Hello! Putting a pencil to paper to plan out an engine build for my '57 Chevy 3100. I reaaaaaaaly want a 427 big block. I don't want a later fuel injection setup, so I'm looking at carbs. I really like to spreadbore configuration because you can cruise on the quarter-sized primaries, but nail the pedal and kick in the monster 2 1/4" secondaries with that cool-sounding "whuahhhhhhhh". The obvious choices (for me, at least) are Holley vs. Rochester Quadrajet, so I have a few basic questions. How "buildable" are Q-jets? Can you change jet size etc, or are you stuck with the configuration of that particular carb? Do Holleys have any inherent advantages over a Q-jet or vice versa? Are there any particular models of Q-jets that are factory high performance models, or are there any that are particularly desirable vs. others? I picked up an early Q-jet at the Lake Compounce swap me for $15. It's a core for sure, but it's a side feed gas line (vs a straight in) set up for an old-school bi-metallic intake mounted choke coil. It's the type I'd like to use, but I'd like to know if I'd be wasting my $$$ before I send it out to have it rebuilt/rebushed, etc. Thanks... Chris
Before you invest any money in a Q-Jet rebuild check the CFM size and application for your particular combination needs. They are a great carb and easy to rebuild yourself, read all you can on any upgrades or mods needed. Nothing wrong with a properly built Q-Jet but if your not a do it your selfer and want plug and play get the Holley......................
I love Holleys but Q-jets have their advantages too. No carb is going to be right for your particular combo without some tweaking. If you like the q-jet and want to learn about it, go for it. Devin
Check the carb for original app. as stated and for throttle shaft clearance. also the soft plugs in the bottom of the float bowl need attention as they probably leak. There have been several fixes for this over the years and some were better than others. I think that Q-jets are pretty tunable although the secondary tip in can be tedious to get right. JMO
I would go with the Q-jet. Make sure to get a good CFM model. Two places that need attention are the throttle shaft bores in the base and the well plugs mentioned.
Q-jet or Holley, I don't believe that one is any better than the other, one if just different than the other. There is really no way to compair them they use a different metering system. I prefer Holleys over the Q-jet, it is a personal preference. No way to tell you if your core is rebuildable, I am not sitting right ther with you. But either as a rule can be rebuilt if you are competant. I don't have a 427 to sell you or you would be on your way to pick it up, if you really want a more typical GM carb and want it to be performance oriented you should be looking for a carter AFB. I had one once that was 850 CFM off of a caddy but the AFB that would have come stock on your 427 will probably suffice unless your 427 turns out to be a tall deck engine, they were a low compression truck motor.
Bean - Do not have an engine on hand, still in the early planning stages...although if someone came up with a rebuildable 4 bolt main engine at a good price, sure, I'd be on it. I've actually been looking, but it seems as if people around here want huge dollars just for a block. Saw a complete, running, built one on CL about a year ago for $3000, but I didn't have the truck at that point. I've rebuilt Q-jets in the past...it's not that hard, but as everyone mentioned, they typically need more than just a kit. I'm not set up to replace the soft plugs or rebush the throttle shafts, that's why I would sent it out. Chris
I thought about putting a spread bore on mine for the same reasons. But I never did because I figured any gain in fuel economy would be offset by that "that cool-sounding "whuahhhhhhhh"" every time I put my foot in it.
I have a '57 Chevy P/U with a 427, GM 400 trans and an Edelbrock carb which will be replaced with a Q or Holley. You may want to consider intake manifold selection and availability before committing on carb. Seems strange you are starting your build around a carb first but guess you have to start somewhere..........................
q-jet is a good carb but i have been using holley for a while, i built my 34 about ten years ago with a holley and it has been a good performer, also have a holley on my 29 been running it for two years, both with 351's make your own decisions and have fun
There is a third option you did not mention. Carter produced thermoquad spreadbore carburetors in 800, 850, and 1000 CFM. Which carburetor is the best? The BEST carburetor for YOU is the one with which you are currently most familiar; or want to learn about. Personally, I recommend (and use on my own vehicles) Carters. All three brands can be modified; however the advantage here is Holley, as every parts store in the universe carries parts for Holley. There are more Q-Jet parts available today than there were 20 years ago, but still mostly available mail order only (unless you live within driving distance of one of the Q-Jet gurus. Carter parts, at least for the thermoquad, are pretty much mail order only, but they are available. Jon.
I first got my sbc t-bucket on the road with a spread bore 650 dp Holley, I then changed it to a standard square bore 650 dp Holley. That square bore was a little faster over all but it sure didn't kick you in the pants like that spread bore when you dumped it. I wouldn't look at anything less than a 850 cfm on either the quad jet or the Holley spread bore, that's what the factory put on them.
