rocker stand ht.

[Ed McLawhorn Jr.]

Installing first set of rocker shafts and need to know what would be the limit on shimming rocker shaft stand ht? I seen from manufacturers somewhere in the .90 to .100 range. After using a mid lift method for geometry, it's requiring in excess of .150 in shims to have the narrowest contact on valves. Can one shim stands at .150 and be reliable?
These are the new scorpion shafts for a set of super stock heads for a 283. Ratio is not crazy as they are 1.5 and 1.7's. Scorpion directions are a little limited as they say to shim stand until contact patch is in the center of valve. A check tool was not included in rockers like T&D or Jesel, just notes.

If I shim to have roller in/near center of valve, I only have to shim .025, but width of contact patch is apprx .090 wide. I'm not satisfied with contact patch as it seems like a lot of wasted motion even though that's the way instructions were prepared.

Seems like there is a lot of different/misinformation about rocker geometry depending on whom you speak to. Any help on stand ht limits and/or best setup method would be appreciated. Getting closer on this project...hoping to get out some this spring.

Ed

[Mike Taylor 3601]

I have had stands shimmed that much before,no problem just make sure bolts are long enough, I would make sure they engage all the threads available.
Best spot will have roller slightly toward intake when closed, centered about mid way, slightly toward exhaust at max lift.
A lot of people don't like the tools Jesel,T&D supply for stand height,alot say throw them in garbage,but I disagree,I like them and have always came up really close to where I needed to be.

How much longer are your valves? I have had stuff with long valves before that I had to have different stands made for,when you get up so high the roller will set out towards exhaust on tip of valve,have had custom stands made that moved whole stand towards intake,while was at it had stand made thicker so would have less or no shims.
On new set Jesel exchanged for the difference in cost of regular stand and custom stand was'nt much at all,guess they still will do this has been awhile since had to do that
Mike Taylor 3601.

[Mike Pearson]

I have run several engines with well over .100 under the stands with absolutely no problems. The heads I have now were built by Dave Layer and they have no shims. Dave mills the bosses to the correct height. He does some really nice work.

[Ed McLawhorn Jr.]

Mike, my heads are also from Layer, but mine are much older. I purchased these used from a guy who changed combinations. He had them prepared by Layer in late 1999 for 2000 season. He dropped a valve and messed one up around 03. He had Dave prepare a replacement head but never repaired motor. The head from 1999 has standard valves and the head from 03 has .050 longer intake valves.
Since Scorpion is new to sbc shafts, probably do not have option of having new stands made. I may be able to slot holes slightly and move stand some to help move contact closer to center of valve at mid lift.

Ed

[Mike Taylor 3601]

Ed,
Standard length and .050 longer should'nt need to be relocated towards intake,but have'nt used any of those brand,either
Start getting around+.200 or longer when start getting into that. If you look @ valve/rocker studs they are angled towards each other,so the longer the vavle,the higher the rocker sits,the closer the rocker gets to valve.

If I did have to get into moving stands, I would be sure I needed to go that direction before I did some mods.
Maybe able make or find insert screw in head,so could fasten stand w/3/8 or 5/16 bolt so could hold stand in place to check and see what moving stand toward intake would do,I would use soft springs if not doing so.


You may just have to move stand height around,to where it looks the best,and travels the shortest across tip of valve.
I tell you what you may try, stick stud in head and use pushrod checking tool, like plastic manley one,then take that pushrod length,center adjuster in your shaft rocker and shim stands to where valve lash is close enough that you could adjust valve lash,and see what that does.
Supposedly best is to have roller slightly towards intake,when valve is closed,about mid lift centered,max lift towards exhaust,w/about .050 or less travel across tip of valve.
Mike Taylor 3601