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There were a few engines, but not many, that used hardened valve seats - in cars, trucks, tractors, etc - long before the US changeover to unleaded fuel. Deere didn't have any that I recall. The first hardended seat inserts I ever saw in a Deere were when they added turbos to diesels. Before that, the diesels had soft cast-in-head seats also. I also add that the diesels also had a recession problem - and Deere diesel engines are very touchy when it comes to valve-in-head recess specs. Do one valve job by grinding and refacing - and the valve heads get too deep - and you get an engine that starts poorly in cold weather. Once the intakes get deeper than .025" and the exhausts deeper than .040", problems show up.H-D wrote:Tetraethyllead had the beneficial side-effect of lubricatin' the valve & seat contact 'patch'. An additive to 'help' the valves & seats IS beneficial! The possible exception to this are some air-cooled engines (Corvair for sure) which had harder than average valve seats. Did y'all know that the EGR valves which were initially employed by the automakers to lower combustion chamber temps (which lowered NOx) also had the beneficial side-effect of allowing more total spark-advance & a more agressive spark timin' curve? Ya never know what 'good' will come outa the Yankee government!![]()
I've worked on many tractors that idled and ran fine, even though the idle-mixture screw didn't do very much when turned in.Paul Buhler wrote:Hi: My 420 c sort of lopes when idling . . .
When I try to adjust the idle screw, the tractor runs smoothest with the jet completely closed leading me to guess that the idle jet is worn, or that I have an air leak between the carb and the cylinders somewhere. . . .
Any ideas on how I might isolate the problem would be appreciated. Thanks. Paul
Yes, I worked for two dealers in that area and also in Chester - another black dirt farming area. Lettuce, onions, and lots of migrant pickers.Paul Buhler wrote:
BTW, Did you work near Pine Island, NY? Your mention of black dirt farming elsewhere leads me to ask. I grew up near there, and saw many lightweight crawlers with wide stances used on a regular basis for planting, tilling, and harvesting.
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