Here is a little test we performed.
While we were working on an Edelbrock RPM head, we took a break to test it with some manifolds and an 850 cfm Mighty Demon carburetor. 1st column is the OOTB Edelbrock RPM head, 2nd column is the RPM head after some blending and the following columns are the indicated OOTB intakes all using the same 850 Demon. The M1 is a single plane and the 4bbl iron is from a '69 Road Runner
Lift....OOTB RPM...blended...stock iron...RPM....Torker II...M1....Victor
.100.......70...........72...........69...........71.........71........72.......72
.200......143..........150.........131.........145........148......148.....150
.300......201..........212.........172.........195........201......201.....202
.400......243..........254.........187.........228........242......234.....240
.500......271..........276.........199.........240........254......254.....261
.600......285..........290.........203.........251........264......266.....271
.700......293..........302.........204.........256........269......273.....280
.800......295..........315.......................261........273......276.....285
