I've posted this here rather than on the Electronics board due to a larger audience and a better chance of getting my question answered.

I'm in the same dilemma a lot of guys are in. I have an original LG4 car, and have swapped in a larger motor making substantially more power, and soon to be even more. The problem is with the inadequate ECM programming. The timing advance curve on this ECM is pathetic, and hinders performance. I want to be able to adjust my timing when I want, without any DIY PROM or any expensive custom PROMs... and I would like to keep my CC QJet. The only way I can think to accomplish this would be to swap in a regular non CC HEI. But without the ECM seeing the proper distributor nothing is going to work right.

I want to emulate the CC HEI in my car while running a regular non CC HEI. From what I can figure there are 4 wires running from the ECM to the HEI module. One is the bypass wire, which I should be able to eliminate altogether, along with the spark timing output. They are only outputs and the ECM couldn't care less where they go. The third wire grounds through the HEI module, so I could just ground that terminal out. The fourth wire is a reference pulse input. This is my question. What kind of input is this? A ground pulse? And if so, is it a constant pulse or is it relative to engine RPM, in which case I could splice into the tach wire and provide the reference that way (crossing my fingers).

Any help is greatly appreciated!

 

If you're going to eliminate the computer controlled Qjet carb most people also install an earlier non-computer controlled HEI distributor. It's a drop-in. Then you can change timing advance the old fashioned way- with different springs, weights and an adjustable vacuum advance canister (all available from Crane).

If you want to KEEP the cc-Qjet just about any off-the-shelf chip for your car will give a MUCH better timing curve than the stock chip (especially the LG-4 chip). That's the PRIMARY reason aftermarket chips make more power than stock in computer controlled engines. They do little to change the WOT A/F ratio of the cc-QJet.

 

I want to KEEP the CC QJet. I've finally got this thing dialed in correctly and it's running flawlessly. The gas mileage is incredible at around 26-27MPG highway. I'd hate to start all over again.

Tried that. I ran a JET Stage 2 chip. Did nothing for performance. I noticed more of a gain advancing base timing 4*. It's now set at 12* base and total timing is only like 32* I'd really like another 6-8* to play with.