GM HEI Dist

[SKuri]

I was parusing through the D and C Extreme site, and came across their custom GM distributor. It says it has a single wire hookup, but now i'm wondering... is this the dist i'd need to do a closed loop TBI? Since the ECM is going to be curving the timing, how is this done with a single wire hookup? HELP!!

[Bill usn-1]

It won't.
You need the duraspark conversion or the GM small cap that mark does or use the harness from AFI that lets you use your ignition with no timing control from the ECM. Fuel only. Then you can use the $350 D&C dist. DUI is also making one now for the IH motor.
You can do a google search for them. Won't be any cheaper tho!

[SKuri]

So If I were to use the GM TBI setup, ecm, etc... will this wiring harness connect to the duraspark? Or at this point will i NEED to do the GM conversion?

[Bill usn-1]

You lost me....

If you do the GM FI conversion using all the GM parts then you will need to use the duraspark conversion dist or Marks small cap conversion.

If you do the GM FI conversion using the GM parts with the AFI wiring harness or the whole AFI FI conversion then you can just use your stock ignition and dist and the FI will be for just fuel not ignition timing.

Hope I said that clearly?

[SKuri]

yea that's clear. I want to make sure that the timing is going to be controlled also. Sorry if i didnt make that clear.

[Bill usn-1]

Just so you know AFI also sells the conversions that provide for fuel and timing.
Didn't want you to think it was fuel only the way I wrote it.

[Eagle-Mark]

is this the dist i'd need to do a closed loop TBI?

Closed loop has nothing to do with the distributor. Closed loop is when your O2 sensor is heated up and the ECM is using that signal in it's equation.

Some systems like Holley can be purchased and run without an O2 sensor and some it's an option. I'm sure the GM system could be run without it as long as it was programmed into the chip. But why run without? It's an excellent resource for the ECM, cheap and easy to install in a bung welded to the exhaust pipe close to the exhaust manifold.

I think what confuses people with the fuel injection is it needs a signal from the ignition to run. So a tach filter will give the ECM the proper signal and you have fuel injection. But for the ECM to control the ignition timing it needs the EST module. The Ford Duraspark conversion works well with or without fuel injection. But with fuel injection it will work properly with the EST and disable the advance features. Or if you take the distributor from a GM EFI car it has the EST built inside. Graph the two and you have EST. The GM distributor has no vacuum advance or mechanical advance. It is all controlled by the ECM.

If you are going fuel injection for sure, build the EFI small cap distributor. You will be in less than any large cap hei and have full ignition control. By the way there is a large cap hei distributor used on some earlier fuel injection cars that had no vacuum or mechanical advance.

The reason the distributors got so big when the HEI ignitions came out was the hotter spark would arc or misfire. So the larger cap moved the contact points farther apart. Then the large cap went no advance and started to throw the spark out earlier the chance for arcing is greater. The newer small cap HEI ignitions use a channel in the rotor and a guard in the cap so the spark is directed down a channel and has less chance of arc or misfire. It also takes the coil off and mounts external keeping things cooler.

Since I am half asleep I take no responsbility in this information being correct :eek:

[Bill usn-1]

To back Mark up, there are some good answers on the main FAQ page that were submitted by Norm at AFI.
IH FAQ

There is additional info at the AFI web site.
AFI FAQ

HTH

[Eagle-Mark]

Besides the FAQ's there is one that everybody should read BEFORE installing your system called troubleshooting.

http://www.affordable-fuel-injection...-injection.htm