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-   -   Ironhead Shovster build take2 (http://xlforum.net/forums/showthread.php?t=2077210)

Maxeffort 29th March 2021 00:13

Quote:

Originally Posted by billeuze (Post 5886481)
So, in the shovel FSM I found this which I assume is what you are calling the "valve stem protrusion":
Valve stem extensions from cylinder head boss: 1.600-1.645.
What I measured is 1.675. close but slightly higher than factory specs


No, I think the exhaust valve side is off. The above deviation form valve stem protrusion specs supports this as do some other measurements I took (which I'll post in another update shortly). And to correct it I'd have to lift the rocker box slightly (or use valves with shorter stems). So lash caps wont work in this case. I will do some test measurements though with some different thickness washers used as spacers instead of a gasket to see how that changes the valve side geometry of both rockers. Then if required, I could adjust the low one with a lash cap - although they should be both close to the same


Less valve protrusion/ shimmed rocker box is going to make the pushrod to rocker angle worse.

It will be interesting to see what that contact looks like at the valve tip.

needspeed 29th March 2021 00:22

Quote:

Originally Posted by Maxeffort (Post 5886523)
Less valve protrusion/ shimmed rocker box is going to make the pushrod to rocker angle worse.
It will be interesting to see what that contact looks like at the valve tip.

I agree.

I should say that I'm not the best person to give advice on shovelheads as I've never worked on one. Actually a lot of what I learned has come from reading this thread.

I found this thread that may explain (or confuse):rolleyes: the subject of valve stem protrusion. I don't know.

http://knuckleheadtheology.blogspot....-pans-and.html

I have a '70 to early '78 shovelhead FSM that shows the measurement 1.500 to 1.545 to the guide shoulder, same as in the linked thread. Apparently around 1979 seals were added and the measurement is 1.600 to 1.645, but measured directly to the head casting.

Your measurement is a little long and out of spec but if it were shorter your pushrod side would probably get worse.:(

Because the rocker moves in an arc, the pad that pushes on the valve rubs across the stem when going from open to closed, leaving a contact patch of a certain width. In my opinion, good geometry on the valve side centers that patch on the stem as much as possible.

You can see this patch by painting the stem with marker, machinist blue or even a dab of grease. This may be easier than trying to measure the angles of the stem to the rocker pad to the shaft center.

billeuze 29th March 2021 01:42

I admit I have a hard time visualizing if the rocker shaft needs to be raised or lowered to correct geometry. I pretty much need a working model in front of me to see how it is working. Once I work on this a bit more it will be more clear to me but at this point I get mixed up by things that linguistically appear to be reverse logic: pushing down to get valve lift for example.

I totally understand the arc movement and how it plays out on the contact patch of the valve stem top. But it is hard to see and measure precisely. I guess I can see what results I get with marker or grease or machinist blue if I can find some.

kitabel 29th March 2021 03:37

The term "geometry" is somewhat confusing, since it incorporates both design-in features to the rocker arm, as well as adjustments.
The two rocker arm levers are not directly opposed (like a see-saw), but instead incorporate the valve stem angle (40?) on the long (valve) side), and the angle aligning the pushrod with the tappet and cam lobe on the short (pushrod) side.
The first angle is correct if the stem height, lift etc. are original. The second angle must be wrong since it aims the pushrod at the big twin cam... which isn't there. The alignment different between the XL cam actually moving the valve and the big twin cam is off by a bit on the intake cams, and much worse on the exhausts.
There is no adjustment (stem height, lash cap, pushrod length, rocker box height) that cures this, it requires re-clocking.
The question is not "is it correct with the stock shovel or Evo rockers?", the answer is no.
The real question is "is it bad enough that I want to fix it?".
Your choice.

billeuze 29th March 2021 04:29

And I think the intake is close enough that I’m not worried about it. But the exhaust, I haven’t decided yet, but I think it I should probably fix it

billeuze 7th April 2021 05:30

so I've been trying to settle on the best rocker geometry on the valve end first. then once that is set, I'll move on to the pushrod end. This evo thread has a lot of good rocker geometry info: http://xlforum.net/forums/showthread...ocker+geometry (and a lot of misinformation but reading through to the end gets most of the misinformation corrected).

One thing that thread suggests is that the best rocker geometry is the one that gets you maximim lift. This makes sense because with the rocker arm perpendicular to the valve stem at half lift is the setting that will give you the most up and down vector during the arc travel of the rocker. The more you move away from perpendicular at 1/2 lift, you get more sideways vectors as the rocker arm sweeps towards the top or bottom of its arc. But in practice, I found that you can't use max lift as the test for finding perfect geometry. I raised the rockers boxes incrementally, measuring total valve lift each time. The max lift just kept getting higher the more I shimmed the rockers - even after I had raised them to the point I could visually see that they were beyond the optimal geometry. why would that be? I noticed that when the rocker boxes where without shims, it was mostly the insides of the rocker arm pads that made contact with the valve stem. Then, after some shimming, it was more the center of the pad that was making contact and finally with even more shimming, it was the outer tips that were making contact. Using the outer edge of the rocker arm pad means a higher rocker arm ratio compared to using the center, therefore creating more lift even though past the point of perfect geometry. Eventually I found that taking phots of the rocker arm pads at zero, 1/2, and full lift and comparing them side by side was really the best way to see what is happening and it gives me a pretty good idea what shim height to use:
each of these photos is left to right: zero lift, 1/2 lift and full lift:

