Duncan_GT

Alright for my 393 I'm ready to install the intake. I'm looking at getting the Trickflow R intake (not the Box R), and it comes in 75mm and 90mm. I talked to a buddy of mine, he suggested the 75mm. He had one on his 306 (yes i know, completely different ball game displacement-wise). He said the 90mm would be for boost applications. Mine is all motor.

1) What would you guys run?

2) Is the 90mm for boost or is he just an idiot?

3) Is it safe to assume that the 75mm would be like trying to sprint and breathing through a straw? That's the analogy I think of when trying to decide.


I'm thinking the 90 but I want to be sure before I drop the money on it. **I think I've asked a question similar to this awhile back but can't find the thread.**

reldla1996

For a 393, unless you're going with a mild cam, I'd go with the 90mm. For a 306, 75mm is plenty, but for more cubic inches, bigger makes a difference.

Duncan_GT

If I do go with the 90mm, I need the adapter elbow since its going into a 94-95 car. But the elbow only comes in 75mm. Is this going to affect it? I would think it would choke it just as much as a 75mm plenum opening.

Venomantidote95

I currently use the edl-2945 intake on my 94 on my 347 will be using the same upper with the 3886 lower a 75mm tb is enough for 400+cuin non-boosted apps!

If you use a 90mm on anything you will affect the intake air-speed, pending the cubic inch and heads and camshaft along with compression ratio it may be an adverse affect poor lowend flow and acceleration!

Your drinking straw idea is right on but you have to look at the size of the person doing it just like the size of the engine! Is your person skinny, fat, atheletic, etc so on and so on, !
I will be using the same 75mm tb on my 421 once i`m to that point!

A 90mm swap is costly and you cant use the sn induction setup....

Venomantidote95

65MM
TESTED @ 5" - 280 CFM
CORR @ 20" - 560 CFM
CORR @ 25" - 627 CFM
CORR @ 28" - 664 CFM

70MM
TESTED @ 5" - 332 CFM
CORR @ 20" - 664 CFM
CORR @ 25" - 744 CFM
CORR @ 28" - 787 CFM

75MM
TESTED @ 5" - 390 CFM
CORR @ 20" - 780 CFM
CORR @ 25" - 874 CFM
CORR @ 28" - 924 CFM

Here is some flow data on the average commonly used tb sizes!

Duncan_GT

I have no clue what any of that means.

Its a 393 stroker, Trickflow 205cc heads, I have no idea if the camshaft is "mild" or what, and 9.7:1 compression. I have mixed opinions after searching the forums, some say 90 others say 75

reldla1996

If the elbow is 75mm, all of this is moot, you're effectively stuck with a 75mm opening.

Duncan_GT

I'm gonna do the fox tb swap so I dont need to use the elbow. In that case, will the 90mm hurt performance (air velocity) in the lower rpms?

reldla1996

Larger diameter equals less velocity, physics demands that answer. According to the book 5.0L Ford Dyno Tests, by Richard Holdener, for a 426 stroker, a 90mm TB made more power and torque, with a broader torque curve, from 2500-6000 rpm versus a 75mm TB, specifically by 9hp and 8ft lbs tq. Keep in mind this would preferably require no restrictions in front of the TB smaller than the TB, including the MA. On my 369, I'm running a 80mm TB, and a 90mm MA, connected by a 4" tube (necked down at the TB).

Duncan_GT

I'm going to run 42lb injectors. Do you think a 90mm maf is too much? Especially when its going to bottle down to 75mm