I have recently rebuilt a 350 4bolt to put in my 91 Z. Its a 355 with corvette L98 heads, and has a ZZ4 cam in it with 1.6rr. My question is....do I need bigger injectors for this cam? It idles and drives fine..so I dont think I need a different PROM, but it just seems like it leans out on the higher side of the RPM. I know that TPI's die out about 4500, but this motor just seems like it wants more fuel? Would a adj fuel reg. fix this? The 02 sensor confirms the leaning, but its kinda old and needs to be replaced.....any help would really be great. Thanks...

 

Replace the O2 sensor. Aside from that, have you done a general tune up recently in regards to your ignition and fuel injection system, fuel pump and otherwise?

It could be one of these simple/cheap things before you decide you might need to bump fuel pressure &/or edit the prom.

 

Yes I just did a tune up about a week ago....I used Ac Delco plugs(.045)...Taylor wires, MSD distributor, coil, cap and rotor(timing set at 28* adv at 3000rpm). The car also has a new Holley fuel pump and a K&N fuel filter. The injectors came from a 90 Vette TPI, but they are 22lb right? Im almost certain thats what mine originally had. Ill change the 02 sensor in the morning....dont know why I didnt change it to begin with.....

 

22# inj's should be plenty for that cam. You sure they are clean and flowing correctly???

 

with a modded motor, you cant really go wrong with an afpr, there a good tool for tunning.

 

well...I changed the 02 sensor today....and also got a new afpr...from TPIS....I set it to 50psi like they said...and drove it down the Interstate...it runs great now. I havent had a chance to check the 02 sensors reading, but it seems right now....and smells right if that makes sense. Also, just wondering how much my 170deg t-stat affects the mixture??? It definitely seems better though......