So I'm thinking about what I'm going to do in the next couple of weeks while the snow piles up and it stays cold. And I'm wondering if I should try to rebuild my Q-Jet and give it a try, instead of sending it out to someone like Hobbe's in NH. Debating if it would even be worth it. They would glass bead it, etc, and i'd have to soak and scrub, but hey, Carb Cleaner is cheap in a 5 gallon pail, and I can scrub, and re-soak, and small parts I can easily sandblast at work. And I'd learn something in the process.

Edelbrock or Holley have thousands of write ups on forums with pictures, etc. Can't find one with a Q-Jet.


Looking for something kind of like this, for a 70's Q-Jet.
http://ramchargercentral.com/technic...rock)-rebuild/

 

It's hard to beat the Qjet section in your Chassis Service Manual.

 

+1.

If you want extra information, Cliff Ruggles's book, or the book by the other guy whose name I always forget, are good, too.

And, remember, all of that fancy plating and stuff is really nice while the carb. sits on your bench, but once it's installed in the car, it's close to invisible under the air cleaner, and after a few thousand miles, it'll start to get cruddy, so what you can see will look just the same as before.

- Eric

 

Rochester Carburetors by Doug Roe (and Bill Fisher) has a wealth of knowledge in it on the Q-Jet.

 

I have not read the Ruggles book, but most of the diagrams and theory in the Roe book came straight out of the material in the CSM. If you are looking for info on a stock rebuild, go with the CSM. If you want info on modifying the carb for a non-stock engine, then the Roe or Ruggles books are useful.

 

I haven't read the Roe book, but Ruggles focuses on modifications, with some information about disassembly, cleaning, etc.
I liked the book, but I didn't feel that it added much to my knowledge of stock rebuilding (though it did add a little, and some people seem to benefit from reading the same things phrased in different ways).
It did induce me to remove the air bleed tubes for better cleaning, which "didn't go well," and which caused me to have to buy replacements from Cliff (the well beneath them was perfectly clean... ).

One suggestion of his was to drop the old check BB into its hole, then tap it gently but firmly with a pin punch to smooth any irregularities of the seat, before discarding the BB, which I liked.

- Eric

 

Call Hobbe's first and see exactly what you get for your money. I would consider refinishing to protect against ethanol fuel. If you do it yourself, consider Cliff Ruggles rebuild kits, a little pricier but worth it. Good luck.

 

How would refinishing the pot metal protect it against a non-aggressive chemical?

- Eric

 

x2

I also have Doug Roe's book. It's a great help and I've rebuilt Q-jets a number of times. Plus, it's cool adding to your library of car books.

As Joe said though the CSM would work fine for a stock rebuild. The only thing I would be cautious of is to make sure the CSM has a legible exploded diagram. I know some reprints have images that can barely be seen.

 

Yet another reason to only buy an original paper CSM.

 

X2 or 3, on the CSM for the carb rebuild. BTW, the digital version I have from Dave Graham literature is very good quality, and I like being able to enlarge it as needed. I have found it to be handy if you can afford having it and a original paper version.

 

Heres what i did, using the CSM and ruggles book rebuilt a good q jet, car ran great but throttle bushings needed replacement (on my todo list) so I bought a remanned q jet on rock auto for $300, i then sent back a freebie qjet to get back the core charge of $100.

i then used the CSM settings to set up the remanned qjet and swapped in my hanger, rods and jets from my good qjet that need t bushings.

The remanned carb runs mint on my car I hit the gas it goes from idle to 5k rpms. no bog no heistation

as received the main jets in the remanned qjet had the numbers ground off, the secondary air valve was way to tight and a couple other adjustments were out. so i think going thru the remanned made a difference in how it performed...YMMV

 

One hour video. I am not qualified to judge how good it is.

 

Another vote for using the CSM to rebuild. Got my 1 gal carb dip, rebuild kit, and had at it one evening. The CSM was better than the Ruggles book for the actual rebuild, although the Ruggles book gave the details about why the bits and pieces were put together the way they were and how they could be improved.

Good Luck!

 

Thank you, but no link, huh?

It's kind of customary when referring someone to a resource on the internet to provide one, seeing as how you're already there and all.

No matter, here it is:



And JPC, I think this is exactly what you were looking for.

- Eric

 

Sorry, didn't know how to do on my phone.

