Stripped Choke Knob Repair

[pjmoreland]

I switched to the smaller '67-style knobs on my '68. The choke knob I bought was stripped out. Since these knobs aren't all that common, I decided to repair it. Here's what I did:

1) Drilled out the hole in the back of the knob to 27/64" to the maximum depth without breaking through the front of the knob.

[pjmoreland]

2) Tapped as deep as possible with a 1/2"-13 tap without jamming it against the bottom of the hole to avoid damaging the front face of the knob

[pjmoreland]

3) Cut a section of a 1/2" bolt to the correct length to bottom out in the knob and be flush with the back of the knob when tight.

[pjmoreland]

4) Drilled and tapped a #10-24 threaded hole through the center of the bolt section. Used a couple of nuts to hold it still while drilling and tapping.

[pjmoreland]

5) Used a #10-24 screw and nut to tighten the bolt section into the knob.

[pjmoreland]

Here it is installed.

['68OrangeSunshine]

Nice machining. I prefer a manual choke too. Electric chokes and bi-metal strip automatic chokes are too fiddly to adjust. Also with the wildly divergent climatic conditions in Arizona -- desert heat, or mountain elevations. no flatlander setting will work full time. Best to have manual control. My '68 C/10 w/ 292 had a ptoduction manual choke. I had to convert a Holley R8007 4160 390CFM to run manual. When I reengined in 2005, I bought an Edelbtock 1404 -- 500 CFM, manual choke.
My old '67 K/10 Suburban, ''White Fang,'' had a 454 and a 625 CFM Carter AFB. I lived with the automatic choke until on two occasions, the choke went off on its own at the wrong times. Once I was working in a pit mine and descended several levels -- a few thousand feet. I had to jam a Craftsman screwdriver into the carb to keep the valve flaps open. Later, that winter I was in Pinetop at about 7 - 8000' on the Mogollon Rim, and my choke choked off again. I used the screwdriver trick again. As soon as I could, I put in a manual choke. I think That's a generic HELP section knob and cable. New -made for vintage application parts were not available then... pre-internet days.
On my '71 GMC Jimmy, I got a vintage-correct choke knob and cable [with metal knob insert] to match the Custom trim level of that rig. Carb is a Carter AFB 9635S - manual choke. I drilled a 3/8 hole in the plastic instrument panel and mounted it under the Wipers switch.
Works great.
I am having a gripe with the The GMC's original Headlight Knob and shaft. It pulls out OK. Headlights go ON/OFF But it's stripped, so when I turn it, it spins rather than adjust the dash light brilliance levels. Cheapest solution would be to pull it out overnight, and let a few drops of Super Glue drip down the shaft, and see if that keeps it from spinnning instead of adjusting the dash light levels.
The alternative would be new replacement knob from a vendor.

[I also have a Manual Throttle cable, but I'm missing some parts to fully rig manual throttle on that truck.[

[67C10Step]

Nice, as I was putting mine back on the last time I was thinking how I would repair it if it stripped out. Now I know.

Thanks for the write up!

[Ironhorse]

Good detailed write up. Old fashioned do what ya' gotta' do fix, love it.

If anyone is interested I have a standard face choke knob for 68 and on I will not be using. Send me a PM if anyone has an interest in the knob.

[too much stuff]

Nice job, glad you could save it.

[yuccales]

Perfect fix.

[72c20customcamper]

Well done

[Palf70Step]

Nice work!

[pjmoreland]

Originally Posted by '68OrangeSunshine

Nice machining. I prefer a manual choke too.

I like the simplicity of it and the absolute control it gives you. I had to do some tweaking of the carb linkage on my Edelbrock 1405 to get the fast idle cam to kick in earlier so that it will still hold the RPM up with partial choke. That way I don't have to back out of the garage with one foot on the gas and one on the brake. When I had an electric choke, I didn't like how it would kick out of fast idle the first time I touched the gas pedal after starting. This was problematic for me because my driveway is sloped and I need to give it a little gas to maneuver my way out of the garage. I don't want it coming down off fast idle quite yet at that point though.

[pjmoreland]

Thanks for the compliments, guys. That choke knob weighs a whole lot more than it did before with that big chunk of steel in it. I think it will hold up well though. I found it interesting that the shavings from drilling the knob were colored blue.

[LNP]

Thats some serious good work and machining. Also good thinkin out of the box. I take it the way it was stripped a 10-24 heli coil wouldnt have fixed it?

[pjmoreland]

That very well might have worked, although I don't know for certain. The hole was already quite enlarged. I was being cheap by not buying a helicoil kit.

[pjmoreland]

The original knob design is partially hollowed out with a small tube in the center that is connected to the outer part with three webs. I've included a photo of a NOS 68-72 knob. The repair I outlined above was actually my second attempt. On the first attempt, I tapped the center tube to 5/16, but the remaining wall was too thin and fell apart when I tightened a segment of a bolt in there.

I think you could get away with a helicoil if most of the original material is still there.

[LNP]

I didnt know if it would work but thought it was worth a question. With what happened to yours I would say your way is the best repair. Thanks for the photo of the knob that helps with understanding better.