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

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 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

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

Charlie.  I have to think that your dial indicator setup isn’t consistent when looking for maximum lift.  My own method of choice when checking valve train geometry is measuring the sweep across the valve stem tip and targeting for the minimum sweep to obtain perfect optimum geometry.  I have found though that by biasing the rockers at a point above where ideal geometry occurs, there is typically a power increase and that comes from the valve lift occurring at a faster movement of the rocker when it’s higher.  There are tradeoffs with that though.

Lorena, Texas (South of Waco)

You said one time, if you're going to err, err on being up to .050" higher than ideal, or something like that.

I got back out there and did it the low tech way,  bluing the tip and measuring the scrub pattern and the results indicate that 1/4" should be about right.

Shim, Scrub
0", .110"
.093", .085"
.197", .075"
.250, .065"
.297", .070"
.343", .075"

If the mid-lift method is accurate, and this is not a fluke, that makes for a quick way to get into the ballpark.  My previous finding with the Doves support it.  I determined that .150" of shim was best for those.  The Harland sharp rockers have a larger diameter roller, so everything else being equal, they should need shims which are taller by an amount equal to the difference in the radii of the rollers.



Lawrenceville, GA

I got it done.  Since I had the carb loose, I also increased the secondary jets from 65 to 67.  I went up quite a lot on the primaries but had not yet touched the secondaries.  Rob's experience with his carb give me a great ballpark for where the 570 should be for an engine like mine.  I figured it also couldn't hurt since I might have a bit more flow now.

It was about 11:00 pm so I went on a very short drive just to get it warmed up and see if I forgot to tighten any bolts.  It pulls freaking hard from about 4000 rpm now.  It scared me.  I didn't loose traction or anything it was just surprising - not like I'm used to.  I looked at my tach and it was at 6 grand in no time.  Can't say if it is because of the optimized geometry or jetting change, but something seems to have worked real well.  I might start thinking more seriously about a rev limiter.  Below 4000 feels about the same as did before.

Tomorrow I go for the official test drive, to a local cruise-in.



Lawrenceville, GA

Sounds good Charlie. Is the truck fixed to make the trip to Columbus?

  Dennis in Lititz PA

Explain how to test the travel across the valve. Blue the rocker?

Frank/Rebop

Bristol, In ( by Elkhart)