Joe King

I have a 7 pin HEI distributor but with my new motor swap I am not getting the timing that I need. I don't want to remove the computer but want to try and trick the ecm if possible.

i want to convert to The 4 pin HEI with vacuum advance.
The question I have is if I leave the jumper wire in the ALDL port such as when adjusting the timing, will the keep the engine code 42 off with the 4 wire plug unhooked? I have been reading what the 4 wires go to but haven't figured out what to do with the est and the bypass wire. The reference is just a tach signal and the last wire is a ground (internal)so I got those 2 covered. I believe the ALDL Jumper only effects the est and not the bypass which is where I may be stuck...

Well, stick it to me.

joe_padavano

This will "trick" the computer into thinking the ignition module has failed, causing it to default to limp home mode and sending performance into the toilet. By using a four pin module, you eliminate the RPM and timing signals to and from the ECU, so you effectively HAVE removed it.

By the way, you can't simply install a four pin module and vacuum advance in a CCC distributor - the housing isn't machined for it.

Your options are to either ditch the ECU and use a conventional HEI and Qjet, or get a PROM burner and burn a new PROM with a different advance curve in the ECU.

Oldcoyote

What car and what engine?

joe_padavano

Normally I would also ask that question, but in this case it really doesn't matter. The CCC system works the same from 1980-1990, at least as far is this question is concerned. Doesn't matter if it's a 260, 307, Chevy 305, or Buford 231. The answer is the same in all cases.

Oldcoyote

I am curious what engine he swapped in.

joe_padavano

I completely overlooked the part about the engine swap. It doesn't change how the CCC works, but I missed that completely.

joe_padavano

Leaving the jumper in place will lock both the timing advance and the mixture control solenoid dwell, so again, you effectively eliminate the CCC system when you do this.

olds 307 and 403

Are you getting too much timing? The later swirl port ECM's have super aggressive timing.

Oldcoyote

Maybe he swapped in an LS

joe_padavano

Might make it difficult to put that CCC distributor in there...