Shoe type factory rocker geometry

[scott foxwell]

Anyone here ever messed with the factory shoe type rocker geometry?
Rocker geometry is a real pet peeve of mine and I have a pretty good handle on roller rocker geometry, but the shoe type rocker really throws me.
With a roller tip rocker, the goal for proper geometry is minimum sweep across the valve tip, or 90* geometry where the effective centerline of the rocker is 90* to the valve at mid lift. For reference, this is what we try to achieve with a roller tip rocker:



With a shoe rocker, I'm not sure exactly what the goal is. One thing for sure, the ratio will change throughout rocker movement and you can alter that ratio a LOT by changing geometry (raising or lowering the stands). With a roller tip rocker, the distance from the center of the pivot (trunnion) to the center of the roller tip is fixed and for all intents and purposes, so is the contact point. Not so with a shoe rocker.
I can bench set-up a shaft roller rocker system on the head to get the perfect geometry. All I need to know is the lift, but that doesn't seem to be the case with shoe rockers. I did some experimenting last night with my FE heads and stock rockers. The first thing I thought I;d do was set up where the contact point of the rocker was my reference, and I;d set up the stand height so that a straight line from the center of the shaft (fulcrum, pivot, whatever you want to call it) to that contact point was 90* to the valve at mid lift. This sort of made sense intuitively.
Here's what I mean;



This pic shows the valve at half lift and where the rocker sits now. I use the top of the retainer as a reference to my 90* to the valve relationship. You can see that if I wanted to achieve my goal, the stands need to come down some. I can actually figure it mathematically since I can measure the height of the valve tip off the rocker pad but this is good enough for illustration purposes.
At this setting, I put some gear pattern grease on the tip of the valve and looked at the sweep pattern. This is what I get:




WIDE pattern on the valve. Centered, but WIDE. Well, I thought that was probably just a function of the way the shoe worked on the valve. Then I started moving the rocker and valve through it's motion and watching the tip. The shoe starts way back on it's heel, and as the valve opens, moves to the toe. Big time. Looking at it from a geometry stand point, this HAS to be changing the ratio, a LOT.
What I need to do is put this on a block with the cam and compare lobe lift to valve lift and record the ratio changes. I'll get to that. But for now, I'm just looking at the sweep on the valve tip and I'm wondering if I can change that, or if it will stay this way because of the shoe design. In my mind, I sure would like to reduce all that sweeping motion if I can.
So knowing I can't go shorter (without cutting rocker stands) to get my desired setting, I figured let's see what happens when I start ADDING stand height, just for reference.
These next pics will go in .030" increments all the way to .120".

Raised .030"




.060"




.090"




.120"




I can see that by the time I added .120" of shim, the pattern definitely got narrower. (Notice, the contact on the rocker never seems to change much but does seem to get narrower as well). Less sweep means less side loading on the valve and less guide wear, less overall friction but when I start looking at the position of the rocker and how it acts on the valve, I'm not nearly convinced this would be better. The problem is, I really don't know what "right" is for a shoe rocker, and what operating parameters an engineer is shooting for when designing around one. The other thing to consider is the push rid side of the rocker and I know what the correct geometry is on that side. Maybe that will be the deciding factor. Next step is to get the head on a block, cam in with lifters and see what the lift curves look like. I just thought this might be a fun discussion for anyone interested.

[blykins]

I do it the same way I do roller tip rockers:  minimize the sweep. 

I usually end up with at least a .060" shim with factory style rockers and the valves that I use here.  On engines with billet end stands, that requires making a long shim so that the entire end stand is supported.   You will have a much wider pattern than a roller tip.  Hard to get away from it.

Make sure and choke your adjuster way up.   You'll probably find that you can make a cup pushrod end clear the rocker arm with either zero or only one thread showing on the adjuster. 

[scott foxwell]

I do it the same way I do roller tip rockers:  minimize the sweep. 

I usually end up with at least a .060" shim with factory style rockers and the valves that I use here.  On engines with billet end stands, that requires making a long shim so that the entire end stand is supported.   You will have a much wider pattern than a roller tip.  Hard to get away from it.

Make sure and choke your adjuster way up.   You'll probably find that you can make a cup pushrod end clear the rocker arm with either zero or only one thread showing on the adjuster.

Thanks for that. I feel like if I keep adding shim the pattern will get narrower and narrower but I also know that moving too far away from the center of the arc isn't a good thing...not sure where to stop.
The other thing is, you could change the radius on the shoe and the rocker would act completely different. I wonder how they calculate what radius to use on the shoe. It's like a little cam lobe all of its own...

[blykins]

I'd wait until you get the engine mocked up and see if you're losing any lift. 

[scott foxwell]

I'd wait until you get the engine mocked up and see if you're losing any lift.

Yep. I know what the cam designer wants so I'll probably set it up to get as close to that as possible.

