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I have a '66 K10 with a fresh engine that meets '66 EPA emmision controls. Its just a simple Goodwrench, 8.5:1 compression, skeleton crate. Sitting on the truck is a rebuilt Qjet bolted to an Edelbrock #2101 intake manifold. Sitting on the bench is a Edlebrock squarebore #1406. This is what came with the truck when I bought her. Oh high performance gurus, which carb is the better for this application? Which carb is the easiest to tune for life above 5000'? Stick with the Edelbrock manifold I have, or is there a better model?

Given the application, a slow 4x4 where any power above 4500 rpm is pretty much wasted, what would be your recommendations for cam and exhaust manifold switchs?

Keep the Q-jet, they are very adaptable and can flow huge amounts of air if you make sure the secondaries can open all the way. You can adjust the secondary mixture by tweaking the spring tension on the air door (top butterfly) and the small primaries give you good gas milage and low speed performance. The secondaries meter fuel based on mass air flow so they are self- adjusting for altitude. You can get away with just richening the idle mixture screws for most situations. I used one with an Offy manifold on a Buick 225 on my jeep CJ-5. I couldn't kill it.

The other nice thing about the Q-Jet is the central float bowl, it will still operate nicely at really bad angles, it is the next best thing to fuel injection. No other carb can match it for steep grades.

For low rpm stuff, just use the stock or a mild RV cam and cast manifolds or really long headers (2 feet or longer). Most of the headers that you can buy, especially the block huggers, are way too short and hurt low rpm performance. A HEI or MSD ignition is a good investment too, it will really help your low end.

I have an aftermarket, 4x4 specific cast ehaust manifolds. As you mentioned it takes long header pipes for torque, but that puts the collectors down in harms way, and if the collectors take any type of decent hit the reulst is usually an exhaust leak up and the header/head mounting.

The QJet is a 750 CFM while the Edelbrock is a 600 CFM. Some folks have told me that I would never get the a 750 CFM to do anything but run rich given my application and altitude. You also mentioned fuel injection. What is out there in the way of kits? General pricing?

While the max flow of most Qjets is 750 cfm (some are 800), the rules that apply to Holleys and such don't apply to q-jets. The reason is that the secondaries are actually operated by air flow, and if the air flow isn't high enough to open them all the way then it doesn't. It basically self adjusts its CFM from about 150 (for the primaries) to 750 completely automatically, delivering the right mixture across the whole range. A 750 cfm Q-jet will work on any engine from 200 - 500 cubic inches without changing much more than the idle mixture and speed. I put a Q-jet from a Buick 350 on my Jeep's buick 225 and had to do very little tuning.

There are a few fuel injection kits out there but be prepared to spend at least $2000 getting it to work. You are usually better off swapping in a crate motor that already is set up for fuel injection.

Okie dokie. Got me convinced to stick with the QJet - anyone want a Edelbrock? The only thing I have lying around for a tune up guide is the Rochester section of an old 1973 Motor's Manual. I'd expect the Qjet is generic enough I can work things out from this older manual(?)

Several good auto parts stores sell a Rochester Techbook that tells how to rebuilt/tune/modify Q-jets for different apps. There were several distinct different models of Q-jets, and they have their own quirks. The only one to avoid is the one with the electrical connector on top from late '70s-early '80s. The connector is an electric power valve controlled by the primitive early emissions computers. Not the hot ticket for aftermarket use.

The older Q-jets are very popular with the V8 Pontiac crowd, as the same well prepared Q-jet will work on a 326-455 pontiac with minimal tuning.

good luck
chip

Lots of needed information to really make a suggestion, so will try the "shotgun" approach.

First, smog emission no longer need play a part in your decision (assuming you live in the USA). Federal smog emission requirements took effect with the 1968 model year. California smog emissions originally took effect with the 1966 model year; however California law SB42 rolled the more-stringent California requirements back to the Federal level for 1974 and older. Since the Federal level for 1966 wasn't, then smog testing need no longer be a problem (unless you have a local retrofit law).

Not familiar with the mentioned manifold, but use a carburetor that is matched for the manifold. If you want a spread-bore carb, use a spread-bore manifold. If you wish to use a square-bore carb, use a square-bore manifold. Don't use a adapter to adapt square to spread or vice versa.

