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Topic Review (Newest First)
09-23-2012 09:06 AM
77amc They each have their place and following.
Long ago I had a truck with a 'self rebuilt' Q-jet and it got good mileage but the power wasn't there like I thought it SHOULD be.
Did some horse tradin and acquired a bright and shiny Holley. Spent about 30 on adapters/gaskets and linkage stuff, but It was like a new engine!! BUT
I only got about 10mpg and don't have a backfire. It will blow out the power valve. I've never heard (personally) of a Holley on a mild performance engine that got GREAT mileage..

I had a 66 Impalla with a self built 350/th350/3.31 gears with a Carter/Edelbrock 600 on it that got 19-25mpg with a 284/284 Summit bracketmaster. (...should've never sold that car) Just think if I had a 260 or something!

BUT, after reading Cliff's book, I saw where all the trash can get stuck in the Q if it's not cleaned PROPERLY. And all the other adjustments that HAVE to be addressed for them to run like from the factory.
You gotta remember that when peeps start to 'adjust' a carb, it's usually NOT in the right sequence. (Have you ever seen used carbs that have pound marks on top near the float bowl? ..that's right, tuning with a HAMMER )
I've even ran into a off idle stumble that i would have sworn it was the carb, Messed with it and still stumble.. Ended up to be the distributor. NOW, I had to go back, set the timing/advance THEN go back to the carb and re-adjust it.

The primary's are tiny for good economy and the 1 7/8" secondarys can really launch from a stop or to a passing gear.

Hope you get to figure it out, but it can be frustrating also.

E
09-23-2012 12:46 AM
jessedenny47
Junk it

I would throw that Quadjet in trash or make a door stop out of it. Put yourself on a good Holley.Sorry not trying to be mean but I have had nothing but problems out of Quadjets. But that is my opinion.
09-22-2012 08:39 PM
fasteddy_1947 Yes, was talking to a man today who is running one. swears by it. Told me all I need do is buy a 25 cent adapter plate to lift it high enought to clear manifold w/throttle vaves, and it bolts right on. Always been Chevy w/rochester and have fought successfully the push to try a Holley. My nephew swears by his Holley, but he's a Ford man too, so gotta figure. The other suggestion of the Edlebrock replacement sounds worth looking into too. A user here says he loves it. can get from local parts store, but don't know what the price range is for it. Something to do tomorrow. Either might be better than sinking a whole lot of tiime and money into rebuilding a questionable Q-JET.
09-22-2012 03:07 PM
against all odds Actually, here is another alternative to whether to buy a reman or rebuild q-jet:

The holley 4175 is the spreadbore, bolt on replacement for the q-jet. It is available brand new for about $400.

This may be an alternative for anyone not wanting to "mess" with rebuilding a q-jet or taking chances with remans. It's something i'm considering also.
09-22-2012 01:11 PM
77amc
Quote:
Originally Posted by against all odds View Post
P.S. Concerning the Rebuild vs. junk. You might try contacting edlebrock---they should/might still have unsold Performer RPM (basically the q-jet replica after they took over manufacturing rights) available. i don't think they advertise this anymore. But they did recently.

i did not want to reveal that last fact, but it appears that it's unlikely that my planets will align to make getting one a reality for me. So i though i would spill the beans.

Incidentally, i wonder why edlebrock discontinued this wonderful carburetor?
Most likely because I NEVER SAW ONE FOR UNDER 450.00.. Dang!! So ya buy the rights (with fuel injection market exploding) price them beyond reach of most gearheads, and expect to make a killing by outsourcing to Mexico (basically down the street-coast) ... And now they will probably NEVER be in production again. Way to go Vic!

Did you ever talk to Cliff? Really nice guy. Talked with me for over 25min just shooting the crap about carb/engine combo's and what to look out for as in years and linkages.

He might even have a good 'builder' on a shelf.
Heck, what are you actually looking for in a carb? I might even have ***..

E
09-20-2012 01:05 PM
against all odds P.S. Concerning the Rebuild vs. junk. You might try contacting edlebrock---they should/might still have unsold Performer RPM (basically the q-jet replica after they took over manufacturing rights) available. i don't think they advertise this anymore. But they did recently.

i did not want to reveal that last fact, but it appears that it's unlikely that my planets will align to make getting one a reality for me. So i though i would spill the beans.

