XT Valve lash results may we
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=46979
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Topic: XT Valve lash results may we
Posted By: captaindana
Subject: XT Valve lash results may we
Date Posted: 10 Mar 2012 at 5:32am
| discuss my findings from yesterday? The engine was not up to operating temp. It was 35* in the pole barn shade. Cyls 1 through 5 all had exhaust valves which measured from .018 at the narrowest to .027 for the worst which was cyl #1. Cyl 6 specked .016 on both valves and every other intake valve specked .016. So what do these 5 exhaust valves have in common? If some carbon/rust/junk/fod was in their seats causing them to not fully seat I believe when I got there and measured the lash the measurement would read as I found...too wide, correct? Also if the five exhaust valves were not fully seating my compression would be low. The other day when I was compression testing cyl#1 which had shown 300 psi the previous day showed about zero. That is why I took the gauge to be caliberated. But now that I found it's exhaust valve had .027 clearance to the tappett I do believe it must have been not seating, correct? Yesterday before I adjusted any tappets after the initial measurement I would pry the valves down quite far and let them spring back quickly trying to dislodge anything which may have been in their seats. I believe as I progressed in sequencing I could hear the increased compression as I bumped the starter. Any input is greatly appreciated guys. I am learning and I love it!!! Thanks, Dana |
Replies:
Posted By: MACK
Date Posted: 10 Mar 2012 at 7:11am
| .018 is about right cold. MACK |
Posted By: skipwelte
Date Posted: 10 Mar 2012 at 8:43am
| Warm it up real good, set the lash at what ever the spec is hot then use it as hard as you can. You may just have worn parts causing excessive lash. Valve lash should be adjusted every couple thousand hours, nobody probably did, now is a good time to level the field. Good luck. |
Posted By: Gerald J.
Date Posted: 10 Mar 2012 at 10:10am
|
Banging the valve closed with the spring may feel good but its not going to nearly as effective at crunching carbon deposits as working the engine hard. The spring probably has 120 pounds force with the valve closed. Combustion pressure is probably more like 1500 psi in a diesel, spread over the about 3 square inches of a 2" diameter valve makes 4500 pounds on the valve head to make it close. Then when the valve lifts for exhaust there's a bunch of combustion product flow to blow the crunched crud out. Gerald J. |
Posted By: BrettPhillips
Date Posted: 10 Mar 2012 at 5:56pm
|
I'll second that. Warm it up, check the valve clearances, then warm it up again gently and thrash it as hard as you dare for an hour or more, then gently cool it down afterward. If the symptoms persist after that, you may be in need of a valve job or ??? |
skipwelte wrote: