Valvetrain Geometry

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I wonder what angle on the gen 3 hemi is? Sorry if that is way off track.
 
yea
92b said:
I wonder what angle on the gen 3 hemi is? Sorry if that is way off track.
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Yeah I already went off the rails with my post.

Sorry guys, maybe I'll start a thread looking for cad drawings/blueprints.
 
Earlie A said:
Wonder how much it could be corrected with lifter bushings? And how far could you cheat a cam core? 2,3,4 degrees?

Wonder what Bob Glidden was using for cam cores when he welded his own blocks to 48 degrees?
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He was using custom cores. You can still do that. I know Cam Motion and probably Bullet, Crower and a couple of others will do a custom cores, but it’s not cheap.
 
RustyRatRod said:
That's what I was asking essentially. It could only be done with lifter bushings. I think newbomb mightta missed that. Does it or would it really matter about the cam core? Could you "cheat" that much.....or would you be actually correcting something and remove friction from the whole shoot & match? Maybe we should just all run 1st gen Chevy small blocks. lol
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You would still need the material around the bushing to support the bushing.

Look at the Ritter block or an R3 with the 59 degree LBA and you can see how much materiel there is inboard of the lifters to move the LBA to 48 degrees.

And Cuda416 is correct, you have to rotate the bores to get them over the cam correctly.

So it’s not just moving one angle. That’s why Glidden and Gentilozzi and the rest were cutting out the entire lifter valley and putting it back in. That was a ton of work but it was the only option then.

What’s appealing to me is Chrysler knew the issue for high specific output small blocks and they didn’t do a thing about it until the what? The late 1990’s.

Of course, the jackasses at NHRA killing Pro Stock Truck was the end of all that.
 
And then there’s the issue with the heads.
When you try and run 59* heads with a 48* LBA, the lower end of the pushrods wants to occupy space where the intake flange is.

EBA12661-957E-413C-B65B-A7F6ED4D5196.jpeg
 
Newbomb Turk said:
He was using custom cores. You can still do that. I know Cam Motion and probably Bullet, Crower and a couple of others will do a custom cores, but it’s not cheap.
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Would Glidden have been using cast or billet? Is custom cast even an option today?
 
Earlie A said:
Would Glidden have been using cast or billet? Is custom cast even an option today?
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I believe they were 9310 cores.

Jenkins talked about getting custom cores ground with semi and unrelieved lobes on them.

I’ve seen one semi relived cam in my life and never an unrelieved lobe core.

That was in effect trying to compensate for the small diameter cores by not
 
Thanks to @gzig5 for sending me an old style PRW 1.6 rocker to compare to the new style. The data in the first picture shows the results of actual valve motion testing of the two rockers. The rest of the pictures show the differences in the two. Old rocker is shiny, new one is dull. In the picture with both rockers on the shaft, the old style rocker is in the background.

There is no real difference in the valve side of the rocker arms except for the shape of the long arm. Looks like it was changed to increase spring clearance. The fulcrum length (distance between the rocker shaft centerline and the roller tip centerline) does measure a bit different between the two, but that could just be manufacturing tolerances. These are Chinese rockers and even the new rockers vary by several thousandths from rocker to rocker.

The real change in the rockers is on the pushrod side. The angle of the adjuster and the adjuster arm has been changed. The old rocker could be considered a '90 degrees in valve closed position' rocker. The new rocker could be considered a '90 degrees at mid-lift position' rocker. In this regard the new style rocker is an improvement over the old.

If you look closely at the second picture you can see a couple of other differences. The old style rocker has two individual bushings with a space between. New style is one solid bushing with a small machined groove in the center for oil distribution. Look closer and you can see the valve side oiling holes. The old style has a larger hole that feeds oil onto the top of the rocker. This hole is not restricted in any way and with 8 rockers on each shaft it's hard to see how there could be any shaft oil pressure. The new style oil hole is smaller, under the long arm and is drilled off-center. The off-center location restricts the oil flow and would help to maintain oil pressure in the shaft. Seems like shaft oil pressure would be important in a bushing style rocker.

