4age smallport on carbs

[hardon]

im converting my 4a to twin webber carbs and planning on using the msd 6al-2 programable ignition. i have read that i can use a bluetop dizzy and am currently looking for one. just curious as to why i cant use the smallport dizzy? i have searched everywhere!

[Bento]

I think it has something to do with the amount of wires on the dizzy itself?

BP/Bluetop = 3 wires

Please correct if incorrect

[Hen may possibly be a nut]

The sensors in the guts of the two differ.

Bigport/bluetop/3wire - Has a pickup which gets 24 pulses per cam rev, and one that gets 4 per cam rev.
Smallport/whatevertop/4wire - Has a pickup which gets 24 pulses per cam rev, one that gets 1 per cam rev and a third which also gets 1 per cam rev, but is offset by 180? degrees (may be 90, would have to check) to the first.

I can't see why a smallport dizzy wouldn't work, unless the MSD is hardwired to expect the inputs a bigport dizzy gives.... OK, just went and did some reading on them and it looks like the MSD just gives a spark every time the dizzy sensor gives a pulse. So therefore a bigport dizzy is needed (4 pulses per cam rev = 4 cylinders firing). The MSD unit seems pretty basic for configurability.

Another option is to use the 24 pulse sensor in you smallport dizzy, but just cut all but 4 teeth of the sensor wheel. Bang, 4 pulses per rev for $0.

Hen

[hardon]

i will just get bluetop dizzy. save me the mucking around, thanks alot hen