73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Fuel Systems and Drivability => Topic started by: Mr. Machanic on December 21, 2023, 06:38:47 PM
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Hot diggity!!!
I was looking for a doner-jet.
Found a local 1705 7213. Mine's a 8213.
I couldn't ask for better and the price was great.
To me it's worth the education.
When I worked on bikes (GL1000) I was always willing to pay for a chance to get educated. Because ignorance is way more expensive than knowledge.
I am a technical manual nut and I'll drive hours for a doner project.
Any who, this carb is about to get the works.
It has loose butterfly rods that need bushings installed.
There are rods missing and who knows what else.
My goal here is to rebuild this carb and then swap it out with the one on the truck and then rebuild that one and return it back to the truck.
This way, I don't lose the use of the truck and I still have a running carb, in case I bugger this one up beyond servicability.
Fingers crossed.
BTW, has anyone used the Kevin R. Hill book, The QJ MPG Secret...?
I've read it...the jury is still out.
I do have 4 manuals on the truck and a .pdf on QJ's. All of which I've read.
If you happen to know of a good QJ manual, please let me know.
I will take photos as I go and if you have any insight or suggestions, feel free to post...
..as long as it's not a suggestion to throw on a Holley....my high school from the same era as the truck suggested that already...he's not helpful either...lol
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I personally wouldn't run anything on a driver car but a QuadraJet if I didn't have EFI. https://cliffshighperformance.com/ is one of the goto places for Quadrajet rebuilds or info. The owner wrote this book: " "How to Rebuild & Modify Quadrajet Carburetors" available on his site.
story on how to modify for todays Ethanol gas: https://www.motortrend.com/how-to/quick-tech-ethanol-friendly-q-jet-rebuild/
Well Plugs and shaft bushing were the main issues on them from the past.
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His book was ordered last night...along with a couple others.
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This is the original 78 QJ on the Big 10.
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Here's the same 1705 QJ, just a 77 instead of a 78.
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Got it all pulled apart.
Oh, that was fun! Seriously.
In the throttle plate, the primary shaft is worn and it shows on the shaft. It's .005 or .006 undersized. The unworn diameter is .308 and the worn spot is .303 and it is easy to see the movement in the throttle body plate.
I can seem to find primary shafts. Secondarys are easy to find. Just not the primary.
Any websites that may have a good one?
Thanks.
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Looks like you pulled it from the bottom of a pool...hope she cleans up, will be watching this thread. I've done my share of QJ rebuilds with mixed results.
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What is this "thingy"?
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So....
I was not aware of this broken boss when I purchased the doner.
It was night time and out in the middle of sellers drive. (No excuses, just info)
The tube is slightly bent, but I can straighten that, or make a new one. No big deal.
The boss repair will be an interesting challenge.
But first, a bath. As my kids used to say, "It's poofy." They couldn't say, "filthy".
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The plan is to sleeve the boss.
First, the tiny raised ridges on each surface is taped off so they are easy to see.
Next the body is lightly clamped up to angle plates as the little plane is indicated flat.
Then the boss is indicated in to align the spindle to its center.
Once all of that is done, the fractured pieces are removed and then the boss is given a clean deck.
You might notice the 3/16" tube hole is not concentric to the boss, so the center of the hole is picked up and that becomes the new center.
Now the boss can be externally bored to generate a true and straight boss to receive the sleeve.
The endmill is switched out for the boring head and a minimal amount is removed to accomplish the desired geometry.
Measurements are taken and a sleeve is machined to match.
A light press fit is made and then the 3/16" hole is reamed thru to the original hole.
The sleeve was made a few thousands long and now it too is decked off to match the adjacent boss which supports the vacuum plate.
Burrs and chips are removed and it's done.
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Sorry, can't load more than 1 pic at a time.
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Another pic
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Missed resizing a pic...my bad...
Forgot to give ya some numbers.
The original boss was .312 diameter plus the draft and .870 height.
By the time it got all cleaned up, the boss was .284 dia. X .400 height.
The sleeve is .370 with a bore for the boss.
So the finished boss is .370 dia X .870 height.
That's only .060 larger than original.
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How many of you have broken off this little tab?
Well, count me as one among ya.
As part of the damage when the afore mentioned boss and tube was hit, the bracket with the vacuum actuator was badly bent. So I took a small punch and slowly worked the little metal tab open so the vacuum act. could come out It was more than she could handle and that tiny tab all but fell off.
So, do I cut another piece of metal and weld it in? Man, that is some fine work and I do not have a TIG unit. Well, the family happenins made me set it aside, but my mind was working on it while we were away.
Back home and I grabed a 1/8" stick welding rod, hammered off the flux and cut off about 5".
I ground a little step to give the solder a place to bite and cleaned it all with a wire wheel.
Set it all up on a fire brick and within a few minutes it was silver soldered in.
A little filing to get the fit and the actuator dropped in.
Once painted and ready for final assembly then the finger will get "adjusted" with a hammer. Here's to fingers crossed hopeng the silver solder can take a little "adjustment".
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You seem to have many issues with that Carburetor. I would find another that is in better condition or buy one already rebuilt. It would be about the same cost to do the repairs and rebuild your own.
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I agree. This carb is a hot mess.
But, it is doing exactly as intended and that is to serve as a teaching tool.
I did not want to tear into mine, having never tore into one.
The goal is to make a reasonable effort and possibly have a usable carb.
