Hi guys,
I am turning to you for help with my TBI transplant project. I got a 72 Ford with a 400 M-block.

So, what did I do?
-I got a TBI system from a 1990 5.7 K-Series truck (7747 ECM).
-Mounted it on the engine's Edelbrock Performer intake
-A Ford DuraSpark II dizzy is connected to a brand-new HEI module (getting a perfect spark at the right time since putting the wires the right way 'round )
-Fuel pump's an Airtex E8094
-New coolant temp sensor, IAC, O2 and MAP sensor are fitted
-I did not fit a VSS
-Set the dizzy phasing
-Made first steps towards a custom bin

Sadly, now strange things happen and I am lost as to the cause: When the spark advance crosses 30°, the ignition seems to cut out. I even blew my muffler with a massive misfire. As the ignition problems occur no matter what rpm, whenever I set the advance to cross 30°, I hooked the car up to an engine tester and found this:

Yep, each plug gets fired twice. I have no idea how and why that happens. I already switched the P/N cabling to shielded wires in case there's interference, to no effect. Now I don't have any more ideas this side of changing the HEI module, but I somehow doubt that's the culprit.

I truly appreciate any help...

 

Usually when the ignition cuts out above a certain advance, it is due to incorrect rotor to cap phasing. What happens is that when the spark occurs it crossfires to the previous cylinder. Which already fired and the engine dies.

As for the dual sparking, put a scope on the pickup coil wires that go to the ICM. Should look like this:

https://www.thirdgen.org/forums/v6/5...ml#post4410495

RBob.

 

Here's my dizzy at TDC. Keep in mind that it turns counterclockwise... The long white line is the position of the #1 cylinder plug connector.



I already shielded my wiring, but I am not good enough with a scope to tell if the signal change at higher revs is cause of the higher revs or cause something goes terribly wrong...

 

So I took an oscilloscope out to record the dizzy signal while revving the engine until the problem occurs. Here's the result:

Looks fine to me, but I am by no means an expert.

We logged the second test run on my buddy's laptop. Will post the log as soon as he mails it to me tomorrow.

 

...and here's the log!