The Stovebolt Site Forums The Shop Area Engine Shop Carb overhaul

The Carter YF 964S (was on my '52 GMC when I bought it 13+) years ago started having problems about 6 months ago. When it sat over night the float bowl would drain down, which meant I had to crank the engine over a bunch before it would start. Also, the mileage dropped from about 13 MPG to around 6.

I removed the Carter and installed a Zenith 28 (which was the proper type for my 228, but not the exact model) that I had. It ran okay, but not near as good as the Carter.

I bought a kit for the YF and installed it last week. Truck seems to be running fine, although idling a bit high. I filled the gas tank this morning and will report MPG results after the next fill up.

BUT ....

Two of the 10-28 edit:actually 10:32 screws (see picture) that hold the top feel like they want to strip out the threads in the body of the carb. They are still holding somewhat and the carb doesn't appear to be leaking. The only "fix" I can think of would be to drill and tap the two blind holes in the body to #12 size machine screws.

QUESTIONS:

Anyone have a better idea?

If #12 screws are the answer, should I use 12-24 or 12-28.

Maybe just a drop of green Locktite on the threads. It's not the correct fix but if it's not leaking at the moment. I would do each screw one at a time, so as not to lose the gasket seal.

I'm pretty sure I have some 10-32 helicoils in my box of stuff, which is what I'd use. 10-28 is an uncommon thread pitch, so I'd confirm what you have first. If you do drill for #12 screws, match the pitch to what the #10's are (10-32 fine or 10-24 coarse).
The #12 screw heads would look weird, being bigger.

I don't know "green" loctite Craig, but I'll look it up.

Kevin, I had 28 tpi on the brain while thinking about the #12 screws. The current screws are 10-32 (I think). I didn't realize they made helicoils that small. How big do you have to drill the hole in the carb for the helicoil? There isn't a lot of meat available.

Get some longer screws and see if they run all the way through into some remaining good threads. If you feel any resistance, stop and remove the long screw and run a tap all the way through.
This has worked for me in the past.

Basically to install a helicoil, the drill size is the same as the major diameter of the size you're installing. So you're not really taking out that much metal. I have just run the helicoil tap through a part with fully stripped threads without drilling. The set I have is 10-24 and needs a 13/64 drill. Drill size for a 10-32 helicoil would be the same. It looks like you can get a 10-32 helicoil type thread repair kit for under $30 on Amazon. Actual Helicoil brand is crazy expensive now.

As Kevin mentioned, genuine Heli-Coil kits ARE expensive, but if you shop ebay, you can generally find them fairly close to the price Kevin quoted for the Amazon kit.

There used to be a cliche: "You get what you pay for".

Sometime ago, I paraphrased that cliche as follows: "You generally DON'T get what you don't pay for".

Over the last 50 years, I have installed hundreds of genuine Heli-Coils, with NEVER an issue.

I did test some of the less expensive knock-offs and then threw away the castings.

You get ONE opportunity to correctly fix the stripped threads, and then you get to replace the carburetor.

Which is the most expensive; the Heli-Coil kit or a carburetor ?

Jon

One other suggestion:

Which ever way you go, DON'T try to use a hand drill. Make a suitable fixture to attach the carburetor to the base table of your drill press, and CENTER the bit for drilling.

Once you have the hole drilled, UNPLUG the drill press, and use the drill press head to hold the tap, and rotate the drill press head by hand.

Even a genuine Heli-Coil would have issues if not installed "plumb".

Do it right, the first (and only) time.

Jon

Great suggestions Jon.

I have a drill press and a question. How much force on the downfeed handle?

For now (and until I detect a leak or have to tear down the carb for some other reason) I'm just going to let well enough alone. I will get a genuine Heli-Coil set and hopefully that will keep me from ever needing it.

Bill - just enough to get the tap started a couple of threads, and then it will take care of itself.

In the "for what its worth" category, the really "tricky" ones are the throttle plate screws. When still doing carburetors, we used to have a lot of units sent to us with a twisted throttle plate screw. We actually received a four-barrel once with ALL eight throttle shaft screws twisted.

Heli-Coil makes the inserts in different lengths; when doing the throttle shaft repairs, use the "short" inserts, or better yet, don't twist off the screws.

Jon

I removed one of the screws and checked thread pitch. It is definitely 10-32.

Jon: I'm looking at a HeliCoil 5528-3 kit. But the specs show that the lengh of the insert in the kit is 0.285". That should be about 9 turns of thread on the screw. The blind hole into the carb body is more than twice that deep. Do I need a different set of inserts? If not, do I install the inserts at the beginning of the hole or down at the end?

HeliCoil lists these inserts in 10-32:
• 1D (Short): ~0.190 inches overall length (OAL)
• 1.5D (Medium): ~0.285 inches overall length (OAL)
• 2D (Long): ~0.380 inches overall length (OAL)
• 2.5D: ~0.475 inches overall length (OAL)
• 3D: ~0.570 inches overall length (OAL)

What happened to Carl's suggestion about tapping the hole for longer screws? Seems a lot easier and less risky that a Helicoil fix.

I also did this on a carburetor for another vehicle.

Bill, Usually the inserts that come with the kit are long enough for most uses. You can also stack inserts in the hole if you need more threads (drive the first one to the bottom and then thread another insert in on top of it.) But for your application, I'd say that 9 threads would be fine (installed at the top of the hole.)

I hear what Jon says about the knock-offs, but I have used them successfully. I do have genuine Helicoils in various sizes though, and prefer them if readily available. I've even used Helicoils on stripped weld nuts (the one on the stake pocket for the tailgate hinges.)

In my opinion there is no risk trying what I recommended. If it doesn't work, one can just go with a helicoil fix.

I would also vote for at least attempting to use longer screws.

Just do not fall prey to the stainless steel ads, go for zinc plated steel just like the original.

Jon

Try tapping the carburetor housing for a 5MM X 0.8MM thread. That's about .009" larger than a 10-32, and it should allow you to get a full thread in the housing without having to use Helicoils.

toolsadvisers.com/what-size-drill-for-m5x0-8-tap

Jerry