Hyd Roller vs Hyd Flat tappet on SM heads

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Newbomb Turk said:
AWESOME. Would you mind showing the sweep for 1 inch lift?

Although I’m not sure if rocker lengths, ratios and such.
Click to expand...

Yeah i think posting the .600 lift and 1” lift would prove or disprove Bewys point.
More lift equals wider sweep.

He also said a longer rocker will create a narrower sweep.

Can you (EarlieA) if it’s not too much trouble, post one with 1.5” shaft center to roller center distance?
 
Cuda416 said:
Slow down, your arguing with someone who isn't arguing with you.

I'm just pointing out a potential issue with the drawing. Do you want your point to be based on correct, or incorrect info?

Carry on...
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I wasn’t arguing. It’s pointing out how much too wide an .080 sweep really is.

I apologize because I thought it was you who posted that wide sweep.

It was Cookietruck. It doesn’t really matter who it is.

It matters that people who come along later and read these threads get the correct information and not a bunch of bullshit like you see in this thread.

Guys run their stuff that wide and get away with it. You also see failed rockets long before their service life is up, and the aluminum rocket gets the blame when it’s really a geometry issue.

It’s also crazy to see how unstable the valve train is when the geometry issue off.

Plus the performance loss from bad geometry and the valve moving off the seat very slow and speeding up around the nose, when in fact you want the valve moving off the seat as fast as can be done reliably and have the valve slow down around the nose.

If the valve is slow off the seat and fast over the nose, you have the valve spending more time where curtain area is small and flow is limited, and then when the valve is near max lift it’s moving too fast where you have the most flow. That’s backwards.

You want the valve to move slowly around max lift where head flow is the highest.

So there are several issues getting corrected with geometry.
 
cookietruck said:
Yeah i think posting the .600 lift and 1” lift would prove or disprove Bewys point.
More lift equals wider sweep.

He also said a longer rocker will create a narrower sweep.

Can you (EarlieA) if it’s not too much trouble, post one with 1.5” shaft center to roller center distance?
Click to expand...
A longer stroke creates a larger travel arc, which means the same angular travel will result in a reduced amount of horizontal travel.
 
Newbomb Turk said:
I wasn’t arguing. It’s pointing out how much too wide an .080 sweep really is.

I apologize because I thought it was you who posted that wide sweep.

It was Cookietruck. It doesn’t really matter who it is.

It matters that people who come along later and read these threads get the correct information and not a bunch of bullshit like you see in this thread.

Guys run their stuff that wide and get away with it. You also see failed rockets long before their service life is up, and the aluminum rocket gets the blame when it’s really a geometry issue.

It’s also crazy to see how unstable the valve train is when the geometry issue off.

Plus the performance loss from bad geometry and the valve moving off the seat very slow and speeding up around the nose, when in fact you want the valve moving off the seat as fast as can be done reliably and have the valve slow down around the nose.

If the valve is slow off the seat and fast over the nose, you have the valve spending more time where curtain area is small and flow is limited, and then when the valve is near max lift it’s moving too fast where you have the most flow. That’s backwards.

You want the valve to move slowly around max lift where head flow is the highest.

So there are several issues getting corrected with geometry.
Click to expand...

All good man, no harm no foul.
 
cookietruck said:
Yeah i think posting the .600 lift and 1” lift would prove or disprove Bewys point.
More lift equals wider sweep.

He also said a longer rocker will create a narrower sweep.

Can you (EarlieA) if it’s not too much trouble, post one with 1.5” shaft center to roller center distance?
Click to expand...

It already disproved his theory that at .600 lift your .080 wide sweep was correct.

Don’t take this as me picking on you. It’s just you happened to post a perfect example of what bad geometry looks like.

To claim that at .600 lift your sweep is as good as it gets is nonsense. It’s like some guys read books and magazines and take that as gospel.

I hope you contact Mike at B3 racing engines and talk to him.
 
Here's the 1" lift.

IMG_3292.jpg
 
Here's the 1.5" arm. The Hughes roller is 0.535". The way I see it a 0.300" roller tip would not affect the sweep distance. It would, however, effect the correct installed height of the 7/8" shaft if a 0.535" roller were replaced with a 0.300" roller on the same rocker arm. In reality, if one company used a 0.535" roller and another company used a 0.300" roller, the whole geometry of the rocker arm would be different.

IMG_3293.jpg
 
Earlie A said:
Here's the 1.5" arm. The Hughes roller is 0.535". The way I see it a 0.300" roller tip would not affect the sweep distance. It would, however, effect the correct installed height of the 7/8" shaft if a 0.535" roller were replaced with a 0.300" roller on the same rocker arm. In reality, if one company used a 0.535" roller and another company used a 0.300" roller, the whole geometry of the rocker arm would be different.

View attachment 1716340442
Click to expand...

Thanks for pointing out the size of the Hughes roller. I'll need to look at the geometry later, I have an appointment to go to.

Not part of any argument either way, as usual, just trying to learn.
 
