93 Chevy 350 motor with automatic transmission tbi to carbator
Yes it can be done. Are you mechanical --- Do you want the general requirements or a step by step.
Yes step by step
Yes it can be done. 1.) Parts: Need a new intake and stand alone distributor. Any SBC carb intake to match the carb you are installing. The current distributor sends a signal back to the ECM and receives the spark timing based on other parameters. It is best just to remove it and use a regular HEI ignition with vacuum advance. Also will need to adapt the trucks throttle cable and T/V cable to the 700r4/4L60 tranny. Caution if your truck has the 4L60e with the standalone TCM on the Drivers side inner fender you will need to attach the TPS to the new carb. You may also need a rpm reference (I will look into if you confirm that you have the 4L60e, there will be a multi wire harness going to a large plug on the drivers side of the tranny verses the 700r4/4L60 with has 3-4 wires and a T/V cable from the passenger side up to the throttle body). Fuel system changes see the end. 2.) Ensure you set the crank at TDC on #1 and observe the rotor inside the dist. If your pointing at the wire going to number 1 on the cap you are at TDC compression/firing if it is pointing the opposite way you are TDC exhaust stroke. Doesn't matter just remember which one and make a reference line on the firewall of where the rotor is pointing as a base line for reassembly. 3.) Disassemble the top of the engine down to the intake. 4.) Install the new intake, HEI distributor (installing the dist with the vacuum pointed towards the front pass corner of the truck with the rotor aligned with the mark you made earlier at the same TDC. You may need to try a few times to get the gear correct on the cam. Sometimes the oil pump drive shaft needs to be turned to align with the slot on the dist. Spring plug wires are as per before. You will need to run a wire to the power connection on the dist. Must be hot in run and crank (you can attach to the power in the original wiring harness. I would not cut in just solder and tape incase you want to switch back. Best to get the actual plug for the HEI power lead as the engine will die if it becomes disconnected. 5.) Assemble the rest of the motor as it was before, you may need to modify some of the vacuum lines. Good idea to label where they came from on the TB and try to match them up to a spot on the carb. Run a new vac from the lower portion of the carb plate to the vac port on the dist. Tape up all the unused wires and plugs from the efi system. 6.) Last would be the fuel. The TBI has a pump in the tank and no place to install the mechanical pump in the block. The best option would be to use a by-passing regulator used on performance engines etc. Get mine through summit racing. You will need to run the pressure tubing to the reg inlet and tie the bypass to the return line back to the tank. The outlet can be ran straight to the carb. The '93 uses o-ring style flared connections. I would measure the outside diameter (OD) of the pressure tubing and get a tube to -6 an fitting then run a 3/8 braided hose to another an fitting on the reg (usually 3/8 npt by -6 an) (I use the Summit brand hose fittings for cheap projects and brand name for high perf applications, but no failures on the cheap ones). The hose can be cut to length and install whatever ends you need (straight, 90 or 45). The return is lower pressure and a barbed fitting with hose and hose clamps can be used. Set reg at 5 - 7 psi, if you don’t install a gauge start at low pressure and turn it in until fuel flows to the carb but not high enough to overpower the float and flood the carb, the float should shut the fuel off to the carb allowing the unused fuel to by-pass back to the tank. I believe the fuel pump is controlled by the ECM and you may need to force the relay to run at all times when the ignition is in run and crank. I hope I didn’t miss anything. Recommend a cheap shop manual to assist with the small stuff.
What is wrong with the EFI system!
it keeps cutting out I've done all the changes but the transmission doesn't want to shift the motor will race in park reverse neutrality will go fast in reverse but put it in drive and it won't race.
Whoa! You converted everything already. What tranny does it have? The 700r4/4L60 with the T/V cable from the passenger side of the tranny to the throttle linkage on the carb or the 4L60e with the TCU and the multi-wire plug to the drivers side of the tranny. I need more clarification on "It keeps cutting out" Ok and by race you mean rev up? In drive it is gutless, no power? What about if you manually shift into first? But before you test if it is the 700r4/4L60 properly setup the T/V cable (hold the release on the large block and slide the center section away from the carb, tightening the cable, then let go of the release. Push the throttle wide open and the bracket should self tighten to the correct tension). If it has the 4L60e you will need to reconnect the applicable sensors to allow the module to control the tranny.
were is that located at
Ok the 4L60e. The stand alone TCU (if you have it) will be on the drivers side inner fender. If you don't the truck will have the newer PCM which controls the motor and tranny. The harness from the 4L60e is big and you can follow it to see which you have. In either case the tranny needs to see the throttle input to control the transmission. You need to remove the TPS (Throttle Position Senor) from you throttle body and connect it to your carb. Measure the sweep of the throttle body (total angle of rotation from idle throttle stop to WOT (Wide Open Throttle)) then measure the same on your carb. If the shafts rotate the same amount of degrees then you can direct couple to the carb (if there is room). If the angle of rotation is to different (or no room to direct couple) mount a secondary lever and connect to the throttle via link and mount the TPS to the pivot of the second lever. Measure the distance from the throttle valve pivot point to your link connection point. Vary the ratio of the distance between the pivot point and the link pivot point on the secondary lever to bring the TPS back within range. Shorten the distance between points if the carb rotates less than the TB or lengthen if it is more. I usually use rod ends with the studs and cut a slot in the lever. With a locking nut you can move the rodend up or down from the 1:1 position easily to get the TPS set to the factory rotation. A OBD1 scan tool or ALDL cable would let you connect to the PCM to verify you are not going out of range or you could test with a multi-meter. But as long as the TPS is set at idle where it was on the TB (mark it when you pop it off) and rotates as it did in the throttle bod you will be fine.
There are a few companies that make aftermarket TPS that are easier to work with. I believe JET's can be mounted and is strong enough to support the secondary lever to attach the link. I will try and find a part number.
It was TCI that I was thinking of. http://www.tciauto.com/tc/4l60e-4l80e-remote-tps-w-mounthtml/ Here is what they sell. You can see the lever on the TPS. If you found a 700r4 T/V cable bracket and old T/V cable you could build it like this. Just need a TPS bracket and a lever to connect to the cable. Some small engine throttle's have those cable clamps with the pivot.
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