The spread-bore design works extremely well on the street.

Q-Jets were designed for a specific application (not aftermarket). As such, migration of a Q-Jet from the original application may work well, may work OK, may work poorly. While all pre-1971 Q-Jets were 750 CFM, this is a WOT (wide-open throttle) measurement. The CFM delivered at less than WOT depends on the original calibrations.

We like to categorize engines as "torquers" or "screamers". Chevy small blocks are screamers (high RPM). Pontiacs are torquers (high torque, but not so high RPM). Mixing a torquer carburetor with a screamer engine, or vice versa; is normally going to require some internal modifications.

Biggest current drawback to the Q-Jet is tuning parts availability.

The book you should procure if you plan to do any modification of a Q-Jet (or any other Rochester) is "Rochester Carburetors" by Doug Roe and Bill Fisher, published by HP Books.

Personal suggestion for a Chevy 4x4 with a small block is a Carter TQ part number 9800. This TQ is an 800 (200 primary, variable to 600 secondary). The 750 TQ is 150 primary and variable 600 secondary. While you won't probably ever need 800 (or even 750), the truck really likes the extra 50 on the primary. Again, this is a spread-bore design, and requires the use of a spread-bore manifold.

Jon.

Sell the Edelbrock 600 on Ebay.. they get good bids.. even when they are broken..

Q-Jet, bar none. I grabbed lots of different metering rods and hangers when I was bracket racing, so there out there and easy to find the tuning parts you might need.
If the Q-Jet is from another 350; no mods will be necessary, just adjust your air door spring tension to suit your altitude.
People will give Q-Jets away because they HAVE to have a Holley or Carter AFB (Both would work, but are junk,IMHO), so picking up extra parts is a cinch.
Stay away from the 800 cfm model (it has the larger primaries). Those are for large displacement torque motors and will be too rich for a 350 sbc.
The #2101 manifold will work, or an aluminum manifold from a mid-'70's sbc will work; just block off the EGR port. The Q-Jet will bolt right up with no adapters.
Carb adapters rob your CFM, so avoid them if at all possible

I've never seen so many people agree on the q-jet. Most write them off as junk, and for good reason. The pot metal casting is junk. Another major flaw is the throttle shaft, which wears the housing and causes leaks around the shaft, requiring bushing the shaft hole. However, when you get a good one that will stay tuned, they're a good, economical carb. They do kill your torque curve when the secondaries open at wide open throttle. But for everyday driving, they're tough to beat. I only wish I could afford the Edelbrock Q-jet, it looks like a winner.

I had a slobber-jet on my Cutlass in high school/college and the only problem I really had with it was the that secondary metering wells leaked. I tried the dense foam pad that was supposed to seal up the leaks to no avail. I finally disassembled the carb and thorougly cleaned and sanded the wells. I then coated the entire wells area with epoxy and let it cure for a couple days. This stopped the leak from the metering wells. Hot Rod had quite a few tech articles about Q-jets in the day (20 years ago) and I used quite a few of their tips. If you can find a brass float for a Q-jet, I would use that. It seemed like the composite floats would eventually get saturated with gas, making the engine run WAY too rich.

Jon,

According to Edelbrock's literature the manifold is designed for use with ther 600 CFM models, their Qjet and cast exhaust manifolds. I'll look for the Rochester book. I'm a whiz with this stuff when it comes to bikes so as long as I have a guide book I can work my thorugh things.

You are on the money about the smog. I'm in Nevada and don't have to worry. One of the reasons I made the move to setting up this truck for daily use was to get away from modern smog controls. One of the reasons I went with the basic 350 crate was the power characteristics. Anyting more exotic would be a waste for this truck - give me a 60s vintage 2x4 with a high speed rear end I could enjoy a screamer. With a 283 I would have been hammering 3rd on the mountain roads. For the most part I doubt that I drive it off the torque curve. As is is, down on the flat valley floors the torque lets me get away with 3rd gear rolling stops. However, up on the mountain passes there are a couple of passing lanes just above 8000' feet where I need the secondaries to kick in crisply to put the snails behind me, especially those F350 diesels - I have a duty to make sure they understand what it means to run with the big dogs.

BTW, the engine already has the Summit HEI distributor (the one thing the previous abuser did right), but otherwise the ingnition is stock.