4350 vs. 2150

[scotty1998]

I know this is has been explained before but I may have access to a stock 4150 and intake. The question is, is it worth the money and effort to switch out the two barrel setup? In weighing it out, I'm basing my decision on several things.

1) Difference in fuel consumption. Now obviously if you're not heavy on the pedal, I think this should be negligible. In fact, it might even be better with the 4-bbl when properly tuned.

2) Pick up and performance. I would think the obvious reason for going to 4-bbl is to increase hp and for off the line performance. However, since I'm driving my rig as a weekend grocery gitter for the most part, is this worth it?

3) Ease of installation. Is this a monumental switch over or can I just swap intake, and bolt the 4-bbl on? What about the choke assembly, vac hoses, fuel lines, throttle assembly, etc? Alot of work? Are there any hidden fabrications/part purchases that I should know about?

4) Overall performance. Am I asking for more maintenance/adjustment headaches with the 4-bbl?

5) Anything else I should know about or consider?

Thanks in advane for your advice!

[addicted]

If you don't plan on doing anything but cruising around on the weekends, I wouldn't go through the hassel unless you have to take the intake off because it is leaking or something along those lines.

I would think the hardest part will be adapting the throttle valve and kick down linkages to the carb, but it shouldn't be too tough.

[Ristow]

i assume you meant the 4350 motorcraft,not a 4150 holley? i changed your title to help your inquiry....i hope i assumed correctly.

if you get the various bits with the factory intake or carb,like hot air lines,it'll be an easy swap. throttle bracket,cable,fuel line should all fit,or be an easy mod to make fit.

[scotty1998]

Ooops, you're right 4350. Thanks for the change and the advice.

[djongeward]

If your talking about an OEM intake with the spread bore it is an easy swap. I put in the OEM square bore intake with the 4300. This intake is more versitile as you can put in any square bore carb. I've got so sick of monkeying around with the 4300 that I got a Holley ORA 475 to replace it. The Holley is much more user friendly. I got the OEM intake and carb for free so being the cheapskate that I am, I rebuilt the 4300 and installed the whole thing. The AMC 4bbl intake weighs a ton, or at least 100 pounds of cast iron. If I was to do it over again, I would have put on a Wyland or a Performer intake. I may still, but I just don't want to hassel with getting that hunk of iron off of my 360.

As a side note, I get better gas mileage with the 4bbl carb than I did with my old 2bbl. About 14 average and 18 on the highway. The 2bbl gave me 10 to 12. I account this to tuning and new or rebuilt everything, electric fan, and rarely going into my secondaries. I have a feeling I'll be going into my secondaries more with the new Holley. :drivin:

[scotty1998]

Holy crap 18???

This was kinda what I was thinking might happen if you're light on the pedal and you stay in the primaries. I had no idea the intake was that heavy too. Was the 4bbl a tough match to replace the 2bbl what with choke fittings, throttle, vacuum, etc?

[babywag]

1) Difference in fuel consumption. Now obviously if you're not heavy on the pedal, I think this should be negligible. In fact, it might even be better with the 4-bbl when properly tuned.

2) Pick up and performance. I would think the obvious reason for going to 4-bbl is to increase hp and for off the line performance. However, since I'm driving my rig as a weekend grocery gitter for the most part, is this worth it?

3) Ease of installation. Is this a monumental switch over or can I just swap intake, and bolt the 4-bbl on? What about the choke assembly, vac hoses, fuel lines, throttle assembly, etc? Alot of work? Are there any hidden fabrications/part purchases that I should know about?

4) Overall performance. Am I asking for more maintenance/adjustment headaches with the 4-bbl?

Thanks in advane for your advice!
#1 Fuel economy will be better if you drive mellow
#2 You will notice an increase, even as a grocery getter.
#3 About the simplest upgrade you can perform
Minor mods required to retain "factory" emissions etc., but worth the effort.
#4 If you go squarebore (recommended) maintenance/adjustment easy & minimal.

Personally spreadbore 4350 is prone to problems (leaking, poor fuel mileage)
If you opt squarebore intake you can use a reliable Holley :)

I have had both, and I am not a fan of the motorcraft 4bbl in either form factor.
Holley has always been a winner in my book though. Owned quite a few, once you get them dialed in they rock.:thumbsup:

[scotty1998]

Tony,

Thanx for the advice. I'm pretty well convinced by your description that this would be a good upgrade. So, the 4350 was made by either Motorcraft or Holly or Holly for Motorcraft? What am I looking for when I'm searching for a used 4bbl? For example is there a specific model number or am I just ensuring it was the 4350 made by Holly.

