Roller rockers, difference between brands?

[skinny z]

One point Miller stresses is that this method of working through geometry ensures that the information on the cam is translated accurately to the valve.
Seems straightforward enough.
Once the valvetrain is used as a tuning aid, I believe it was described earlier in this post as extending the dwell at max lift, then the whole thing kind of unravels as it's no longer mid-lift.
Getting it accomplished as per the text in the previously attached document looks to guarantee two things: One is that the valve follows the motion of the cam lobe profile and the other is that the travel across the valve tip is minimized and that ensures minimal stress on the components involved. Namely the guides and valve stem.
As always, your mileage may vary.

[Geoff2]

I don't see how the information can be 'accurately' transferred from lobe to the valve if you only look at mid lift geometry on the valve side. What about what is happening on the PR side?

If you want to see how much of a ratio change there is on the valve side, get hold of a worn factory rocker & have a look at the valve tip pad. A 1/8" -3/16" scuff mark. That is how much the pivot distance changes, & hence the ratio.

[Mark O'Neal]

Compression ratio is a static measurement that has little to nothing to do with cylinder pressure.

Rocker ratio is a static measurement that tells you the difference between a centerline and two contact points. Everything else is incidental.

[Tom68]

I don't see how the information can be 'accurately' transferred from lobe to the valve if you only look at mid lift geometry on the valve side. What about what is happening on the PR side?

If you want to see how much of a ratio change there is on the valve side, get hold of a worn factory rocker & have a look at the valve tip pad. A 1/8" -3/16" scuff mark. That is how much the pivot distance changes, & hence the ratio.

Miller addresses both sides of the Fulcrum in his rocker geometry, if indeed it's what he says it is it will be 90 degrees both sides at one point in the travel with the correct length pushrod and close to it with an incorrect length.

Yer sled rockers don't have a choice, the ratio increases as their lift increases, I'm sure they quote the mean ratio.

[skinny z]

I don't see how the information can be 'accurately' transferred from lobe to the valve if you only look at mid lift geometry on the valve side. What about what is happening on the PR side?

As posted earlier.

[quote=" ]
The midlift methods mission statement is :
Rocker Geometry is the correct DESIGN and INSTALLATION of the rocker arm so that its relationship to both sides of up-and-down motion is fully realized by BOTH. This is of course, the pushrod, and the valve (respectively).
[/quote]

[smokie]

Thanks for all the responses. I'm just taking it all in.

From what I gather, different brands of rockers will put the sweep pattern in different locations. The only way to find the sweet spot is going to be just trying different brands and seeing where they ride. What would you people that do this every day start out with brand wise? I'm thinking Harland Sharps or comp cams ultra mags.

My machinist says just to get a pushrod that puts the sweep pattern in the center of the valve and it won't hurt anything, myself I don't trust that. A factory vortec pushrod puts in right in the center at about a .125" sweep pattern. I like my guides not being worn out, so that's out of the question. The only other machinist in town is his brother and I worked for him years ago at his shop and let's just say I won't ever walk into his shop again. Nobody else around here are into hotrods, except a couple Mopar guys, so finding a couple singles of different brands is out of the question

Could I email or call the rocker companies and ask for their dimensions of the rocker arms and just compare several different brands like that? Or should I just buy a couple of singles from different manufacturers? Which brand should I start with?

I do appreciate everyone's input and advice.

[skinny z]

As mentioned before, when taking the pushrod length out of the equation a far as a tuning aid is concerned (and I'll need that one spelled out for me as it's contrary to what I've been taught), the narrowest sweep across the valve tip does two things: One is that it imparts the least sideways load to the valve guide and the second is that it ensures that the lobe profile information is accurately transmitted to the valve.
.125" I know from experience is a failure waiting to happen with bronze guides.
I target .040" and it's achievable. This is naturally lift dependant.

I'd surprised if the rocker arm phone rep could even get that information. Buying singles would suck but a selection of rockers is about the only way to know what works with your heads, engine architecture, phase of the moon, etc.
It'd be nice to able to get a loan of several varieties and check.

FWIW, I'll be working with the Crowers backset version as it gives an excellent valve side indication but now that the pushrod side has been brought more into the spotlight, I'll have to examine what I may have messed up there.

Gotta like Speed-Talk. Just when you think you have it figured out...

[Tom68]

Jim Miller would be worth asking any questions you have.

If you go for 90 degrees at mid lift most rockers will need about 200 thou longer pushrods.

Most rockers will be same distance from fulcrum to roller tip pivot.

If you run longer valves you'll almost definitely need offset fulcrums to get contact centered.

If roller tips do what they are supposed to do valve guide life shouldn't be a problem from side loading, if they roll freely with load they can't side load.

The contact doesn't have to be in the middle but if you get to close to the edge you will hammer the ends of the stems that could then chip.

Standard Vortec, comp Rocker sitting on, no lifter preload.

20221229_110707.jpg

[smokie]

Jim Miller would be worth asking any questions you have.