[66FAIRLANE]

Make sure and choke your adjuster way up.   You'll probably find that you can make a cup pushrod end clear the rocker arm with either zero or only one thread showing on the adjuster.

I thought you would want the adjuster pretty much where he has it. Straight line between tip pivot point, shaft pivot point & pushrod pivot point. Any movement either way in the adjuster and you would start to loose rocker ratio.., no?

[TomP]

In that first picture i'd rather have the rocker closer to the center at max lift and not worry where it is with the valve closed and no pressure.

[blykins]

Make sure and choke your adjuster way up.   You'll probably find that you can make a cup pushrod end clear the rocker arm with either zero or only one thread showing on the adjuster.

I thought you would want the adjuster pretty much where he has it. Straight line between tip pivot point, shaft pivot point & pushrod pivot point. Any movement either way in the adjuster and you would start to loose rocker ratio.., no?

On the engine in full running form, the pushrod will not be in line axially with the rocker arm adjuster.  So if the adjuster is hanging way down, your pushrod end spends time dancing back and forth instead of translating all movement to the valve.  The closer it is to the rocker body, the less wasted movement.  Obviously you can't get it too close or the pushrod cup makes contact.

[Barry_R]

You will also find that the pushrod tube will contact the rocker body as you back the adjust up.  Some detailing on the rocker casting helps.  That noted, backing the adjuster up is the right idea as far as lift goes.  When its way down the pushrod will sweep "in and out" a lot getting into trouble with the intake hole and side loading the cup.

[scott foxwell]

Make sure and choke your adjuster way up.   You'll probably find that you can make a cup pushrod end clear the rocker arm with either zero or only one thread showing on the adjuster.

I thought you would want the adjuster pretty much where he has it. Straight line between tip pivot point, shaft pivot point & pushrod pivot point. Any movement either way in the adjuster and you would start to loose rocker ratio.., no?

There is an "ideal" geometry for the pushrod side that follows what I do with the roller tip rocker on the valve side. The center of the ball on the pushrod end is the pivot point. You want an imaginary line from the center of the shaft through the center of the ball, to be 90* to the pushrod at mid lift. Same as the valve side. I would want the adjuster out as little as possible just to maintain rigidity but it I'll set them up with the geometry as close as I can get it.

[scott foxwell]

You will also find that the pushrod tube will contact the rocker body as you back the adjust up.  Some detailing on the rocker casting helps.  That noted, backing the adjuster up is the right idea as far as lift goes.  When its way down the pushrod will sweep "in and out" a lot getting into trouble with the intake hole and side loading the cup.

Thanks Barry. I'll look out for that.
What are your thoughts on the valve side of things?

[Barry_R]

At least drop down to an 11/32 stem - valves are really long at +/- 5.425, so they are heavy.

You can get a big intake in there but the exhaust gets tight against the wall - a 1.720 will physically clear on a 4.070 bore but will scrub the wall when its running - I would not go past 1.680 anymore

[scott foxwell]

At least drop down to an 11/32 stem - valves are really long at +/- 5.425, so they are heavy.

You can get a big intake in there but the exhaust gets tight against the wall - a 1.720 will physically clear on a 4.070 bore but will scrub the wall when its running - I would not go past 1.680 anymore

I have 2.05 and 1.65 11/32 x 5.425 valves from REV. The only down side is they have a /25 tip so while you have PLENTY of installed height, you have to use a -.05 lock to clear the retainer. FWIW this is pretty much standard length for BB Chev valves I use and they run anywhere from 2.25 to 2.35 int, and 1.88 ex. THOSE are heavy. These FE valves...they're not heavy.

[Ford428CJ]

I end up using .060 shims with POP or stock stands. Blue Racer rockers with this set up.

[scott foxwell]

I end up using .060 shims with POP or stock stands. Blue Racer rockers with this set up.

That looks good but you're talking about a roller tip rocker. Factory shoe rocker is altogether different.

[Cyclone03]

Bringing this back from the dead because I'm trying to set up my non-adjustable rockers and hyd roller. 

POP stands, rev valves, ED heads by Barry. New valve  job by a trusted local Ford guy.

Checking spring installed,heads not installed I just used a dial indicator to set to max lift.

At zero lift the pattern is right on the heal of the valve so close to the edge,it is on the edge.
At .600" lift the pattern is WIDE 3/4 way across the valve.

I shimmed the stands up .050" and the heel moved onto the valve and the pattern tightened up stopping past center ,again close to 3/4 way across.

Going to .100" tightens the pattern up ,call it all 1/3rds,the pattern is well centered.

Now here is another observation. I set my valve tip zero down .100",remover the shims and bolted the stands down. It is so close to the same result as the .100" shim it looks like the best option.

What am I missing?