Incidentally, i wonder why edlebrock discontinued this wonderful carburetor?
09-20-2012 09:32 AM
77amc I might be interested in ************

************
E
09-19-2012 10:21 PM
fasteddy_1947 Thank you for the comeback on that. Have ground out the manifold and made some 'shims' (angled seats)out of half inch hex nuts. haven't tried them yet and they're just rough-cut for an idea..just spearmenting now. Also, that Q-jet does have new throttle bushings in it so am going to see what the one got coming (maybe tomorrow) has for linkages and stuff. The book say that maybe some parts not interchangeable, so will have to get the magnifying glass out for real close look. Once I figure out what the linkages are supposed to do, can make reasonable replacements. Just waiting now for the other carb to come in the mail. Will see if can fit that manifold in the meanwhile and these shims don't work, think of something else. Thanks also for the links to the manufacturers of the spacers. Thought somebody would see the problem and make the fix, just didn't know where to look. Like said before, just don't want to invest lot of time is something that is just eventually going to end up in my scrap metal barrel. Things are looking much better, now that I see that there are respectable sources for both the information and the parts. Thanks for all the help
09-19-2012 11:23 AM
cobalt327
Quote:
Originally Posted by fasteddy_1947 View Post
Nother question: Am I going to be able to modify the Q-jet manifold to fit the later model (1994) 350 cylinder heads (72 deg center bolts) ? Or do I need to start looking for earlier heads with the 90 deg bolts? This project getting convoluted. This 350 isn't same as when I started. New block, new crankshaft, tossed the TBI for Q-jet. New heads will make it whole NEW engine. (hey I got it cheap!) I value any help and ideas I can get on this, as I don't want to make this project a lifetime chore. Thanks : )
Yes, you can mod the early intake to fit the later heads. Elongate the bolt holes and fabricate (or buy) some washer/shims to compensate for the difference in the angles. This has been on quite a few threads here and elsewhere.

If you now have TBI heads (aka "swirl port", casting numbers ending in 191 or 193), changing them will cost a small amount of bottom end torque, but will gain you a lot of mid/top end by swapping to a set of Vortec heads. The Vortecs take a different intake than either of the other earlier types, though. And they use self aligning rockers and center bolt valve covers. But they out perform all other production SBC heads by a good margin.

BTW, I sent you a PM earlier that basically said you might find that trying to rebuild a carb that's missing parts isn't worth the trouble. But depending on what's missing, that's not always the case.
09-18-2012 09:00 PM
fasteddy_1947 Nother question: Am I going to be able to modify the Q-jet manifold to fit the later model (1994) 350 cylinder heads (72 deg center bolts) ? Or do I need to start looking for earlier heads with the 90 deg bolts? This project getting convoluted. This 350 isn't same as when I started. New block, new crankshaft, tossed the TBI for Q-jet. New heads will make it whole NEW engine. (hey I got it cheap!) I value any help and ideas I can get on this, as I don't want to make this project a lifetime chore. Thanks : )
09-18-2012 08:46 PM
fasteddy_1947 The primary shaft has brass bushing already. Can feel no "slop" in it, so not going to mess with it. You are right, though: nothing like the 2g. I like the 2g. Have been running it for years and years. have had that manifold and carb on 4 different sbc's and have driven it cross the country and back. Time for something new, but don't want to start something that is going to end in scrap pile, like my toaster did this morning when I tried to fix it. {got a big barrel in back of my PU for scrap metal. every little bit helps : ) }
09-17-2012 08:58 PM
cobalt327
Quote:
Originally Posted by fasteddy_1947 View Post
Got nifty cheapo Q-jet from seller on e-bay. Was happy as that pig in slop when it came. like everything else I ever got, first thing had to do was take it apart. Being older than dirt, my second thought was to find something out about this animal, before start messing with it. Am right at home and happy with Rochester 2 bbl and have been running one on my '51 coupe (327) for 20 years (time to do something else). So, everything I read says get the Cliff Ruggles book first. So I did. Wow, this thing aint nothin like I thought it going to be. Not even close to the 2 bbl. But got it, so gotta do something with it. Wasn't worried bout specific configuration, as it eventually (maybe) going on 350 in 39 coupe. So on initial and subsequent inspections here's what apparent problems with this are. 1) It has been backfiring through the primaries. Heavy soot/carbon build-up in air passages (primary side). 2) Missing stuff: choke pull-off, choke to secondary lockout linkage (and I don't know what other linkages). 3) The throttle valve shaft was turned 180 deg w/linkage to secondary throttles turned 180 the other way. Primary throttles wouldn't close, but didn't figure out why until got it down and saw that if take linkage/levers off and turn throttle shaft 180 deg. the throttles work as they should. Once got it down and started cleaning, found that accelerator pump check valve well in fuel bowl was leaded over (?). Under the lead is the ball. the cap screw is gone. Have basically identified the original application for the carb. and am pretty confident that will be able to get stuff for it, someplace. But don't know if it is going to be worth the effort. Am wondering if anyone has any good tips, or if I should just toss it or make ashtray or something out of it. Have second (junk/parts) Q-jet coming this week. Will go from there (maybe). Right off, am I missing something obvious, and what else do I need to be looking for on this?
I feel ya' on trying to buy a decent core of eBay. The thread "http://www.hotrodders.com/forum/wort...ew-213347.html" tells some of what I went through not too long ago trying to buy a decent core.

