F-600/391? 4Vor 2 V ?

got a question For those that have had either Carb set up on their FORDs...just set a low mileage nice 391 in the 1975 Grain truck It has a 4 and 2 tranny ,, salvage yard thinx 4V Holly carb needs a rebuild .. Although started and run often in the last 10 years it has seen little real action ,and No doubt the Holly has GUNKY issues and needs a rebuild ... Last DEC, We jusT rebuilt the 2 V on my 330 . And That Truck really run fine and smooth until it let loose a rod . Dangit !.. Will I get better mileage with the Holly if I have it rebuilt and set by a expert ?Or should i just swap intake manifolds and run with my sweet 2 V ?.. i know the 4V will deliver more HOSS, which is not a big issue for Me ,,. I would rather have fuel mileage,,B-I-L suggests that 4V may be more economical for my runs .. I run 50-55mph on a nice easy 45 mile round trip to the elevator. The most I can get on it is 320 Bu of corn , I don't plan to make long hard runs.. thanx for your advice .. jh

The easy way is to go to your local hotrod shop and get a 4bbl to 2 bbl adapter so you dont have to mess with changing the manifold.
The front mounting ears and carb barrel location are the same on that Ford 2 bbl and the Holley 4bbl.
One I had was just a 1/4"steel plate drilled for a 4 bbl pattern with an extra set of stud bolts fitted about 2/3 of the way to the rear to catch the rear 2 bbl mounting ears, and the rear 4 bbl openings blanked off.
It set the 2 bbl right over the primary barrels of the 4 bbl manifold and blanked off the rear barrels. It worked great and only raises the carb 1/4 inch.
Not a hard part to fabricate from steel plate using a 2bbl and 4bbl gasket for a pattern.

Those 4V Holleys gave enough trouble with the end bowl gaskets and seemed to use plenty of fuel, all though lots of grunt if you stuck your foot in it. Does it have a vacuum governor? if so that will give you trouble sooner or later. I would switch it, like you said, the 2V's really ran sweet.

a 4bll will get better milege than a 2 bbl if set up correctly AND you keep your foot out of it.

There ain't NEVER been a Holley 2 or 4 BBL carb on a medium-duty farm truck that contributed to "good" mileage.

The deal is, you have some stuff that needs to be moved and you want POWER you buy some gas.

I CHALLENGE anyone to argue that point!

I would rebuild the 4 barrel. There not hard to do. Gas mileage shouldn't be worse unless you are into it hard causing vacuum secondaries to open.
May be better if the primaries are smaller.
It's a matched set, heads ,ports, intake, carb.I would not mix an match parts.
Past owner of F-750 tandem 20 foot box. That 391 needed every horse she could muster. Mark

Holleys are actually very easy to freshen up, you never did say how it actually runs now. Very rare that anything is actually wrong with one unless the gaskets dried out from sitting, and the newer gaskets don't shrink like the old ones. The main thing is to keep the governor functioning, if it's working right, let it be- just run some cleaner through it, set the acc. pump to spec, adjust the idle screw with a vacuum guage. If it's a 391, IIRC the governor would be at about 3400, and no need to spin it over 3000. They're actually pretty trouble-free engines, EVERY one I've seen that was grenaded had a car-type Holley on it without a governor, since the old carb needed a touch up, the owner priced a new governor carb and feinted, instead of putting a kit in the old one, and the drivers started running it at 4000+ rpm. They WILL grenade if over-revved, they CANNOT rev like a car 390- the bottom end parts are very heavy, and the large-stem valves are also heavy, and the valve springs are not for high rpm. Shift it at 3000, keep your foot out of it, and the mileage won't be that bad, and it'll chug along for a long time

I own a carb shop . You'll be much happier and lot less headaches if you stick with what you have ,rebuild the 4bbl . swapping carbs always ends up a cobbled mess. Govenor operation is needed or you will trash that motor . If not you , the first person other than you to drive it will. Rebuilt 4 bbl gov carb is not cheap. Not that hard to do ,,just lot of labor and pricey kits, Think the last one we did run around $400 . That includes R&R and adjusting everything , timing etc . Need any pointer once you get into it feel free to give me a hollar .

and i challenge you to actually read what i posted...i dont care for holleys at all 2 or 4bbl...but a 4bbl WILL get better mileage than a 2.

