All Big Six Fabbing intake on efi lower.

Relates to all big sixes


Well-known member
Look for advice feed back your crazy kinda stuff.

Am I on track?
Carb or sniper will sit Level im unsure how high to put the carb mounting surface.
Was thinking 2" but that seems high. Now thinking to put it at 1"

Also wondering about hood clearance. Rig is a 76 f150

But 1" seems to be pretty close to runner mouths

I have no idea about intake volumes and stuff. This intake is crude plate welded together forming a funky shaped box.
Cant be worse than the 1barrel and intake right?

Head is currently getting 1.94 1.60 valves and porting, cam 252h .030 pistons, its not a high compression motor. Heads getting surfaced is all.

Looking to make about 300hp by 3000rpm šŸ¤Ŗ ok maybe not but im wanting decent low end probly wont run the rpm passed 3000.

Thanks for any advice comments or your crazy kinda stuff.

Thank you


  • 20211124_221528.jpg
    1.7 MB · Views: 8


Well-known member
Haha I was joking about 300 at 3000 I doubt any 300s make 300 at that low of rpm.

Maybe 100- 175 at that rpm.

Driveability at low rpm 1500 to 2000 is what im after


Well-known member
I made something similar. Mine is 4" wide and a little taller than you're planning I think. Mine is designed to use the plenum elbow and throttle body off of a 2v 5.4L F150 from the late 90s. Hasn't run with it yet though - still building the rest of the engine.IMG_20210913_100607382.jpg


Approved Vendor
Supporter 2018
The total plenum volume should not be more than about .75 to 1 times the cubic inch of the engine for a stock-ish build. On a pretty healthy engine build, you can push the plenum volume a bit further, and it's common for forced induction plenum to be 1.5 times the cubic inch and beyond. For wanting lower RPM benefits, I would stay below 1 times the cubic inch to maintain good airspeed and throttle response.


Well-known member
If you go the carb route, I think two carbs with a divider plate in the plenum would give better fuel distribution, especially with firing pulses being even on the front and back three cylinders. I have read that a connecting hole in the plate is benificial and the diameter of the hole can be tested for what works best for the engine's use. Carb or sniper I wouldn't smooth the transition from the plenum to ports anymore than the picture to "reatomize" any liquid fuel in the plenum instead of it sticking to the port walls.


Well-known member
Thinking ill order something to bolt on before I finish.20211125_220239.jpg
The Plenum is 175ci

Im looking at holley truck avenger 470 or sniper 2300.

I might go sniper since I didnt put money into the intake. Just time.

Thanks for the advice. Helped out alot.


Well-known member
Whats the best way to face carb.
I think like this 20211126_194239.jpg

Like this is easier to hook up throttle
Carb is a 1.21 venturi 2100 I think will work. I actually have to both 1.21


Well-known member
I dunno that would be 700cfm
I think a single 350cfm two barrel might be alittle big for low rpm


Well-known member
Im not running enough cam to make use of the fuel , comp 252 cam.

Im shooting for 1500-2500rpm Grunt

Those guys are pushing 5000rpm more of a hot rod type set up that isnt ideal for slow speeds.

Ill probly be going to the holley 2300 sniper at some point.

I did wonder about bolting a handfull of single barrel carbs on it.


Well-known member
You will gain the benefit of better fuel distribution with twin carbs, all u have to do is use the smaller 2100s. Guys run 600cfm carbs onotherwise stock 300s and they run fine. My stock 300 had a large 2100 on it when I got it and I swapped to a 390 holley 4bbl, there was a noticeable increase in power everywhere in the powerband as well as an increase in fuel economy. I think if anything a small 390-450cfm 4bbl would give you better low end performance


Well-known member
Frenchtown said he used a Clifford 2x4 intake with twin 2100s on a streetrod he built and it ran amazing and pulled down low no problem
Last edited: