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Fuel Injection for early hemis

From: Hank Dozier
Remote Name:
Date: October 16, 2002


OK....I am not total knowledgeable of the nuances of the Holey TBI ssystem, being more of a port-injection specialist, but there should be no great issue with adaptation of one to an early hemi. Several things need to be discussed, and I may miss something in this response. If I do, and remember, orif someone else has pertinent information, feel free to comment or annotate this message. You will need to adapt your distributor or acquire one that is compatible with the Holley system. As Holley states that they sell systems for Chryslers (and I hope they mean V-8s, not the 4.2L Jeep I-6 engine), they should have a distributor that is comaptible with their system that fits the 318 series LA engine. Depending on which hemi you are using, you may have to lengthen the distributor shaft to fit. Measure your distributor from the point where the flange contacts the upper horizontal surface of the block to the end of the flat drive tang. This is the length you will need on the new distributor. Powerplay/Hot heads makes a collar that can be used to make this extension. You cut the shaft and press on the collar, and then add the lower tang end back on to the correct length and drill and roll-pin it in place. Now you have the correct functional distributor that will provide the signals to the Projection. For the Air Temp and Water Temp sensors, you need to find appropriate places to put the sensors. Try and use existing holes in the manifolds for these items. Use adapter unions if they are larger than the supplied sensors, which are most likely GM parts and therefore 3/8" NPT. Place the air temp sensor in the manifold, NOT the air cleaner, if possible for best response measurement. The Pro-Jection throttle body will have to be mounted on a custom plate, as the old Square-bore WCFB or 2bbl BBD base is not the same pattern. This will be a custom plate, but try and line up the discharge bores over the manifold bores, if at all possible. The MAP sensor (Manifold Absolute Pressure) may attach directly to the throttle body. If not try and mount it on the firewall so that a short length of rubber hose that runs DOWNHILL attaches it to the manifold vacuum port on the TBI unit. This is done to prevent condensation of fuel vapor from causing a liquid-lock in the line. You will have to mount a fuel pump. This can be done by modifying your tank, or mounting outside of it BELOW the pickup point in height close to the tank. Make sure you shield the pump from exhaust heat and rocks! You also have to run a return line back to the tank unless the system is "returnless", which I doubt. Do this with 1/4 to 5/16" bundy line, and you can hook into the filler tube of the tank near the entrance to the tank. Optinally, you can add this to the sender plate if large enough. If you do the latter, run a line down close to the bottom of the tank to minimize areation, as you have a vented tank! The wiring should be straightforward from the kit, but try and keep the sensor leads away from the plug wires and coil. Cross at right-angle if necessary. Make sure the ECU is case grounded back to the battery as well as frame of the vehicle for EMI resistance. If the kit comes with a base calibration, try and get the one for a 318. If the only thing avaialble is SBC, then start with a 5.0L calibration. Change the maximum advance by speed/load to about 35 degrees. This should be below the knock threshold. You will have to adjust from there, but be aware that if a Chevy knock module is available, the sensor is tuned for Chevy and will not work correctly with the MOPAR engine as the tuning of the sensor is incorrect. The best kit to get is a closed-loop kit, and put the O2 sensor in the exhaust in a plate between the exhaust manifold and the pipe (have to make it) make sure the sensor is "self-draining", so it doesn't freeze and crack from condensed water. 14.7:1 (stoichiometry for gasoline) is a pretty even split between lean-best fuel cal and engine damage. You can trim your fuel curves in using the sensor, and force open loop later if desired. That is the basics. You will need to experiment with cold start fueling and cold idle calibration to get the driveability you desire. For a good primer on calibration, get the ACCEl/DFI calibration guide off the ACCEL site under the "" web site. The author (Ray Bohacz) give a pretty good overview of their system in particular, but applicable to other Speed/Density systems as well. If you want port injection (more complicated), this system is pretty good, as is the FAST/Felpro and the Haltech systems.


Last changed: July 19, 2018