Valve Adjustment Question II

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How do you know when the timing pin locates TDC? I assumed that the pin would go farther in than it does, but it didn't for me. Having no one to turn the crank for me, I turned the crank in increments of a 1/2 inch at a time and then kept trying to see if the pin would go further in. I would like to know more out of curiousity than anything else as I probably won't ever use the pin to adjust the valves. When I couldn't find TDC with the pin, I modified a technique used on gasoline engines to find TDC when your timing marks are off. However, in place of using a piston stopper in the sparkplug hole, I determined, with a feeler gauge, when the intake valve closed and the exhaust valve began to open on number one. Using these reference points as the outside marks on the harmonic balancer (hope it is called this) allowed me to use the center point between these two marks as TDC. Seemed to work okay. Reckon asking this shows I have more time on my hands than I need, thanks.

 

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Only if you were very lucky would you be able to get the locating pin to drop in place by turning the crankshaft 1/2" at a time. The feeler gage method you used is more accurate than you need to adjust valves but I wouln't trust it for timing the injection pump. I don't think you can go wrong following the procedure outlined in Issue 29 of the TDR (page 44).

Lots of good info in the other valve adjustment thread on this forum.

 

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You have to be EXACTLY on for the timing pin to engage the hole on the gear. I found it be getting close to TDC by looking at the valves on #1 cyl. I then had a partner VERY SLOWLY barr the engine while I applied pressure on the pin until it popped in the hole. Be very careful and make sure you stop barring the engine the instant the pin engages the hole. The pin is made of a plastic/resin type material which can shear off once engaged. At this point mark your harmonic balancer and make note of it (drawing, picture etc. you do not want to do this again because it is a real PIA!!!). DO NOT FORGET TO DISENGAGE THE TIMING PIN before you bar the engine 360* to set the rest of the valves.

Most people say you do not have to be this precise when setting the valves, but I like to try and be as precise as possible.

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'95 2500 SLT 5 speed 4x4

 

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The first time I did my 98 I asked a mechanic at Cummins South how they did it and he said he never used the timing pin for valves, just the visual/feeler gauge method on #1. Right when both valves close you are there. There is a little backlash in the train so I would gently bar it back a little then forward and make sure I was right. The reason I asked them was that my pin was so hard to move that I gave up on it. The mechanic said they only use it when timing the pump. Another tip if you didn't already figure it out..... I put a small mark on the harmonic balancer lined up on the edge of the sensor after I found TDC so that when you bar the engine over to do the second part of the adjustment, you just come back to your mark. Also, the next time you do the adjustment, just go to your mark to start with. Especially if you are going to use the timing pin, put a mark on there to make it easy to get real close to TDC.

 

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Thanks for all the replies. I did mark the harmonic balancer for futur refernce. Actually, I had no doubts that I had found TDC since I am into gasoline engines on a regular basis. I have been reading this TDR for the last year,. . ever since my truck started having every common problem discussed in this forum starting with the fuel guage, the fuel shut-off solenoid, the batteries, the starter, and lastly the auto transmission frying for the second time. This forum has been real helpful, both in the advice and also a place to vent,. . ala my second blown transmission,. . and since I just joined, I wanted to add my two cents worth in.

 

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Does anyone know if its is better to have the valves a little tight or a little loose? And what would the results of either be on performance? I was wondering about this, because Diesel Injection Services in P. A. adjust the valves on some of the bigger Cummins engines at . 013 Intake and . 023 exaust. I also have had several diesel mechanics tell me that the valves have a tendency to get tight not loose. And if they went to long without adjustment it could damage the rocker boxes.
Thanks
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[This message has been edited by McGrady (edited 01-22-2001). ]