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Post Info TOPIC: MSD Blaster 2 Coil - Tach Issue


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MSD Blaster 2 Coil - Tach Issue


My 66 uses an MSD Ready to Run distributor (no box). I run a stock small cap to keep it looking original. My coil started to leak oil so I bought a new black MSD Blaster 2 coil. Once installed my vintage Sun SST 802 R tach would read way too high at idle. I switched it to a stock type coil and the tach works perfect again. I will say spark is greatly improved with the MSD coil. Seems to start a bit better. Not sure if it runs any different. The primary resistance is much lower on the MSD coil, .6 vs 1.8 ohms. Anyone every encountered this and know if a fix for the tach issue?

Thanks in advance

Rob



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I'll bet a 1 ohm resistor in line with the tach signal input would fix it. Is there not a "Tach adapter" for just this problem?



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65 Laurentian post, 67 Grande Parisienne 4 door HT. 
 


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I dont think 1 ohm in series with the tach will help. Im thinking the lower resistance of the MsD coil causes less voltage drop across the coil. So, the tach gets a higher voltage wave at the same frequency. Possibly something that matches the input resistance of the tach to create a voltage divider. Ive heard 10k ohm, I tried it with no luck. Same problem.

Maybe i should try a potentiometer. I could increase or decrease it to find a correct ohmic value?

Ill try a 1 ohm and post the result. 1 ohm wont have any drop across it in series with the tach, but Ill check it out.

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I just measured the input resistance of the tach. Its 250k ohms so its no wonder the 10k ohm resistor did nothing to make it better. Ill try a 50k and a 100k ohm on Tuesday.

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