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Ranger Gress's M20B25 Valve Adjustment Method
Finding TDC. When the rocker arm is between the lobes on the cylinder's "pair", then you are at TDC. Cylinder pairs, 1 & 6, 2 & 5, 3 & 4. Rotate the crank with a 22mm wrench until the #1 rockers are in between the cam lobes. Because of cylinder pairing, the cam lobes for #6 are now at the bottom of the cam, so go adjust the rockers on #6. Once you are done, rotate the cam such that #2 rockers are in between the cam lobes and then adjust the rockers on #5, and so on. IYou need something to turn the eccentric on the rocker arm. BMW makes a special tool for this that looks like a 6" piece of coat hanger except it is kinda springy to bend in the middle. You don't need it. Use a coat hanger and push down on the eccentric with one finger hard enough that you can feel a little resistance with your feeler gauge. It's hard to describe how much pressure to use. Think of the weight of a cup of water...it's in that ballpark. If you feel a little resistance in moving your feeler gauge, you are ok. After tighting the nut you should be able to get your .010 gauge back in. If you can't, then do it again and apply less pressure. If you can get at .012 gauge in there, then do it again and apply more pressure. The amount of pressure to put on the eccentric is not the hard part. Your finger will be calibrated by the 3rd valve. The harder part is figuring out exactly how to place the gauge such that it gets in the gap. It's easy to think that the gauge can't get in because there isn't enough gap. When in reality the gauge isn't getting in because it's not place precisely at the gap, or your not pushing down on the cam end of the rocker. This is the part that takes more practice. Use a feeler gauge that has the last inch bent at an angle. Tap the rocker on the cam side to make sure the valve is seated. Pushing down on the rocker on the cam side, check the gap with a .010 feeler. If it feels loose, check it with .012 also. If it feels tight, check it with .080 also. If you think it's wrong, still pushing down on the cam side of the rocker, adjust it. Once you think it's right, check it with .012 and .008 again. Once you are absolutely sure it's perfect, move on. Once you are done, check everything again with .008, .010 and .012. Then button up your valve cover and run the motor a little. Then shut down the motor, pop the hood up and let the engine cool for a couple hrs. Then take off the valve cover and check everything all over again. The above sounds like one long pita, I know. But I found that I was somehow never quite getting the adjustment right. Most often because the feeler gauge wasn't going in because it was caught on the little nub that sticks up from the valve. If I check something 5X tho, even I can get something right. |