Ironhead Shovster build take2

[brucstoudt]

well i'll be different.in the shimmed at.075 pic. the rocker arm appears to be centered over the stem at half lift.offset equally in both directions at zero lift and full lift.call it a comprimise.

[billeuze]

Originally Posted by brucstoudt

well i'll be different.in the shimmed at.075 pic. the rocker arm appears to be centered over the stem at half lift.offset equally in both directions at zero lift and full lift.call it a comprimise.

Well from what I’ve learned, centred over valve stem is less important than rocker arm angle. In the article linked by Maxeffort, they say to scribe a line on the rocker arm marking line from rocker arm pad to center axis of shaft, and use that to test for correct geometry (perpendicular to valve stem at 1/2 lift). I did a crude version of this it told me that my last photo (+.155) is actually the best geometry of the three. But visually, the second photos look better to me. I will revisit the other method to test. I will scribe a more accurate line and confirm my findings. I may be going to a thicker shim after all.

[brucstoudt]

''visually'' that's what i was using.visuallizing that that correct angle would be centered on the valve stem at 1/2 lift.

[Maxeffort]

Originally Posted by billeuze

Well from what I’ve learned, centred over valve stem is less important than rocker arm angle. In the article linked by Maxeffort, they say to scribe a line on the rocker arm marking line from rocker arm pad to center axis of shaft, and use that to test for correct geometry (perpendicular to valve stem at 1/2 lift). I did a crude version of this it told me that my last photo (+.155) is actually the best geometry of the three. But visually, the second photos look better to me. I will revisit the other method to test. I will scribe a more accurate line and confirm my findings. I may be going to a thicker shim after all.

The only caveat is the Shovelhead rocker system may not have been designed to be 90* to the valve at mid lift. (Modern rocker systems are, but not always the old stuff).
I would be still be looking at that, but also considering what part of the rocker pad is contacting the valve and the contact pattern on the valve tip.

I will agree (now that I’m viewing on a bigger screen) that #2 with .075” shim looks good as far as the rocker pad on the valve tip.

[RicThompson]

Since pushing the valve stem sideways tends to wear guides out you're smart for thinking things out thoroughly. I would be looking into cutting up and modifying the rocker boxes to position the rocker shaft where it needs to be for the correct geometry. I'm not 100% certain on this but I believe the S&S Shovelhead engines utilize a twin cam style shovelhead rocker box. That maybe your ticket right there.

[Maxeffort]

It’s easy to get carried away with this stuff. It’s good to check and research.

But taking a moment and remembering that this is an all Shovelhead top end
and the OP has decided to correct the pushrod cup angle by cutting and welding.

I think all that’s needed on the valve side is to optimize the rocker box height. It’s not going to be radically different than stock. There is increased valve height from the head work/valve job. There is the stack up of parts, but that’s about it. It seems reasonable that a modest shim job will put it into good shape.

[kitabel]

So far, much of the comments have been w/r/t getting the rocker's contact pad in a good position as to lift, scrub pattern etc.
When this is done, the short (pushrod side) exhaust rocker levers are both going to be pointing to directly above where the shovelhead cam would be, which is many inches away from where the actual XL exhaust cams are.
The intake levers are doing the same thing (not aiming at the cam lobe), but the error is much smaller.

[billeuze]

Originally Posted by kitabel

So far, much of the comments have been w/r/t getting the rocker's contact pad in a good position as to lift, scrub pattern etc.
When this is done, the short (pushrod side) exhaust rocker levers are both going to be pointing to directly above where the shovelhead cam would be, which is many inches away from where the actual XL exhaust cams are.
The intake levers are doing the same thing (not aiming at the cam lobe), but the error is much smaller.

correct, MOST of the comments have been regarding the valve end of the rockers because that is what I'm focusing on now. The pushrod end has been discussed a few timed here as well as my intention to focus on it AFTER I settle on what to do with the valve end. Because the is the logical order to do it.

[billeuze]

Originally Posted by RicThompson

Since pushing the valve stem sideways tends to wear guides out you're smart for thinking things out thoroughly. I would be looking into cutting up and modifying the rocker boxes to position the rocker shaft where it needs to be for the correct geometry. I'm not 100% certain on this but I believe the S&S Shovelhead engines utilize a twin cam style shovelhead rocker box. That maybe your ticket right there.

Im not cutting up the rocker boxes - that would be going way outside the scope of this project. I'm also not going to consider using S&S rocker boxes. I don't have unlimited funds and am trying to work with what I have. besides my current rocker boxes have already had the pushrod cover sockets welded and machined by Ron Trock Sr. to point at the ironhead cams. New rocker boxes would still require that to be done and I don't have the tooling for it and since I am in Canada, it would probably cost me more to ship them back and forth to Ron Trock Jr. than he would charge for the work.

Originally Posted by Maxeffort

It’s easy to get carried away with this stuff. It’s good to check and research.

But taking a moment and remembering that this is an all Shovelhead top end
and the OP has decided to correct the pushrod cup angle by cutting and welding.

I think all that’s needed on the valve side is to optimize the rocker box height. It’s not going to be radically different than stock. There is increased valve height from the head work/valve job. There is the stack up of parts, but that’s about it. It seems reasonable that a modest shim job will put it into good shape.

Yes

[billeuze]

Originally Posted by kitabel

Changing the box position can be done in any increment you like... but adding material is annoying (thin shims). You only get .766 to .788 X the height change at the stem due to the valve's 40 degree angle (shovels are 40 and 38?).

Yes, It seems strange and I wondered if I had miss-measured. So I googled and found that its true. I learned that more precisely the intake angle is 40.25 degrees and the exhaust is 38.25.