Stovebolt.com Forums The Shop Area The Engine Shop Rochester 4 Jet versus Quadrajet

IMHO best feature of QJ: the 750 primaries are smaller than most 2 bbls.

This video shows a SBC 350 disguised as a 283 but with a Holley sniper EFI. I’m not a fan of the cam he has but the engine looks old school.

In my own opinion I'm not a fan of the Sniper system. To me it feels like a cobbled setup, the fuel lines, the return to the tank and the mass of wiring. Speaking from hands on with this setup if you're going to use a Sniper it.would be best if it was planned from the start. The Sniper works no doubt, just a lot of work and not a lot of reward.

I second JonG on using the 2 barrel, it's simple and it works. With your mild cam a 2 barrel will provide plenty of power and good drivability. I did some research on the 4 barrels mentioned earlier, the cost of finding a suitable example is overwhelming, I would think you could find better use for the money.

The original 4-G or WCFB WILL give better driveability than a two-barrel.

Driven in an adult manner (only driven in anger on rare occasions ), it will also deliver better fuel economy than the two-barrel.

And no offense meant to anyone, I don't understand the cost of one of the 4-G carbs as being overwhelming, especially when a Sniper is in the conversation. There is a tagged original used, but looks like rebuildable, on ebay right now for a c-note. And what is the cost of a Sniper, with air cleaner, fuel line, linkage, and learning curve?

The small 2-barrels are currently MUCH more expensive, as every hot-rodder in the world KNOWS the small Chevy two-barrel is just right as the center carb in their home-brew tripower.

Jon

Ok, time for me to learn something new.

Why would the four barrels deliver better economy and drivability vs the two barrel?

The 2-BBL has to have big enough throttle bores and venturis to handle full throttle operation, and most of them don't have a very sophisticated part throttle system. A 4 BBL can have small primary venturis that start flowing fuel just off of idle, and they can be calibrated in such a way that the first 2/3 or 3/4 of engine speed is handled by the primary barrels only. The secondaries are used for 3/4 to full throttle only- - - -opening quickly for passing, load pulling, trailering, etc. If a driver keeps his foot off the floor, the primary barrels do most of the work, more efficiently than the compromises a 2 BBL has to make.
Jerry

The primary venturii of the original 4-barrel, as Jerry mentioned, are smaller than the venturii of the 2-barrel. Thus, at the same volume of air flow, the venturii air velocity is increased. The increased venturii air velocity improves efficiency.

The efficiency change is even more pronounced when changing out a single barrel WITH A PROPER MANIFOLD AND CARBURETOR to a 4-barrel. When I replaced the single Holley on a 300 CID six with an Offenhauser 4-barrel intake and small Carter AFB, I improved fuel economy by better than 80 percent! Granted, the Holley needed rebuilding, but still.......................

Again, the design of the Q-Jet is such that the primary side is small, thus maximizing venturii air velocity.

Jon

I found a decent looking Carter WCFB. It might sit on the shelf for a while, but at least I have a carb to go with my 4 barrel intake if I ever need it.

Good explanations and examples, Jon. Thanks.

Thanks to Jerry for his as well.

Just a heads-up- - - - -the intake manifold in your picture needs a little bit of machining. Exhaust gas from the heat riser has eroded the gasket surface and will cause rough running unless it's machined smooth before it's installed. The horseshoe-shaped passageway in the WCFB throttle base carries exhaust gas from the heat riser, and over time, the gases erode the carb base and the manifold. Any good machine shop can set the manifold up in a Bridgeport mill and flycut the gasket surface a little to clean it up. There's also a thin stainless steel heat isolator plate available to protect the manifold from further deterioration.
Jerry