AMC 360, help me choose a carb

[CJ7nvrstk]

I have a built 360 in my CJ that I used to race in hill climbs and sand drags. It's 0.040 over, 262 cam (I think, can't remember exactly), 4bbl Edelbrock intake topped with a 600 CFM Holley and with some light porting and polishing as well. I no longer am doing the high speed stuff and am just rock crawling now. I know my current carb is not up to the task. Propane and EFI are out of the question due to cost.

So here is my question; I need a carb and am not impressed with what I'm reading on the Truck Avenger, I'm not an Edelbrock fan, have had many say go with a Q-jet but have also had some say the Motorcraft 2100 is hard to beat offroad. I can get an adapter so I wouldn't have to replace my 4bbl intake but fear the 2100 just isn't enough carb for my motor. What do y'all think? I know there are plenty of suggestions out there. Let's hear them.

BTW, will be throwing stock exhaust manifolds back on and running a single outlet exhaust.

 

[Woolyworm]

Go with a 2100. Closest thing to fuel injection- love mine up down and sideways. Do a little research on the Venturi sizes available. I've got a 1.08 on my AMC 304 . You can feed a 360 fine with a 2100 from what I understand. I think you'll need the 1.12 but do your homework on that.


Wooly

 

[Posi]

My choice with the 360 and edelbrock intake you have would be an MC4350

 

[elwood blues]

CID x RPM / 3456 x VE% = CFM

360 x 4500 / 3456 x .80 = 585.375

The biggest 2100 is stamped 1.33 and those are rated at 424 cfm. I would say to not go smaller than a 600 cfm, which you're just not going to find in a 2bbl, the biggest one I know of is the Holley 500 cfm 2bbl race carb.

There is a motorcraft 4100 version, they came stock on Ford muscle cars, I can't remember which ones, bigger V8s, they're getting VERY hard to find because classic Mustang owners want them so badly.

 

[CJ]

On a different note, what is your budget for the carb?

 

[caveman]

My vote is for the motorcraft 4100. It will give you better fuel mileage as long as you don't use the extra 2 barrels but their there in case you want to use all the power that the 360 has.

 

[Hedgehog]

I have to ask Caveman and Elwood - Are your carb equations for high RPM running or everyday driving? It probably has been covered before but I must have missed it, but this is the first time I've heard a recommendation for a LARGER than the stock 2100/2150 carb to be run on an AMC 360. Especially running at relatively low RPM rock crawling. Am I missing something? Maybe so.

 

[ksouthw80]

regardless of use of "said" size of engine, in my experience it is better to go on the small ( not too small) side of the cfm side of things. there are way too many things to discuss on this matter but know some of the strongest reciprocating engines have smaller than popular sized carbs.. One of the most important things is to spend the time to set the carb up. I have a AMC 304 with a 500 cfm carb leaned out with a touch of advance timing and its a maniac. bigger was never better.. seek out an everyday engine builder and ask for simple advice on carb'd engines..

 

[Woolyworm]

I like the 2 over the 4 for responsiveness. Yes, the 4 will deliver more air and fuel. What say those with a 360?


Wooly

 

[CJ7nvrstk]

Thanks for all the responses.

As for budget, I would like to stay under $300 but my main concern is getting the best bang for the buck and being able to keep running. Low rpm, off camber.

 

[caveman]

I have to ask Caveman and Elwood - Are your carb equations for high RPM running or everyday driving? It probably has been covered before but I must have missed it, but this is the first time I've heard a recommendation for a LARGER than the stock 2100/2150 carb to be run on an AMC 360. Especially running at relatively low RPM rock crawling. Am I missing something? Maybe so.

The 4100 acts like a 2 barrel for normal driving with good economy. Only 2 of the 4 barrels open up until you press the throttle down all the way and then the other 2 barrels open up to give more air and fuel for more power.

 

[Saddle Tramp]

The MC 4300 and 4350 were 2nd and 3rd generations of the 4100 and used on the AMC V8. (1970 to 1974 for the 4300, 1975 to 1978 for the 4350) I’m not a carb expert but my understanding is that these carbs are just 4 barrel versions of the MC 2100.

