that we can say with any certainty that the spring life has been shortened to any degree greater than normal.
First I didn't test the springs when they were new so their true pressures then are an unknown. All we have to go on is the advertised specs. So far that, in my experience, has not been a source of reliable information for any new component on this engine.
Second other than the 10% normal loss of pressure from running, who but an engine builder that tears down engines frequently to rebuild them with used components can say what the spring pressure on their valves is after 1500, 5000 or 50,000 miles. Who test that? Normally, not the average Joe.

I'm not confident that a chassis dyno would be a reliable indicator of poor harmonics unless the effect was so pronounced as to create large fluctuations in power. Now the early sign off of the engine power could be an indicator.
Since the power we are looking at is going through the transmission then the rear end and finally to the tires, it seems to me that smaller fluctuations might not be observed due to the dampening effects of the drive train components.

Excessive wear to the valve train certainly illustrates a problem though.
First order of business is to correct the geometry. That's what I plan to do.

If the pushrod is looked as a tuning fork (which it kind of is) then I'll be changing the frequency of the tuning fork by changing the length.
Now while I'm at it I see no harm in increasing the seat pressure which by circumstance will increase the open pressures and run the spring closer to coil bind. Keep open pressure under the limit of the rockers and it should be good to go.
I can't see why, just because a spring has a recommended install height, that is cannot be altered as long as over the nose and seat pressures are acceptable and coil bind clearances are sufficient.
If one way a spring coil dissipates it's energy is to touch another coil or another spring then running the spring closer to coil bind can aid in dissipating the energy of the adjacent coil. This would alter the harmonics. Change the coil surge frequency and perhaps keep it on the seat.
Should that not be enough then further steps can be taken like changing to different springs.

I would like to find the problem and fix just that. I don't wholesale change out a bunch of stuff to fix an issue. I like to fix the specific problem.
If my Q-jet develops an issue I like to fix the issue with the carb not bolt on a new carb.
If I cannot fix the specific issue then maybe try changing things out to resolve the issue. Although I can't remember that I've ever had to do that.
I know much of modern auto mechanics involves changing components until the right one fixes the problem, and that will work, but then you never know the specific cause or solution of the specific problem.
Especially if you changed many things at once. So next time a similar issue comes up you still don't know how to fix it other than changing components until it's resolved. If you got lots of $$ to burn and no interest in the cause that works.

So I'm gonna see how it goes. Like I said little is lost if it doesn't work. But at least I would know what doesn't work. That's a good half way to knowing what does work.

scott foxwell

Again, plenty of spintron testing and engineering to show that running closer to cb will help settle the spring, and running too far from cb will do the opposite. This is not "engine" specific, either...it's pretty common design knowledge for any mechanism running a spring at a high rate where harmonics are an issue.

scott foxwell

I think you have a pretty good handle on all this.

REELAV8R

Ya know it's always hard to say what is exactly meant by certain comments on a forum.
You can't get the inflection in the voice or the expression on the face or the body language either. So lots of times things are taken wrong and some folks get insulted. It's an unfortunate side effect at times and it happens. Ehh...move on.
This is one of the reasons I usually try to just stick to the subject at hand.

When I post a problem, any and all ideas are fine with me. I'll decide which I want to take and which I don't.
Some Ideas may spark a thought in my head that is not exactly what someone said but took my focus in that direction and gave me the some solution.
Some Ideas I think fit perfect and others I'll keep in my back pocket as a back-up should the first idea not pan out.

In any case I have no problem with what ever the poster believes I may need to check. It's always possible to miss the obvious.
Can't see the trees because of the forest kind of thing.

vettebuyer6369

Guys, this looks like a pretty useful technical thread that the OP seems to be pleased about, regarding getting help. It would be a shame to delete it because people must continue personal squabbles.

There's more than one participant. I've tried to clean up most of the unnecessary commentary.

Please continue the comments and keep them on-track for the OP's sake. Additional bickering and piling on will result in sanctions for all participants.

REELAV8R

First Vettebuyer, thanks for cleaning up some of the responses.

Second I have been doing a little research to find reasons for spring surge and poor harmonics in a valve train. Here is some information I found in a hot rod article that might be of interest to those building or setting up their own valve trains.

From this article.
http://www.hotrod.com/how-to/engine/...-valvesprings/

Since the Dart heads are generically set up as a roller cam head it can leave entirely too much space from coil bind. In these cases with new more aggressive ramp rates this can set up an undesirable resonance and actually cause valve float or poor harmonics. The spring depends partially on contact with other coils to control it's movement.
In this case it may actually be necessary to shim up the valve spring to reduce the installed height and run closer to coil bind, as Scott pointed out, to stabilize the coils.
As the article points out the cam controls the rate of the valves decent to the valve seat not the spring. The springs job is to make the valve follow the cam's profile. So greater seat pressure is not a detriment to wear.
Over the nose pressure can be, but roller cams are designed to take more than flat tappets. So then lifter collapse would be the limitation mostly, and if the pressures were that high then a solid roller would be in order.

63mako

Been doing this 40 years and learn all the time. Didn't realize that the recommended spring could actually cause harmonic issues from to much space from max lift to CB. Different springs seems like a better solution than shimming them tighter. Your already over recommended spring pressure on the seat and even more pressure at seat and max lift will be pushing your rocker capabilities, stress the lifter internals and increase loading at the roller lifter interface.

REELAV8R

Yeah, pretty interesting stuff.
It kind of looks like the spring set up on these heads are heavy for the application. The springs need a diet. They are heavy and hard to control due to their own weight.
It seems like it could be better in this application to have a lighter spring then shim it up to the pressures I need to control the valve and not waste so much of the spring's energy controlling it's own surging.
Also in that article caught the part about shimming a max of .090" then if more is still needed, use spring locators.