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Six_Shooter
05-14-2016, 12:10 AM
I'm trying to do a quick conversion on one of my cars from carb to EFI, I have a few '7747 but are 6 cyl and haven't found an 8 cylinder '7747 yet. I do however have a '746 that is for an 8 cylinder. Is the NETRES compatible from the '746 to the '7747?
Six_Shooter
05-14-2016, 06:24 PM
Update: I found a '299, in my stash, that is a pin for pin compatible ECM for the '7747. I will likely use this one at least to get the engine running, but would the '299 NETRES be compatible with the '7747?
damanx
05-14-2016, 07:52 PM
Aren't the NETRES chips nothing more than resistors enclosed in a 16 pin dip package?

If so, then do a pin to pin comparison using a DMM.
Six_Shooter
05-14-2016, 09:55 PM
Yes that's what they are... Doing a pin to pin comparison will not only takes hours or possibly days due to the way the network is setup inside then (the "NET" part of the name) but would be inconclusive since I don't have an 8 cyl '7747 NETRES to compare to.

I'm more curious if someone has done this and wether it works or not. I know trying to run with a mismatched NETRES to the bin defined cyl count causes rough running and poor driveability. I want to avoid that.
lionelhutz
05-15-2016, 05:20 AM
Don't the 746 and 747 use the same circuit circuit boards? Since the netres is added into the hardware, the 746 one should be compatible with a 747 ECM.
Six_Shooter
05-15-2016, 07:46 PM
I don't think they do otherwise the PROM would also be compatible, which it's not.

But this morning I went to the wreckers and found a '7747 8 cyl equipped truck, so I grabbed the PROM and NETRES from it.
lionelhutz
05-15-2016, 09:54 PM
I'm pretty sure they're the same circuit board. There is fixed code (ie no calibration tables) on another chip that isn't part of the bin PROM. This code is different which makes the PROM incompatible.
Six_Shooter
05-16-2016, 02:25 AM
At this point for me the NETRES compatibility is a non issue due to the PROM and NETRES I found this morning. Car has already ran on it, so it's good. Now to finish up some of the mechanical (Install the knock sensor in the block and the O2 sensor. Maybe install a VSS, that all depends on how long I will use the '7747 before swapping to an MS2... Which directly depends on how long it will take me to make the adapter harness and get one of my WBO2 sensors back... lol I also need to re-stab the dizzy. I seem to have it about 1 tooth too retarded.