Measuring Rocker Rollout

Measuring Rocker Rollout
By Bill Jones (c)2006 - No Reprint

Here is how I measure rocker rollout.
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-The one part that slips onto the top of the valve is like a "C" washer with a vertical stand of about 1-1/4" in height brazed at a 90 degree angle to the washer.

-After it is brazed I machine it so that the roller tip can push against one side and the horizontal dial indicator is centered directly out from the crown of the roller wheel.

-the vertically mounted dial indicator tip presses down with a light spring to sort of hold the C washer stand from tipping backwards as the roller tip moves to an open position where the vertical indicator tip then tries to tip the C washer stand over backwards.

-It takes a little help by hand to hold the C washer stand in place when you start approaching about .700" lift and continue up to an inch in lift.
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-this C washer stand is fairly complex to get it to fit in there and to get the indicator pressures to hold it in place---a little hard to get it machined nice and smooth etc.
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-the long bar was bolted to the valve cover rail---then the head was installed on my mill---tilted to the get the exhaust valve straight up---then I machined a slot to allow a mounting place for the dual dial indicator mount and a mounting hole was drilled and tapped.

-this was done four places so that all cylinders can be checked.

-After figuring out he mount and fabricating the mount and the C washer stand---getting to where I could actually check the exhaust----I then did the same procedure to get mounting positions on the long square bar for the intake.

-Then I had to make an intermediate attachment extension so I could use the same dual indicator mount to check the intake.
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-an example of what this shows me is:

1-I ran the valve open to 1.000" lift and recorded the roller tip roll starting with the horizontal dial indicator at zero with .100" preload----and with the vertical dial indicator at zero with 1.020" preload to measure the valve lift.

2-I opened the valve in .100" increments to 1.000" and checked and recorded the roll out and roll back in which started at zero and rolled out a maximum of about .093".

3-here is a chart of the results----all numbers are OUT from zero lift unless noted with a - sign

valve ---roll out/in---
lift---------int--------exh
.000"-----.000"-----.000"
.100"-----.031"-----.031"
.200"-----.054"-----.054"
.300"-----.071"-----.073"
.400"-----.083"-----.085"
.500"-----.089"-----.091"
.600"-----.090"-----.093"
.700"-----.080"-----.079"
.800"-----.050"-----.051"
.900"-----.028"-----.031"
1.000"----.002-"----.005"

4-This is with a light valve spring holding the valve closed and operating the rocker by hand---no shims were under the rocker stands.

5-Application will be using about a maximum net lift of .940" (raceready---after valve lash) on the intake and about .918" on the exhaust.

-cam is to be .520" intake lobe lift and .510" exhaust lobe lift with 1.85 rockers on both.

-The .940 x .918 lift numbers do NOT account for any lost of lift due to the elasticity of the metals.

6-Now that the tool is built I can get serious and measure the REAL rollout and get it adjusted with rocker stand shims with the racing valve springs installed.

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