tbi swap small block to big block

[kauzenkaos]

i recently swapped a built sbc long rod 400 (350 rods instead of 400 for piston skirt breakage issues) in the place of the 350 in a 90 blazer i used a performer intake and a tbi adapter plate to convert over from carb 1st im looking for the CFM of a stock tbi 2nd can i swap the 350 tbi with the 454 tbi without a pcm change my idle speed in gear is like 500-550 rpm in gear and will make 200 rpm jumps if i sit too long at a red light other than that engine pulls pretty hard through entire rpm range at wot and holds steady at cruise but i feel like ive lost some power compared to the holley 750 carb previously installed and i know this inst the place but im in looking for a 4l80e 5.7 processor and engine and trans harness for my 4l80 trans swap so i dont have to stick shift the valve body

 

[dyeager535]

I think stock SBC throttle body is somewhere around 500CFM.

You really shouldn't be running it without the right injectors/tuning (at LEAST higher fuel pressure, but that's a bandaid) as you are undoubtedly running lean in open loop and hard throttle, and there are at least one or two people on here who have destroyed 383's by trying to run them lean, with 350 parts.