One thing I do like about the old style rocker - the roller tip protrudes farther than the two arms.

IMG_3856.jpg


IMG_3854.jpg


IMG_3849.jpg


IMG_3852.jpg


IMG_3855.jpg


IMG_3853.jpg
 
Can you get a weight difference between them? The ribs on the new one look thicker but the profile of the arms is different so maybe not a big difference?
 
Newbomb Turk said:
I believe they were 9310 cores.

Jenkins talked about getting custom cores ground with semi and unrelieved lobes on them.

I’ve seen one semi relived cam in my life and never an unrelieved lobe core.

That was in effect trying to compensate for the small diameter cores by not
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WHAT? There's something you haven't seen? I'm floored.
 
RustyRatRod said:
WHAT? There's something you haven't seen? I'm floored.
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Yup. That stuff was old by the time I started messing around with this junk.

BTW, I still can’t find my Jenkins book but I’m pretty sure he was getting General Kenetics to grind some of his cams.

I couldn’t think of that the other day.
 
Newbomb Turk said:
Yup. That stuff was old by the time I started messing around with this junk.

BTW, I still can’t find my Jenkins book but I’m pretty sure he was getting General Kenetics to grind some of his cams.

I couldn’t think of that the other day.
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Yeah, that was probably right about the time Harold was working with them.
 

Some really interesting points about mechanical resonance here. Resonant frequencies are caused by harmonic vibration matching oscillating or rotational speed. I suspect that aluminum rockers help act to absorb some of that as well as reduce (possibly eliminate) it with the reduction of oscillating mass if the rockers are designed with the mass properly balanced across the body of the rocker. Sort of like aluminum main caps are used in big blocks to reduce the shock transferred directly into the bottom end. Or aluminum rods for shock absorption in fuelers.
 
Garrett Ellison said:
Some really interesting points about mechanical resonance here. Resonant frequencies are caused by harmonic vibration matching oscillating or rotational speed. I suspect that aluminum rockers help act to absorb some of that as well as reduce (possibly eliminate) it with the reduction of oscillating mass if the rockers are designed with the mass properly balanced across the body of the rocker. Sort of like aluminum main caps are used in big blocks to reduce the shock transferred directly into the bottom end. Or aluminum rods for shock absorption in fuelers.
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Years ago I worked in a coal burning and steam generating powerhouse. The steam turbines that generated electricity were up to 8' in diameter and 10' or so long and rotated at 3600 rpm. The rotating mass was several thousand pounds. In going from 0 to 3600 rpm (or 3600 rpm to 0) the turbine would go through at least one critical speed. You really didn't want to be standing next to the machine when the rpm hit critical speed.

Harmonics and resonance are very powerful. I don't know the answers to some of your observations other than to say you are hitting on important issues and some of the elite rocker arm companies spend time studying these things.
 
Earlie A said:
Years ago I worked in a coal burning and steam generating powerhouse. The steam turbines that generated electricity were up to 8' in diameter and 10' or so long and rotated at 3600 rpm. The rotating mass was several thousand pounds. In going from 0 to 3600 rpm (or 3600 rpm to 0) the turbine would go through at least one critical speed. You really didn't want to be standing next to the machine when the rpm hit critical speed.

Harmonics and resonance are very powerful. I don't know the answers to some of your observations other than to say you are hitting on important issues and some of the elite rocker arm companies spend time studying these things.
Click to expand...

It's an interesting and common thing to be sure. I work in an "IT" based environment and when HP announced their C7000 blade chassis (the nerds will know) the cooling fans were so well engineered, they actually programmed into the controller a "skip speed" so the fans (modeled after R/C ducted fans) would avoid running at a specific speed and not sound like an F16 taking off. The skip speed was the rpm at which the fan went resonant.
 
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