HEI dizzy

[dzorde at aesprodata.com.au]

     Hey everybody,
     
     Hopefully there are a few out there that know about the early Chev HEI 
     distributers with the built in coil.  Basically I am after some sort 
     of an idea what the tacho output waveform should look like, since I'm 
     not sure if the module in my dizzy is OK.  It is a 4-pin module.  The 
     waveform I get goes to about 45V for the 1st 1/3 of the pulse, it then 
     drops to about 15V for the remaining of the pulse.
     
     
     45V        |-            |-
                | |           | |
                | |           | |
                | |           | |
                | |           | |
     15V        | ------      | ------
                |       |     |       |
                |       |     |       |
     0V         |       |-----|       |-----
     
     Obviously the pulse is not quite as square as above, but I am 
     wondering if this seems correct, because it seems to drive the tacho 
     in the computer crazy and the car seems to idle roughly while 
     misfiring above 1500rpm.
     
     Also what is a good size spark plug gap to use with these, I have read 
     anything from 0.028" - 0.075", I'm using a 0.04" gap with a 350Chev.
     
     Hope someone can help
     
     Dan        dzorde at aesprodata.com.au