The Stovebolt Site Forums The Shop Area Engine Shop Carburetor Assembly Screws- Thread Repair Procedure?

Carter YF 2100s Carburetor (55.2 235)

The air horn is attached to the main body with 7 slotted, high-profile, fillister-head screws (edit- this is how mine is assembled); I believe they are 10-32 machine screws from my measurements. The thread diameter measures to 0.183". corrected

1. Are these 10-32 screws? Or, what size are these carburetors supposed to be assembled with?

Two of the bosses within the carburetor main body are stripped out (not completely, yet), and need some sort of repair.

2. Is this area of the carb safe to do a heli-coil repair? If so, what size thread/screw repair should I go with (same as Q1)?

3. Is there any other preferred repair method in this location? Pictures

Thanks in advance-
Brad

First: I think you mean .183. A #10 is .190. Those Fillister head screws are very hard to find. I ended up getting an old carb, cheap, and salvaging the screws. A socket head cap screw is the same approximate profile and may be an option.
Repair of the holes never works out very well. Get another carb to use as parts. There are some locations you can drill out the threads and use a screw and nut. I don't do that, but it's another option.

The screws are available still in gun metal black. This is because the gun industry uses them.

http://www.brownells.com/

080-050-032WB
Size 10 - 32 x 1" (12 of them for $5.99)

I got mine there. Then you don't have to mess up the carb with tapping them different when the walls are already thin enough.

Thanks for the size confirmation & another source to buy them (I corrected my decimal placement above ). The screws are not very difficult to find, but there is nothing wrong with the screws I have.

The boss, or protruding point inside the carburetor (that these screws go in) is where there is thread damage; this is where I was asking about the heli-coil possibility.

Many thanks!
Brad

Sorry, got off topic with screws. I do not think there is a "good" solution except a new carb body. Should not be hard to find and better piece of mind. The helicoil requires a larger tapped hole, a certain depth/thickness, problems with blind holes, expense, tools and possible "screw" up.
Maybe get a donor for parts or rebuild a used one.
Example:
Make Offer

Jon/Carbking posted a list and included these. (you know this info already)
2100s � 235 engine aftermarket manual choke 1953~1956
2101s � 235 engine aftermarket auto choke 1953~1956

you can email him from his profile page for his thoughts on thread repair or he may see this thread. He is THE guy for YF. He has a carb shop, to say it mildly.

I do have another carb body to use as a last resort, the same YF 2100s, but I would prefer to try some repair on this one... (many different reasons there) I re-checked & one of the threaded locations, where the throttle & choke linkage attachment is located, can be repaired with a screw & nut. That leaves me with one hole to repair.

Comparison between the hole required for (1) a heli-coil insert for a 10-32 screw vs. (2) the hole required to tap for a #12 is about the range that could possibly work, maybe?

I might sleep on the ideas & yes, I've thought about giving Jon a call. They stay busy- I do remember that when I ordered the repair kit.
Brad

Heli-coil should NOT be a problem if your are careful (use a drill press to get the hole plumb, and NOT too deep). I have heli-coiled several of these carbs.

If you tap for a #12, you will have to drill out the hole(s) in the airhorn as well, just adding to the possibility of error.

And if you put in non-standard screw size, the next rebuilder will NOT salute you with your favorite beverage!

Heli-coils come in 3 different lengths (short, standard, long). Use the short ones in the YF.

Here is site that specifies drill sizes for heli-coils:

https://www.carbidedepot.com/formulas-tap-helicoil.htm

Jon.

Look on Ebay- - - -dozens of 10-32 Helicoil options there.
Jerry

.. and I'm trying to minimalize my chances of error-making. Not that I wouldn't notice it eventually, but I hadn't thought about having to also drill out the airhorn, as you mention.

I'll check back in after I get some heli-coil; anything else to be aware of ? Particularly with how this cast metal on the carburetor reacts to a slow churning drill-press? It seems fairly 'soft'. (I have not researched exactly what the Carters YF is made of)

Thanks
Brad

Thanks, Jerry; anywhere local that might have the inserts?