No shims, just the gasket:
https://i.ibb.co/gP9SMsw/gasket-only.jpg

shimmed to .075 above gasket height:
https://i.ibb.co/pjRr3X6/plus-075.jpg

Shimmed to .155 above gasket height:
https://i.ibb.co/HhV4GK9/plus-155.jpg

The other effect we can see in the above photos is that as I increase the shim height, we are also moving the axle of the rockers in towards the center of the cylinder because we are lifting the axles straight up rather than up and out 40 degrees to (approximately) follow the valve stem angles.

The center of these three photos looks to me like the geometry that is closest to perpendicular at 1/2 lift and it is also the one that has the rocker pad more in the center of the valve stem. Although the bottom photo is the one that gave me the most valve lift (.502"). So I ordered some .080 aluminum sheet to make shims.

Next I will start figuring out how much I should adjust the angle at the pushrod end to make those ends of the rockers arms perpendicular to the pushrods at 1/2 lift. This will have to done by cutting them apart and welding them back together. I'll be using these old rockers as tests/mock-ups to get the angle right. And I've ordered some new rockers that I'll send out to real welder once I get the correct angle worked out.

Maxeffort 7th April 2021 15:11

Quote:

Originally Posted by billeuze (Post 5888534)
so I've been trying to settle on the best rocker geometry on the valve end first. then once that is set, I'll move on to the pushrod end. This evo thread has a lot of good rocker geometry info: http://xlforum.net/forums/showthread...ocker+geometry (and a lot of misinformation but reading through to the end gets most of the misinformation corrected).

One thing that thread suggests is that the best rocker geometry is the one that gets you maximim lift. This makes sense because with the rocker arm perpendicular to the valve stem at half lift is the setting that will give you the most up and down vector during the arc travel of the rocker. The more you move away from perpendicular at 1/2 lift, you get more sideways vectors as the rocker arm sweeps towards the top or bottom of its arc. But in practice, I found that you can't use max lift as the test for finding perfect geometry. I raised the rockers boxes incrementally, measuring total valve lift each time. The max lift just kept getting higher the more I shimmed the rockers - even after I had raised them to the point I could visually see that they were beyond the optimal geometry. why would that be? I noticed that when the rocker boxes where without shims, it was mostly the insides of the rocker arm pads that made contact with the valve stem. Then, after some shimming, it was more the center of the pad that was making contact and finally with even more shimming, it was the outer tips that were making contact. Using the outer edge of the rocker arm pad means a higher rocker arm ratio compared to using the center, therefore creating more lift even though past the point of perfect geometry. Eventually I found that taking phots of the rocker arm pads at zero, 1/2, and full lift and comparing them side by side was really the best way to see what is happening and it gives me a pretty good idea what shim height to use:
each of these photos is left to right: zero lift, 1/2 lift and full lift:

No shims, just the gasket:
https://i.ibb.co/gP9SMsw/gasket-only.jpg

shimmed to .075 above gasket height:
https://i.ibb.co/pjRr3X6/plus-075.jpg

Shimmed to .155 above gasket height:
https://i.ibb.co/HhV4GK9/plus-155.jpg

The other effect we can see in the above photos is that as I increase the shim height, we are also moving the axle of the rockers in towards the center of the cylinder because we are lifting the axles straight up rather than up and out 40 degrees to (approximately) follow the valve stem angles.

The center of these three photos looks to me like the geometry that is closest to perpendicular at 1/2 lift and it is also the one that has the rocker pad more in the center of the valve stem. Although the bottom photo is the one that gave me the most valve lift (.502"). So I ordered some .080 aluminum sheet to make shims.

Next I will start figuring out how much I should adjust the angle at the pushrod end to make those ends of the rockers arms perpendicular to the pushrods at 1/2 lift. This will have to done by cutting them apart and welding them back together. I'll be using these old rockers as tests/mock-ups to get the angle right. And I've ordered some new rockers that I'll send out to real welder once I get the correct angle worked out.

You might get more lift, and you’ll find that the effective ratio is actually increased. That can happen, but you also get more scrub across the valve tip.

If the first photos (no shim) is the most correct, even, least scrub, I’d go with that and correct the pushrod cup angle. It will be the best solution.

Since you are interested/willing to research and read, here is another tech article by Jim Miller

http://www.sbintl.com/tech_library/a...m_geometry.pdf

kitabel 7th April 2021 15:28

1. that's a stud, not a shaft
2. that's a roller, not a pallet
3. he's selling his own product

Maxeffort 7th April 2021 16:33

Quote:

Originally Posted by kitabel (Post 5888601)
1. that's a stud, not a shaft
2. that's a roller, not a pallet
3. he's selling his own product

Ok Mr Negative.

There is plenty of good info there and shaft rocker systems are discussed.

billeuze 7th April 2021 17:04

Thanks for the article Maxeffort. It looks like a good one. I'll read it over fully later when im at home.


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