School me in Rocker Shaft Shimming.

-
The problem is the rocker is to long, or the valve stem tip height is to short. A lash cap will solve the issue.

Are these stock valves, or stock type?
 
MRL Performance said:
The problem is the rocker is to long, or the valve stem tip height is to short. A lash cap will solve the issue.

Are these stock valves, or stock type?
Click to expand...


I think you may be on to something. I believe my valves are at least "stock type" but my rockers are old (probably old enough to buy beer).

I did read that the old Harland Sharps were a bit long and have been re-designed to correct this kind of issue.
 
I've heard of engine shops having to grind custom shims before. I have never heard of anyone grinding the stands on the heads.
 
I asked this question, because it is very easy to convert over to 11/32 valves with just a liner and use SBC valves. But you have to use SCB valves that are .100" longer to get the stem heights right on the SBM heads. If you dont, then you have to use a lash cap.

Its a simple fix and it only cost about $35 for the lash caps and $30 for locks if you need them with the lash cap recess.
 
MRL Performance said:
I asked this question, because it is very easy to convert over to 11/32 valves with just a liner and use SBC valves. But you have to use SCB valves that are .100" longer to get the stem heights right on the SBM heads. If you dont, then you have to use a lash cap.

Its a simple fix and it only cost about $35 for the lash caps and $30 for locks if you need them with the lash cap recess.
Click to expand...



Thank you for all this great info. I will double check on the valves and see what I have going on.
 
Measuring my valve steams I came up with what I believe are stock type valves. .372/.371 ish.

Found this pic of my heads/springs

DSC00107.jpg
 
I was going to ask if you had a pic..lol
If I read right, when the valve is at mid lift, the tip of the rocker is towards the exhaust side of the valve tip. Where does the tip sit at zero lift? At max lift?
 
You already have the recess locks for lash caps, so all you would need is the caps themselves.

If you want it "perfect", you may have to use lash caps and do some shimming. The price you pay for perfection, sometimes its just a time consuming task.
 
At zero, very near the center.

At max it approaches the exhaust side edge. (not close enough to roll off but some correction is needed.)


Looks like lash caps and possibly a combination of lash caps and the shims I have may get me where I want to be.


EDIT: Looks like MRL Performance and I were making a post at the same time.

What is a good source for the lash caps?

And thanks for all the good posts, this has been a very helpful thread.
 
I dont think standard shims will help at all. The tapered helped as much as they could but the real issue is the valve job. The valve is too tall as it is assembled and raising the shaft will aonly make it worse. I think the "repair" could be removing the shims totally and running the lash caps. They will extend the surface the tip rides on which will add some stability. But they will not fix the problem, which is the sideways push on the valve stem that the poor geometry makes. It takes away power and can wear the guides more quickly. To really fix it that valve job should be addressed.
 
moper said:
I dont think standard shims will help at all. The tapered helped as much as they could but the real issue is the valve job. The valve is too tall as it is assembled and raising the shaft will aonly make it worse. I think the "repair" could be removing the shims totally and running the lash caps. They will extend the surface the tip rides on which will add some stability. But they will not fix the problem, which is the sideways push on the valve stem that the poor geometry makes. It takes away power and can wear the guides more quickly. To really fix it that valve job should be addressed.
Click to expand...

That is not what I have been seeing during my testing. Lash caps will rase the tip, moving the roller back.

That combined with my tapered shims that also move the entire shaft toward the center of the engine should get me where I need to be.

A shorter valve would clearly make the issue worse (easy to see if you are looking at things in person).
 
You must log in or register to reply here.
-

Back
Top