Jon, the link you just provided answered my next question.

Brad

You might try Grainger on Jordan lane. They're usually pretty insistent on selling to "business only", but it's worth a shot. I think my farm qualifies as a "business" if necessary. Fastenal might be another possibility.
Jerry

http://www.mcmaster.com/#helicoils/=yrnmve

They are great for a lot of things. What I like about them is you can order small quantities.

The local O'Reilley Auto Parts store carries the standard kits.

Drilling won't be as difficult as tapping. Use some oil on the tap when tapping for the helicoil.

Jon.

Wilco. I'll update how it goes once I get the inserts.

Brad

Helicoils work really good for this. I have saved a couple rare carburetors with them. Use a drill press to get the straightest possible hole, and I like to use the drill press by hand to get the taps started straight. Once it gets started, hand tools will finish the job. Napa can get any set you need. You will need the complete kit, not just inserts.

Joe

The Heli-coil insert kit is ready for me to pick up today, but I went ahead and did a parts exchange between my two YF 2100s last night (as somewhat advised)- put the good Carburetor shop kit in the other YF (without the stripped threads). Here's some pictures . I'll try out the inserts on the damaged threads tonight if I have time.

FYI- "Standard" Heli-coil insert kits (1/4"-20, 5/16"-18, 1/2"-13, et cetera) are available at all the parts stores & several hardware stores. 10-32 size is not considered "standard" in this sense, but was stocked close enough geographically for an 18 hour delivery store-to-store. (Just in case anybody ever has to get them.)

Brad

Thats great news Brad. Be sure to let us know how it went. It would be great to have a how-to article on this. I know the Rochesters have such thin metal at these boss areas, it's a miracle they have lasted this long. If there is a good way to save these cores, I am all for a decent solution that doesn't incorporate JB Weld! Carters are much better made IMHO.

Brad, nice clean professional work and work area. Good choice to make the switch. Also good ideas from others about helicoils. Getting more experience with those will help in your future fixes.

Deve- I'm not up for a how-to article right now, but I did take some pictures when I repaired the first hole with stripped threads. Remembering to snap photographs was more difficult than the actual heli-coil repair procedure.

For a 10-32 Heli-coil thread repair insert: Drill a 13/64" hole, tap 10-32, insert the coil with the tool, & you're done. (These steps are per Heli-Coil®)

There is a lot more precision involved & I took heed of all the advice above. Thank you all for chiming in. This was the smallest diameter thread repair I've ever done. By a lot. There is ZERO room for error as thin as the carburetor wall is. The heli-coiled hole holds the screw so well, in fact, that I would be tempted to put inserts in all the holes... if it weren't for the zero room for error aspect. Heli-coil thread inserts work.

Thank you all very much for the advice. Here are pictures of the Carter YF 2100s I am repairing.

Brad

Looks good, and you are right, they really hold tight.

Joe

Thanks, Joe- hey, how do you go about starting the tap with the drill press? I liked the idea, but didn't want to try it on this. Makes sense & I guess I'd just raise the table & workpiece to the tap, right? And just hand turn the chuck?

Brad

I use a cross slide vise to center the hole exactly under the tap which is held in the chuck with moderate pressure- - - -I want the tap to be able to slip in the chuck jaws rather than break if it binds. Lower the tap to the hole with the drill press quill and hand turn the chuck to get the tap started. After it starts cutting, use a drill bit or a piece of round stock in the chuck key holes to turn the tap and chuck together. Once it's cutting well, loosen the chuck and use a regular tap wrench to complete the thread. Use plenty of cutting fluid. I use the same procedure to drill and tap very expensive rifle receivers for scope mounts.
Jerry

Brad,

Thanks for taking the time to show us the processes you employed for the repair. Good work.

Paul

Yeah, I can totally relate! I have my camera right where I need it and even then I forget to take a really needed picture and end up taking whatever it is apart and do it again. If I had any sense I would make a list of the procedure, and what pictures would be good. But noooooO! Glad it worked out for you Brad. The pics are important for the next guy! Looks great!

