4-cyl HEI in GM Autos?

[Garfield]

On Thu, 27 Nov 1997 10:16:33 -0500, Clare Snyder <clsnyde at ibm.net>
wrote:

>Why would the advance be different? It is X number of degrees, period.
>The six cyl unit should work just fine. Even an eight should work. Check
>with NAPA, you will likely find the same module used on the 305 and the
>4.3 carbureted engines. Mabee even the same on 4.3 and 5 litre efi.
>Take your 6 and a timing light, and check the advance curve with the ecm
>disconnected. Does the advance slowly advance, or does it jump?

Uh, I already said, I DID that. Once more with feeling: It jumps +8deg
when it starts the advance ramp at about 2Krpm, and then "ramps", not
jumps, up another +10deg as I open the throttle. Just fineNdandy what
I'd like.

As to it working on a 4 just same as a six because "it's the same # of
degrees", think about it. The module doesn't know the rpm except by how
many pulses it's receiving. And it doesn't know "degrees" either, only
pulses and how far apart they are in absolute time. Doodle some on paper
to check yerself on this. A degree is a degree is a degree, but a pulse
isn't a pulse isn't a pulse, ifyaknowadamean.

Garfield

P.S. Easiest way to see the module CAN'T work the same on 4s, 6s, and
8s, is to consider at what rpm the advance is gonna kick in at all. Eh?
If it's at 2Krpm on a 6, at what rpm will it be on a 4? You've got 2
less pulses coming to the module per rev, on a 4 vrs a 6. But the module
doesn't know this. It's just counting pulses per time period. So how's
it gonna know the rpm? if it doesn't know the #cyls? it's dealing with.
N'est ce pas?