Throttle body size,cubic inch, RPM, 8 stack efi.

Newbie here looking for help on throttle body size from anyone with an 8 stack EFI intake , Im looking to get a Morrison crossram for my 408 windsor it currently has a victor ,1000 cfm TB , comp XR280 solid roller , Trickflow R Heads, all forged internals ,engine revs quickly to 7000 happily , 10;1 COMP, makes 564 HP .if you have an indivdual runner intake could let me know the size of your engine TB size/length ,hp, rpm ,and if the tb size you chose is good or falls flat etc. . have choices from 46-48-50-52-54 mm , Cheers Vaughn.
 

Terry Oxandale

Skinny Man
I use 48s on mine, and had often thought of increasing the size, until I found some information on the Jenvey site that provides information about max HP for a given diameter. According to them, a 48mm should be good for up to 74 HP/cylinder. I'm running an LS2 (6.0L) at about 62 HP/cylinder, and it is extremely quick (almost too quick) to my 6800 RPM redline. I use long runners (5"), and long tubes (11"), plus head intake port length and the ITB depth to obtain the total induction length per other calculators. It should be about 18", but mine is a tad longer. A purposeful induction design allows full HP potential, and lengths of the system for an ITB is pretty important for max efficiency. As I've implied, it does NOT fall flat at any point in the power band, and has great response (but the linkage is very progressive).

Quoting their site:

Basic references for BHP per cylinder, assuming ca 120mm from butterfly to valve head and a max of 9,000 rpm are;
Up to 30 BHP - 30mm, up to 33 - 32mm, up to 39 - 35mm, up to 46 - 38mm, up to 51 - 40mm, up to 56 - 42mm
Up to 65 - 45mm, up to 74 - 48mm, up to 80 - 50mm, up to 87 - 52mm, up to 93 - 54mm.
These power figures may be increased by up to 10% in a purpose designed and well proportioned system.
As butterfly to valve distance increases, butterfly size will need to increase in proportion to system taper and vice versa.
Lower revving engines and those with injectors placed before the butterfly will generally accept a larger body.
 
Last edited:
Back
Top