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Old 01-14-2020, 08:38 AM
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What is the best carburetor?

I know this is a very broad question that will be specific to each application and personal preference. I have a 1969 Buick Wildcat. I just replaced the 430 with a fresh .030 over 455 upgraded oiling system. TA performance stage 1 aluminum cylinder heads, mild hydraulic roller (dosent require a stall and plenty of vaccum) TA roller rockers, Edelbrock dual plane intake with square bore or spread bore carb pad. Big tube headers and 3 inch exhaust. MSD style ignition. The car is a cruiser that will go on pretty long winded trips, I want something dependable but not sacrifice too much on the performance side if I do want to have a little fun. I'm leaning towards an Edelbrock because I've had good luck with them in the past. I've read a lot of good things about quadrajets if they are built properly. I dont have anything against Holley carb's just not familiar with them. Thanks for reading guys and looking forward to your opinions!

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Old 01-14-2020, 08:53 AM
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The Qjet is arguably the most sophisticated 4bbl ever built. Personally I prefer them on street-driven cars. The small primaries and large secondaries are a nice compromise for cruising and performance. Most people who crap on them lack the patience or skill to set them up properly.
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Old 01-14-2020, 08:55 AM
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Is there a "guru" I should order one from or would you go with like the brand name "Jet" quadrajet?
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Old 01-14-2020, 09:45 AM
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There is not one carburetor that is the best of everything and the best carburetor there is as all three styles the Qjet and Holley along with Edelbrock all have some pros and cons when it comes to certain things and areas of advanced tuning and parts available that you can get for the three different styles. For all out performance Holley is the best for getting the most advanced tunning you can get but fuel mileage is not one of its strongest points compared to a Qjet or to a lesser degree a Edelbrock carb.

The Qjet can perform well in certain applications if modified to where it needs to be but was never meant to be an all out performance carb like most holley carbs are and neither are Edelbrock. The Qjet is a slightly more complicated carb to tune for performance stuff since they were meant more for factory built engines and not race engines vs Holley carbs and you have to do some major modifications and recalibration on them that most carb tuners out there don't know much about and there is so many various Qjets because of changes over the years it can be tricky to get one that is the right one for certain applications.

It can be made good to work well is street and strip but will need a lot of changes done to it to run with engines with big cams and high flowing heads etc but the Qjet is the hands down most efficient carburetor for fuel mileage wise as it has such small primaries and bigger secondaries to allow the big flow if needed. On holley carbs they are easy to adjust and have way more easier ways to super fine tune them vs a Qjet or an Edelbrock and more parts are available to get for them but they won't give as good as mileage but still can get good mileage if tuned good but you will never get it as close like a Qjet or slightly lesser Edelbrock.

Edelbrock is kind of like a middle ground carburetor as its easier to somewhat tune and adjust certain ares on the carb vs a Qjet especially the AVS versions and is kind of like a more simple Qjet but it still won't get quite the fuel mileage the Qjet can but they are easier to setup for a daily driver vs a Qjet for the average carb guru tuner who does not know advanced tuning on carbs which I am basically saying the guys who don't know how all the circuits transition from one to another and how they all need to be tuned together and not just the changing rods or jets and turning screws and that is all which is just basic tuning.

That is why a lot of people who don't know advanced knowledge about carburetors don't like holley carbs as they only know basics about them like changing jets and adjusting the idle mixture screws and thats it but it takes way more then that to tune them and the thing with most regular holley brand carbs they don't give one options to advanced tune the carburetor such as the idle circuit by having the ability to change out the idle feed restrictors in the metering blocks along with the power valve channel restrictors but with quick fuel brand holley carbs and others like them they do give that option and its like changing out the metering rods on a Qjet or an Edelbrock carb to fine tune the idle circuit which effects the calibration of the carburetor to be more rich or leaner while cruising around town.

On basic holley carbs like the old vacuum secondary 600 1850 model or the 3310 750 vacuum secondary carbs or old double pumpers you can't change those areas on them carbs without having to modify them to give better street manors for minor engine builds and really fine tune them to give a way better tune then just out of the box and just only changing jets and adjusting mixture screws. They are all good but one just needs to really learn them inside and out and know what needs to be done get them tuned to there full potential to get the best performance out of them for the application there going on.

