Are Holley 2300 and 2280 Same Bolt Pattern?

Are Holley 2300 and 2280 same bolt pattern? No — and this trips up more backyard builders than almost any other two-barrel swap. The 2300 uses Holley's own compact 2-barrel flange, while the 2280 copies the Motorcraft-style pattern found on Mopar and AMC engines. The bolt holes simply don't line up.

That mismatch matters when you're holding a used carburetor at a swap meet, or when your intake manifold was cast for one pattern and the carb in your hand is the other. Bolt them together with the wrong gasket and you'll chase vacuum leaks for weeks.

This guide shows you exactly how the two flanges differ, how to measure yours in five minutes with a ruler, and when an adapter plate saves the day. You'll also get the application lists, the mistakes to avoid, and the answers to the questions people ask most about these two carburetors.

Are Holley 2300 and 2280 Same Bolt Pattern: The Short Answer

No, the Holley 2300 and Holley 2280 do not share the same bolt pattern. The 2300 is Holley's classic 2-barrel design with its own compact flange, while the 2280 was built to replace the Motorcraft/Autolite 2-barrel carburetors fitted to Chrysler and AMC engines from the factory. Because each carburetor was designed to bolt directly to a different family of intake manifolds, the mounting holes, throttle bore spacing, and overall flange shape are different.

Here's the practical version. If you pull a 2300 off a Ford small block or an early Jeep engine, it will not bolt to a Mopar 318 intake that expects a 2280-pattern carburetor — and vice versa. The bolt circles don't overlap, so no amount of gasket shuffling will make it work without an adapter plate.

The key takeaway: match the carburetor to the pattern your manifold was cast for, not to the CFM number on the air horn. Both carbs flow in a similar range (the 2300 comes in roughly 350 to 500 CFM versions, and the 2280 around 435 CFM), which is exactly why people assume they're interchangeable. Flow is not the problem — the flange is.

• Holley 2300: Holley 2-bbl pattern, common on Ford, Jeep, and universal applications
• Holley 2280: Motorcraft-style pattern, common on Chrysler 318/360 and AMC V8s
• Direct swap between the two: not possible without an adapter

What the Holley 2300 Flange Looks Like

The Holley 2300 series is the two-barrel cousin of the famous 4150/4160 line, and its flange reflects that heritage. It's a compact, roughly rectangular casting with two progressive throttle bores and four mounting holes — one near each corner. The bolt holes sit close to the bores, giving the flange a tight footprint that fits small-displacement manifolds with limited pad area.

On most 2300 units, the center-to-center bolt spacing measures in the neighborhood of 2-13/16 inches across the bores and about 3-1/4 inches front to back, though you should measure your specific unit because casting variations exist across decades of production. The throttle bores themselves are offset — the secondary bore sits slightly rearward of the primary — which is characteristic of Holley's progressive 2-barrel design.

The 2300 pattern is the one Holley used across its own 2-barrel family, including the 2300-series replacement carbs and the 350/500 CFM models sold for universal use. You'll find it on Ford applications (where it often replaced the Autolite 2100), early Jeep engines, and countless hot rods running small 2-barrel intakes.

One detail worth noting: the fuel inlet on the 2300 is typically on the passenger side, and the choke is an integral integral-style housing on the air horn rather than a remote unit. Both matter when you're checking clearance against your existing linkage and fuel line before committing to a swap.

What the Holley 2280 Flange Looks Like

The Holley 2280 was engineered as a direct replacement for the Motorcraft/Autolite 2-barrel carburetors that Chrysler and AMC installed at the factory. That single fact dictates everything about its flange. Holley didn't use its own pattern — it copied the one already machined into millions of Mopar and AMC intake manifolds, so the 2280 would bolt on without adapters. (See Also: Are Galvanized Bolts Ok for Treated Wood)

The result is a flange that looks similar at a glance — two progressive bores, four corner bolts — but with hole positions and bore spacing that don't match the 2300. The 2280's bolt pattern follows the Motorcraft 2-bbl layout, and its throttle bores are sized and positioned to suit the Mopar manifold pads. If you lay a 2300 gasket over a 2280 base plate, the holes visibly miss.

You'll encounter the 2280 pattern on Chrysler 318 and 360 V8s from the 1970s and 1980s, plus AMC engines including the 304, 360, and 401. If your project car is a Dodge Dart, Plymouth Duster, Jeep Wagoneer with an AMC V8, or an early Jeep CJ with a 232/258 inline six fitted with a 2-barrel, odds are good the manifold wants this pattern.

The 2280 also has its own quirks: many versions use a divorced choke rod that connects to the exhaust manifold, and the fuel inlet placement differs from the 2300. When you're planning a swap, check the choke style and inlet side against your engine's existing hardware before you buy.

