Progressive 2 barrel orientation

[Blairsville Ed]

I’m preparing to put a Holley 5200 on my 240. I’ve already milled a large rectanglular opening in the manifold and I’ll be machining an adapter plate to transition the carb to the manifold.
However, I’m wondering which way to orient the carb. Parallel to the manifold or perpendicular to it. Since it’s a progressive 2 barrel the primary would be offset of center if I mounted it parallel.
Any ideas as to way would be better.

[Harte3]

JMO, for practical purposes there would be no difference. Orient it for the easiest throttle hook-up, drive it and have fun! And don't forget the pictures of your set-up.

[Blairsville Ed]

Current set up

[Blairsville Ed]

Current set up, pic 2

[pmuller9]

If the plenum wedge stays the Carb will need to be perpendicular so both barrels straddle the wedge evenly.

A wedge does not need to be so high where it displaces a lot of plenum volume.
A small rise from the floor with a rounded top and curved sides would be sufficient.

[Blairsville Ed]

I actually started with a short wedge after I had completed the mod, but I had a substantial full throttle bog. I made it a little larger which helped, then I made it larger still. That almost completely eliminated the bog. It gave me a good throttle response as well.
I was thinking about a dome shaped piece for the 2 barrel.
I read a post from another site suggesting that I mount the carb with the main jets pointing forward.

[sdiesel]

Dome shaped.
its what im looking for to put in the basement of my one barrel plenum.
the wedge with its flat planes might create some low pressure spots?

the dome if small enough on the floor of the plenum will give the air flow just a little bump to redirect. maybe no more than 3/8 of an inch or so.
this is what my uneducated intuition gives me.

[Blairsville Ed]

The bottom of the plenum is cast with ridges. I think this was done for a reason.
Should I machine some ridges in the dome shaped turtle?

[Blairsville Ed]

Offset adapter block for Holley 5200

[bubba22349]

The bottom of the plenum is cast with ridges. I think this was done for a reason.
Should I machine some ridges in the dome shaped turtle?

I think the ridges in the plentum Floor are to help keep fuel suspended in the air / fuel mix (by some turbulence). Nice work on those parts! Good luck

[Blairsville Ed]

Carb mounted
I must have a vacuum leak. It would not idle so I removed the primary idle jet and now it idles perfectly with no idle jet.
What’s a good way to find a vacuum leak?

[pmuller9]

How many bolts hold the adapter plate down?

[THE FRENCHTOWN FLYER]

I look for vacuum leaks with a propane torch. It works even better if you wrap some tape around the air inlet openings so you get straight propane gas. Wave it around the engine and look for it to pick up RPM. That will lead you to your vacuum leak.

[1986F150six]

I tried this and it worked: https://www.bing.com/videos/search?q=Sc ... &FORM=VIRE

The air cleaner was removed and the carburetor was sealed using a good quality duct tape.

[THE FRENCHTOWN FLYER]

I think rather than smoking the cigar I'd just live with the vacuum leak. But that's just me.

[1986F150six]

I think rather than smoking the cigar I'd just live with the vacuum leak. But that's just me.

But, I did not inhale....

[Blairsville Ed]

I found the vacuum leak. The base gasket that came with the rebuild kit is .310 thick. There are large plastic spacers at each hole that were .315 thick. Torqueing the carb mount nuts just tightened up to the spacers creating a nice large vacuum leak. I cut the spacers down to .250 thick and now it seals well.
The idle jets were too small but I could get it to idle with the mixture screw 5 turns out. I went up in the jet size from #50 to #70. It idles nice with the mixture screw at 3-1/4 turns out.
Other web sites indicate that the idle jet should be sized so that the mix screw is around 1-1/2 turns.
Has used an AFR meter? Narrow band?

[THE FRENCHTOWN FLYER]

...I went up in the jet size from #50 to #70. It idles nice with the mixture screw at 3-1/4 turns out.

Whoa.
Do you mean you increased the main jet from #50 to #70? Increasing the main jet size only minimally affects idle A/F ratio to the tune of about 1% or 2% per number. But going from a 50 to a 70 would increase the main circuit area almost 100% making you super rich at WOT.

Maybe changing the idle air bleeds or modifying the idle transfer slots would be a better fix.
I'd do some WOT runs and read the plugs directly after a WOT pass.

I would think a 240 (4.0 L) doesn't require much more airflow than the 2.3L-to-3.0L hi revving fours most of those Holley / Webers were designed for. Ergo, the stock jetting shouldn't be very far off.

[Blairsville Ed]

It was the idle jet that I changed.
The main jets are stock, 40 primary, 32 secondary.

[THE FRENCHTOWN FLYER]

OK, I'm up to speed now.

BTW, I like your manifold clamp(s).

[Blairsville Ed]

This Holley 5200 is a fun carb to tinker with ( if you like to tinker)
I’ve researched the Jeep site as well as the small block inline side to gain insite into jetting this carb.
This is what I have learned so far:
Adjust the idle mix with a vacuum gauge connected to ported vacuum and maintain 0” of vacuum.
Change idle jets to get the mixture screw to 1-1/2 to 2 turns out for best idle, mine is at 2-3/4 turns out
Test the idle transition by increasing the engine speed to 1800 rpm and turn the mixture screw out. If the engine speeds up( mine sped up 250 rpm) the idle jet is too small

My problem is that my idle jet is a #80 which is the largest. The Ford 250 and the Jeep 258 guys are running #75 idle jets.
I don’t know if the 240 needs are different, plus my motor has .030oversized Intake valves, Chevy rockers and I did some light porting to it.
Are these inline sixes different in there carb needs?

[Blairsville Ed]

The #80 idle jet looks good.
I was able to put a small mirror down the primary barrel and watch it as I increased the engine speed. The primary Venturi starts to dribble gas at 1700 rpm. So I backed off the speed to 1500 and adjusted the idle screw to see if the motor would speed up., it did not. If I went a quarter of a turn lean it started to slow down.
So with the idle jet good I changed the main jet to a 160 from a 140. I ran the motor up to 2000 rpm the slowly closed the choke. The motor slowed down. The 140 was too lean, the 160 might be too rich. I’ll watch the spark plugs.
Next will be the secondary circuit.

My impressions of driving the truck with the 5200:
Very smooth idle
Smooth transition
Climbing a grade, the YF was more responsive if I keep the 5200 out of the secondary barrel but, if I put the pedal down the 5200 comes to life with better acceleration than the YF.
It should produce good mpg if I keep the secondary closed, but it is nice to punch it and feel the 240 pull.

[Blairsville Ed]

I missed the question concerning the adapter plate mount. There are 2 screws that you see in the pic and there’s a 3/8 stud for the other side which you cannot see. I machined a flat spot around the bottom of the intake manifold where the exhaust gases would flow to heat the carb. I also machined a clamp plate for the stud to pass through that matches the area where I machined the intake.