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Reamers for bushing throttle shaft.

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HolyHarp

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#1
I have a Nissan Z16 engine carburetor with a very loose throttle butterfly valve shaft. Unless someone has a better idea, I want to bush the holes. I'm looking at a bushing with a nominal OD of 10.5 mm and an ID of 8 mm. I believe I need 2 reamers for this job. I've never had occasion to use a reamer before and I'm not sure which type to get. I'm thinking of a set of adjustable reamers. I'm not sure how to pilot them.

I wonder if there is a simpler way to do this; does Loctite/Henkle have some product that would solve my problem?
 

benmychree

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#2
If the reamers are of the Critchley type, pilots are available that screw on the end of the reamer and have a closely fitting tapered sleeve that slides on the pilot.
 

Bob Korves

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#3
The stock for the bushing is not likely to be found as 10.5mm material, but can be machined down to the desired size from larger stock. What is the material? Brass? I do not recommend that you use adjustable reamers for that job, they are too fragile and fussy to use in smaller sizes and will not leave a parallel bore to desired size without much care and some luck, especially for a novice. Measure the shaft accurately along it's length and decide the size that you want for the bushing I. D. You will want it snug on the worn pivot area of the shaft while also large enough to slide over the unworn portion. It might make sense to turn down the entire shaft to the smallest current diameter for a better fit and to make installation of the tighter bushing possible. Some of that depends on the layout of the installation, and we do not even know what model carburetor it is. When you know for sure the reamer size you are looking for, you can try to buy one that size. Report back if you need more help. I have lots of reamers, and so do others here, but you are in Thailand, which makes things much more difficult. The bushing could also be made from solid stock, bored to size on a lathe, and then turned to the desired O.D. If there is room to work, the bushings would be best reamed to size after installation in the carburetor. You want the butterfly valve to fit the venturi closely and without binding, and that requires accurate locating of the throttle shaft.
 

HolyHarp

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#4
Thanks folks. Looking at ebay offerings it seems that reamers usually come with a 1:50 taper. Is this the type of reamer I need?
 

12bolts

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#5
Geoffrey, is the butterfly shaft worn or is it the holes in the throttle body?
Depending on where the wear is, and access after installing the bushings, I would consider making a single bushing as long as the overall length of the total butterfly, turned to OD to press into the throttle body, and reamed to suit the butterfly shaft. After installing that so as to keep the 2 bushings aligned. Then cut the unnecessary section out of the throttle.

Cheers Phil
 

HolyHarp

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#6
I must confess that shaft is worn as well as the holes in the throttle bodyI'm not too keen on turning the shaft down because I think it would be hard to center. I could mount it in a collet which is pretty accurate. I can't think of an accurate way to support the other end of the slender shaft.

I believe that drilling/boring the brass bushings undersize and reaming them afterwards using the shank of the reamer as a pilot (if possible), might make the holes aligned.

Thanks, Geoffrey
 

cg285

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#7
there may be commercially available reamers for your application. i have one for quadrajets so there may be others available.
 

chips&more

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#8
Is this enough wear to cause a vacuum leak that will effect engine performance? If you want to do something about it no matter. I would just lathe out to size (ID & OD) the brass bushings. Leave the shaft alone. Yes, it will not be perfect. But will be better…Dave
 

Asm109

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#9
The bores always wear egg shaped. If you just ream the hole and press in a bushing, the center of the throttle shaft will shift because the reamer follows the "center" of the egg shaped hole. This means the relationship between the throttle plates and the bore is hosed up. Also relationships between butterfly and any idle or transfer ports is messed up too.
What this means is you have to find a way to locate the center of the unworn portion of the hole and then BORE a hole ON that center.
then you can press in a bushing and ream a hole to size.
This is not beginner machining, this is journeyman final exam level work.
 

Bob Korves

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#10

C-Bag

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#11
Back in my dark days as a line mechanic I used to do that process. I was cornered into it because of on my VW's the spring return side of the carb body would wear out and cause a vacuum leak. This would cause all kinds of mayhem with the idle mix and actually in running as this was unmetered air making one side of the engine(cyls 3&4) run leaner and even hotter. Making an already bad situation even worse. One day a salesman for an outfit that sold the "kit" for installing brass bushings came through and I bought the kit. It had nothing for actually aligning and drilling the holes. I ended up making a jig out of some 6x6 precision ground aluminum angle as the base and one of those drill guides. I used a reamer of the original size of the shaft to set up the carb body and drill guide and clamped the carb and guide. Then drilled the body. Installed the bushing and then ream to size. The other tricky thing is to remove the butterfly. Removing the screws without destroying the shaft is a trick. I used brass screws to replace the old ones and then peen them in so they don't vibrate loose. After it worked so good with my old VW I started doing QuadraJunk's so they could pass smog and got to where the Chevy garage came to me to fix their QJ's.
 

cg285

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#13
with that setup you ream the hole, pound in the bushing and you're done
 

f350ca

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#14
I've only done a few, but they all had worn shafts, that necessitated making new ones or replacing them with stock ones.

