$15 DIY throttle shaft bushing replacement... Write-up on p.1 ***Edit: Write-up posted towards the bottom of page 1*** So who's done it? Looking for drill / reamer and bronze bushing dimensions so I can fix this vacuum leak around the primary throttle shaft. Most of the kits are ~$65. I should be able to buy tools and parts for less than that :error: Think this one will work? McMaster-Carr P/N 6391K153 SAE 841 Bronze Sleeve Bearing for 5/16" Shaft Diameter, 3/8" OD, 1/2" Length What size drill should I use to get the appropriate press-fit? Thanks guys -Justin
I don't know exactly what you are doing but most of the time when you ream a hole, you want to drill, end mill then ream. The end mill will make sure you have a straight hole because the reamer will follow the hole that is already there. So if the drill walks and you don't use an end mill to straighten the hole, the reamer will walk resulting in a bad hole.
The primary throttle shaft on my Q-jet is loose, this is because the steel shaft rides in holes drilled in the aluminum throttle body. The usual fix is to drill the holes out to a larger size and press in self-lubricating bronze bushings. That's what I'm trying to do. Not sure if fixturing it up in a mill is needed since I'm enlarging an existing hole. Some kits have a ground down drill bit that self centers, and others have a 5/16s rod you use to line up the plate with your drill press / mill prior to drilling to a larger size.
At the point that I need to have that work done, I'll haul it to a machine shop and have them install a thinwall bronze valve guide insert. Unless you're going to do several of them--or you are willing to spend additional money because you appreciate "the challenge" of doing it yourself--you might as well have a pro take care of this.
My experience: I found the parts I needed in mcmaster carr, and tried to drill the holes with a hand drill. Ruined my baseplate. Ended up buying a kit from tin indian performance because I plan on bushing more in the future. I should have bought the kit to begin with. It has a pilot tip drill bit that guides itself in straight. hard to mess it up. Luckily I found a spare baseplate in good condition at the local swap meet. Parts are cheaper in mcmaster carr for sure, but I recommend a drill press at the least for a DIYer, based on my experience. as for the press fit I think .001-.002 would be fine. you could do an exact size drill and use the red loctite too. Tin Indian, like several other places also offer the rebushing service. Good luck
I've had my kit for about 20 years; can't even remember who I bought it from. I bought several sets of bushings at the time and still have a few left. The tools will pay for themselves if you use them, not wise to skimp on tools in my mind. I may be old, but I don't see $65 being a deal breaker; you will have more than this in a new baseplate if you mess up. Jim
Gesslers Head Porting sells a 10 pack of the bushings for $20. He said (months ago) the DIY kit would be avail soon. Maybe he has them now, but hasn't updated the web page yet.
I ordered several different bushings from McMaster-Carr along with a precision driveshaft to use as an alignment tool with my drill press. I'll update this thread with a write-up on how to do it right or a horror story on how I did it wrong ray: Either way, it should be amusing :Brow:
Results, as promised. My primary throttle shaft had .030 diametrical clearance and required bushing to tighten up the shaft and prevent vacuum leaks. The inner bore was fine, only the outer ones were worn. Here's what I did: 1. Line drill press vice with aluminum angles to prevent damage to the throttle plate. 2. Slide 8mm precision ground rod into both the inner bore and the drill press chuck, loosen the vice and slide everything around until the throttle shaft bores are perfectly aligned with the drill press. Be careful tightening the vice because you may disrupt the alignment! 3. Remove the 8mm rod and install a 3/8th inch drill bit, set the drill depth to the bushing length plus a 1/16th or so. Drill. 4. Repeat 2 and 3 for the other outer bore. 5. Tap the new bronze bushings in with a plastic hammer, if they're loose apply red loctite. There is risk involved here, if the part shifts while you're drilling you'll end up with an off center hole. One of my holes ended up .005 off center, so I opened up the bushing .0025 to compensate. Spend the time to triple check step 2 and you'll avoid this mistake :TU: The bushings I used were oil-impregnated bronze for a 5/16th shaft with 3/8 OD and 1/2 length. I think 5/8 length would fit and provide additional support for the shaft, the 3/4 length bushings I had looked too long. Total cost for this project was $30, mostly because I ordered 5 different kinds of bushings in quantity to allow for mistakes. I hope this helps somebody, I'll post the McMaster-Carr P/Ns for the parts I used on Monday. -Justin
Parts list: www.mcmaster.com 1. 6391K164 SAE 841 Bronze Sleeve Bearing for 5/16" Shaft Diameter, 7/16" OD, 5/8" Length ($0.75 / ea.) 2. 6112K44 HARDENED PRECISION METRIC STEEL SHAFT, 8 MM OD, 200 MM LENGTH ($5.70 / ea.) 3. 3/8th inch drill bit (I'm assuming that you have this already) Buy a bunch of spare bushings and this'll run you about $15 shipped
nice work, nice thread. why did you get so many extra bushings? if any mistakes would be made it would be to the base plate wouldnt it? I cant see myself working to within 5 ten thousandths of an inch ("so I opened up the bushing .0025 to compensate.") if i drilled the hole in the baseplate .005 off. That's the width of 5 human hairs! Im all for crisp throttle response but geez! LOL
In your instructions you said you used 5/16 ID 3/8 OD, but here in the parts list you indicate 5/16 ID and 7/16 OD. Why is that?
Hey Gary, FYI: Justin hasn't been on here since June. Not sure if he will respond, but someone who has done it might. Best Wishes,
"There is risk involved here, if the part shifts while you're drilling you'll end up with an off center hole. One of my holes ended up .005 off center, so I opened up the bushing .0025 to compensate. Spend the time to triple check step 2 and you'll avoid this mistake :TU:" Folks, this method is NOT recomended. It is simply impossible to have a standard 3/8" drill bit follow a hole in perfect alignment even if you take the time to clamp it up in alignment with the drill press. The drill bit, having flutes, bends quite easily as it bores its way into the material. Without a "lead" so self guide the cutter, it will "walk" and take it's own path 9 out of 10 times, if not 10 out of 10 times. One must also realize that the original bore diameter was not a very tight tolerance. Factory throttle shafts on NOS units will show up to .008" side play right out of the box. Add this to any errors in your set-up under the drill motor, combined by the fact that the bit will bend as it bores it way through the hole, and it is a recipe for DISASTER!......Cliff
what do you mean by lead? if this is true then all the kits are ineffective because they all come with a bit and give similar instructions. Even if you use the long bit the goes into a couple of the bores to align itself. If it is off by .008 from the factory then that would be enough wobble to get it wrong. What is the best way to DIY then? and how do the pros do it then?
In order to stay on center the bit needs to have a lead, or section that extends thru the bores to keep the cutter on center. The cutter on our custom bits is pretty far up on the shank of the bit. It is not possible for a drill bit to follow a hole and stay on center without a lead. It will also flex and go off center all the way around, and more a much bigger hole than the actual diameter of the bit. This happens because the bit doesn't cut evenly all the way around and at the same time, just on two sides. Chuck a bit up in a lathe sometime and spin it. While it's spinning carefully take a screwdriver handle and push against the flutes. It will amaze you as to how far off center and easily the bit will flex. Bottom line here, after seeing folks attempt this for over 3 decades, it is NOT recomended, get the right type of cutter, and bore the correct size hole exactly on center in less time than it took me to type this sentence. No drill press is required, or even recomended. Just clamp up the throttle body between two blocks of wood, bore the holes, set the bushings, assemble.....Cliff
Drill bit with a pilot: http://www.gesslerheadporting.com/g...c7b7f6b11e781f0a8525756500062c37!OpenDocument