The only 2 bbl carb that resembles the Q-jet is the DualJet. It's basically the primary side of a Q-jet and was used in the late '70s and early '80s. You prolly have a Rochester 2G on the engine now; it bears no resemblance to the Q-jet.

You can still get quite a few different Q-jet carburetor linkages. There are other parts suppliers, too.

After you get the core that's coming, see what you need and go from there. If possible- and if needed- taking some clear photos will help see what's up.

It sounds like the throttle shaft(s) were removed. Often the throttle blade screws are broken off because the peened over ends weren't ground off first so hopefully yours aren't broken. The secondary throttle shaft can be a bear to reassemble, so unless there's a real need leave it as-is.

You'll want to check for excessive wear of the primary throttle shaft. If it's excessive they can be bushed but this is expensive. There are other trouble spots to watch out for as well.
09-17-2012 08:36 PM
RWENUTS Get some parts and make it run.
Carburetor Parts for Rochester Quadrajet, 4G, 2G, Mercarb & Carter AFB, AVS, Thermo-Quad Carburetors
09-17-2012 08:21 PM
fasteddy_1947
Rebuild or junk Quadrajet?

Got nifty cheapo Q-jet from seller on e-bay. Was happy as that pig in slop when it came. like everything else I ever got, first thing had to do was take it apart. Being older than dirt, my second thought was to find something out about this animal, before start messing with it. Am right at home and happy with Rochester 2 bbl and have been running one on my '51 coupe (327) for 20 years (time to do something else). So, everything I read says get the Cliff Ruggles book first. So I did. Wow, this thing aint nothin like I thought it going to be. Not even close to the 2 bbl. But got it, so gotta do something with it. Wasn't worried bout specific configuration, as it eventually (maybe) going on 350 in 39 coupe. So on initial and subsequent inspections here's what apparent problems with this are. 1) It has been backfiring through the primaries. Heavy soot/carbon build-up in air passages (primary side). 2) Missing stuff: choke pull-off, choke to secondary lockout linkage (and I don't know what other linkages). 3) The throttle valve shaft was turned 180 deg w/linkage to secondary throttles turned 180 the other way. Primary throttles wouldn't close, but didn't figure out why until got it down and saw that if take linkage/levers off and turn throttle shaft 180 deg. the throttles work as they should. Once got it down and started cleaning, found that accelerator pump check valve well in fuel bowl was leaded over (?). Under the lead is the ball. the cap screw is gone. Have basically identified the original application for the carb. and am pretty confident that will be able to get stuff for it, someplace. But don't know if it is going to be worth the effort. Am wondering if anyone has any good tips, or if I should just toss it or make ashtray or something out of it. Have second (junk/parts) Q-jet coming this week. Will go from there (maybe). Right off, am I missing something obvious, and what else do I need to be looking for on this?

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