Considering that the CPI engine is batch fired like the TBI, there is more in common in regards to the fuel delivery system than one would think.

Another glaring problem is the fuel pressure difference. A TBI motor only requires 10-12psi while the CPI motor requires ~60psi. This would require a fuel pump (and likely tank) change in the older vehicle.

As far as using the long block from the CPI motor (this would be the easiest option), you would have to check to see if the TBI motor has a balance shaft. If it doesn't, the intake manifold may not have sufficient clearance for the balance shaft in the CPI motor.

 

Did tbi's come with a balance shaft at all? I thought that was only in the cpi/vortecs?

 

Possibly not, but the clearance issue is still valid.

The cam will also be different between the two, but I know that others (hanr3 for one) have used the newer engine block in TBI applications before and I believe they stuck with the newer cam. I can't remember if he had problems with balance shaft clearance though or if he just removed it.]\

Sticking with the TBI intake & throttle body adds reliability as well. CPI fuel systems are very prone to problems.

*EDIT* - A '91 Vin Z engine would not have a balance shaft, but the 93-95 Vin Z engines did.

 

The entire fuel system inside the cpi has been completely replaced, fpr, injector spider etc. entirely rebuilt the engine and decided to just replace the entire fuel system to prevent any issues with that later on

 

Even with new components, it is still a problem prone design. The TBI injection system is WAY more robust from the injectors to the fuel pump than the CPI system.