Side-by-Side Comparison of the Two Carburetors

Since the two carbs look like close cousins, a direct comparison makes the differences obvious. Both are progressive two-barrels, both were sold as emissions-era replacements, and both flow enough air for small-block V8s and sixes. The flange, applications, and hardware details are where they part ways.

Read the table this way: if your intake manifold has the Motorcraft-style pad, the 2280 bolts straight on and keeps factory choke linkage working. If you're building something custom, or you want jet and metering block parts on every shelf, the 2300 is the easier carb to live with. The CFM difference between them is small enough that it rarely decides the choice — the bolt pattern usually does.

How to Measure Your Carburetor or Manifold Bolt Pattern

Five minutes with a tape measure settles the question definitively, and it's the smartest thing you can do before ordering any carburetor or gasket. Here's the process.

1. Remove or lift the old carburetor so you can see the manifold pad, or flip the carb over to expose the base plate. Clean off old gasket material so the holes are easy to find.
2. Measure across the throttle bores, center of hole to center of hole, for the bolt pairs running left to right. Write the number down — this is your lateral spacing.
3. Measure front to back between the front and rear bolt holes on the same side. This is your longitudinal spacing.
4. Measure the throttle bores themselves (diameter of each opening). Two-barrel bores typically run around 1-1/16 to 1-3/4 inches depending on the carb, and bore position can confirm which family you're holding.
5. Compare against a known gasket. Hold a Holley 2-bbl gasket over the pad. If the holes align, you have the 2300 pattern. If they miss, try a Motorcraft-style gasket — if that one fits, your manifold wants a 2280.

Measure center-to-center, not edge to edge. Measuring hole edges adds the hole diameter to your number and throws everything off by an eighth of an inch or more. If your carb is still bolted down, you can measure the exposed flange holes on the manifold pad without removing anything.

Photograph the pad with a ruler laid across it. Parts counter staff and online sellers can identify the pattern from that single photo far faster than from a verbal description.

Adapter Plates: When They Work and When They Don't

An adapter plate is a phenolic or aluminum spacer, usually a half inch to one inch thick, drilled with the 2300 pattern on top and the 2280 pattern on the bottom (or vice versa). It lets a mismatched carburetor bolt to your manifold, and for many street builds it's a perfectly good solution. But it's not free of consequences.

The gains: you keep the carburetor you already have, you add a little plenum volume and heat insulation (phenolic plates reduce fuel percolation on hot days), and you can often correct a slight bore mismatch by choosing a plate with tapered or matching bores. Quality plates from reputable carburetor accessory makers include gaskets and studs. (See Also: Are Les Paul Style Bolt on Neck Guitars Interchangable)

The costs: every adapter raises the carburetor, which can cause clearance problems under a low hood, and it changes the geometry of your throttle and kickdown linkage. Divorced-choke setups are the biggest headache — the 2280's exhaust-manifold choke rod has no way to reach a raised 2300, so you'll need to convert to an electric or manual choke. Fuel line routing shifts too, since inlet positions differ between the two carbs.

When adapters don't make sense: if the throttle bores of the adapter don't align reasonably with both the carb and the manifold, you create a step that disturbs airflow and can hurt low-speed response. If you need more than about an inch of spacer to make it work, or if the linkage becomes a Rube Goldberg arrangement, buying the correct-pattern carburetor is cheaper than the frustration.

Common Mistakes When Swapping a 2300 or 2280

Most failed swaps trace back to a handful of avoidable errors. Knowing them ahead of time saves weekends of frustration.

• Assuming all 2-barrel carbs share one pattern. This is the classic error. There are several distinct 2-bbl flanges in the hobby — Holley, Motorcraft, Rochester — and they don't interchange.
• Reusing a crushed or wrong-pattern gasket. A gasket that overhangs the bores into the airflow, or one that leaves an open edge to the outside, creates a vacuum leak that mimics every other tuning problem.
• Ignoring the choke type. Swapping a divorced-choke 2280 for an integral-choke 2300 (or the reverse) leaves you with a disconnected choke rod and a cold-start problem. Plan an electric choke conversion if needed.
• Forgetting the throttle and transmission kickdown linkage. Raising the carb with an adapter or changing patterns alters linkage geometry. On Mopar V8s, an incorrect kickdown adjustment can cause transmission damage — the kickdown lever must move fully and promptly.
• Overtightening the base plate bolts. These small fasteners thread into soft aluminum. Snug them evenly in a crisscross pattern, roughly 80 in-lb or less, and recheck after a heat cycle.

One more subtle trap: some replacement carburetors were rebranded or rebuilt with mixed components, so the air horn stamping doesn't always guarantee the base plate pattern. Always verify at the base plate, not the ID tag.

