I checked the passenger's side and am confused again.  On the passenger's side I measured more lift with no shims.  I only used the .197", .250" and .297" shims and saw the same trend as the driver side, but did not achieve as much as with no shims.  I think there must be something I'm doing while getting it set up that is making the measurements unreliable.

Using the other method, with the centerlines perpendicular to the valve stem, I get about the same result as I did on the driver's side.  When I do this, I also like the relation of the adjuster screw to the pushrod.  At half lift, they're just about in line and at full lift and no lift, the angles are about equal but opposite.

I'm going to go with the second method, 1/4" shims and 8 3/8" effective length pushrods.  Hopefully that will be the right choice or at least something that will make it a little better than it is now.



Lawrenceville, GA

I double checked last night before putting the driver side back together and everything looks good at .250".  Tonight I'll look at the passenger side just to make sure they're both about the same..

Of course, now I can't find where I read about the mid-lift method for rocker geometry.  It is a way to ensure that you have the minimum travel across the valve stem.  If an imaginary line between the shaft centerline and roller centerline is perpendicular with the valve stem at half lift, then it should achieve the ideal scenario outlined in your geometry article.  The tip will move toward the exhaust side from closed to half lift then back toward the intake side between half lift and full lift and should end up in the same position on the stem closed, and at full lift.

If I find a good article, I'll make a link.  It will explain it better than I.

I found this and after reading the first page, it sounds like what I remember, but it doesn't look quite like what I remember.
http://www.sbintl.com/tech_library/articles/rocker_arm_geometry.pdf



Lawrenceville, GA

Charlie.  Your second set of dial indicator numbers looks reasonable.  Your methodology for the half lift method is a new approach for me but also looks like a good double check to the dial indicator readings.  As long as both methods support each other in the results, then all should be good.  The quick fix for your valve covers being too shallow for the raised rocker arms would be use double valve cover gaskets.  I did that for the 2009 EMC engine which used the stamped steel marine valve covers.

Lorena, Texas (South of Waco)

I tried again tonight.  For some reason, I got results that seem to make sense.  I don't know what I did differently.  I tackled it two ways, using the dial indicator as before, and looking for a 90 degree relation of the valve stem and roller centerline to shaft centerline at half lift.  Does this look more like you would expect, Ted and is my logic about half lift sound?

Tonight's results:
Shim, lift
.197", .453"
.250", .458"
.297", .454

Re the 90 degrees at half lift:
I started by measuring the lift with no shims, and then set it at half lift.  I found that a 3/16" allen wrench lined up almost perfectly with the od of the roller axle when set on the spring retainer, so I laid that across the retainer and measured from the od of the rocker shaft to the allen wrench.  I measured several times since it's tricky to do while leaning under a hood, to make sure it was accurate.  I got about  .260". I measured the shaft at about .775" and the roller axle at about .275"

So from center of the roller to the allen wrench is about .138"
That means the rocker shaft centerline needs to be .138" higher than the allen wrench.  Center of the shaft is about .388" + .138" = .526" to the od of the shaft at the correct shim height.  .526" - .260" = .266" of shim required.  I can't do .266" of shim so I started at .250".  Since I know it needs to be .526" higher than the allen wrench, I made a gauge out of an index card that I could use to compare against the distance between the wrench and od of the shaft.  At .250" it is about perfect.  At .197" it is a bit low and at .297" it is a bit high.

To find half lift, using the .250" shims, I start with the valve closed, with the indicator at .600".
Full lift was .142", so lift = .600" - .142" = .458"
.458" / 2 = .229"
So I set the indicator at .229" + .142" = .371" for half lift, to check for the 90 degree relation.

If this is all good, then I will also need taller valve covers in order to use the 1/4" shims



Lawrenceville, GA

More results, getting better, but still weird, I think.

Shim, lift
.172", .451"
.197", .448"
.222", .452"
.243", .449"

I'm not comfortable using the standard length rocker bolts for any more shim so that's where I stopped tonight.

I took a measurement between the valves to the G head casting.  Maybe that can give you a ballpark idea of the length compared to stock?  I get 2.004" (2.024" -.020", the ruler).  The picture is to show where I made the measurement, not how, I realize it looks like I'm measuring between stems.  Mummert might be able to say for sure the length since he did the heads. 
Would it be a good idea, after so many checks, to put it back together and run the engine to get oil up to the cam before I continue?





Lawrenceville, GA

Charlie.  I’ll suggest simply shimming the stands up some more.  I would have expected more change in the values than what you are currently seeing though.  Increase the stand height to 0.200” and 0.250” heights and see if that makes for a significant change in the valve lift one way or the other.

Lorena, Texas (South of Waco)

I checked the lobe lift when I was having the pushrod trouble years ago.  That is good.  There has been no indication of trouble with lash checks since then.

Assuming that I'm doing things right, how do I interpret the results in terms of the right amount of shim?



Lawrenceville, GA

Charlie.  Your methodology sounds good.  Your 0.457” target for valve lift sounds good with the 0.015” lash value so no problem there.  Just double check that the lobe lift is indeed 0.295” so that is not a variable.

Lorena, Texas (South of Waco)

I'm adjusting the pushrod for the same .015" lash that I run everyday, not 0 lash.  The water pump pulley is the same diameter but I am just going forward, to peak, then backwards to fully closed.  I set the indicator at .600 with the valve closed, so open indicates low .150s.

Is what I expect to see correct?  A gradual increase to peak and then a gradual drop off?  Or perhaps if the stock stands are just right or too tall, simply a decline with more shims.

I'm sure I've checked, but is it possible that some sort of mechanical interference is causing these results, guide to retainer or coil bind?  I don't feel any resistance while turning the crank but maybe it's not significant enough to feel, yet.




Lawrenceville, GA

Charlie.  If you are zero lashing the pushrod, then the target lift at the valve is expected to be 0.472”.  If using the water pump pulley as a reference, then I’m assuming you’re simply going forward and backwards for all your readings.  If the water pump pulley is not the same diameter as the crankshaft pulley, then constantly rotating the engine in a forward direction will have the water pump reference mark you have out of sync with the crankshaft pulley after one full turn of the engine.  At this point, your numbers are not showing the amounts of difference I would have expected to see with the increments of shims you are using.  Double check that you have sufficient preload on the dial indicator that will record at least 0.500” of valve retainer travel.

Lorena, Texas (South of Waco)