I have owned edelbrock carbs and many styles of holley carbs and for me I know a lot about carburetors and I have gotten the best results with holley for all out performance vs edelbrock and not saying edelbrock can't work well as they can but if you look over 75 percent of the folks who run all out racing motors will most of the time will be running a holley style carb for that reason. But that is just in my experience and research on the subject like this.
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Old 01-14-2020, 09:46 AM
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The best known QJet guru is Cliff Ruggles. SMI does a very, very good job as well.

If you're an Edelbrock guy, look into the 800cfm AVS2. This is an AVS carb with a set of annular boosters in the primaries, for 300 and change NIB.
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Old 01-14-2020, 10:31 AM
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I have used Rochester Q-jets since I had one a my new 1969 Firebird 400.

I recently purchased a factory rebuilt 1970 Rochester 800 CFM Q-jet from a local parts store and immediately had it up-graded by a local rebuilder who specializes in high performance Q-jets. I then installed it on my 1962 Chevrolet that has a 350 CI engine. The shop did the usual up-grades but I don't know what they were.

In addition to having a Q-jet up-graded by a specialist, I recommend using a 1967-1970 Rochester Q-jet to start with. Avoid buying any of the 1971-up Q-jets.
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Old 01-14-2020, 10:53 AM
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I admire the modularity and tunability of the modern Holley-style carb; but to be realistic with myself, they're WAY more than I understand. To me, its like custom valving shocks; yes there are people who need them, but Im not one of them and i'll probably get myself all kinds of screwed up trying to play with my new toys. Excessive adjustability is a blessing and a curse. If you aren't good at taking notes and making incremental changes? Ridiculously adjustable things probably aren't your friend.
That doesn't mean you can't learn, but start small and keep a carb around that might have less fine tuning capability, might give up some mileage, but doesn't stink up the neighborhood or go dead lean and torch a piston. Keep that on the car while you get your head around tuning a modern Holley carb.

At this point in my life, (Im 38) I'm probably better off learning EFI software than getting elbow deep in a Dominator.
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Old 01-14-2020, 11:08 AM
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I’ve had a couple smi quadrajets.
He’ll tune it for your set up.

https://www.smicarburetor.com/
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Old 01-14-2020, 11:14 AM
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Thanks for all the input guys, I havent completely ruled out some type of fuel injection either I really didnt want to get into plumbing fuel pumps and finding one that will work with my intake. Not saying it's off the table just leaning more towards a carb.
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Old 01-14-2020, 11:30 AM
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I traded the Rochester Q-jet on my 1969 Firebird 400 race car for a 1966 Pontiac GTO tri-Power and lost 0.5 second the quarter mile.

After that, I quit drag racing with my Pontiac Firebird 400 and bought a 1963 Pontiac Catalina 421 HO and had it professionally restored for show only.

A 1966 Pontiac Rochester tri-Power looks good but it only has 650 CFM wide open, whereas a Q-jet has 800 CFM wide open. The Q-jet on the Pontiac 455 HO has 850 CFM wide open but those Pontiac 455 Q-jets are difficult to find in rebuildable condition.
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Old 01-14-2020, 02:22 PM
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The Edeldrock intake with dual square and spread bore bolt patterns is throated to clear the spreadbore secondaries. For squarebore carbs this often causes weird effects when their secondary throttles suddenly dump into a large open area. But your build seems aimed at a mild build and use so sweating high rev issues is probably not something that should keep you awake into the wee hours of the morning. It also is a manageable problem be simply using a tapered adapter between a square bore carb and a spread bore machined throat of the mounting flange.

