Saturday, August 21, 2010

Tuning valve clearance on rocket arm engine types


Problem
check and adjust the clearances of the valve opening on engines with rocker/arm timing.

Solution
this is an example based on the Universal Diesel 5416 engine but if you take any other engine that uses this design, the instructions are pretty much the same. For example, Moto Guzzi motorcycle engines can be tuned much the same way.

In a 5416 engine, the first step is to remove the valve cover. This is remarkably easy on this engine since only two bolts keep the cover in place. Remove the bolts and carefully lift the cover. Note: some engine have the optional breather. The breather is hold in place by two more small bolts, simply remove those and lift the breather out of the way before removing the cover.

Then pick one rocker at the time and follow the instructions from the engine manual to rotate the engine to TDC for that rocker. Basically what you need is the camshaft to be at the lowest point for that arm thus giving the rocker the most clearance. You *could* just rotate the engine by hand looking for the TDC. I do not condone this method but I do admit that it works for old engine where finding documentation can be nearly impossible. Once the rocker is at it loose state, use a wrench to loosen the nut while using a flat screw driver to keep the arm from rotating. Once the nut is loose, place a feeler in between the rocker and the top of the valve and screw in/out the arm until the feeler can fit snugly in the gap. Now carefully tighten the nut making sure you hold the screwdriver firmly in place so the arm does not rotate. Repeat for each rocker arm and you are done. Trust me, it sound more complicated than it actually is.

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