MSefi.com read only forum (Jan.15,2018)

BBC 454 with tunnel ram intake and dual 5.7 TBI. MSII V3 code 2.89
I am running it on a run stand and except for the MSD dist, fuel pump, fuel lines and regulator everything else is worn out junk. I got it running a few days ago on fuel only so didn't set anything in the ignition section of TS. I am using an external GM 4 pin module. I was controlling the ecu from the - termial of the coil. It would run but with tach spikes and injector misses. It would keep running if I kept it about 2000 rpm as the inertia would keep it turning until the fuel came back. I kind of thought the coil wire was maybe the problem so I piggybacked another GM 4 pin on the 1st one and split the vr signal to both. I then sent the signal from the second module to the ecu and it runs well with no spikes and with a bit of VE work I will be ready to move on to ignition control. Upon reading the ignition setting I saw the tach signal masking and wondered, and therefore the question, would that have halted my tach spikes instead of doing it as it did? I will probably go with a GM 7 pin module next but being as I live on a small island and only go to town every two weeks it will be awhile before I go again and want to fool with the injection in the meantime.

the answer is no it doesn't help in my case

If you are triggering off the coil, you should leave the default 50% mask setting. This prevents the ECU from looking for a tach signal until about half-way into the tach interval (time between cylinder sparks). The reason you want this is that all coils ring (produce electronic noise right after they fire). This can be seen by the ECU as fast tach pulses when they are really just noise. This can cause the ECU to drop sync and try to re-sync. There can be other sources of noise, like alternator spikes, but you really need to leave the masking in place and 50% is a good number.