Greg
 

C-Bag

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#15
this is the quadrajet tool. it has a long pilot and a depth stop

View attachment 269203
That would have been a nice rig, but that isn't what the kit was. I think the name of the outfit was WinCo? The reamers I have all have the guide nose on them that I don't see on machinist reamers. I went to find my old rig but it all had been repurposed. I bailed on the biz in '88 so it's been a while :). The kits I see online are $200! I guess it's with that special reamer there. It will be interesting to see how the OP does because if I remember the carb correctly it has this insane multi linkage from the carb body to top.
 

westerner

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#17
Is this enough wear to cause a vacuum leak that will effect engine performance? If you want to do something about it no matter. I would just lathe out to size (ID & OD) the brass bushings. Leave the shaft alone. Yes, it will not be perfect. But will be better…Dave
I started doing QuadraJunk's so they could pass smog and got to where the Chevy garage came to me to fix their QJ's.
I have a question- just how tight was the throttle shaft to body when new? Who has THAT number? There is no lube, other than gasoline and dirt!
What I am saying, is this- If the shaft- to- body clearance has worn to the point it has become a detriment to driveability, then ANY reduction in that wear will improve driveability. As soon as you come off idle, what is the path of least resistance for airflow? If you make it TOO tight, that will surely affect driveability!
I am a bit of a QuadraJet fanatic. I have them on my Ford 302, my Ford 460, and my Mopar 440. I have built several, over many years, for fun and profit. The throttle shaft measures .308 inches. Do we have any reloaders reading this? You take the neck off a fired 30-30 Winchester case (Because it is LONGER than other 30 cal case necks), drill your carb throttle plate somewhat larger (no precision tooling required) than the brass OD, slather the holes with JB Weld, stuff the brass and shaft thru. The throttle shaft will align the brass, the brass will settle straight because of the JB, and then fit your butterflies after the JB sets up. The toughest part of the whole job is removing the screws holding the butterflies to the shaft, and finding their replacements. The improvement in idle quality (which is the only thing this whole thread is concerned with) will be dramatic. At any flow beyond idle, the wear between throttle shaft and body becomes entirely insignificant.
 

HolyHarp

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#18
Right now the engine dies when the clutch is disengaged and the accelerator is not pressed - it dies at idle.
Unworn portions of this throttle shaft are .3085 If I use 5/16 (.3125) bushings then I'll be making the fit a little better.
I don't have a Winchester case.
MH22nd says that an RC1 fit is .2 to .6 thousandths clearance.
The smallest boring bar I have will just fit in a .339 hole.
I guess no one makes a .309 reamer nor a 7.86 mm reamer.
I'm thinking of looking for a used carburetor at a wrecking yard.
 

dtsh

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#19
Perhaps turn some O1 steel or similar to the appropriate dimensions and make a D-bit reamer? Might not even require hardening assuming the carb body is aluminium or similar material and it being a once and done type task.
 
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Bob Korves

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#20
I have half a dozen 3/8" nominal chucking reamers with 5/16" shanks. The reamer sizes are actually from .374 to .3755", and not all of them are as sharp as I would like... I was not overly impressed with the idea of using the reamer backwards. No taper to start the hole concentrically, and all the loading on the sharp corners of the flutes. I think it would tend to make oversize holes with a rough bore that is off center. A sharp piloted reamer with a tapered entry would be the best bet for keeping the holes centered, to size, and with a smooth surface. Actually, something like a scaled down king pin reamer set would probably be about ideal.
 

HolyHarp

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#21
20180609_130556.jpg throttle body is cast iron or cast steel. I might be able to find some drill stock to turn and grind into a tool.
 

Downunder Bob

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#22
There is a very simple way to fix this, it's rough and ready, but it's quick and will be a lot better than what you have.

I'm assuming the carby is out of the vehicle and on the bench. First how bad is the slop in the bush and shaft, again i'm assuming it's pretty bad

Remove butterfly shaft from carby and clean it up as much as possible. in a lathe with a fine file and emery cloth, make sure it is parallel along its length. Clean out the holes in the carb body. clean with acetone or similar solvent. apply some silicone mould or die release to shaft and assemble the shaft with butterfly plate, into carb body,

If possible get a very thin section "o" ring onto the haft at the inboard section up against the butterfly plate, if not possible twist up a length of teflon tape into a fine string, wrap this around the shaft and stuff it into the hole. push it right down to the butterfly plate on both sides, this will stop the adhesive from getting right through.

Now mix up your Jb weld, bondo or whatever petroleum resistant stuff you can get. Make sure the butterfly is fully closed this will help to align the shaft in the correct position, Press the mix into the gap between shaft and hole in housing, clean off outside and let cure.

remove teflon tape from inner ends of shaft you may find an "o"ring pick useful here, Then you should be good to go. If this operation is well done the results are quite good. Not as good as a new one but a heck of a lot better than a worn one, and no special skill or tools required.

The only problem that can occur is if you haven't applied the silicone die release properly to the shaft. an alternative is to use a teflon spray that dries and then a thin smear of grease.
 