'Comon now, Pard.

"Fuel mileage" shouldn't even be in the thought process on this.

6-7 empty or loaded, 300 6 pop or a 428 mule, just 'taint gonna matter........... Unless you have one of the few real shallow rear ends in it.

Lot of rental outfits and mail carriers would order the skinny rear ends. Wouldn't pull itself up to the curb, but would sure roll down the hiway. :>)

Allan

(quoted from post at 21:23:53 01/31/11) a 4bll will get better milege than a 2 bbl if set up correctly AND you keep your foot out of it.

Click to expand...

Exactly. Keep the 4 bbl.

THANX GUYS.. general consensus is to rebuild HOLLEY 4-V, GOt a guy nearby that should be able to do it and set it up right ,. reason i was reluctant ? Just keep hearing horror stories about 3 mpg / no performance , AND HOT SIPHONING??? .. from no DOUBT untuned worn out Holleys ,. 25 yrs ago had a expert set up a new 650 Holley 4 -V on my 429 1969 Mercury Marquis convertible ,, that Ride got 19 + mpg overall on a 2500+ mile swing down to Disney world then out to Ft Worth to see sis and family ,,. gave me 15 yrs of Wonderful performance,. then the car sat for 2 yrs in the body shop ,, after that it seemed to be hot siphoning ,,/ took it to a guy that shuold a been able to fixit ,, still in business today as --orralls Carburation / 200bucks /NO FIX ???? , after aserveral trips back and way too much time... in exasperation gave me half my $$$
Back ? shhesshhh???, .. Ford neighbor and i tinkered with it , and was test driving the sweetheart ride and she CAUGHT FIRE , had a jacket to JUST BARELY smother it out ,, suffered Minor BURNS!,... THAT horror experience ... compounded by the fact the fuel tank can gravity feed to carb in this truck , makes me leery of HOLLEYS. maybe i need to install a fuel shut off valve and remove that fear ... btw , got a sweet running Edlebrock on the MARQUIS that my son set up now ...

I've got 370's in both 2 and 4 bbl. I don't notice real difference in mileage, but they are always pulling a heavy load. The 2V is my favorite carb, honestly. You can tell there's a difference when taking out, but I just use that 2 speed rear to make up the difference more. That 2V sure is a smooth running carb - I'd put that one on there and never look back.

I would first see if any of your carbs. have a power valve. If they both do then go out and buy a brand new one that does not. Those power valves have caused me more carb. grief then anything.

I have a rebuilt 391 short block, bored .060 over and balanced. I have no need of it and would sell reasonable. Email: [email protected]

If the 2 barrel is an Autolite/Motorcraft I would swap it in in a heartbeat. Course me & Holly's ain't never got along so it's a personal grievance. In the old day's you had to tweak the Holly's at least once a month to keep it purring right. A stock Ford carb doesn't change so you set it & forget it. BTW - there ain't no way you're gonna have a 4 barrel on a hauling truck and not kick it in all the time getting up to speed.

thanx , but rite now, hope engine problem is solved, but yes that sounds like sumthin i would had looked at if you are not too far . or could drop ship reasonably . my heads and manifolds shoud fit from what i have learnedd.. tip ..,, list your e-mail to increase a reply that you will see without comin back to post ,, also you could list this short block in classified on the left ,, also in classic trucks lower left...

motorcraft 2 V here .. Holleys are fine til they mess up ..from my chair nearly had heart failure when the proven holley caught fire on my beloved Marquis convertible.. agreed about the general presumption hauling truck will want the back barrels power when getting up to spped and maintaining speed on hills ,,.but testimony seems to suggest otherwise to make me believe that performance is improved with a well tuned holley 4 V and mileage is the same or perhaps better than a 2 V