Quadrajet manifolds are common as grass, but good working Q-jets seem to be few and far between (or expensive new/rebuilt from Holley) are there any sources for good rebuilders/calibrators with which you guys are familiar or less-expensive replacement equipment? Also, I've heard rebuilding older Q-jets that haven't been run in a while is nearly impossible because the internal passages are usually clogged, if that's true, is there a good way to clean them? Thanks.
i'm not a fan of quadrajets , maybe because i don't know much about them...the guys that know say that they are the best carb ...i won't argue either way edelbrock makes a spreadbore Q-jet replacment...about $450 i'd just adapt a square bore carb , like an edelbrock performer...edelbrock makes an adapter for this...part number 2732...they are about $6
Funny, we were talking about Quadrajets last night. The book a friend has says to never open/mess with the idle circuit, its just to complicated or something. My Pops likes 'em, though. Personally, my favorite spreadbore carb would be the Chrysler Thermo-quad. Great carb, a little work on them and they can flow 1000+ CFM. Had loads of experience with them, but they are UGLY. Big nasty black plastic/phenolic body. If you will be able to see it and want it to look good, go find another carb. Otherwise, hang that air cleaner low over it, and pretend it looks nice.
Nothing wrong with a Q-jet. They do have some things that can cause difficulties, and are a little harder to tune in. If a super stock racer can run 10's with them, they can't be that bad. Any old carb should be taken apart and cleaned well, including all the fuel and air passages sprayed out. As long as the throttle shafts are not worn bad, the Q-jet is something you can rebuild at home. Just pay real close attention how it comes apart, such as all the linkages and the screws holding it together. Q-jets can be adjusted for the secondary tip in by a small allen head screw under the top that controls the spring tension on the secondary flap. Not too hard to adjust if you pay attention to what it does. You can also get different metering rods and jets, but most Q-jets from the 60's to early 70's have decent jetting and rods. The later smog ones can be used with some parts swapping. Q-jets get the slang name Quadra-junk because people do not take the time to understand how they work. Not because they are a piece of shit. They are actually a very good carb for the street, as long as you set it up correctly.
Buy Doug Roe's book (HP books?) a quality rebuild kit (NAPA) and a jet set from Edelbrock. I collected a boatlaod for parts back in the eighties so I can pick and choose the cams and asorted little parts. Hit your local pick and pull and grab 4-5 carbs. The earlier the better.
I actually ran that setup on my Camaro for a while and I wasn't real impressed with it, it's like the mixture loses velocity going from the small secondaries into the gigantic holes in back, I switched to a Weiand Stealth with an Edelbrock Performer and I can't complain at all. The Q-jet's appeal to me is that it has a reputation for getting decent mileage if you keep your foot out of it and some really good engines were designed to use it as original equipment (like the 275hp 327 on my garage floor). I suppose the alternative would be to buy an Edelbrock Performer, grind the Edelbrock logo off it and paint it orange. Come to think of it, that's probably cheaper than buying a new Q-jet replacement.
My dad used to run Q-jets. He used to pick them up cheap when he lived in the south cause everyone wanted holleys.
38chevy454 Thank you for your support of the Quadra Jet. Makes me feel good that somebody else out there likes them too. My Q-jet experience comes from 12 years of owning my "other" car. My daily driver is a '70 Buick Lesabre 4-door. Its my family car(baby seat and everything) In those 12 years and almost 200,000 miles, I've rebuilt that carb 4 or 5 times. I've gotten better than 20 mpg on road trips before. This is the Buick 350 in a 4500 lb car though, and I've also gotten less than 10. It just depends how it's driven.
Later ones actually have a solenoid that would be a pain in the butt on a hot rod. If you want, just get a Tomco from one of the kiddie autoparts stores and bolt it on. I did that with a 350/350 combo and it worked great. Just tell them you need a carb for a 197* Camaro with whatever tranny you are running. $150 bucks later, you are out the door. Then buy the book and start to play.
What, no one mentioned the spreadbore Holley? Oh yeah, cause it's a Holley... That said, I second the TQ. As long as you use a post 72 Thermoquad, you're golden. Actually black plastic. Look up this dude, demonsizzler, at www.thermoquads.com . He can hook up your carb, or sell ya one off the shelf. I've had real good luck either way, QJ or TQ. You pays your money, and take your choice... Jay
If you want to use a Q-Jet, give Lars Grimsrud a call. He's a well known (at least in the vette world...) Q-jet/Distributer rebuilder and tuner. Lars Grimsrud 1285 Cressida Court Lafayette,CO 80026 303-604-6376 [email protected] He's got a website, www.tunedbylars.com but it isnt up by the looks of it. He's got a bunch of papers out on the web as well... http://www.corvettefaq.com/redir.asp?site=215 http://www.corvettefaq.com/redir.asp?site=620 http://www.corvettefaq.com/redir.asp?site=26 He's helped me in the past with assembly issues... Great guy!
