Nothing Special's '71 Bronco

[Gary Lewis]

Nothing Special wrote

Looking at the 48 jets under a microscope, the output end looks pretty square, with just a simple chamfer on the input end.  So I should be able to get it pretty close.  And my intent is to just get it pretty close, then to order a range of "real' jets around wherever I end up.  (And we'll see how many years it takes me to actually do that if "pretty close" is "good enough" )

I was just keying on Bob's statement.  

[Nothing Special]

Yeah, I think Gary and I are pretty different in this area.  But I think we both do a pretty good job of appreciating the differences!

[Gary Lewis]

Yup.  And yet I have a t-case shift lever that.....

[Nothing Special]

And on another note... Success!!!

I stuck in my custom-made 52 jets and took it for another test drive.  It's still pretty cold here (high today was about 35 and it's snowing again) and the temp gauge still didn't get to where it normally runs.  But there was no misfire in steady-state cruise!

It's not perfect.  There's a brief flat spot when I accelerate from cruise.  So maybe I need to move the accelerator pump linkage (it's in the farthest-out hole which gives the least squirt for the throttle movement).  Or maybe the power valve does need to open sooner.  And it does stumble a bit when dropping down to idle, sometimes even dying.  But it's running better than it's run in over a year, so right now I'm happy!

[Gary Lewis]

Yippee!  

On the flat spot, if it truly is what I'd call a flat spot I think you are still too lean.  The accelerator pump covers up a quick transition, but to me a flat spot is when you are just easing into it and nothing happens until the PV opens.  If that's the case I'd say you are still too lean.  Either that or the PV needs to open sooner.

And, by the way, that is exactly the situation my '72 F250 w/a 390 and a 2100 had.  At cruise nothing happened until the PV opened.  I changed to bigger jets and that solved the problem.

[Nothing Special]

Gary Lewis wrote

....  On the flat spot, if it truly is what I'd call a flat spot ....

If I slowly roll into the throttle it sort of feels like it loses power briefly, then starts to pick up, slowly at first, then it builds pretty quickly.  So I'm pretty sure it's going lean.  Wether jets, accel pump or power valve is the best way to address it?  That I don't know.

I should also point out that "everyone" says I should be running at ;east 4.56 gears, if not 4.88s, with a 302, 33" tires and an overdrive trans.  And this is in 5th gear.  If I drop a gear or two it lights right up.

Still, I'm pretty confident that it's going lean, and sometime I'll do something about it.  Maybe soon, maybe not.

[Gary Lewis]

I don't think it is the accelerator pump, but that's an easy try so I'd do it were I you.

Then I'd drill another set of jets to 54 and try them.

Last would be the PV.

But that's just me.  See what others say.

[Nothing Special]

I can probably live with it the way it is now.  But there does seem to be some room for improvement, so I'll keep poking at it a bit more.

To that end I drilled out my new 49 jets to .055".  A little bigger than the .054" that Gary recommended (and that I'd've preferred.  But I made my 52 jets using a #55 drill bit (0.052" OD).  The next larger drill is #54 at 0.055".  So that's what I now have.

I stuck the 55s in tonight but didn't feel like going for a drive, so I'll try it out another day.

I did have another question come up.  On a Bronco forum I'm on someone said that a hesitation on tip-in could happen if the weight above the check ball is missing.  I do not have a weight above the check ball, but I really don't have room for one either.  There's only about 0.190" between the top of the ball and the bottom of the screw.

I don't know how big the weight is supposed to be.  But since I got this carb I've bought two rebuild kits.  Both came with a metal cylinder that looks like it COULD be the check ball weight.  But it's .25" OD and .68" long.  Both of those dimensions are significantly too big to let it fit.

So am I missing something?  Or did some Autolite 2100 carbs not have the weight?

[Bruce moose4x4]

Pull your screw out and look at it most are hollow to let the check weight go up into it.

[Nothing Special]

It is hollow.  I assumed that was to let gas get through it.  Does the weight go in it too?