 

[DHugg]

Go with a 2100. Closest thing to fuel injection- love mine up down and sideways. Do a little research on the Venturi sizes available. I've got a 1.08 on my AMC 304 . You can feed a 360 fine with a 2100 from what I understand. I think you'll need the 1.12 but do your homework on that.


Wooly

Yep, me, too! I've read of, new held in my hand, MC2100s at 1.21 venturi, think I saw a chart with 1.28.

 

[CJ7nvrstk]

I came across this on a Mustang site.

venturi size is the number in circle on side of carb .
here's a list of what = what
size cfm
.98 = 190
1.01 = 240
1.02 = 245
1.08 = 287
1.14 = 300
1.21 = 351
1.23 = 356
1.33 = 424

Thanks for the help

 

[Fastatv]

I have a 360 and I'm running a 2150. I'm not sure what CFM it is, but its extremely reliable, plenty of power down low and on top. Pulls great up to around 4000 ( I haven't tried to exceed that rpm ), and I rarely get over 2500 rpm's. I guess you might ask yourself " do you need a 4bbl "? Let us know what you decide.....

 

[lutry]

This is what the 79 FSM says concerning the specs for the 2100 according to the different engine/Transmission specs:

 

[elwood blues]

I have to ask Caveman and Elwood - Are your carb equations for high RPM running or everyday driving? It probably has been covered before but I must have missed it, but this is the first time I've heard a recommendation for a LARGER than the stock 2100/2150 carb to be run on an AMC 360. Especially running at relatively low RPM rock crawling. Am I missing something? Maybe so.

A little late with this answer; after all of the research I've done in to carburetors, the one thing I consistently found was that most CFM rating on carburetors are overexaggerated, some of them 15-25% depending on the manufacturer.

I've ran a 1.14 bore (300cfm) MC2100 on my L6 and I've ran, and currently run, a Holley 390cfm 4bbl. I honestly prefer the Holley 390, I've got a big enough spring in the vacuum secondaries that I have to really get on it for them to kick in, last time I checked I was getting 16mpg, it's not that I didn't like my motorcade/autolite carbs, the problem, IMHO, is that you're buying a used carb, no many haw many times you rebuild it, it's worn out, and there aren't only a couple of places remanufacturing those carbs, and they're not cheap.

I do not believe that less is more in the case of carbs, you need to find the correct carburetor for your engine. The formula I showed you in my other post is how you calculate an engines CFM requirements.

I understand what the FSM states, but you have to remember that the FSM was written in 1978, with a gas/oil shortage going on, car manufacturers being forced to install catalytic converters and smog pumps on cars, just because that's what AMC put on those engines, absolutely does not mean that it's the optimal carb for that engine.

In your case CJ7nvrstk I'm sticking with what I said that you should be looking at a 600cfm carb

 

[Woolyworm]

A smaller CFM 2 barrel carb will give you crisper throttle response every time. If I want to mud bog, I need volume, if I want to rock crawl I need good throttle response. I have a AMC 304 not a 360 but there isn't much difference. I have had s Holley 600 4, a truck avenger 450 CFM or something like that and the MC 2100 1.08 I currently run. The Holley 600 was okay on the road but a lot less responsive IT SUCKS OFF ROAD ALWAYS BOGGING AND SPUTTERING ON INCLINES. The Avenger sucked as well. I run a MC ignition with the big cap and TFI ignition upgrade the jeep hammer writes about. I think the engine may have a mild cam in it. I wheel on occasion with caveman and he can attest to the hill and off camber work we do. That combo kicks *** on and off road and I get about 14mpg. I'm running an old edlebrock SP2P 4 barrel intake with a machined aluminum adapter to the 2 barrel carb with the carb about an inch off the intake. I tried a few used 2100's then finally went with a professional rebuilt from the carb guy on eBay named ehrmannmp. It was $280. Tell him what you have and he'll tune the carb for you.


Wooly

 

[caveman]

Woolys set up works great no matter which direction he points it.

 

[lutry]

for 295 you get a new one from him, not rebuild:
NEW MotorCraft 2150 Jeep/AMC/Eagle/Pacer Carb Upgrade 258/4.2 1.08 Venturis