Good procedure description- thanks Jerry!
Paul, don't mention it; it's my take on what it's all about (info-sharing). I looked at the pictures & I need a how-to class on picture lighting, however!

Truck is priority for now...

Brad

One observation: This carburetor I am working on is a spare, meaning- I have a 'good' one. I recommend a practice attempt with these inserts on a similar material or similar carburetor body before moving to the actual unit under repair. For a 10-32 thread repair, to insert a 10-32 screw, you will be tapping with a 13/64" tap. If this is confusing, try to tap a 10-32 hole that is stripped- using a 10-32 tap...

An explanation of the measurements in the photos:

The screw thread length to be inserted through the carburetor bowl cover assembly, and into the main body is 0.4785" (measured with lock washer installed) ; subtract the carburetor bowl cover assembly thickness of 0.2495", and we are left with 0.2295"

The 10-32 Heli-coil insert is 0.1815".

I drilled the 13/64" hole to just shy of the 0.454" existing hole depth. For a depth gauge, I measured the tap thread exposed prior to running the tap (0.8765") and measured until I was close to 0.25" depth: 0.629" (to insure the 0.2295" of screw thread had somewhere to go). The 0.25" depth I was aiming for is my calculated estimation of what the "not going too deep" Jon/Carb King mentions, is.

0.8765" - 0.629" = 0.2475" on the tap depth, so I was a little off. This is plenty of depth for a 0.1815" insert, and 0.2295" of screw depth, either way.

Hope this helps. Edit- I forgot about the gasket thickness...

Brad

Brad - looks like you are doing a fantastic job with this. Once complete, the helicoil will be better than new.

Drilling "plumb" holes for tapping purposes, another possibility:

I have a milling vice attached to the tailstock of an older lathe. Setup can be time-consuming if one is only going to do one hole, but if several are needed......

Once the hole to be drilled is properly set in the milling vice, leave the tailstock slightly loose, so it can slide on the table.

I then place the tap in the headstock, UNPLUG the lathe, guide the tap into the hole, and turn the headstock by hand. The tailstock will slide, allowing a perfect thread to be cut. Don't forget to oil the tap.

And Brad mentioned the 10-32 was the smallest thread repair he has attempted. Before we got a set of "slitting saws" (to cut slots in metal) for the lathe, we repaired several throttle shafts with 6x32, 4x40, and even 3x48. Difficult, but doable. Now, depending on the overall condition of the shaft, especially how the arm fits and the wear where the shaft contacts the throttle body, we will either install the helicoil, or machine a new shaft.

Lots of enthusiasts overlook some really top quality older tools. We bought a mid-1950's Sears Professional 12 inch lathe with some issues a few years ago for $400. Turns out the PO couldn't understand wiring diagrams and miswired the reversing switch. A new reversing switch and lathe works perfectly. Lots of really good (but old) made in the USA precision tools out there just wanting a good home.

Jon.

The one problem I have with tapping is how I never get a nice square start with the tap. I have this cheap drill press and the chuck really has no place to grab to turn it by hand. Someone should devise a wheel that you put around the chuck that turns with it, to grab while using the dual slide vise for holding. Maybe its just me? Also in blind holes I like to use a flat bottom tap.

Deve - in a pinch, find a steel rod that can be inserted in the holes in the chuck used for adjusting the chuck.

Jon.

Removing the drive belt from the drill press spindle pulley makes the chuck a lot easier to turn. Then use a pin punch in the chuck key holes as the tap gets harder to turn once the tapered part of the tap enters the hole and the full thread engages. On a blind hole, start with a plug tap, then go to a bottoming tap if you want a full thread to the bottom of the hole. I don't know if Heli-Coil taps come in the three standard types, taper, plug, and bottoming. I usually buy taper taps and grind them off to make plug or bottom taps. It would be very important to get a full cut to the bottom of the hole when tapping for a thread insert because the bottom few threads would tighten up the coil if a full-depth thread isn't cut before installing the insert. You'll only get one shot at doing it right.
Jerry