what not to do while installing cajuns tachometer board. (Page 1/1) richard in nc MAY 15, 04:38 PM i was trying to fix my oil pressure guage built into the tach.i have a new sender and already tried grounding the center prong.when i installed the cajun board i unbolted the old board.there were push on speed nuts holding oil guage.i destroyed them getting them off.i thought no problem,the outer nuts will hold it together.it turns out the speed nuts are needed to make guage work.all my guages work now for the first time. olejoedad MAY 16, 07:59 AM You could have saved yourself the time and trouble by having Forum member JGunsett repair and recalibrate your factory gage for a very reasonable price.