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Going to rebuild this 4100

3K views 45 replies 13 participants last post by  trialsguy 
#1 ·
I have a rebuild kit from NPD and I'm going to go through this 4100 to see if there's anything in it that could be causing my problems.

I found this link that Vanilla Gorilla provided - http://www.hurtle.com/cars/mustang/fixes/carb/ - about the 2100. Is this generally the same process on the 4100? Or does the NPD kit come with good instructions? I have never been inside a carb before so I'm trying to prepare for potential pitfalls.
 
#2 ·
You're tearing apart a Pony Carbs carb because you doubt it? Why would you do a thing like that? Those folks have never, ever made a mistake. :lol:

But yeah, a 4100 is more or less 2 x 2100 so it will be extremely similar.
 
#3 ·
The first time I did my 4V Holley on the 68, I found an exploded view diagram of the carb (I think it may have been in the rebuild kit.) I enlarged it to at least an 11" x 17". As I pulled the carb apart, I checked off each part to verify that I saw it and that it was there. As I reassembled the carb, I put a second check mark to verify that it was back in.

Just make sure everything is put back together and that all the gaskets are installed properly. It's real easy to get gaskets backward. Don't assume that the way the old gasket came off is tht correct way. Refere to the assembly drawing as well (as you remove the gaskets.) Also make sure everything is clean, clean, clean.

Dave
 
#4 ·
I have known first timers to blow the instruction diagram up large enough that as parts came off, they laid them on the large diagram. Did the same as the cleaned them. Worked good for him. Be careful with the cleaner. Did you get a can of cleaner (local parts store) to soak the larger parts in?
 
#5 ·
I haven't gotten any cleaner (other than the spray bottle I have) because it's never been uesd (other than by me to unsuccessfully start my car). Maybe Pony didn't put it back together right or it had some rubber deteriation from sitting, but the metal and internals are spotless.
 
#6 ·
Get the cans of B12 (I think) to soak the parts in overnight. Blow out all the passages with compressed air.
Dave
 
#7 ·
No matter how clean it all looks, soak it in the B12. That way you KNOW it is clean. Do not assume anything at this point. Only do this once, so do it complete.
 
#11 ·
I was only able to get one of the four jets out. I stripped a second trying, but I don't think I got any crap in any places that would cause a problem. So I'm soaking the carb with them still in. Is that ok?
 
#14 ·
I did this myself just a few weeks ago for the first time too. The 4100 is a very easy carb. You should have no problems.

I hope you have the Mustang Shop Manual. As you rebuild the carb. the manual explains how to adjust each part dry (no gas) or bench tune up.

This will get your carb. in the ballpark so that when you install it back in your car, the car will start right up and only need minor tuneup or adjustments.
 
#15 ·
Wow, so Pony doesn't remove the jets? Cheesy. I use a piece of cereal box cardboard wrapped (in a "V") around the end of a flat blade screw driver that is slightly smaller than the slot. Jam that baby in, put a crescent on the shaft (Craftsman square shank screwdriver) and free up 40+ years of 'not gonna move.' This might not help you now depending on the amount of damage to the slot on the jet. Wish I had caught this thread sooner.
I've said it before. For what Pony charges that carb should come with a lap dance with a happy ending.
 
#17 ·
yes yes yes yes. PM sent.

Ylexot, I can't say for sure that Pony left them in... this is a carb that they did back in 1996 and it sat wrapped up in a box since then. It came with my car when I bought it a year ago. They may have left them in, or they may have just over-tightened them, or I may have just not had a big enough screwdriver. I wish I'd seen your tip earlier, but no big deal.

As I took everything apart, I didn't see anything offhand in there that could be making it operate badly, but there were some bits of gasket left over on the bench that I don't know where they came from. They could have come out of the carb I guess, but I didn't see them fall out. I just can't think for sure what they would have come from. Fortunately the secondary diaphragm is in good shape because the kit doesn't come with it and I forgot to order it.
 
#19 ·
hehe... I missed that earlier. This thing had a recipt of like $450 or something in 1996.

OK, I am almost done reassembly. I still am completely convinced that I am creating a paperweight, but we'll see.

I am looking for reassurance in a few areas that I've noted during re-assembly:

1) I have no sign of a dashpot, nor do I see any sign of where one would attach, unless I'm staring right at it and don't realize it.

2) I see a sequence for a ball, gasket and screw for the "pump inlet check," but I don't see where it would go. My directions appear to indicate that it would just to the front side of where the air cleaner post screws in.

3) My kit came with two of the Pump Diaphragm Assembly, but I only have a place to use one. Is this just an extra part?
 
#20 ·
1) Is your car a manual or automatic trans. Believe the automatics only used the dash pot. There should be a bracket that screws on the carb that the dash pot is attached to if you have an auto trans.

2) That's correct, don't forget the little steel weight rod that fits in the hollow screw.

3) There are two accelerating punp diaphragms, one at the front and one at the rear of the carb. The primary in the front and the secondary at the rear. There is a ball check at the secondary that goes in a hole at the center top of the secondary pump housing.

Just a note, There is a thick gasket that fits on the power valve, do not over tighten the power valve so you do not distort the gasket.

Doug
 
#21 ·
My car is an automatic, but I have no way to tell whether this carb should have been on an automatic or a manual.

As for #2, I don't know where to actually put it. The only thing I have in to that area where I could drop a ball in is the little hole next to the big hole where the air cleaner screw goes. Is that it?

And my secondaries diaphragm is different. It is much larger and is labeled as a different part on the diagram. The one that was on the carb was fine so I put it back in. The kit did not come with a new one.
 
#23 ·
For no. 2). It's called a Booster Venturi Screw. I fits between the two capped holes in front of the air cleaner stud hole and close to to the float bowl.

If you have two primary pump diaphragms, is one different than the other? There were two or three different types used in the carbs. Pick the one that matches the one you removed.

Doug
 
#24 ·
Typically a manual transmission will have mechanical secondaries and automatics will have vacuum secondaries. Does the car have a diaphram that's connected to the secondary throttle shaft? On a vacuum secondary, the primaries will not open on the bench when you open the primaries. On a mechanical, the secondaries will open.


Don't worry about the dashpot for now. I ran without one for 20 years before I even knew it was supposed to have one.
Dave
 
#25 ·
Based on what you're saying, I'm pretty sure it's a vacuum secondary. I can open the secondaries on the bench, but not by engaging the primaries. I have to push on something else behind the choke area.
 
#26 ·
That secondary diaphragm on the back of the carb is what controls the secondary throttle plates. It's not really a accelerator pump. It is actuated by the secondary throttle shaft and vacuum from the intake manifold thru a passage in the carb. The ball check controls the rate at which the secondary throttle plates are allowed to open.

Doug
 
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