[Gmecm] TBI Swap - Iron Duke Tech IV

[Andrew Gibson]

I'm glad I'm not the only one trying this conversion! Only mine is going on a 250 CID Chev 6 cyl. Mechanically you sound fine. For your fuel flow the large steel line going to the throttle body is pressure, little one is return. Any excess/unused fuel is returned to the tank. You may be able to raid the fuel lines and pump off the olds and make them work on your jeep. (PS: the carb has a float to prevent too much fuel inside the bowl. Just like your toilet at home)
   
  The most difficult task to conquer is your rpm feed. You may be able to attain spark control (Computer controlled timing) as well with this setup, but I haven't dug into that yet. I'm still researching and testing. For simplicity, there is a 5 wire connector with 4 wire in it that attached to the ignition module. Cut it off. Locate a unsuspecting gm tbi vehicle in your local boneyard and remove the two electrical connectors from the module and cut them with about 6" of wire on them. Visit the parts store and get a ignition module and pickup coil for a 4.3L v6 roughly the same year as the donor of the connectors. (Or just skank them while at the wrecking yard.) Solder the 4 wire connector onto the wires of your harness where I told you to cut them off. The colors will match! Cool huh. It gets better. The 2 wire connector from the wrecking yard needs to be attached red to switched positive (The other old ignition module connector has this! Same color too!) white is coil negative if
 you want the computer to do spark control. If not seal the end up with heat shrink tubing for later use, just in case.
   
  Mount the module somewhere safe (Firewall is good) with carefully tightened self tapping screws and dielectric grease on the underside (It grounds and transfers heat there) Cut the pigtail off the ignition pickup. Inside your distributor there should be a ignition pickup. If using the ecm for spark control, cut off the wires to the pickup at the connector and solder & heatshrink 2 longer wires to the pickup. Twist the two wires around each other to reduce noise and solder your donor connector on. Plug it into the module with dielectric grease to prevent corrosion. If you are going to use existing spark control just splice the longer wires onto the module wires and run them. MAKE SURE YOU DO NOT PINCH THE WIRES WHEN RUNNING UNDER THE DISTRIBUTOR CAP! Cut a notch in the cap if you have to.
   
  One other item. IF you are going to use the ecm for spark control. The advance mechanisms in the distributor must be locked solid. This includes the centrifigul advance under the rotor and the vacuum advance. If not hook your advance vacuum hose up appropriately at the TBI unit. There are two vacuum sources, ported and manifold. Either one could have been used. Mix it up and it will not run right.
   
  Good luck and keep us posted!

			
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