Newbomb Turk said:
It already disproved his theory that at .600 lift your .080 wide sweep was correct.

Don’t take this as me picking on you. It’s just you happened to post a perfect example of what bad geometry looks like.

To claim that at .600 lift your sweep is as good as it gets is nonsense. It’s like some guys read books and magazines and take that as gospel.

I hope you contact Mike at B3 racing engines and talk to him.
Click to expand...

I understand what you’re saying. If i needed it perfect i would def contact B3. In this instance I will call this good enough to run and move on with the build.
 
Thanks guys [ Cuda416. Cookietruck et al ] for veryfying what I said in posts #46 & 60.
 
And thanks to Early A for his excellent drawing in post #71. This drawing shows another 'anomaly' with rockers that affects the final valve movement [ lift ]. I didn't mention it earlier because it would have complicated things. This is one reason why the overall ratio can vary so much as shown in post #61.
Looking at post #71, look at the max lift, & look at the vertical line drawn from the roller pivot to the valve tip. The distance from that contact point on the valve tip to the fulcrum pivot represents the 'lever length' on the valve side of the rocker. Notice that this distance is longer than the distance from the fulcrum pivot to the roller pivot. The diam of the roller will have an affect. You have similar variances on the prod side of the rocker. All adds up to the discrepancies that show actual measured ratio v advertised ratio.

img325.jpg
 
Here's another drawing to illustrate ONE effect of roller tip diameter. I made this drawing so I could understand a little more about rocker geometry. I'm not interested in who is right and who is wrong. You guys are bringing up some fascinating topics that I want to understand.

So here's the point of this drawing. IF the rocker geometry is set up for minimum sweep (and I'm not saying it always should be) then roller tip diameter does not change the valve motion. The total sweep angle to achieve 1" of lift is the same for both roller tips and the valve lifts after 10 degrees of rocker rotation are identical. Roller tip diameter does affect optimum location of the 7/8" shaft centerline with respect to the top of the valve.

In this example we are looking at one half of the rocker arm and we are designing that half of the rocker arm the way we want it. It the real word we would be choosing parts that are already being manufactured and installing them on a rocker pedestal that may not be in the proper location. In that case the other half of the rocker arm, the rocker shaft location and the roller diameter would start affecting valve motion because geometry is not optimum.

The way I see it, the most important dimension for minimizing sweep is the distance from valve tip to rocker shaft centerline measured parallel to the valve.

Not saying I'm right, just stating things the way I see them. This is good stuff. I'm interested in other points of view.

Apologies to the OP if this is turning into a hijack. We can continue this elsewhere if need be.

IMG_3298.jpg
 
Earlie A said:
The way I see it, the most important dimension for minimizing sweep is the distance from valve tip to rocker shaft centerline measured parallel to the valve.
Click to expand...

Agreed, but I'll point out my comment regarding the diameter of the roller tip changing things still stands if you only change that one variable which is what I was referring to. If the only thing that changed was the roller tip dia, it "rotates" the arc down. When that happens, the horizontal travel increases slightly.

In these two drawings, you changed the height of the rocker fulcrum at the same time, which is of course required to make things work.

I'm not arguing, just learning by looking over everyone's shoulders.

Your efforts are appreciated as it's good to see these things represented in a way that shows the geometry.
 
Cuda416 said:
Agreed, but I'll point out my comment regarding the diameter of the roller tip changing things still stands if you only change that one variable which is what I was referring to. If the only thing that changed was the roller tip dia, it "rotates" the arc down. When that happens, the horizontal travel increases slightly.

In these two drawings, you changed the height of the rocker fulcrum at the same time, which is of course required to make things work.

I'm not arguing, just learning by looking over everyone's shoulders.

Your efforts are appreciated as it's good to see these things represented in a way that shows the geometry.
Click to expand...
I agree with you. It seems that with a stock SBM rocker shaft location, a large diameter roller tip makes the geometry worse.
 
Earlie A said:
I agree with you. It seems that with a stock SBM rocker shaft location, a large diameter roller tip makes the geometry worse.
Click to expand...


The roller tip certainly changes geometry.

I know there are two schools of thought on geometry and some variations from that.

Going off my memory there is 2/3 lift and 1/2 lift, meaning at 2/3 lift the rocker is 90 degrees to the valve.

1/2 lift means the rocker is 90 degrees to the valve.

This is basic stuff Mike covers on his page.

That geometry affects how fast (or slow) the valve moves off the seat and how it moves around max lift.

The amount of adjuster protrusion will affect rocker ratio.

The farther up the adjuster is, the higher the ratio. The lower the adjust is, the lower the ratio.

I haven’t done the math to know if that changes valve speed off the seat, but at this point I don’t really care. I set my stuff up to be faster off the seat regardless.

That’s why it’s important that the right information gets out there.

If the builder misses on one or both of these parameters then you get a valve train that is not happy.

IMO it matters about what is correct and what’s not.

That’s not to say there are times where someone may need to use the 2/3 lift method.

Which IIRC is what Chrysler did, but I could be wrong on that.
 
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