Description
Product Overview
The iFJF 1901 Thunder AVS2 500 CFM carburetor is the next evolution in the Thunder carburetor lineup, featuring enhanced annular flow boosters for even finer fuel atomization. With 12V electric choke, non-EGR calibration, and a clean satin finish, this 4-barrel is purpose-built for small cubic-inch V8 and V6 engines where crisp throttle response matters more than maximum CFM. Ideal for restomods, street rods, and daily drivers with 260-327 CID engines.
Key Features
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AVS2 Annular Boosters — Second-generation annular discharge booster design with improved fuel distribution across all 8 discharge holes. Noticeably smoother idle and better tip-in response than first-gen designs.
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500 CFM Precision Calibration — Calibrated specifically for 260-327 CID small block V8s. Avoids the tuning headaches of oversized carburetors on small engines.
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Electric Choke — 12V automatic choke with adjustable housing. Cold starts in any weather without a manual choke cable.
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Non-EGR Design — No EGR port or provisions. Ideal for pre-emissions vehicles, off-road builds, and engines with EGR systems removed.
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Satin Finish Aluminum — Clean, understated appearance that doesn't yellow or discolor. Resists fuel staining and corrosion.
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Quick-Change Secondary Metering — Swap secondary rods in under 60 seconds with a screwdriver — no carb removal needed.
Compatibility
| Engine |
Displacement |
Best Match |
| Chevy Small Block |
262-327 CID |
Mild street cam, stock heads, dual-plane intake |
| Ford Windsor |
260-302 CID |
Stock to mild build, great for early Mustangs |
| Jeep V8 |
304-360 CID |
Good for Jeep CJ/Wagoneer with square bore manifold |
| AMC V8 |
290-304 CID |
Direct fit on square bore aftermarket intakes |
Specifications
| Parameter |
Value |
| Part Number |
1901 |
| CFM Rating |
500 CFM |
| Barrel Type |
4-Barrel Square Bore |
| Choke |
12V Electric |
| Primary Jet |
0.095" |
| Secondary Jet |
0.095" |
| EGR |
Non-EGR |
| Finish |
Satin Aluminum |
Why AVS2?
The AVS2 upgrades the classic Thunder/Edelbrock design with annular flow boosters — the same technology used in high-end racing carburetors. Instead of a single fuel discharge point, each booster has 8 precision-drilled holes that create a cone-shaped fuel mist. The result is more complete combustion at part throttle, smoother transitions, and fuel atomization that rivals EFI at a fraction of the cost.
Frequently Asked Questions
Q: What's the difference between AVS and AVS2?
A: The AVS2 uses annular discharge boosters (8-hole ring) instead of standard down-leg boosters, providing finer fuel atomization. This results in smoother idle, better throttle response, and improved part-throttle fuel economy.
Q: Does non-EGR mean I can't use it on a street car?
A: Non-EGR simply means the carburetor does not have exhaust gas recirculation ports. It works perfectly on street cars — especially pre-1975 vehicles that didn't have EGR or vehicles where EGR has been removed for off-road use.
Q: Can I use this on a 350 Chevy?
A: A 500 CFM carburetor may be slightly restrictive for a built 350 at high RPM. For stock or mild 350s, it will work but may limit top-end power. For performance 350+ builds, consider our 600-650 CFM options.
Q: Does this come with a fuel line and filter?
A: A 5/8"-20 inlet fitting is included. The fuel line and inline filter are sold separately — we recommend a 3/8" braided line with serviceable filter.
Q: How do I set the idle mixture?
A: Start both mixture screws at 2 turns out. With engine warm and choke fully open, turn each screw in slowly until RPM drops, then back out 1/2 turn. Adjust idle speed to 700-800 RPM.
