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Ford 2100 Carb Question

7K views 9 replies 5 participants last post by  timothale 
#1 · (Edited)
Hey all, I have a Motorcraft 2100 on my 69 Mustang that I need to have rebuilt it's leaking from every seal. Yeah I know I should put a 4 barrel on it, but the budget is tight at the moment and it just won't support they additional cost for a new intake etc. My 2100 has the 1.08 venturi size but I was thinking of looking for one with a 1.23 venturi for more flow. The other question is will the stock intake on a 302 support the flow from said larger venturied carb. If so I'm wondering if the gains are worth it.




Engine bay is coming along slowly but surely
Thanks
Mark
 
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#2 ·
The big throttle plate 2150 is rated at 350 cfm at half the vacuum drop a four barrel is measured at, just remember that when comparing cfm ratings.

I loved these carbs since they are so simple and hard to kill, at one time you could go into the junkyard and pull jets from a selection of Motorcraft carbs and get anywhere from 47-62 in jet sizes without costing you anything.

The larger carbs came on 351W and bigger engines like the 390's etc. getting hard to find today. Yours is rated at 287cfm and unless you really need more airflow like racing its not worth the swap, maybe 5-10HP at most on a modded engine at higher rpm.

I suggest you rebuild what you have, the 302 has the smaller intake holes to match your carb but can easily be bored out to match the 350cfm version if you want. Hardly worth the effort when a four barrel dual plane with a 2bbl adapter is a better investment and gives more power.

The later 2150 carb is the one you want and already has provisions for the umbrella accelerator pump check as opposed to the leaker ball check versions. Make sure you get the tag off the carb as there are many versions of this carb although the kits usually are universal with a variety of gaskets to fit all of them.
 
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#3 ·
Thanks 4 jaw for the input, for clarity if I were to find a 2150 I would need to mod the intake to allow for the higher CFM? I've always got my eyes open for a used manifold but sometimes buying those from ebay or where ever is a bit of a crap shoot. I know this sound kind of dumb but I've even been looking for a stock 4bbl intake. Even those are not easy to find in good shape. I'm not looking to race just a nice driver that's reliable that sounds good and runs good. I've been using this engine to teach my sons how to work on cars. I've got a lot done over the last few months, much slower than normal because I've had them do some of it. I really do appreciate this forum. Thanks to everyone who's given me advice.

Mark
 
#4 ·
The throttle plate holes in the 302 intake are the smaller size I believe, you could bore them out on a mill to fit but the stock manifolds are poor and heavy.

I liked the old Streetmaster intakes with small open plenum and 2bbl carb adapter for better mixture distribution and near stock low rise plus each cylinder could pull from both barrels extending the rpm capability of the carb.

This setup only works on a small open plenum manifold not a two plane. It works well with stock or RV cammed engines.
 
#6 · (Edited)
there are mostly a few issues with the shape of the back of the carb base.. that can cause massive vacuum leaks.. some are straight across.. others have rear legs that stick out slightly.


there are a few tips... about rebuilding 2100 and 2150s..

before you set the float free by unlatching the wire retainer on the float pin..

place a finger on the float tab above the needle and seat.. so the float goes up to the adjustment level.. use a scribe to mark the float level by scratching the inside of the bowl.. this allows you to put the float back exactly where it was.. float levels vary upon application...

once i get it all apart.. there are a lot more things than i will describe here.. like making sure the accelerator pump body is flat. so many are warped..

lets look at the removable booster venturi's...

i use a piece of 0.023" stainless steel welding wire.. an almost empty roll actually fell off the back of a truck.. i picked it up and went after the welding truck but i could not catch them.. so i use it on carbs and stuff..

i use it very carefully to work thru the various tiny openings in the booster venturi... have a look at the images...

do you see the dime sized discs that are on the top of the booster.. please be sure to spray up the emulsion tubes with some carb or brake cleaner.. make sure that there are NO leaks.. if the crimped seal around those leaks.. you will have a horrible operating carb..

i also keep the check ball that goes under the weight and booster hold down screw separate.. as i am going to reuse it one more time.. i take a small phillips screw driver. i don't recall if i used a #1 or a #0.. and lightly twisted it into the seat down in the float bowl under the hold down screw.. i am basicly burnishing it.. smoothing it.. if the used check ball is not rusted.. i drop it in the hole after blowing the hole out.. i use a pin punch to lightly drive the check ball into the shiny seat area... remove the check ball and toss it as there is now a flat on one side.. that if you reused it.. you would get a random flat spot on acceleration.. hence using the old one.. not the new one..

the pictures all have text with them..

you won't believe how much more responsive your carb will be.. with all the tiny passages free of corrosion.. build up.. scum. please don't modify the opening sizes... just make sure they are free of debris..


by the way.. the grand child of these 2100 4100 carbs is the holley 4110 and 4111... summit sells them currently as the summit branded 8600 .. and the idle feed restrictions and accelerator pump restrictions are right in the booster body so they are easy to calibrate.. the big difference between the 4100 and the 4110/4111 holley is the holley/summit versions use a holley style secondary vacuum chamber on the side .. where the 4100 autolite carbs had it on the back of the float bowl.
 

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#9 ·
around here I have pulled the aluminum factory Mustang -Capri 4 barrel manifolds at a You Pull It wrecking yard for $ 25. And I have a bunch of 4 barrel holley's I have collected cheap over the years.
those might be 4180 holley carbs with the base plate idle mixture screws... one of my favorite carbs..

How To Understand The Holley 4180 - Mustang Monthly

just don't ever mess with the idle mixture screws unless you count how many turns out they are so you can put them back..

they also don't have any bowl vents. and must use the big elbows.. the bowl vent solenoids to properly vent the float bowls..
 
#8 ·
Ford carb castings.

In the old days I used to see quite a few ford carbs with casting die mis match leaving sharp edges in the bore where the 2 mold dies came together. I would use a piece of sand paper wrapped around a wood dowel the smooth them , not enlarge then. and I used to see the same mismatach in the ports on small block ford heads.
 
#10 · (Edited)
5.0 holly carb.

The holly 5.0 carbs were modified to be able to pass the govt emission tests on ONLY the front 2 barrels. Somewhere in a file cabinet in the shop I have one of the mustang magazines with an article written by a Ford engineer on how to modify those Holly carbs.
5,0 carb fires
some guys would leave off the aluminum heat shield and the egr heat would damage the gaskets and fires resulted. If I remember right the manifold bumps out for the egr and you have to make sure another carb fits or use a spacer that will cover the egr manifold passages.
 
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