Setting cam geometry, Peak cam lift or peak valve lift? Options

[VaccaRabite]

Jake's site is down it seems, so I am going to ask this here.

I am about to set my pushrod geometry, but I am having a brain fart.

Do I use the peak cam lift or the peak valve lift.

I think that it has to be within 5% of peak valve lift, but I am just not sure, and I don't want to mess it up.

Also, does anyone have a copy of Jakes article for setting geometry? I pretty much remember the procedure, but I'd like to re-read it before I continue to make sure I have it right.

Zach

[DNHunt]

Zach

That's not anything like I did.

I ran the shaft of the dial indicator parallel to the valve stem shaft so I could measure total lift of the valve. I then divided that number in half and used the adjustable pushrod to find a length that resulted in the adjuster screw being parallel with the valve stem at half lift. Changing the length of the pushrod would change lift some so it was a trial and error kind of thing.

I also used shims under the rocker assembly to help with how much thread I had for moving the adjuster screws in the rocker arms.

As I understand it the most important issue is lateral forces on the valve stems causing wear of the valve guides. Having the adjuster screw parallel with the valve stem at half open results in the least amount of wear. As I remember, it is better to give up a little lift to have the right orientation at half lift.

Dave

[VaccaRabite]

Zach

That's not anything like I did.

Yeah it is. I just suck describing it properly. (IMG:style_emoticons/default/laugh.gif) What you described was what I remembered. What I had forgotten was the 1/2 lift step.

I knew there was a step at 1/2 lift, but I could not remember what it was. As soon as I saw your picture, I remembered it - as I remember staring for about 30 minutes at my first valve a year ago trying to determine if it was perfect or not.

As it is, it took longer getting those darned spiral keepers on that KB pistons use. So I am just now ready to start pushrod geo.

Of course, at this point I have just enough time to get a shower and pick my son up from daycare. So, geometry will have to wait for Theo to go to bed for the night.

Zach