What is stock jet size for a 2100 on a 302?

[Nothing Special]

Sure. https://quadrajetparts.com/

 

[Nothing Special]

I put the 50 jets in and it seemed better, but still a little flat and pepped up with a bit of choke.

So today I drilled out my original 48 jets to .052". Success! No miss or flat spot at cruise!

Now I'm getting a slight hesitation as I roll a little more throttle in. I'm thinking I'll try opening the new 49 jets up a bit (.055" is the next size drill bit). I could also move the linkage on the accelerator pump to get a little more squirt for the same throttle movement. I suppose i could also change to a power valve that opens a little earlier. But I don't want the power valve opening at cruise, so I'm thinking that's the last thing to try.

 

[jckkys]

The accelerator pump circuit has only about 0.020" nozzle in these 1.08" venturi 2100s. The smallest nozzles Holley sells is 0.021" and the 390 CFM 4 bbl uses 0.025" nozzles. The primaries on the 390 CFM are smaller than your 2100. So maybe larger squirters would help cover any flat spots you experience as throttle is increased. The tuning procedure for Holleys is to increase size till you get a puff of black smoke then go back down a size. Ford squirters aren't selectable so you have to be careful. It's hard to make the hole smaller. You can also move the pump rod to a higher hole in the pump lever on the throttle shaft to increase the volume of the pump shot.

 

[Nothing Special]

I wasn't thinking about changing accelerator pump nozzle size. I was just thinking about moving the linkage. I currently have it in the farthest out hole which gives the most throttle travel for a given movement at the accelerator pump (the easiest way to visualize it). Or conversely, the lest movement at the accelerator pump for a given throttle movement (the most helpful way to state it). So moving the linkage in to a lower hole on the arm would give me a bigger shot.

 

[jckkys]

Early, as in the '60's, 2100 set up instructions recommended moving the rod up 1 hole in the winter when cold air calls for a richer mixture. Unlike Holleys and Carters the Ford carbs aren't supported with a selection of accelerator pump nozzles. The Summit M2008 carbs that are copies of Ford 4100s, do have a selection of nozzles that fit in the booster venturis. These primary boosters can be retro-fitted to Ford 2100s. It's a lot to go through, but with a Summit carb you can make a 2100/4100 just as tunable as the Summit and more tunable than Holleys.
Hesitation can also be slack in the accelerator pump linkage or a missing check ball weight.

 

[Nothing Special]

.... Hesitation can also be... a missing check ball weight.

That's something I was wondering about. I do not have a weight on top of the check ball. But there's really no room for one. I only have about .190" (basically the diameter of the ball) between the top of the ball and the bottom of the screw. If I even just put a second ball on top of the first I think it would tend to plug the hole in the bottom of the screw any time the check ball came up enough to let gas through.

Are there some Autolite 2100s that didn't have a weight?

 

[jckkys]

The weight fits in the recess in the booster hold down screw and is slightly longer than that recess at 0.884" and is 0.108" in diameter. The check ball itself is 0.188" diameter. So the ball won't fit into the hold down screw. All 2100, 2150, and 4100 carburetors have these. The 2150s have a different ie. longer head on the hold down screw for the weird variable air bleeds, but the check ball and weight are the same. I have spares and am willing to send you one. I just need your address in a PM.

 

[Nothing Special]

Thank you!!! PM sent

 

[Nothing Special]

The check ball weight arrived in the mail today! Thank you again jckkys!

In the meantime I've been driving it without the weight and with 55 jets. It's running great! I do end up pushing the choke in pretty fast, so it's probably running a bit rich, but it doesn't seem to mind.

So I think my next step is to put the 52 jets back in, along with the weight, to see how that works. And probably get some 53 and 54 jets so I can fine tune it.


One other question, is there a rule of thumb for how many jet sizes to go down for different changes in elevation? I'm taking the Bronco out to Moab (elevation 4000 feet but some of the trails get higher). I'm thinking that ideally I might want 1 - 2 jet sizes smaller for that change from Minnesota (~700 feet elevation). I don't know that I'll worry about it too much, but I thought I'd see if anyone had any insights.

 

[Seventee]

Edelbrock uses the rule of "2% leaner for every 1500". Not sure how that correlates to jet changes in a stock carb. Honestly I wouldn't worry about changing jets but you may want to tweak your idle mixture screws for optimal idle when you get there.

 

[Nothing Special]

Last night I put the check ball weight in and also went back to the 52 jets. I'm calling it good now! It's running smoothly all the way through the range with no discernible misfire. I can get the choke off pretty quickly, but not so quickly that it seems wrong. So if anything I'm probably still a bit rich, but probably not very much.

One other thing I can do now that I haven't been able to do for a few years is start up, even on a slight uphill, without touching the gas! I have the idle at about 900 rpm according to my tach and I can pretty easily get it rolling at idle without stalling the engine!

I do have a couple minor issues. One is that when I'm coasting at idle and hit the (hydroboost) brakes pretty hard the idle speed will drop. If I also turn the steering it'll drop a bit farther. A week or so ago it would sometimes die when that happened. It's not dying now(just making me think it will). So I probably won't worry about it for now.

The other is that when I shut it off hot and try to restart in a minute or more later it'll be flooded. I've had this issue before, but it'd be nice not to. It'll start right up if I hold the throttle open to clear the flood, but it'd be nice if I didn't have to do that.

Anyway, I'm getting close to leaving for Moab and I still need to get the motorhome ready. So while I might still find something to putz with, I think I'm going to call the Bronco done for now!

 

[Rustytruck]

Are you using the thicker insulated carb gasket with the plastic insulator rings in the stud holes?

https://northeastclassicfordparts.c...ft-2100-2150-1966-1977-early-ford-bronco.html

 

[Nothing Special]

No, just a normal gasket. I know I'm getting a fair amount of heat there.

 

[Nothing Special]

This thread popped up around the same time I was dealing with my issues here, so I jumped on it. But in the interest of keeping thos one complete for anyone finding it later, I did get one of these insulated "gaskets."

It's a terrible gasket, way too hard and doesn't seal well at all. But with stock gaskets on both sides of it it does work as an insulator. It didn't completely solve my issue. It will start after a hot soak without opening the throttle, which it wouldn't do before. But it takes a lot of cranking.

Anyway, it's good enough now that I'll live with it for the foreseeable future.