CarNoobLovingIt

I've been reading and reading and getting different opinions on this so I'd figure I would ask people on here for opinions. I'm upgrading my TB and Plenum and I've been reading that the BBK 78 mm is far too big for a N/A set up so I'm asking about the 75 or 70 mm. I don't plan to do FI but I do want the most out of my engine. So is the 75 mm too big?
Also, what's the verdict on spacers? I've read that some people say they're pointless...

school boy

On the throttle body, a 70mm will work just fine on N/A engines. the 75mm or 78mm are overkill but wont hurt anything performance wise. The pinch point is the outlet of the plenum. Its the same size on all these setups. Basicly go with what you want, I personally had the 78mm combo until I went with a SVO manifold. On the spacer, its a waste unless you have clearance issues of some sort.

DeathRattle

Agreed. I have a 75 on my car...along with an upper plenum and PP intake manifold. 75 can bring in more than a NA engine can use but you won't be hurting anything. But then again, when you think about it, the Bullitt has a dual 58mm TB. So if you have future plans for forced induction, then get the 75,

CarNoobLovingIt

I've only seen 2 different plenum options. The accufab and the SR Performance.
Any preference on the two?

CarNoobLovingIt

So there's no negative effects to a 75?
I just don't want to buy it, install it and tune only to find out it's to much air and it's actually hurting performance.

SonicBlue98GT

I run a 75mm Dragon TB with my P51 Intake and have no feel of power loss. I am going to be FI, thats why I have the intake but you can't go wrong with a 75mm. Here's some proof that 75mm is better than 70mm, even with no power adder. You can spend the big money for Accufab, and gain a few horses but save $100+ and go with one of the other brands.

Stock Accufab C&L Dragon Trick Flow
RWHP 265.97...272.38 (+6.31)271.13 (+5.16)270.69 (+4.72)270.19 (+4.22)
RWTQ 303.54...310.42 (+6.88)306.05 (+2.51)307.27 (+3.73)306.61 (+3.07)

http://www.allfordmustangs.com/forum...no-charts.html

school boy

Youre not going to lose any performance. You would have to go much bigger than a 78mm to be too big. The 2v bullitts use a cobra throttle body and they flow more than the 78mm. Your fine with any of them.