My wife's '69 427 Corvette has a 650 cfm, speadbore Holley, Q-jet replacement carb. It's been a great carb over the years and routinely turn out 17+ mpg's. Plus it helps the BBC make a TON of torque throughout the range. I highly recommend one for any mild BBC.
Your 1st sentence I really want a 427. Better work on a 2nd choice before worrying about a carb. 427s are getting scarce except for the truck and bus engines. The argument on the Holly and the Quadrajet is like Chevy versus Ford . If you have enough green you can own a 427 tommorow.
most Q-jets were 750 cfm but the big 500 caddy's and I think olds and Pontiac 455's used an 800 cfm version. you can tell the difference by looking down the primary venturi's . 800's will be visibly larger. q-jets are a little more complicated to tune due to having to remove the top of the carb to get to the primary jets&rods, and etc. but properly tuned they are the finest street carb made. there is an excellent book out called Rochester carbs that has extensive tuning and modification info. I always wanted to try 2 Q-jets together on a big block, cruise on the tiny primaries then slam those huge secondaries open!
Q'Jet and Thermoquad have tuneable midrange. Holley does not really have a tuneable midrange. Drag-only, or drag-biased = Holley Street = Q'Jet or Thermo. Just MHO Cosmo
Just FYI, Quadrajets come in 3 sizes. 750cfm is the most common, big GM engines were sometimes fitted with an 800cfm version and later Edelbrock bought out an 850cfm version #1910. After much research I discovered how to tell the 800cfm at a glance. This is especially useful if you have only one carb in your hand and can't compare two next to each other. The 800cfm Quadrajet has a bump on it's 3rd venturi that you can't miss once you know what you're looking for. Here's a picture I made up for a Buick forum I used to run. You can see the "bump" on the right hand side. If you see a pile of Q-Jets at a swap meet always stop and open their primary choke flaps and peer inside. Buy any 800s you see, they are desirable. I like Quadrajets for the street for the reasons mentioned above, good economy when driven lightly but that whoosh you get when you stand on it and the rush from (correctly tuned) secondaries is legendary and makes a great sound.
Passenger car 427's never came with AFB carbs, although old Caddys came with AFB's none had 850 cfm .
I'll offer a bit of a wake up. If you want a 427, b u i l d o n e. 454 blocks, while not cheap, are plentyful. Guess what? SAME BORE!! You may need to buy 2 engines, or just look for a 396 crank. Guess what? SAME STROKE!! the only 'special' parts you need are the pistons and they're available without promising your 1st born son. I asked around at a swap meet once and found 1 guy had 2-3 396 cranks for $200ea. Get a good 454 block for under $500, you're in. Heads, rods, all easy to come by beuase the rods are the same. 4 bolt mains? Seriously? SERIOUSLY? I ran a roller cammed 477 with 11.5:comp on 2 bolt mains. Trap speed was 7200, and even when I accidently stuffed about a 400+ shot of happy gas through it and tore it up, the mains and crank laughed it off like a mosquito bite. Can't say the same for the rod, piston or bore but, ah well, it was fast. You got great advice about selecting the overall package with regard to manifold, cam, etc, but I'll add that you want some oval port heads for this. Avoid the truck "peanut port" heads, but any others will do with the right compression/cam selection. Me? I'd build a 427 with about 10.5 compression, hydraulic roller, old school Tarantula or Scorpion intake (the twisted one), a Holley 780 df/dp dialed in for the best cruise/WFO conditions. You'd be all in around $3K if you shop smart and have a good machinist. BBC assembly is the easiest of all V8s IMO. DO NOT DRINK THE GROOVED CRANK KOOLAID!! Walk away if someone says you need it. I'll be glad to assist in numbers and ideas if you get some parts together. A motor like that would have a very early "hot rod" vibe, doncha think? It would beat that "WOOOSH" sound all to hell in the power/kool dept...
I am not a proponent of Holley carburetors,,,most guys I know think they are the best carburetors available on the other had I have had a couple over the years and had various problems but nothing major. On a hot summer afternoon I was sitting at a red light in my 40 Ford with a SBC and the Holley loaded up and I imagine the float stuck and the engine caught fire. That was the end of Holley's for me,,I know that could have happened with any carburetor but I wanted something else,,the Quadrajet was next and sense I am not one that has to fool with a carburetor all the time it was a simple fix for me. Due to the lack of availability of good quadrajets I now run Elderbrocks,,I haven't experienced any problems thus far and have them on all 3 of my hot rods. Again,,I am not a carburetor tinkerer,,I put them on and drive. HRP
If you go Q-Jet, I'd recommend Sean Murphy Induction. They offer several flavors for street: http://smicarburetor.com/products/sfID1/28/sfID2/9/sfID3/32 They rebuilt my electronic Q-Jet (E4ME), including replacing the throttle position sensor and electric choke, and did a damn good job. The thing was a piece of art. Once the computer re-learned everything it ran like a champ, straight out of the box.
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