 

You can do it.
You have good advice above. I suggest taking pictures so you know where everything goes. Make sure you get good quality parts. (I now sell kits).
You can use carb cleaner or brake cleaner aerosol to clean out inside and outside. Make sure the internal passages are blown out and clear.
When you reassemble, if you get stuck, call or email me. I can send pictures to show you what goes where to help you through.
I can also rebuild baseplate with bushings, if you just need somebody to do that.

 

Yeah, my issue was, like other mentioned, the diagrams are almost unreadable. It's not much of a guide. :/


Hmm. Interesting. How new is the Q-Jet you got? I'll have to look through Rock-Auto. Was there anything special about the one your ordered?


Thanks Eric, I'll have to watch this a couple times!

 

What kind of copy do you have?

I can read this just fine, and an original paper CSM should be even clearer.

- Eric

 

Float level is critical, I was lucky reusing floats but that was before this ethanol garbage. If you remove the APT stop, count and write down the number of turns from seated or from removal, which makes sense to you. As said a quality rebuild kit is key like Cliff's kit. Make sure your pull offs hold and clean everything really well, either fine wire and or compressed air in the passages. If it doesn't turn out like you want, send it off to a rebuilder.

 

Note that only later QuadraJets, from about the mid-'70s onward, had the APT adjustment.
Don't go looking for it if your carb is earlier.

- Eric

 

x2

I went cheap when I bought a carburetor rebuild kit for a Holley one time and it was a mistake. Just spend the extra $10 and get a quality rebuild kit.

Plus, make sure you wear eye protection when using carburetor cleaner. You don't want that stuff in your eyes!

 

Mine was an old download, I think from wildaboutcars for the 1972 Model Year series. Maybe it's been updated, I don't know. I don't have a subscription for the site.

Your link it quite a bit better, thanks! The images on page 9, that are a little hard to see( the actual photo's of the carb) are like what all of the images on my scanned copy are like. Thanks for the link! I assume 1970 carbs are identical (except internally in rods and jet sizes for hi - vs low-compression motors)?

I should probably look into getting an original one, if for nothing else, to carefully separate the pages, make high-res scanned copies for the garage and put them in plastic sleeves.



Please don't hold my "youth" against me, but what is an APT stop, and is it that beneficial to have where I should try and get a carb with one?

 

I know it's Chevy, but check it out!

http://forums.superchevy.com/super-c...-read-up-on-a/

 

APT is "Adjustable Part Throttle". It is an adjustment screw where you can adjust lean/rich mixture at part throttle operation.
Early Quadrajet's had them in the baseplate, and the screw is very difficult to remove in most cases. Later 70's, they moved to the main body and had access through the air horn.
The APT will set the point that the primary rods descend in to the jets. By adjusting how deep the rods go, you can adjust the part throttle rich/lean mixture.

On my performance builds, I knock out the air horn plug, thread the hole and make the APT screw accessible from outside, so it can easily be adjusted.

I think my adjustment sheet attached has some pictures.

 

In addition to Carb cleaner, is there any reason I can't, or shouldn't use Isopropanol(99%) or even Cleaning Vinegar when trying to remove some of the surface grime?

My first thought is to take the carb, fully assembled, and drop it into a gallon of either, let it sit overnight, and then start from there. At least the heavy gunk will be off it it. But would that not be advantageous to the stuff on the inside?


-That's a really good idea, I like the idea of doing that. Thank You. And I appreciate the offer to help me when I get stuck, thank you very much.

 

I would advise using a purpose-made carburetor cleaner.

You can buy in in 1 gallon paint cans at the auto parts store for about $20. The can will only contain about 3 quarts.

You want the nastiest stuff you can get, which may be as strong as the commercial stuff, which is really nasty.

You will need a coverable metal container that your carburetor body will fit into, as it will not fit into the gallon paint can.

You soak for a period of time (follow the label instructions), then hose off forcefully, then blow through with compressed air.

- Eric

 

Thanks. If thats the case, I could just use Acetone or Even MEK from Work, and soak everything in it. I thought the IPA or Cleaning Vinager might be a good place to start. I didn't want MEK or Acetone strong attack any of the rods or springs, etc.

Lots of people (who easily have access to MEK) seem to have good luck with it. And disposal is easy(at work) so it might be a good alternative.