Did exactly that on the Quadajet,Advance Auto had a sale and then the guys that worked there hooked me up with another 15% off(be nice to them,tell them about your ride and they will be nice to you.). Mine was said to be for a 1971 Camaro, has worked great on my 29 RPU,starts right up from cold,no bog and pretty good gas mileage. And don't forget that quad sound when you stomp it! Makes all the crack heads toss their stash!
Pretty sure the base is the same because I used one off a big Olds one time,what I noticed was the fuel inlet on them was sometimes off to the pass. side or straight out the front,
I've been trying to find out the difference between a GM Quad jet and a Chrysler Thermo jet. I have learned that Rochester and Carter made Quad jets and I'm not sure who made Thermo jets for Chrysler. Anyone?
Q-Jet . The most versatile and tuneable carb ever made. 750 Q jets were used by GM on everything from the 230 OHC six to the 500ci Caddy. The Super Stock cars are now in the 8's ,running them. I've built hundreds of them ,since about 1970. You don't want to start with a core that's had water in it. You'll never get the jets out of them, amongst other problems. I like the large primary ,1.21 venturi (800 cfm) 75 and newer emissions version. Forget about the 81 and newer feedback models with the plug on top . Needs a computer to adjust primary mixture. I didn't write the book on them, but I AM in the book (Doug Roe's Rochester Carbs)
theres supposedly a great Q - jet rebuilder here in the Motor City..Acme Carb in dearborn..Ive been to the place many years back and ive heard good things about them.. I spent something like 300 or so bucks on what was supposed to be a new Q-jet that was never used on a car..(so NOS?) not nitrous.. anyways..its a complete un tuneable POS..and it will probably cost me another 150 to get this Acme guy to get it right.. Hell all that money and time spent..I wish i had known about Dickster 27 before i parted ways with my cash..I could have gotten closer to having a 3X2 on my 327 by now and it would F-Ing work!..sorry for the rant.. ive heard thay can be good carbs..I just have shitty luck with this one
The Rochester quadrajet was released on 396 Chevrolets in 1965. Some 7 nanoseconds after the first engine was started, the term quadrajunk was applied; and (my opinion, richly deserved). But most new products have "teething" issues; and Rochester had lots fewer than Holley when the end bowl units were released in 1957. I knew many mechanics who could not say the name Holley without coughing. Anyway, Rochester fixed one of the major issues in 1966, another in 1967, and another in 1968. The 1968 carbs were REALLY decent carbs. The final major issue was fixed in 1970, and (my opinion) the Q-Jet was the finest street carb available at that time. Get the newer book on Modifying Rochesters written by Cliff Ruggles. Friendliest carb book I have read in 50 years! Carter built millions of Q-Jets for GM as original equipment. These carry the GM 7 digit part number, are are identical to the same numbered Rochester Q-Jet except for the text "made by Carter". Carter also produced a series of aftermarket replacement Q-Jets, that carry the Carter 4 digit followed by the letter S number. While Rochester did not produce aftermarket Q-Jets, thus did not publish ratings on the various models; it is commonly accepted that the small venturi (early versions) are 750 CFM, the single booster versions 850 CFM, and the larger venturi (a few 1971~1974, and most 1976 and newer) were 800 CFM. Carter released the racing versions of the thermoquad in 1969. There were two sizes: 850 and 1000 CFM. The first production versions of the TQ were released in 1971 and were 800 CFM. Most of the pre-1980 versions are either 800 or 850 CFM. Some of the post 1980 versions were only in the 550 CFM range up to 850. Post 1975 can be difficult to deal with because of the large airbleeds (smog emission). Again, my opinion, but the 1972 and newer TQ's superceded the Q-Jet as the world's finest street carburetor (and also great for racing in a straight line). The performance TQ's were/are part numbers: 4846s - 850 CFM manual choke (racing) 4847s - 1000 CFM manual choke (racing) 9800s - 800 CFM GM linkage electric choke 9801s - 800 CFM Chrysler linkage electric choke 9810s - added an EGR port (with plug) to 9800s 9811s - added an EGR port (with plug) to 9801s. There are four generations of the TQ. Parts are not necessarily interchangeable among generations. The four generations are: 4846s and 4847s (press-in jets) 4846sa and 4847sa (screw-in jets) 4972s and 4973s (first production, screw in jets, but different than generation 2) Everything else. Jon.
Q-Jets can be great and one of the best performing carbs. The problem is there is alot more parts to them and the right parts for a specific combo to customize it for your specific ride can be very hard to find. Therefore my favorite spreadbore carb is the 650 or 750 cfm spreadbore holley. The ease of a holley plus the better mileage and low speed throttle response of a spreadbore.
Probably not, but the later SBC EGR intakes really cook the base gasket in that area. Something to look for.
Just look up "Cliff's High Performance Q-Jet" and you well be very happy!!!!! I had to wait in line to get my Q-jet from Cliff, but well worth the wait for the performance.
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