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Conference napalm::musclecars

Title:Musclecars
Notice:Noter Registration - Note 5
Moderator:KDX200::COOPER
Created:Mon Mar 11 1991
Last Modified:Mon Jun 02 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:182
Total number of notes:5467

155.0. "Factory tachometer wiring" by HOTLNE::MALESKY () Tue Jan 31 1995 09:06

    I have a 1985 GMC Cabalero (ElCamino) that had a 4.3 V6 in it.
    I installed a 305 IROC engine and connected the factory tach. wire
    to the new distributor. The tach is reading too high. Is there 
    something I can do externally to the tach wiring to correct
    the calibration? Add an in-line resistor? The wire on the firewall
    for the tach has what appears to be a condensor in line with it.
    Is there a different one maybe for a V8 that I can change to correct
    the problem? 
    
    John  
T.RTitleUserPersonal
Name
DateLines
155.1not a resistor.....CSC32::J_KALINOWSKIForget NAM?....NEVER!Tue Jan 31 1995 10:296
    
        You need to modify the amount of *pulses* going to the tach....
    you had 6, now you got 8.  See?  All GM tachs have settable jumpers
    to match what engine you have.
    
    -john
155.2How are you at tack removal ?TROOA::SCHERFTue Jan 31 1995 10:3310
    
    MOST OF THE GM TACH'S I'VE SEEN MUST BE REMOVED TO FIX THIS. ON THE
    BACK, THE PRINTED CIRCUIT BOARD HAS A SMALL FUSE OR DIODE SOLDIERED
    ACROSS TO POINTS. YOU SHOULD SEE SEVERAL POSITIONS MARKED 4,6,8.
    	YOU NEED TO MOVE THIS TO THE 8 POSITION. THE TACK WORKS ON THE
    ASUMPTION THAT THE HEI DISTRIBUTOR WIL PRODUCE X AMOUNT OF PULSES
    in revolution ie 6 for the 4.3. you are now producing 8 in one
    revolusion so it thinks the motor is turning a higher rpm than it truly
    is.
    						Jeff Scherf	
155.3HOTLNE::MALESKYTue Jan 31 1995 11:086
    .1,.2
    Thanks. I'll remove it this weekend and see what the pc board
    reveals...
    
    
    John