[djongeward]

Holy crap 18???

This was kinda what I was thinking might happen if you're light on the pedal and you stay in the primaries. I had no idea the intake was that heavy too. Was the 4bbl a tough match to replace the 2bbl what with choke fittings, throttle, vacuum, etc?

Everything bolted up and fit just fine except the vap can. It is essentially the same setup emmisions wise. Some minor non issue issues are different PCV set up, a bit different throttle cable clamps (or what ever you call them). I just kept mixed and matched. The temp sender needed to be kept from the origional. Really minor stuff. But this is OEM to OEM remember. The 4bbl intake I got was complete down to the stove pipe hookup and everything else. I couldn't tell you what you would have to do to an aftermarket intake like a Performer.

The primaries on the 4300 are way smaller than the OEM 2bbl. I hate this carb. I lovingly rebuilt it and it treats me bad. I'm looking at my new Holley as I type. Waiting for my wife to get back from the coast to swap it in. Need the wag to get around. Holleys are so nice.

[scotty1998]

Hmmm. I'm wondering whether you've got a rotten one or are do they all behave like that?

[Ristow]

they were decent carbs,but even rebuilt,they're 35+ years old now.

[scotty1998]

So I'm resurrecting this thread to ask another question. I've been doing my homework on the 4350 and the dilemma seems to be square bore or spread bore. Spread bore is primarily for the 4350 and not much else unless you want to go through the hassle of an adapter so, I'm pretty much convinced that the square bore is the way to go so that I have a good selection of aftermarkets. However, it seems to me that the 4350 should be better on fuel consumption because of those tiny little baby primaries. Fuel consumption savings is one reason I want to go to 4-bbl but now I'm worried that the aftermarkets won't be able to match this and I could actually lose in that category. Sorry for the long post but what is the take on this?

[joe]

Getting better mpg's with a 4v carb works on paper but in the real world it's an old wives tail cause "everyone" puts their foot into it more often when you run a 4v. (otherwise why have one?)
So if you're just driving on paper you're gold mpg wise. If on the pavement you're pyrite(fools gold).

[fulsizjeep]

Krista's 77 401 Waggy has the original 4350 on it. I have put a kit in it twice since 2000. It now has 107K and 32-33 years on it. I have a working spare 4350 from a 75 we parted. In my opinion, it is a good design and gets good mileage. We both spend some time in the secondaries on the road and it still gets 13-14 mpg average. But, I am considering putting a Performer intake and Truck Avenger on it now.

Once my 88 GW had the 4" lift and 32s with 2.72 gears, the mileage went from 14-15 stock to 10-11 with the 2150 even though it performed really well for on or off road. With the 401, AFB 750, 3.73 gears and 33s I get about the same mileage. I think the smaller primaries on the 4350 make for better mileage overall and even better on paper like Joe says.

When my 401 was in the 76 Cherokee, I had a helluva time keeping the 4350 running right on it. I finally picked up 2 other 4350s and from 3 built a carb that worked but the secondaries rarely opened for some reason. I could never get better than 10 mpg with it on 235s and 3.54 gears. The top plate does warp over time. That could be from previous wrenchers that have abused them too. I 86'd the 4350 when the 401 went in my GW and got $40 for the intake.

I know a few members here who have put a Holley 500 CFM 2 BBL on stock intakes and been very happy with them compared to the 2150.

Long story short - I think it is a tough call to change out a 2150 and 2 BBL intake for the 30+ year old spreadbore equipment.

[Mark Wilde]

When I still had the 360 in my Jeep I did this swap and never looked back. There was a mild performance increase, it smogged like it was fuel injected (the tech said it was the cleanest Jeep he ever saw) and the starting reliability is phenomenal. That's mainly why I did it...the 2150 I had, had serious starting issues that 2 rebuilds and 4 power valves would not cure. Oh yeah, no power valves on the 4350.

It was almost a straight over bolt-on plug-and-play swap. I did have to mod one of the cable brackets slightly, I can't remember if it was the cruise or throttle cable bracket, but the kickdown linkage, choke wire, etc was unplug, replace carb, plug in and drive. My cruise still works even. :thumbsup:

I won't deny it has leak issues. I just had to rebuild it for that...after almost 3 years though. The top plate warps if you monster torque the screws, as will any carb. Mileage? Well, it's a Jeep. I get 10 or so around town and 14 or so on the highway. Aerodynamics have almost as much to do with that as tuning. :cool:

I have no complaints. No funky adapter plates or throttle cable mods, or jury-rigging the kickdown linkage to "make it work" either.