Since switching to the Harland Sharpe rockers, I have not yet checked geometry with them, so I started doing that this week.  Now I have more sophisticated equipment.  I devised and adapter that allows me to use the rod of a dial indicator stand on a stud for a rocker stand, in order to use a dial indicator to measure the actual lift. Now I should get a more accurate indication of what is happening.



I haven't finished, but the results aren't what I was expecting, so I just want to find out from the pros if it seems like I'm on the right track.  What I was expecting is a gradual increase, until lift peaks and then a similarly gradual drop in lift.  What seems to be happening is practically no change at all in lift.  The lift is pretty good, .295" lobe x 1.6 rocker ratio -.015" clearance = .457" and that seems to be in the ball park.

Yesterday I learned the importance of ensuring that I actually start on the base circle - those were some really weird results.  I've placed tape on my water pump pulley as reference so I always start from the same position, which is tdc of compression for #5.  The pushrod is a micrometer style adjustable and I adjust the pushrod, rather than the rocker adjuster screw to get the valve lash right so that the ratio of the rocker does not change.  I check the valve lash after I return to the mark on my pulley to ensure it did not change and make sure the indicator has returned to 0.  I've also checked my accuracy with the indicator setup and am able to get repeat readings within a few thousandths, which I hope is acceptable.

Here are the results so far.

Shim, Lift
.000", .448"          
.025", .445"
.047", .448"
.072", .447"
.093", .447"
.125", .448"
.150", .450"

.150" is where I stopped for tonight and it does look like it could be getting a bit better so I'll try a little more shim tomorrow.  Are those normal results or might I be doing something wrong?






Lawrenceville, GA

Probably depended on how "tight" the stamping press was set up.  When I worked in a forge plant, if the parts were a little too thick, they put a shim under one die to make it hit the metal blank harder.

John - "The Hoosier Hurricane"

Interesting. I only measured one drip tray (came up .040"). Never occurred to me to measure all the rest. Still learning something new every day!

6 VOLTS/POS. GRD. NW INDIANA

Were not the Lincoln stands a little taller than the Fords of that era and fit? Could be a remedy.

-Gary Burnette-

And I found some that are as thick as 0.044”.  Thickness likely varied simply due to run of the mill manufacturing variances.

Lorena, Texas (South of Waco)

.038"

John - "The Hoosier Hurricane"

Hopefully related, & relevent; does anyone know the thickness of the oil deflectors that were under the rocker stands on early y blocks?

Ted, your experience confirms what I have been wondering about for years. Excess lift (lift greater than max flow point) should produce greater flow for an intake cycle. Max flow occurs, stays steady for a bit and then declines as the valve closes. More flow under the curve as we are dealing with a truncated wave whose max value is defined by the head, not the valve opening. A valve lift equal th the point of max airflow yeilds a flow pattern where airflow just reaches a peak and then declines with the valve closing. This peak may not even be max flow as shown by the flowbench due to the inertia of the air.

Nice job of compensating for the increased duration of the cam, something not often done thus masking any potential benefits.

Just as an aside I know truck pullers are running lifts in excess of 1 inch, using roller cams of course. This is an example of trying to maximize air flow by increasing duration at maximum airflow.

If higher stands were readily available that I could mill to the height needed, I'd buy them. Don't know that it is a big market, though.


Lawrenceville, GA

Another chink in the armor of "Common Knowledge"! John runs a lot of lift in the Hurricane also, although not that much. His top end speeds seem to bear out what you're saying. You both have better heads than my "stockers" also.

    Some day we'll have to talk you into a blown engine dyno thrash.

Frank/Rebop

Bristol, In ( by Elkhart)