ok , ok as a ford tech i will way in , 2 designs sucked the third was a bit better, but they put these in a 7 in deep hole and gave terrible access . the largest concerns are lack of routine maintenance ( the manual recommends replacement at 70k) and the resulting galvanic action. these arte a pain to fix in situ , but the c oncern has far more to do with performing maintenance when hot and overdue than the depth of the threads. I have serviced hundreds of these and i have NOT lost one yet (knock on wood) I always allow to cool fully , and saturate with pb blaster before removal and use judicious force to remove. do I agree the design is lacking , yes i do . do i think it is a result of not enough thread no I dont . I believe that maintenance practices and techniques are key here. All of that said the third style with more threads and longer plug stem are more tolerant of abuse but are more likely to stick from lack of maintenance due to galvanic action. in short dont bury a plug 7 inches deep in the center of an aluminum cylinder head
On Fri, Apr 5, 2013 at 6:06 PM, Kent A. Reed <kentallanr...@gmail.com>wrote: > On 4/5/2013 5:46 PM, Gregg Eshelman wrote: > > --- On Fri, 4/5/13, Viesturs Lācis <viesturs.la...@gmail.com> wrote: > > > >> 2013/4/5 dave <dengv...@charter.net> > >> > >>> Hi all, > >>> > >>> The wiki for buttress threads states the buttress > >> threads tend to fail > >>> because only the first 4 threads are load bearing. > >>> > >> Not really true, all threads are bearing the load, it is > >> just that due to > >> elasticity of material first one has the most, last one has > >> the least load. > >> I have formulas to calculate, what percentage of the load > >> does each thread > >> take somewhere in my notes from last year. Basically the > >> rule of thumb is > >> that first three threads take approximately 75% of the load > >> and it does not > >> make much sense to have more than 8-10 threads. > > That must be what the Ford engineers thought when they made all those > overhead cam V8 engines with only 4 threads in the spark plug holes. Theory > met reality and failed. The threads fail and the spark plugs blow out. > > > Weeeellll, let's not forget the confounding effect of > over-/under-tightened sparkplugs. In almost every one of the 5 cars I've > owned, the mechanics have had a bigger impact than the engineers. > Reality can bite in so many ways. > > Regards, > Kent > > > > ------------------------------------------------------------------------------ > Minimize network downtime and maximize team effectiveness. > Reduce network management and security costs.Learn how to hire > the most talented Cisco Certified professionals. Visit the > Employer Resources Portal > http://www.cisco.com/web/learning/employer_resources/index.html > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- jeremy youngs ------------------------------------------------------------------------------ Minimize network downtime and maximize team effectiveness. Reduce network management and security costs.Learn how to hire the most talented Cisco Certified professionals. Visit the Employer Resources Portal http://www.cisco.com/web/learning/employer_resources/index.html _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