I have done quite a few motorcycle carbs from early 70's big bikes and there has been plenty of times when one turns hopeless. It took a only a couple of carbs to learn when it's junk.
I even made jets for one of my bikes.
I really enjoyed that learning process.
A few have said, just throw a holley on it, but where's the fun in that?..lol
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Hot Digitty X2.
I love craigslist.
I found 2 more QJ's for $20 each.
One has numbers the other looks identical but lacks numbers.
Again, these are just "teaching tools".
I have no desire to rebuild either of these, just learn from them.
When I played with bikes, there was a bike salvage yard about 10 miles from me.
They would let me rummage thru the rows and rows of bikes and unbolt whatever I wanted, as long as I didn't make a mess. Great times for sure.
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Finally, after the businesses opened back up, I went to my local bearing house and picked up some bronze cintered (a.k.a. Oilite) bushings for the primary shaft.
About an hour-ish later, the plate was done.
It went very well and was not at all difficult.
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After a little clean up, the shaft was slid in to check fit and alignment.
Boy, did that make a huge difference.
I am super tickled with the results.
Now for a good careful cleaning and it will be ready to go back together.
BTW, of the professional carb rebuild guys I spoke with, the one mentioned they don't resleeve the secondary shaft at all. Apparently, there has been binding issues with the shaft after a few months on the road.
So this one won't get the secondary shaft resleeved.
We'll see how that goes.
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That's a lot of heavy lifting Mr. M! Understandable on secondary bushings, not used very much relative to primaries.
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JohnnyPopper,
I'm not familiar with the term "heavy lifting" but I'll assume it means "not easy work".
If so, I understand. But, to me it is not hard or difficult at all.
Honestly, If someone came to me and asked if I'd toss a couple bushings in that plate, sure, not a problem and $40 would make it worth my while, and I even have the bushing.
Having a hobby of small steam engines, installing bushings and bearings is pretty basic stuff.
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I can see where your hobby skill set comes in handy. Good to know!
In '79 I came across a Fairbanks Morse Z gas engine, pre-spark plug, complete.
I restored it and got to run. My autoshop teacher called them 'johnny poppers'.
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J.P.
Was that Fairbanks the one with firetube ignition?
A friend had a MayTag washer engine that had a firetube ignition.
You heated the tube with a torch until it glowed then it would act like a glow plug and run the engine.
Cute little engine.
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Wow never heard of a firetube! Sounds ingenious.
No, this had a set of spring loaded contact points that were mechanically closed by a linkage arm from the gearing off the crank.
It had a centrifugal governor that would expand when the rpm was correct, cancelling the spark till it retracted, then the next POP.
The firing was intermittent, POP---PO PO POP-POP
I don't think this is the exact model but close.
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Wow never heard of a firetube! Sounds ingenious.
No, this had a set of spring loaded contact points that were mechanically closed by a linkage arm from the gearing off the crank.
The points were inside the combustion chamber.
It had a centrifugal governor that would expand when the rpm was correct, cancelling the spark till it retracted, then the next POP.
The firing was intermittent, POP---PO PO POP-POP
I don't think this is the exact model but close.
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Oh...
A Hit-n-miss engine.
Them be kewl too.
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Polishing the bores.
Not that I'm certain it makes much difference, but someday, somebody may look down this carb and recognize the fact that somebody spent some time on it and "loved" it...lol.
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I don't know Mr. M...
May be the pics but it looks like what I commented earlier, 'found at the bottom of the pool' with all the surface pitting.
Are you going to use a bore hone to clean up the secondaries?
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LOL...
Actually it's cleaning up very nicely.
Wait till I get the one on the truck off...it looks like a racoon took a pooh in it.
I'm using a flex shaft handpiece with 180g round wrap cartridges. My first career was as a Journeyman machinist/moldmaker, so blending uneven edges is no big deal.
The secondaries are very smoof and shiny.
I'll post pics tomorrow.
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Before and after.
Took a bit over half hour.
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Have you received Cliffs book yet.
Invaluable.
Should read through it and will give a new perspective and knowledge.
Cliff can supply all the parts you need and advice. He has a forum and I would assume you can still call him.
I prefer to run the the 76 and later APT (adjustable part throttle)carbs. They are a better design and can be electric choke.
Originality is important also.
An issue you may have is the porous casting in the float bowl can cause fuel to seep through the casting causing problems as well as the casting plugs.
The needle/ seat where it screws into the housing also.
Good possibility the idle tubes and idle channels are clogged or restricted with crud.
This is all covered in Cliffs book.
That little lever thing you were pointing to in one of the pics is an early design APT. Set at the factory.
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Thank you so much.
Yes, I received Cliff's book.
His shop is only 70 miles from home.
I am about half way thru Cliff's book.
I also have 4 other manuals.
Some good, some not.
I would love a chance to spend a weekend with him to work on Qjets.
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Update:
Ordered a choke pull off vacuum actuator.
And it won't slip into the bracket.
And here's why...:
My bracket is made from .090 thick steel.
The actuator's groove which is supposed to nest around the bracket is only .073.
It's .020 too small.
Gotta make a phone call....arrrgh.
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Good news.
I called the supplier of the pull-off.
He requested some photos and I sent a few showing the difference.
Apparently, this was a first instance of the issue and after he checked things out, a replacement has been shipped.
Kudos and 10 stars to Carbs Unlimited.
Thank you, Steve. A good guy.