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Posted on September 19, 2012:
Hello Folks!!! I am now attacking the valve pushrod. This part is made from a piece of 1/8” x 1/4” steel bar that is included in the materials kit.
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The first thing I did was lay out the four hole locations on one side of the bar as the prints require. I then lined up my spindle over the first hole on the bar (.100” in from the end)..
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I spotted the first hole with a #2 center drill and then followed it with a #31 drill bit...
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An 1/8” chucking reamer was then used to clean up the hole.
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I drilled the second hole (located at .631” from the end) with a #43 drill bit. I then tapped the hole with a 4-40 hand tap...
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I tackled the next two holes at 2” and 2.375” (from the end) with a #47 drill at this point.
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I finished off the job by tapping the two holes with a 3-48” tap as seen below. Note: The overall length of the bar will be kept “long” as it will be trimmed to length later on...
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The next job is the pushrod keeper which is made from a 1/4” x 5/16” piece of steel bar (included in the materials kit). I trimmed the bar so that it was exactly .750” long before machining.
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I laid out the first hole at .119” from one end along with the “step” cut at .250”...
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I lined up the spindle on the first hole and zeroed out the table.
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I now used a end mill to cut the step to a depth of .212”...
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I now repositioned the table to “0” and drilled out a #32 hole at the bottom of the step (not shown). I then followed the drill with a 82° countersink bit as seen below.
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I now repositioned the keeper in the milling vise and laid out a cut line at .350” (from the other end) for the second “step” cut. I then milled out the step to a depth of .200”. Note: I used a collet with the end mill to prevent the end mill from walking out of the spindle. It is pretty easy to ruin a part if an end mill gets loose :0P
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At this point I mounted the keeper with a flat head 4-40 screw (included in the basic kit) for the next step.
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I now used the first hole in the rod to center the spindle and then drilled the keeper with a #31 drill followed by the 1/8” chucking reamer...
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The next part to machine is the pushrod plate. This is made from a 1/16” x 1/4” piece of steel of which I suspect is spring steel. This bar was included in the materials kit. I trimmed the bar to a length of .990” as the prints suggest.
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I laid out four marks on the bar at .297”, .453” ,.672” and .828” from one end. Of course these holes will all be in the center of the bar...
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I aligned the spindle on each hole and drilled the four holes with a #41 drill bit a seen below. The bar was somewhat difficult to drill which makes me think it is some kind of spring steel and not CRS as the bill of materials suggests.
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I finished the slots in the bar with my Dremel tool and a carbide rasp as seen below...
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I now gathered up the two 3-48 screws (bolts) and #3 washers that are included in the hardware kit and tested the fit of the push rod plate (not shown).
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The next part to machine is the pushrod wrist pin. This is made from more of the 3/16” steel rod used earlier.
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I laid out two cut lines at .125” and .326” from one end and then turned down the rod to a diameter of .124” as seen below. Note: I did not turn down the outer diameter (3/16”) of the pin as the prints suggest (.185”) so that it can be used with a ball bearing cam follower...
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I parted off the pin at a length of .450” to finish the part. I then tested the pin on the push rod and was happy to see a snug fit. I do not want this pin to be loose as it will promote excessive wear if it is.
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The kit has a drawing for a solid steel cam follower however I decided to use an optional ball bearing to replace the follower (noted on the prints). This will make the cam lobe last forever as well as reduce friction. I will be using a 3/16” ID x 1/2” OD x .196” wide stainless ball bearing from Boca Bearing (Cat# SR3-ZZ). This bearing will fit into the pushrod keeper without modification.
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I installed the bearing on the wrist pin and then assembled the follower for a fit check. Not too bad ;0)
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The next step is to machine out the slot on the engine frame for the valve pushrod. I first set up the engine frame on my granite surface plate and used a height gauge to figure out where the vertical center of the front pushrod guide boss was (on the head). This turned out to be about 2.440” up from the base of my engine but may be different for each individual engine...
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I locked the height gauge in place and then transferred the mark over to the rear pushrod boss as seen below (this is mostly for reference).
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The next step is to figure out how deep the pushrod will sit in the bosses. I first set up the engine on my angle bracket and then laid the pushrod over it’s guide bosses. I then rested the follower bearing on the timing lever edge and then shimmed the front side so that the center of the rod was about .020” below the center of the rocker arm adjusting screw. This offset will keep the rod in an average center of the valve adjusting screw as the rod follows it’s transit.
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You can see the follower bearing resting on the timing lever below...
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After the proper rod height was shimmed on the front end I measured the height of the rod at the front and rear sides so that the engine frame could be adjusted to make the two ends level to the base of my angle plate. After some adjustment I was able to make the rod parallel to the bracket and then I locked down the clamps in preparation for milling the push rod slot.
Note: The pushrod may not be parallel with the cylinder of the engine which is OK as you ultimately want the rod’s ends in their proper place. Leveling the cylinder or frame will not align the rod properly. This particular engine is really close to parallel although it doesn’t need to be...
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I now moved my height gauge down .125” to the bottom side of the rod’s position and then scribed the bottom of the push rod slot as seen below...
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I moved the angle bracket over to the milling table and then aligned the bracket to the table’s travel using a test indicator. Once aligned I locked down the bracket and then rechecked the alignment for good measure (no pun intended)...
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I now set up my wiggler tool to find the center of the pushrod slot. I then zeroed out the table’s “Y” axis for reference at this point...
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I mounted a 3/16” end mill into a collet and started to mill a .190” wide cut through the centers of the pushrod slots (.190” was the actual cutting width of this end mill). I cut to the depth of the mark I made earlier for the pushrod.
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The actual width of the rod provided in the materials kit is about .248” so the slot will need to be widened about .058”. I did this by making a couple of additional passes with the end mill at a “Y” offset of .029” “up” and .029” “down” (from my zero reference).
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I tested the slot with the pushrod and then “trimmed” the sides of the slot until the rod fit perfectly without binding.
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You can see below that the alignment worked very well...
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The next step is to trim the height of the bosses so that the rod’s guide plates will fit perfectly over the pushrod. I installed a 3/4” end mill in a collet and started milling off each guide boss to approach a “step” height of .127”
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I tested the rod in the slot and milled each side until there was a .002” clearance from the top edge of the boss to the rod’s top...
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You will notice that the rear boss is offset lower than the front boss. I’m not sure if this is intended although it doesn’t make much difference where the rod sits in the rear boss. This small “offset” will not make much of a difference in follower geometry IMO...
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The next step is to drill and tap the rod’s guide plate screw holes. First I flipped the angle bracket around to allow better reach of the spindle and then realigned the bracket to the table. I then used the wiggler to find center of the slot and then zeroed out the table. The table was offset .344” “down” and then centered on the “top” of the boss as seen below. This will be the first hole for the rear guide plate.
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I drilled the top hole with a #38 drill to a depth of .380” and then moved the table up .688” (.344” from zero) for the next hole...
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The front boss was next so I offset the table “up” and “down” by .200” (.400” total) from centerline to drill two #47 holes at a depth of .250”...
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I now removed the engine frame and tapped the rear holes with a 5-40 tap as seen below. I then tapped the front boss with a 3-48 tap to finish the operation (not shown).
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Hopefully I will get this engine running soon. At this point I have 120 hours into this build not including my work on the articles ;0) I can’t wait to see if all of this effort will pay of or not! Please join me again for the continuation of the Red Wing Engine Project. Until then take care my friends!!!
Don Giandomenico
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