Can .100 be cut from the tip of the valve (still above the retainer .050"+) ,or is the tip hardened?

So supper wide,near edge to edge or smallest pattern centered?

Hope you guys are up tonight.

[Barry_R]

Use the shim.  Do not cut the valve tips.  Most of them will have a fairly thin hardened (8645 IIRC) wafer friction welded to the top above the keeper groove (so much for the one piece valve marketing hype).  A very few Ferrea ones will be even thinner induction hardened.

[Cyclone03]

Steel or Aluminum for the shim/spacer?

[blykins]

Hardened steel. 

You can use valve spring shims, just make sure the ID of the hole seals around the feed hole in the head.  You can use some grease to keep the shims in place while you bolt the rocker arms down. 

If you're using end stands, you will need to be a little fancy with the shim as it will need to support the entire end stand.

[scott foxwell]

Bringing this back from the dead because I'm trying to set up my non-adjustable rockers and hyd roller. 

POP stands, rev valves, ED heads by Barry. New valve  job by a trusted local Ford guy.

Checking spring installed,heads not installed I just used a dial indicator to set to max lift.

At zero lift the pattern is right on the heal of the valve so close to the edge,it is on the edge.
At .600" lift the pattern is WIDE 3/4 way across the valve.

I shimmed the stands up .050" and the heel moved onto the valve and the pattern tightened up stopping past center ,again close to 3/4 way across.

Going to .100" tightens the pattern up ,call it all 1/3rds,the pattern is well centered.

Now here is another observation. I set my valve tip zero down .100",remover the shims and bolted the stands down. It is so close to the same result as the .100" shim it looks like the best option.

What am I missing?

Can .100 be cut from the tip of the valve (still above the retainer .050"+) ,or is the tip hardened?

So supper wide,near edge to edge or smallest pattern centered?

Hope you guys are up tonight.

If you go back to the beginning of the thread, I did the same thing and got the same results. However, I'm not 100% sure that tightening up the pattern on the valve tip is the right way to go. I think there is more to the shoe type rocker than adjusting the wear pattern. I've asked and asked over the years if someone could explain the geometry behind a factory rocker...no one ever has. I choose to "assume" the engineers had their reasons for how they had the rockers set up on these motors, so my conclusion is to set them up so you get the advertised lift @ the valve. "Techincally", to maintain factory geometry; if you have more than factory lift, you should be shortening the stands, not raising them. You'll notice that because of the design of the rocker, you can change the lift (and events) pretty significantly by changing the geometry. This is because as the rocker goes through it's motion, the actual physical ratio will change as the contact point between the valve and rocker moves outward on the shoe further away from the shaft. You have a cam with specific events that you have chosen...I would set the geometry to transfer that information from the cam to the valve as accurately as possible. JMO.

[Heo]

Without putting my whole soul in to this. I have always
assumed that the idea behind the profile on the stock
rockers is that you should set it up so it  "roll" on the
valve not rub.

So technically you should probably grind a different
radius for different lifts to get the best compromise
between roll ,rub,lift

Often you See the wear pattern on the rocker when a higher
lift cam is used is more wear toward the tip of the rocker
Just a thought...I don't know

[Cyclone03]

Without putting my whole soul in to this. I have always
assumed that the idea behind the profile on the stock
rockers is that you should set it up so it  "roll" on the
valve not rub.

So technically you should probably grind a different
radius for different lifts to get the best compromise
between roll ,rub,lift

Often you See the wear pattern on the rocker when a higher
lift cam is used is more wear toward the tip of the rocker
Just a thought...I don't know

Thanks for your comments.
With no shim the rocker is right on the edge of the valve,so shimming up is required to get the rocker on the valve tip face. My first thought was using the tins,but I cant seem to find where I hid them. I added a .030" shim and just got the rocker on the tip face, .050" allows the pattern to cross the full face of the valve and is centered. More shim from there tightens the pattern,I stopped at .120".

[babybolt]

I've seen rockers where the radius was tightened up for higher lift cams.

[Heo]

I've seen rockers where the radius was tightened up for higher lift cams.

What i was thinking about

[Heo]

Some one less computer illiterate than me should
be able to come up with some "animation" of that

[Cyclone03]

A good test goes a long way.
Busted out the checking springs and dial indicator.
No shim,stand bolted to head. Valve tip pattern started right on the intake edge of the valve and traveled past 3/4 the way across valve. Max lift was .535 on a .581 lift cam.

Next .050 shim. Pattern about 1/4 in and again past 3/4 the way across valve. ,584 lift

.100 shim started the pattern 1/3 away from the intake side and almost to the exhaust side edge of the valve. .587 lift

Like Brent said about .070 is about right. I went to a .0655 (1/16") shim ,got a pattern well centered and .157 wide and .586 total lift on a .581 cam.

Ordered some steel to make some usable shims.