dkv411 Posted September 3, 2014 Share Posted September 3, 2014 I have had a problem lately with the #6 rocker bridge guide pin breaking on the intake side. Had my local shop run the overhead and found the broken pin and with many calls to the dealer that did my inframe for proper procedure they replaced the pin. The next day I had a intermittent dry scraping sound from the back of the head. Found the rocker bridges lost tourqe. Two weeks later same scraping sound pulled the top off everything looked fine sounds went away. Approximately 400 miles later poof lost #6 intake bridge pin.towed into mack dealer in sw Michigan and checked cam and push tubes and visual inspection of the top side of the head everything is in perfect shape they are putting a floating bridge in(???) I had a complete inframe minus the cam in march of last year approximately 125k ago does anybody have a clue as to why this is an issue and will the new floating bridge fix the problem? Or should I sell it when and if I get it back? Quote Link to comment Share on other sites More sharing options...
Macktech689 Posted September 3, 2014 Share Posted September 3, 2014 Valve yoke guide pin failure is caused by bending load on the pin usually caused by misadjustment. installing a pinless yoke will probably solve the problem, MACK has been using pinless yokes on intake valves for over 10 years Quote Link to comment Share on other sites More sharing options...
dkv411 Posted September 3, 2014 Author Share Posted September 3, 2014 So good possibility that my local shop has absolutely no clue on how to run my overhead. That does make me feel better as long as the parts show up today. Quote Link to comment Share on other sites More sharing options...
Macktech689 Posted September 3, 2014 Share Posted September 3, 2014 As long as everything is adjusted and torqued correctly you wont have any more problems. actually those engines were famous for breaking exhaust valve guide pins. Quote Link to comment Share on other sites More sharing options...
Mackpro Posted September 3, 2014 Share Posted September 3, 2014 If its the exhaust pin always breaking , here is the fix.jake.pdf Quote Link to comment Share on other sites More sharing options...
dkv411 Posted September 3, 2014 Author Share Posted September 3, 2014 Interesting reading but it is an intake yoke pin which is probably a good thing seeing as I thought I lost an injector and nursed it off the highway and parked. Quote Link to comment Share on other sites More sharing options...
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