I had an idea today regarding converting a slant six to EFI using a conglomeration of Mopar and GM 3.8 fuel injection parts.

My understanding (based on reading others' experiences) is that one of the main drawbacks to the GM batch-fired and HEI driven ignition system installed on mid-80s Gm products is the control of the timing curve by the GM computer which has been calibrated to match the weight/engine/tranny of the GM car, not the slant six car/body combo.
Would it be possible to run dual HEI systems? What I mean is get a standard electronic ignition distributor and a dual pickup lean burn distributor, swap one of the pickups from the dual pickup dist to the standard EI dist and use the second pickup simply as a trigger for the EFI but then run a regular HEI ignition system off of the normal pickup? That way you have the timing still controlled by the distributor but the fuel injection would also be triggered by the second pickup? Would there be problems caused by the movement of the pickup-plate (advancing the firing of the injectors)?

Reed,

The early Buick 3.8s with distributors and port EFI only need an RPM signal to run the injection.

http://slantsix.org/articles/dibiase_ef ... ersion.htm

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Joshua

....so why not just change the timing curve via chipping or programmable ECU?

The beauty of the 727 GM ECU is its simplicity,,,,,one 7 pin HEI module controls both triggering and ignition.

To set timing on a 7 pin setup you disconnect 1 wire ....you could permanently disconnect it and control timing via any ignition box.

Changing the timing curve on a chip is as easy as telling the chip burner exactly what curve you want. EG if I know what curve worked on my slant and want to change to an ECU controlled setup I just tell Alvin the Chip Monk (my chip burner) what curve I want. Adding vacuum and centrifugal advance to an EFI setup is like using a gas soaked rag for a carb.

......I do like the thinking that led to the idea however...

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Yeah, this is the system i am talking about. I have been told that it is an easy system to adapt to the slant, but it is kind of a plug-and-pray situation since the computer controls the timing and is calibrated to whatever the original application was for that computer.

Chip burning is a good idea. It would be nice if there was some kind of real-time chip burning ability so you could tune as you drive.

But if you don't hook up the timing control wire from the ECM to the 7-pin HEI module the ECM doesn't/can't control the timing.

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Joshua

So if you leave that one wire disconnected the distributor could still function off of the traditional spring/weight centripetal and vacuum advance principles?

Correct - you can leave fuel and spark independent. The spark is an "output" so if you don't use it, those computers can still function. You don't have to use HEI module either, any ignition with tach/rpm out (msd, crane, etc) if you choose. HEI is plenty sufficient, and cheaper though.

Why not just use MegaSqirt and have total control and real time ajustment. Its cheap enough and the new version does about anything you could want. You can run it with about any dizzy you can come up with.


Jess