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Author Topic:   Motorcraft Carbs
killermiller
Dirt Full Roller

Total posts: 34
posted December 14, 2004 09:02 PM  
What Motorcraft carb part number is the one to look for and how do they compare to rochester carbs for hobby stock class cars where the carb is supposed to stay "unaltered" ?

KPLugnut
Dirt Forum Champ
Total posts: 1019
posted December 15, 2004 06:42 AM  
On the side of the body, look for 1.21 or 1.23 (rare). The "121" carb will do fine for unaltered rules, but needs to be modified for Holley jets, and several other internal setup changes to even come close to a stock 1 3/8" venturi Rochester.

KP

LUBEGUY07
Dirt Freak

Total posts: 302
posted December 15, 2004 03:55 PM  
hey kp do u have any of those 1.21 carbs , and if so how much

b4racing
Dirt Forum Champ
Total posts: 626
posted December 15, 2004 05:58 PM  
here is the cfm ratings as compared to their Id #
.98 190
1.01 240
1.02 245
1.08 287
1.14 300
1.21 351
1.23 356
1.33 424

I have heard of one that was almost 600 cfm but have not seen it or found a number to match it. Bobby

KPLugnut
Dirt Forum Champ
Total posts: 1019
posted December 15, 2004 07:36 PM  
I have a whole box of Motorcraft and Autolite 2bbls that are of all types, with lots of spare pcs in there as well.
I'd have to go thru 'em to see if there are any 121's (I know of at least one), but we can also build you one that will work better than any rebuilt core.
As for B4's reply, yes, those #'s seem about right, but I personally haven't ever heard of any stock Motorcraft or Autolite 2bbl ever flowing anything more than the high 300's. Not that there couldn't have been one on some application, but I sure haven't ever found one (yet).
Keep in mind, also, that a well built 2G Rochester will flow 500cfm easily and still be "untouched". Our hobby stock carbs flow more than that, btw... :-)
Anyway, let me know if you just want a core, or a race ready carb and we'll help ya out. Or buy that whole darn box of Motorcrafts from me - I'm tired of trippin' over the thing... :-)

KP

killermiller
Dirt Full Roller

Total posts: 34
posted December 15, 2004 07:48 PM  
Thanks everyone for your input on this, I guess I had heard that the motorcraft carbs flowed more than a rochester, guess I was wrong, and KP I will be getting in touch with you on my rochester carb

LUBEGUY07
Dirt Freak

Total posts: 302
posted December 16, 2004 05:05 PM  
how much would u charge just for the core? and how much for a redone one?

[This message has been edited by LUBEGUY07 (edited December 16, 2004).]

KPLugnut
Dirt Forum Champ
Total posts: 1019
posted December 17, 2004 06:57 AM  
I had a chance to check stock this morning, and I've got four of the 121 carbs, and a big box of mix-n-match misc others. I'll take $75 each for 121 cores, but if we build them into race ready units, they are $350 for the basic job and custom quoted from there depending on how much extra is done.

JLMK,

KP

b4racing
Dirt Forum Champ
Total posts: 626
posted December 17, 2004 12:46 PM  
I got the flow numbers off of a website a few years back. I did not see at what rating they was flowed at kindof like holley 500 is rated at 1.5 hg ad the 4 barrel is rated at 3.0 hg that might have something to do with it. Later Bobby

gahainsey
Dirt Maniac

Total posts: 113
posted December 30, 2004 05:31 AM  
A 4bbl is rated at 1.5 inches 2 bbl at3 (I think) Heres a handy formula for converting from flow at one pressure drop to another.

FlowNewP=FlowOldP*((NewP/OldP)^.5)

Raising a quantity to the .5 power is the same as taking the square root. No Square root symbol on here, though.


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