I've got one that I am attempting to rebuild and another for spare parts. My sticking point now is the small screws in the primary throttle shaft. I've tried over night carb cleaner baths, heat, and alternating the two and regardless I keep breaking off the screws in the shafts. I was able to remove two of the broken pieces and have two that are too short to get a hold of with the small vise grips. Any suggestions as to the best way to get these out without damaging the existing threads? Will I have have to drill and tap? If I have to re-thread, what size is best? Anyone out there have a source for new or used shafts to fit the 72 Buick Rochesters? Thanks! Rick
Wow, how are you tightening these? I have never broken one of those. I would imagine you will have to drill and tap, if it is even salvagable. Make sure you check the center and top to see if they are warped. A great source for parts is Greg Gessler. Check out his section in the vendor section.
They are breaking off while trying to loosen them. Just trying to get the darned things apart to do the shaft bushings... Guessing these carbs have never been broken down before. With the first one I was pretty heavy handed, but the second one I soaked in carb cleaner over night (and several times before this point as I was cleaning the parts) and then tried heat. Tried loosening a tiny bit at a time and then soaking/heating and then loosening and so on but still broke two screws. Frustrating! I sent an e-mail to Greg with the same questions this weekend. I have plenty of "good" screws from other parts carbs, just need a shaft.
Oh, I get it now. Those screws are typically "spread" to keep them from ever coming loose. Probably have to drill and tap. Just make sure to put something on them to keep them tight when you put it back together. I was picturing the two screws in the primary holding the top to the mid section.
The original screws extend all the way thru the shaft and then the ends are staked, or flattened so the screw will not loosen and fall into the engine. To remove the screws, you must grind off the end that protrudes thru the shaft. Another method is to TIGHTEN the screw until the head breaks off, then unscrew the remains out from the bottom.
Thanks guys. I wish I had remembered about the screws being staked... I think I remember reading about that somewhere last year... Bummer! I noticed the shape on the bottom of the screws. Thought I could get a very small screw driver in there to loosen from the bottom but I seem to be having coordination issues as I can't get them loose. Maybe I'll try to deepen the groove with a small grinding wheel... Thank you for the replies! Hoping that either Chris or Greg (or another vendor out there?) have spare shafts to sell if this does not work? Or even someone with a used one in good shape. Would the shaft from a 69 Wildcat 750cfm fit? I have a spare base plate. Obviously the primary plates don't interchange but maybe the holes are lined up the same? Anybody know? Thanks again!!!
I have used a dremel with a Very thin cutting wheel to "groove" the remains of a screw stuck inside the shaft. Then try heat and a small screwdriver to get it out. The groove you will cut will go into the shaft some, obviously. I am about 50% with this method. Other than that its drill and tap. #3-48 I believe is the original size.
I see this frequently, as folks forget to removed the staked part of the screws before trying to take them out. In most cases I can center drill them, and typically they will spin out as the drill bit goes through. If not, I just keep drilling until most of the screw is gone, then chase the threads with a 3-48 tap. If all of the above fail, drill and tap for 6-32 screws, which is what probably should have been there from the start anyhow....Cliff
Thanks Cliff for your PM also. Hope to get back to it this weekend and do a little grinding and drilling before going to another shaft!
That sounds like an easier way of actually doing it.....I'll try that the next go around. Thanks, Tommy
