I stumbled upon a Motocraft 2100 1.33, and I'm wondering how well it'll work with a clifford intake and FI ex manifolds. The rest of the motor is stock, but there is a 5 speed in my 77 crew cab. I also have a 1.23 2150 in the sparts (spare parts) bin I can use. Thanks ahead for any input y'all might have.

Adam

 

The short answer is...no. Some are running 600 cfm carbs.

 

Haha..and I've even been scolded saying 600 is too much. Depends on the carb..some 600s will run fine with no tuning..some will lean out or be too rich. The same goes for any other carb. It may sit just fine and run well with it..or you may have to tune it to what your engine likes. I'm running an offy intake..eddy 600 cfm carb..dual exhaust...comp 260h cam..steel gears..hotter ignition..new springs and lifters. I personally decided to go with 600 because I knew this truck won't be a dd..so fuel mileage won't cost me really..and I figured with the extra valve lift that the engine would'velike the fuel. I think 424 is a prime range for cfm. Some guys say 390 runs more poor and worse gas mileage than a 500 or 600 cfm..then again..like I said..its what YOUR engine may like

 

The CFM ratings on a 2V is different then a 4V. So trying to compare 2V sizes to 4V sizes is like comparing apples to oranges.








lostonmonday either of the carbs you have will work fine. I think the 1.33 is a good size for a single 2V on the 300.

I personally prefer the Autolite 2100's over the Motorcraft 2150's. Just because the 2100 is a simpler design with fewer moving parts. But there are a lot of guys that prefer the 2150's. The 2150's metering rod gives it a little better driveability. But I still prefer the 2100!

 

Good point fordman..but I was refering to a holley 390 cfm haha but no biggie. I didn't know that the cfm works a lil differently in both..but makes sense

 

I know what a 390 is. I've owned a few of them. But the original poster wasn't asking about 4V's. He was asking about 2V carbs. You were talking about 4V's which I know was in response to Harte3's response. But that's the reason I mentioned the different ratings.

The 390 is too damn small for a 300. How many 302's do you see running a 390? The 300 has 50 c.i. cylinders. That's the same as a 400 V8! The only time I'd even consider buying another 390 cfm 4V is if I ever built another naturally aspirated 2.3L 4 cylinder.

 

Ooooh..brain fart haha the 2150 is a 2 bbl..I was thinking a autolite 4100 with 1.08 venturis..total brain melt!! I have seen the light!! I wish there was a 400 straight 8..holy moly...

 

How carb cfm is rated: Carb Myths and Facts

JMO, a 500 cfm carb is a 500 cfm carb...the only difference being at what point in the air flow (hg) it is rated at...not a difference that actually makes a difference as far as the operation of our engines goes.

In theory, a carb cannot be too big for an engine IF the carb can be tuned to limit it's capacity to what the engine can handle and/or the operator recognizes the limitations of the engines capacity and does not try to force feed the engine over what the engine can handle. But, having said that, I wouldn't even think of attempting to tune a 1250 Dominator to a 300 I6...having to eliminate all secondary functioning and running only on the primaries...what would be the point? Bragging rights?

JMO again, the carburetor size cussin and discussin is a bit of an over rated concern. If one wants to use a 350 or 500 cfm 2v carb, use it. If one wants to use a 390 or 600 cfm 4v carb, use it. Regardless of which one is used, it's best to be tuned to what the engine can handle and even more importantly, one best educate their 'foot' in the operation of the go-pedal to what the engine can handle.

 

Well said harte..that's what I was trying to bump around earlier haha..you said it much better

 

Well, said same thing...just differently.

IIRC there was a posting from a member about using a 390 on his snow plow truck...and it was not performing the way he thought it should...so he put a 750 cfm double-pumper on and got the performance he wanted shoving snow around in the middle of the night.

There are just not a lot of absolutes, certainties and 'ultimate bubbles' to zero in on when it comes to carbs, cams, ad infinitum, as one might desire. That would be way...too simple...even if obtainable.

 

ya the simple just isnt out there for us most times in life 'eh....

I have had no issues with the holly 390 myself for what i use my rig for but have seen many run up to a 650 no prob... like said the cylinders are 50 CI and no dif from a 400 setup really.

 

I haven't said thanks for all of you enlightening me on this, so please accept a late, but hearty thank you! I've actually been spending most of my free time tinkering on the truck, even on -2 nights, but tonight I'm taking a break. The carb is still on the shelf, waiting for me to save up enough to buy a new exhaust system (efi manifolds, check!, gaskets, tubing, muffler, etc, er not yet). I'll be sure to post how it runs when I do get it mounted. BTW, if anyone else has done this, how close was the jetting? Thanks again! Adam

 

The jetting depends...there again, not a one-size-fits-all scenario. Run the carb you have for a while just the way it is. Symptoms of too lean or too rich will eventually make themselves manifest and then start making adjustments.

 

I run a 1.14 2100 on my 351w with 51's....16-17 mpg on hwy..
I run a 1.02 2100 on my 300 6 with 51's..and may go down to 48-49...
also running great..

 

From what I remember reading, to convert from the CFM rating of a 1bbl and 2bbl to that of a 4bbl, multiply the CFM by the square root of 2, or 1.41421.

So, a 424 2bbl has the same CFM rating of a 600 CFM 4bbl.

I'm not sure if that'd be too much or not, considering that with the 4bbl, you're only working with 300 CFM primaries while driving, instead of 600 CFM primaries (with no secondaries).

I'm sure it'll work, but it seems like you'd lose some lower end throttle response. Only one way to know for sure though.