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NortonDommi

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#23
It's a Nissan keep it Metric. Locally I can buy a set of 10 machine reamers 2 - 10 mm for NZ $60 and I've seen them cheaper. Thailand makes a LOT of tools so should be available local to you and cheap.
I regularly make bushes and shafts for carbs on old vehicles and small engines. Aluminium tube is good for bushes or bronze.
You have not said what equipment you have access too. You could do the job with a drill press and quality drill bits and have success if just making and fitting bushes. As C-bag said making a jig is the key to success. You will need a mill with a slitting saw to make a shaft though unless you are a god with small bits and a hacksaw or is the butterfly mounted in a rebate? If it is a vice and a file is all that is needed apart from a drill and tap for the screws. Are there O-rings fitted? Some carbs have them on the outboard ends of the shaft.
As a last resort from broke days living in the wop-wops Araldite or similar Epoxy works surprisingly well for building up worn shafts and can also be used to lock bushings in place if you don't have Loctite.
Also what Downunder Bob said.
 

C-Bag

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#24
Right now the engine dies when the clutch is disengaged and the accelerator is not pressed - it dies at idle.

I'm thinking of looking for a used carburetor at a wrecking yard.
THIS to me is the most pertinent info that should have been mentioned earlier. So if you screw the idle mixture screw all the way out, or even in and out, it doesn't matter? Can you even get to the mixture screw? Here in California it was behind a soft plug and you had to remove the carb and drill and pry out the plug. With the mixture screw you should be able to make even a car with a vac leak run. There is a lot of hoses and stuff to that can be "internal vac leaks" like a stuck PCV or Ive even seen brake boosters leak internally.

A worn throttle shaft in my experience could never wear enough to make an engine die with the mixture screw working.

To see if it was the throttle shaft my test was while running I'd spray carb cleaner on that area of the throttle shaft while running with some carb cleaner spray. If it was the throttle shaft the idle would go up and smooth out. Also are you sure the idle solenoid is working? If it isn't it won't idle no matter what you do.
 

tq60

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#25
First stop fussing with the carb and seek out replacement as that is best option.

Next...is that why is does not idle?

Could be many other things wonky causing this.

If it has a carb and is a "smog" engine then it likely has vacuum hoses all over it along with valves and other things that control egr (one likely cause clean this first) or timing or ???

Save the carb for last as a worn shaft can be "adjusted out" via mixture until rest is corrected.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk
 

C-Bag

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#26
I have a question- just how tight was the throttle shaft to body when new? Who has THAT number? There is no lube, other than gasoline and dirt!
What I am saying, is this- If the shaft- to- body clearance has worn to the point it has become a detriment to driveability, then ANY reduction in that wear will improve driveability. As soon as you come off idle, what is the path of least resistance for airflow? If you make it TOO tight, that will surely affect driveability!
There are a lot of minutiae of carbs, especially as big and complicated as the QJ. As a certified smog mech at the time in the most stringent area in the US, stuff that was not a big deal elsewhere made it so cars wouldn't pass. With a leaking throttle plate it wouldn't pass the idle spec but would pass with flying colors at 2k rpm. This is stuff that the hobby mech wouldn't have any clue about without a BAR smog machine and scope.He could set the idle mix on that side of the QJ a little bit richer and compensate to smooth out the idle. And not until he had to have it smogged would he know it wouldn't pass.

You are right about the throttle shaft has to have some play in it. Probably .002-.004. The QJ TP was a poor design IMHO in that it appeared to have a generous boss on that side of the carb. But when you pull the shaft(which the ones I did were all Teflon coated) that boss was relieved 3/4's of the way and only the last like 3/16" was actually the bearing so no wonder it wore out quick! They usually had two humongous return springs that were often pulling in the same direction as the throttle cable! Born to die. And the TP was aluminum IIRC. Or pot metal. Been 30yrs.......
 
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pstemari

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#27
... it seems that reamers usually come with a 1:50 taper. Is this the type of reamer I need?
No, those are for taper pins. You want a straight chucking reamer, probably a new one given the demands of the application.

... I guess no one makes a .309 reamer nor a 7.86 mm reamer....
Any decent industrial supply house will have reamers in 0.0005" or smaller increments. Dunno about metric sizes, but I would assume 0.01mm increments are readily available.
 
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Downunder Bob

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#28
A quick test. Pack some thick grease or evn putty around the the carby shaft if it will idle then the worn shaft is you major problem. If it still still won't idle then you have other problems to sort out first. You may find when those problems are sorted your carby is ok.
 

Downunder Bob

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#29
Another quick and easy fix for a worn carby and shaft. No special tools or skills required. Can be done on the engine without removing carby.

Tools required,A light pair of metal shears or even good kitchen scissors will do. Warning do not use mums sewing scissors.
Materials required: Empty aluminium coke or beer can.

Method: disconnect carby linkages and remove linkage connections from end of shaft. Cut a few strips from side of can so that strip width is slightly less than length of hole in carby body, cut strips to length so that when wrapped around shaft you get a nice clean butt joint without overlap or gap. slide one or more strips into clearance between shaft and carb body until no more strips will fit. Reassemble linkages and you're good to go.This will keep an old carby going for quite a while.
 
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