Description
Product Overview
The iFJF 18025 (1825) Thunder AVS 650 CFM 4-barrel carburetor is purpose-built for off-road performance. Featuring annular discharge boosters, manual choke control, and a durable satin-finish aluminum body, this carburetor delivers consistent fuel metering through extreme angles, rough terrain, and high-vibration environments. Whether you're rock crawling, mud bogging, or trail riding, the Thunder AVS keeps your engine running strong when the trail gets nasty.
Key Features
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Annular Discharge Boosters — Superior fuel atomization at low and mid-range RPM compared to traditional down-leg boosters. Eight discharge holes per booster ensure an even fuel cone for crisp throttle response.
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Off-Road Optimized — Spring-loaded needle and seat design and tuned float levels resist fuel slosh at steep angles — no more stalling on inclines.
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Manual Choke — Reliable cable-operated choke. No electrical connections needed — perfect for off-road rigs with stripped-down wiring.
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650 CFM Flow — Sweet spot for small block V8s (283-400 CID) and mild big blocks. Enough airflow for performance without over-carbureting.
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Satin Finish Aluminum — Corrosion-resistant die-cast aluminum body with a clean satin appearance that stays looking good even after mud and power washing.
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Square Bore Pattern — Direct fit on most aftermarket intake manifolds and factory 4-barrel square bore intakes.
Compatibility
| Application |
Engine Size |
Notes |
| Small Block Chevy (283-400) |
283-400 CID |
Best for 327, 350, 383, 400 with mild cam |
| Small Block Ford (289-351W) |
289-351 CID |
Ideal for 302 and 351W builds |
| Mopar Small Block (318-360) |
318-360 CID |
Fits LA and Magnum engines |
| Mild Big Block V8 |
396-454 CID |
Suitable for stock to mild big block builds |
| Off-Road / 4x4 Vehicles |
Any V8 |
Optimized for steep angles and rough terrain |
Specifications
| Parameter |
Value |
| Part Number |
18025 (also referenced as 1825) |
| CFM Rating |
650 CFM |
| Barrels |
4-Barrel Square Bore |
| Choke Type |
Manual Choke |
| Booster Type |
Annular Discharge |
| Primary Jet |
0.095" |
| Secondary Jet |
0.098" |
| Body Material |
Die-Cast Aluminum (Satin Finish) |
| Throttle Bore |
1-11/16" Primary / 1-11/16" Secondary |
Why Choose iFJF Thunder AVS for Off-Road?
Standard street carburetors fail off-road. Fuel slosh causes flooding on steep climbs. Vibration shakes floats out of adjustment. Dust clogs vent tubes. We designed the Thunder AVS from the ground up for the abuse of off-roading — sealed vent tubes, spring-loaded needles, and a float bowl design that keeps fuel where it belongs even at 45-degree angles. The annular boosters provide better low-end torque response, critical for crawling over obstacles at idle speed. If you've ever had your rig die mid-climb because the carb flooded out, this is the fix.
Installation Notes
- Standard square bore flange — fits Edelbrock Performer, RPM, and most aftermarket intakes
- Use a 1/4" heat insulator gasket to prevent heat soak on hot engines
- Route manual choke cable away from exhaust manifolds/headers
- Set idle mixture screws at 1-1/2 turns out as baseline
- Fuel pressure: 5.5 PSI maximum (use regulator if mechanical pump exceeds this)
Frequently Asked Questions
Q: Will this carburetor work at extreme angles while rock crawling?
A: Yes. The Thunder AVS is specifically designed for off-road use with spring-loaded needle and seat assemblies and optimized float levels that resist fuel slosh at angles up to 45 degrees.
Q: Can I use this on a street-driven truck too?
A: Absolutely. While optimized for off-road, this carburetor performs excellently on the street. The annular boosters deliver crisp throttle response for daily driving.
Q: What's the difference between annular and down-leg boosters?
A: Annular boosters have 8 small discharge holes arranged in a ring, providing finer fuel atomization and better low-RPM torque. Down-leg boosters have a single discharge point and are typically used in race-only applications.
Q: Does this come with mounting hardware?
A: Yes — mounting studs, nuts, washers, and a base gasket are included in the box.
Q: What fuel line size do I need?
A: The fuel inlet accepts a 5/8"-20 thread fitting. We recommend 3/8" fuel line for engines up to 400 HP.
Q: Will this fit my Jeep CJ with a Chevy 350 swap?
A: Yes — this is an excellent choice for a Chevy 350 swapped into a Jeep CJ, YJ, or TJ. The off-road design handles the angles you'll encounter on the trail.
