Originally Posted by no mechanic me
What is involved in changing a 5.7 Vortec from a 97 truck and installing a 5.7 standard fuel injectio motor?
There is not a simple backward path from the Vortec. This crosses emission generations the Vortec being OBD-2 and that before 1996 being OBD-1. The entire design logic and systems applications are completley different. A back date can be done but it is costly, time consuming, and illegal.
The earlier OBD-1 engine can be modifed as a long block to replace a Vortec long block. This requires using the Vortec crank damper that has the elements that trip the crank position trigger the OBD-2 computer is looking for, this also requires the use of the Vortec plastic timing case cover with crank position sensor. The Vortec heads, EFI and distributor will bolt on to an earlier one piece rear seal block.
The Vortec uses a roller cam, it is advisable to stay with the roller so in picking an earlier block you want one with the provisions in the valley to mount the spider and with the taller lifter blocks, on the front it needs the mounting location for the cam's thrust plate. The timing needs to remain as built or you get into a programming issue with the computer which is doable just bring money. The Vortec cam times at 191/196 degrees at .050 lift with .414/.428 inch lift on 1.5 rockers the LSA 112 degrees at .050 lift. To avoid programming changes you've got to stay pretty close to this. You can trade a bit more duration if you also take a wider LSA for example the LT1 cam with 201/208 a lift of .447/.459 with 1.5 rockers having an LSA of 117 degrees.
If you're having problems with the original fuel injection where the remote check valve injectors leak, it is possible to modify the system to use TPI injectors at the port wired back to the wiring that runs the central injectors in pod to completely eliminate the factory Vortec injector arraingement. This greatly improves the L31's injection without having to make big systematic changes to the overall fuel injection and vehicle management systems.