[Gary Lewis]

Yes, the weight goes up into the screw.  See if the cylinders will go in.  I'll bet they will.

[Nothing Special]

Gary Lewis wrote

....  See if the cylinders will go in.  I'll bet they will.

Not even close.  The cylinder OD is bigger that the OD of the screw.  It won't even fit in the hole the screw goes into much less go into the hole in the screw.

But a guy on the Bronco forum said he has extras and offered to mail me one !  So I should be good there soon!

[Gary Lewis]

Good plan.  I might have one if that doesn't work out.

[Nothing Special]

Thank you!  He PMd me and said it's been sent though, so I should be good.

Today I took a little break from the carb work and replaced the radiator.  I was getting a little steam out of the seam between the tank and a tube.  I thought of taking it to a radiator shop for repair (it's a good copper/brass radiator).  But getting a new radiator would minimize the down-time, so I did that.

Also that radiator never really fit right.  It's a 4-core so it's thicker than stock.  And the lower end of the driver's side tank doesn't taper down like the tank on the stock 3-core.  Both of those reduce the clearance with the steering box.  Plus my Bronco has an older power steering conversion using the steering box from an F-series truck which is probably the biggest steering box anyone ever puts in early Broncos.  So I ended up with about " of interference between the 4-core and the steering box.  I made it work a few years ago, but I was never really happy with it.  So another reason to get a new radiator (I went stock 3-core this time).

Everything went pretty good on the swap until I hooked up the top hose.  That's when it hit the fan.  The top hose that is.  The hose wasn't long enough to reach the thinner 3-core without getting pulled too far forward into the fan.  Hoping that I had trimmed that hose off to work better with the 4-core I bought a new one, but it was the same.  So I cut the two hoses and coupled them together to make one hose that works.

Anyway, it's back together now, and no leaks while idling as I picked up.  I'll top off the radiator after it cools and then take it for a drive at some point.

[Gary Lewis]

Glad he's gotten it in the mail.  Hope it does the trick.

Sounds like you got the radiator problem solved several ways - more room, no leaks, and still plenty of cooling for the vehicle.  

You put the #55's in but haven't driven with them, right?  It'll be good to see what that does before you put the weight on top of the accelerator pump check ball.  The 55's may enrichen enough that there isn't much/any pause there.

[Nothing Special]

Gary Lewis wrote

....  You put the #55's in but haven't driven with them, right?  ....

Correct.  I did start it and let it idle in the driveway for a bit.  Not really a test, but I did push the choke in all the way pretty quickly and it still high idled fine.

I think I'll be driving it some tomorrow.

[Nothing Special]

So far so good!

A little putting around town on the weekend.  Never enough to get it completely warmed up, but I could get the choke pushed all the way in and let the idle back down and it was still running smoothly everywhere I was driving it, including idle.

Then today I drove it to work.  Pretty cold morning, so maybe still not getting the engine as hot as it might.  But again, everything it smooth, no hesitation, no stumbles, no flat spots!

With how quick I can get the choke all the way in I suspect I'm running rich now on the 55 jets.  Once I get the checkball weight I think I'll put that and the 52 jets in it.  And I'm pretty sure I'll use the 52s (if not the 50s) for the trip out to Moab (elevation 4000 feet and up).

But it's running really good right now!

[Gary Lewis]

Wonderful!  I really thought it would run well with a bit more fuel, so am glad it is.  And I agree you should lean it a bit for Moab if you can push the choke off quickly.  So maybe the weight and the 52's will be just right.  

[grumpin]

Good news!

[Nothing Special]

Does anybody have a rule of thumb for how many jet sizes to drop for how much change in elevation?  I've found a few different suggestions ranging from 1 size per 2000 feet to 1 size per 5000 feet.  I'm thinking the difference is due to what engine/carb they are talking about.  But I'm wondering if anyone has any suggestions for a 2100 on a 302?