If you go for 90 degrees at mid lift most rockers will need about 200 thou longer pushrods.

Most rockers will be same distance from fulcrum to roller tip pivot.

If you run longer valves you'll almost definitely need offset fulcrums to get contact centered.

If roller tips do what they are supposed to do valve guide life shouldn't be a problem from side loading, if they roll freely with load they can't side load.

The contact doesn't have to be in the middle but if you get to close to the edge you will hammer the ends of the stems that could then chip.

Standard Vortec, comp Rocker sitting on, no lifter preload.


20221229_110707.jpg

The last engine I did was a406 with dart pro-1 215 heads with +.100 valves and I had used Harland Sharps and the sweet was dead center of the valve and was about .035" wide. I do understand that a longer valve can cause this, but it's the first time I've ever ran into it. This is also the first time of fooling with a hydraulic roller and scorpion rockers, which I doubt has anything to do with it.

I'm about ready to yank the heads off and put standard length valves in them, I'm just not sure I can get the 1.80 installed height with these aluminum heads. That would probably be the easiest, cheapest thing to do, if it would work.

[Tom68]

Oh yer, also factor in where the oil hole is clocked, factory is towards the valve, hole shuts when valve opens.

A lot of aftermarket are centered so will have constant oil flow to the roller rockers that don't need lubrication as much as the factory ball pivots do, go figure.

Shouldn't be the end of the world though, LS rockers just piss straight up and they don't have drippers or anything on the rocker covers to direct the oil.

[skinny z]

Jim Miller would be worth asking any questions you have.

If you go for 90 degrees at mid lift most rockers will need about 200 thou longer pushrods.

Most rockers will be same distance from fulcrum to roller tip pivot.

If you run longer valves you'll almost definitely need offset fulcrums to get contact centered.

If roller tips do what they are supposed to do valve guide life shouldn't be a problem from side loading, if they roll freely with load they can't side load.

The contact doesn't have to be in the middle but if you get to close to the edge you will hammer the ends of the stems that could then chip.

Standard Vortec, comp Rocker sitting on, no lifter preload.

Agreed on most points Tom except for the roller tip part. Seems there's some debate on whether the roller tip actually rolls.

viewtopic.php?t=63217

And whether they do or not, if you take it to the extreme and come at the valve tip from an acute angle, there's considerable force that's not directed along the valve stem centreline. I'd think it fair to say that any improvement there is just that. An improvement.

I've got files upon files of various head, rocker, pushrod length, pattern results and valve guide service life. Before I worked through the mid-lift method (and yes I know it's not the be all to end all) and had a resulting wide travel across the tip, although centred, service life varied but always short. Sometimes not even getting to 5000 miles before the guides were wiped. .550" lift, RPMs less than 6500, hydraulic roller.

[skinny z]

The last engine I did was a406 with dart pro-1 215 heads with +.100 valves and I had used Harland Sharps and the sweet was dead center of the valve and was about .035" wide.

That, to me, is the result you're after.

[smokie]

Exactly. The pattern I have now is only about .040", but it's so far out on the valve tip it worries me. What if the valve train becomes unstable? Will the rocker fly over the edge of the valve? Just makes me nervous.

[skinny z]

Exactly. The pattern I have now is only about .040", but it's so far out on the valve tip it worries me. What if the valve train becomes unstable? Will the rocker fly over the edge of the valve? Just makes me nervous.

I experienced exactly this with:
COMP Pro Magnum 1.6.
.100" longer valve.
Narrow but nearly off the edge.
Crower 1.6 with an .050" backset solved this issue. Narrow and centred.
That was on a RHS iron head.
The same condition existed (more or less) on AFR 195's and the same COMP rocker. However the Crower backset option was too much. But, the conventional Crower with a centred trunnion hole, brought all of the elements together for a narrow centred pattern.
This goes back to your threads original question. Yes, there are differences between brands.

I'm not a professional engine builder as many here are. My scope is very finite and pertains to what I'm involved with. The best I can do is relate my experiences and hope that it helps.

[smokie]

Exactly. The pattern I have now is only about .040", but it's so far out on the valve tip it worries me. What if the valve train becomes unstable? Will the rocker fly over the edge of the valve? Just makes me nervous.

I experienced exactly this with:
COMP Pro Magnum 1.6.
.100" longer valve.
Narrow but nearly off the edge.
Crower 1.6 with an .050" backset solved this issue. Narrow and centred.
That was on a RHS iron head.
The same condition existed (more or less) on AFR 195's and the same COMP rocker. However the Crower backset option was too much. But, the conventional Crower with a centred trunnion hole, brought all of the elements together for a narrow centred pattern.
This goes back to your threads original question. Yes, there are differences between brands.

I'm not a professional engine builder as many here are. My scope is very finite and pertains to what I'm involved with. The best I can do is relate my experiences and hope that it helps.

Are those crower rockers steel or stainless steel? What are the crower rockers called? I don't think crower even offers aluminum rockers do they?

Holy shit, 800 bucks for a set of rockers. Good lord that's crazy.