 

What year carb are you building? And yes only the later carbs had APT.

 

The "real" carburetor cleaner seems to combine a non-polar solvent and a corrosive agent (probably acidic), and will aggressively clean, while not causing damage, so long as it is used according to the instructions (soaking for a couple of days would be bad).

Acetone is a non-polar solvent, and would dissolve most if not all oil, grease, and varnish, but would not do more than that.
Vinegar might be fine as a corrosive agent to clean after that, but I don't know how aggressive it is compared to the "correct" stuff, so I can't speculate.

Odds are acetone followed by vinegar would work well, but I would advise watching it in the vinegar carefully.

Another possibility is ultrasonic cleaning - it works great with a good detergent, but you'd need a BIG cleaner (some folks have access to those at work... ).

- Eric

 

I had a "pro" do it at an auto parts store. When I got to the stage of install and running the car I then found that the job that was done, was a waste of money.

It wouldn't idle, it pinged at RPM at milder and above acceleration... The "pro" simply put a kit in, perhaps a mild soak in cleaner.

The small venturi passages were plogged. Before I realized that the primary throttle shaft passage was severely worn allowing a major vacuum leak. I bought a bushing kit and repaired that. Then to find that vacuum leak was fixed, but the thing wouldn't idle. At that point I checked around the local larger town for shops, they could work on it, have the car so they could dink a bit, put it on, try it, pull it off, try something else... That at $90 + an hour.
Took the #off carb, went to a auto store that handles GM/Delco etc, they dug the old books out, found a reman carb for that number. Company advertised the carbs are rebuilt and tuned on an actual motor.

Took it home, installed. Car instantly idled smooth like new. Only thing I adjusted was the cold throttle screw.

In short, unless ya have alot of experience why mess with it...

 

It's a '72 Carb. #7042250.


I'll bring a little bit of MEK home. Between that and carb cleaner, it should be good.



Well for one, I won't learn unless I do it.

2) It's much cheaper for met to buy the kit and do it then send it out.

3) What else and I going to do when it's cold out?

But do you remember what company the re-man carb came from? Any idea about what you spent on it? What parts store did you buy it from?


Also guys A few of you mentioned "good" kits and auto parts store kits. Besides Cliff Ruggles, who else sells a "good" rebuild kit? I'll be changing the needles and jets too, so I'll have to buy those too.

 

I would get one from a reputable parts store or contact Quadrajet Power. I'm sure you can find the correct kit for your application.

The kit I purchased for my Holley was from an aftermarket supplier when I should have bought a Holley kit.

 

I have 3 levels of kits available at my online store. I assemble parts for each kit. All from best quality individual items. And my performance kits are complete with jets, primary rods, vacuum brake/pull off, float and everything you need to refresh your Quadrajet.
And free advice and support!!!
And, if you give up on the repair, I can do any or all for you! Many people send me their base or air horn to rebuild, and they do the rest.

https://www.quadrajetpower.com/onlin...6sort%3Dnormal

 

Do they come with different sized jets, like a kit? Or do I tell you what size I want?

 

I set up the kit to match the engine needs based on modifications. Performance kits come with jets and primary rods on pre-75 Quadrajets. You can specify jet/rod size combo, or I can select for you.

 

Maybe I'm reading wrong, but the custom kit says it comes with new jets and rods (b series) too.

I'm not sure what B series rods are.

I just know a local guy to me with a stock (albeit low mileage) low comp 350(with only addition of dual exhaust) had the best luck with .073 Jets and .046 Rods. So I thought I would start there.

 

B series primary rods are for the earlier type Quadrajet 1974 and older, the 1975-1980+/- 2nd version Q jets are usually K and a different length from the early style to be followed in the 80's smog qjets on the truck with a thicker power tip M series. 73/46 is a good spot I agree

 

I run the same carb on a 70 455. If you're running it on a 350 you should be fine with a good rebuild kit. I use Cliff's.


FWIW, if you're running on a BBO like I am, you need to make some changes if you want it to run correctly. Cliff walked me through the primary and secondary rod changes I had to make so it would run well. I also had to change the secondary air door tension.

 

Remember the 30 rule , meter rod 30 less +/- less than jet for performance applications is always a good baseline. 71-74 jets and 41-44 rods cover most setups well. For a little more economy one or two sizes up on rod from the -30 rule.