Liquid_02

OK, I am currently doing a 408 swap into my 92 GT. Plan on making roughly 450hp and 500lbs/tq before 6 grand as it's going to be a street car. I have not yet bought the engine, as I found a short block for cheaper than i could stroke the windsor block I have sitting at work. But here's the basic set-up I plan on running:

Victor Jr. Heads (non-cnc'd)
Trick Flow R-Series Intake 75mm (Or is there a better one? Want to keep the RPMs down... and edelbrock's seems a little radical.. I think anyway)
Haven't quite decided on which cam yet
Megasquirt ECU (already built it) and EEC-IV adapter kit
42# injectors
BBK Longtubes

Ok, here is why I ask, the 302 I have in the car right now has a 70mm Holley Throttle Body Link on it right now, but Holley doesn't specify CFM's. Going by Accufab's 70mm (the Holley can't be too far off) it flows 787cfm. Now would the 408 need that much air only revving under 6 grand? As I figure it should be pretty much in the vacinity of what I need.

Any help would be greatly appreciated or any other suggestions for the setup

w8less

if under 6,000 the 70 will be a restriction. if it were me i would run a 75 at least.

they do make a R intake with a 90mm opening

Liquid_02

Yes i know they make a 90mm opening, but that would be good if I wanted to race the car, but I don't. 90mm would be more oriented towards hp, the smaller one should create more velocity, so I want to stay as small as possible. Thanks a lot though, maybe I'll throw my 70mm up for sale.. only got about 500miles on it, should be able to get something for it and grab a 75

w8less

[sm=goodidea.gif]

5spd GT

Holley Flow:

65 MM - 750 CFM
70 MM - 790 CFM
75 MM - 840 CFM
80 MM - 892 CFM

lxman1

Run the 70.

jtmustang

i agree too for what your saying i would use the 70 to.

Liquid_02

What the hell, where'd you find that?? I've been lookin for that all over the place. Thanks!

So you guys don't think that the 408 below 6 grand will require any more than 800cfms? I know people say 750-800cfm carbs, but I don't know if you need more or less with a T/B. Just don't want that to be the limiting factor in my reaching near 500hp. It's not a big deal if I do have to get a new one, money really isn't a big deal considering this motor is going to cost me probably 7 or 8 grand by the time it's running, just want to stay as small as possible without being a restriction is all

w8less

the 75 would have you covered regardless. should be a fun street car

5spd GT

I made a call to Holley about a year ago.

Area of some throttle bodies...

60mm - 4.4" ^ 2
70mm - 5.9" ^ 2
80mm - 7.8" ^ 2
90mm - 9.8" ^ 2

Displacement * RPM * VE / (1728*2) = Volumetric flow of the engine in CFM

The 1728 converts from in^3 to ft^3, and the 2 comes from dividing RPM by 2 in order to get the actual number of intake strokes. Many dynos will configure the VE for you.

408 * 6000 *1.0 / (1728*2) =708 CFM at 100 % VE.

I would get a 75-90 throttle body, with no more or no less in my opinion.

Make sure you check the area of your intake a few inches inside the intake tract. Many intakes have less area at their smallest point a few inches in, than the throttle body being run. This means that the larger throttle body is doing nothing.

Time to start porting...

Good Luck.