EFI is tough to beat with a carb for overall fuel economy, easy start up, and smooth drivability. Next down the easy to live with chain in the QJet and Thermoquad these are spread bore carbs, they are out of production so the only sources are rebuilt or rebuildable off various seller sources like EBay, Craig's List, swap meets, etc. They are metering rod carbs as are the Edlebrock Performer AFB and Thunder AVS and AVS2, also, the Holley Street Demon which are square bore carbs. The Street Demon designed by Barry Grant but sold through Holley is something of a major redesign to the Carter 'cum' (latin for following from) the Edelbrock AVS; it is a nice unit that puts the jets on extensions from the top cover instead of facing up on the bottom of the float bowl. This eliminates any problem with dirt circulating with the fuel from getting into the jets.

The standard Holley layout that is available in many forms from mild street to NASCAR. Here it takes enough self control not to overbuy capabilities in tuning and flow than you need, it is easy to buy your way in well over your head. The Holley uses fixed jets with a separate diaphragm operated enrichment valve. Not better or worse than metering rods, just a different approach. It and the Summit carb is dialed in with jet size and power valve cut in vacuum where the previous paragraph carbs use a vacuum piston and resistance springs to manage a stepped metering rod that passes through a fixed jet. The Holley and Summit can be found in square or spread bore models. The Summit is basically a major redesign of the 1960's Ford 4100. The top comes off rather than the end bowls detaching from a main body and it uses annular boost venturies. Inside the configuration is a bit Carter/ Edlebrockish in the float bowls they are just positioned end to end instead of side to side, but you find the jets on the floor facing up. Jets are standard Holley fare and it functions much like the Holley with fixed jets and a diaphram, vacuum, operated power valve.

So there is a broad range of selection when it comes to carbs. The top end Holleys are very tunable, but to use it you really need to be well grounded in carburetor functional theory else you get overwhelmed making complecated changes to solve otherwise simple problems. The less complicated models of everybody's carbs are more plug and play, not that they can't be tuned but generally their basic designs subdue the ability of the end user to do strange things that can allow the tuner to get lost in the near infinite possibilities when things goes wrong.

I got a very nice AVS that way, the guy couldn't tune out a rich condition. I happened to be at the parts store where the manager was refusing to take it back because he had been in it thus voiding the warranntee. He was really mad and said he'll just throw it in their junk barrel. I said I"ll give you 50 bucks for it. He shoved it front of me on the counter, I pulled out my wallet and gave him a nice crisp fifty then ordered a rebuild kit. Once on the bench I discovered one of the floats had a little fuel in it. Ordered a set of floats, put the jets and rods back to stock, corrected his misassembly of the seconday actuation system and choke, misadjustment of the air valve in which he bent the shaft slightly so he tried way beyond spring pressure to force it to work, it didn't, I fixed that. Bolted it on my Frankenmouse for a test, its been there for a year; I liked it so well, I just left it. My only trimming was to up the primary and secondary jets by one size as I run excessive compression and wanted to cover any detonation possibilites with a little extra fuel for chamber cooling. Meanwhile I messing around with cross breeding a spreadbore Holley, adding complication where it isn't needed just scratch an itch I have.

Bogie
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Old 01-14-2020, 02:23 PM
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The best ones are the free ones that still run good but baring one falling from the sky it's hard to go wrong with an off the shelf carb from a Carb company. "Of the Shelf" as opposed to a custom built. It's gonna cost a little more than a generic catalogue type but not as much as a fully custom built and still very very close in calibration. More so than a generic one from a paper book.
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Old 01-14-2020, 04:29 PM
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You're exactly right in the sqaure bore to spread bore adapter bogie I had to do that on another Buick I had. It had a "dead" spot in it and that corrected it.
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Old 01-14-2020, 04:34 PM
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I really want to try one of these FST Performance RT-X Series Carburetors 42750XB

But, it you drive it alot I would go for the Holley or FAST TBI fuel injection, the ease of tuning and driveability is just better.
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Old 01-14-2020, 04:48 PM
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I purchased a rebuilt Rochester Q-jet from Rock Auto parts and had it modified locally.
I ordered a Q-jet for a 1968 Chevrolet with a 350 engine and a manual transmission.

I received a Rochester Q-jet, no. 7029203. That is a carburetor for a 1968 Chevrolet Rochester Q-jet with a 327 or 350 engine and manual transmission. It is for a divorced choke.
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