Special Cases: Mopar, Amc, and Ford Applications

Application details matter more with these two carbs than with most, because both were sold heavily into the replacement market where factories mixed patterns across years and plants.

Chrysler 318 and 360 (1970s–1980s): most of these intakes take the Motorcraft-style pattern, which is exactly why the 2280 exists. If a previous owner installed a different carb, measure the pad — some later intakes and aftermarket replacements use other patterns.

AMC V8s (304, 360, 401): factory carburetion was Motorcraft, so the 2280 pattern is the norm. Jeep Grand Wagoneers and Cherokees with the 360 are common 2280 candidates. Note that divorced choke hardware is usually present and should be addressed in any swap.

Ford engines: Fords commonly ran Autolite/Motorcraft 2100 and 2150 carburetors, and Holley 2300-series replacements were frequently installed. Some Ford 2-bbl patterns differ from the Holley flange, so a Ford intake isn't automatically a 2300 fit — measure it.

Jeep inline sixes: the 232 and 258 used various 1-barrel and 2-barrel carbs depending on year; a 2-barrel conversion usually involves an intake swap, not just a carburetor swap.

Because emissions equipment, choke styles, and manifold patterns changed year to year, confirm your specific engine's year and carburetor list number against factory documentation or a reputable parts catalog before ordering. A list number stamped on the original carb is the fastest way to identify exactly what pattern your manifold expects. (See Also: Are Ls Rocker Arm Bolts Reusable)

Common Questions About Holley 2300 and 2280 Bolt Patterns

Will a Holley 2300 Bolt Onto a Mopar 318 Intake?

Not directly. Most Mopar 318 intakes have the Motorcraft-style 2-barrel pad that the 2280 was designed to match. A 2300's bolt holes won't line up. You can make it work with an adapter plate drilled 2280-pattern on the bottom and 2300-pattern on top, but you'll also need to sort out the choke and throttle linkage, since the 318's divorced choke rod won't reach a raised carburetor.

What Carburetor Replaces a Motorcraft 2100 or 2150?

It depends on which Motorcraft you have. The 2100/2150 two-barrels used on Ford and some AMC/Mopar applications have their own pattern, and Holley's 2280 was built to replace the Motorcraft 2-barrels used on Chrysler and AMC products. Ford 2150 applications are often served by 2300-series Holleys or direct replacement carbs. Measure the bolt spacing and compare it to a gasket before buying any replacement.

How Many Cfm Is a Holley 2280?

The Holley 2280 is rated at approximately 435 CFM, which suits stock 318 and 360 Mopar V8s and AMC engines of similar displacement. The 2300 series spans a wider range, from about 350 CFM up to 500 CFM depending on the specific model. For a mostly stock engine, the flow difference between the two is rarely noticeable; the bolt pattern should drive the decision, not the CFM number.

Can I Use an Adapter Plate to Mount a 2280 on a Holley-Pattern Manifold?

Yes. Adapter plates exist in both directions, and a quality phenolic plate about a half inch to an inch thick will bolt a 2280 to a Holley 2-bbl pad. Check three things first: hood clearance with the added height, throttle linkage geometry, and whether the plate's bores align with both the carburetor and manifold without creating a visible airflow step. Also plan a choke solution, since divorced-choke rods won't reach.

How Do I Tell a 2300 From a 2280 at a Glance?

Look at the base plate and the choke. The 2300 typically has an integral choke housing on the air horn, while many 2280s show divorced-choke linkage and a Mopar-style throttle lever arrangement. The ID stamping on the air horn helps, but rebuilt carbs sometimes wear mismatched parts — so measure the base plate bolt spacing and compare it to a known gasket for a definitive answer.

Are Holley 2-Barrel Gaskets Interchangeable Between Models?

No, and this is where many vacuum leaks start. A gasket made for the 2300 pattern will leave bolt holes and bore edges misaligned on a 2280-pattern manifold, and vice versa. Always buy the gasket that matches the carburetor base plate you're actually installing, and check that no gasket edge overhangs into the throttle bores or hangs past the manifold pad into open air.

Final Thoughts

To answer it plainly: are Holley 2300 and 2280 same bolt pattern? They are not. The 2300 carries Holley's own 2-barrel flange, while the 2280 was built to match the Motorcraft-style pattern on Mopar and AMC intake manifolds, so the two will not bolt together directly.

Before you buy or swap either carburetor, spend five minutes measuring the bolt-hole spacing on your manifold pad, center to center, and compare it to a known gasket. That single measurement prevents the most common and costly mistake in 2-barrel swaps.

If you already own the mismatched carburetor, a quality adapter plate can bridge the gap — budget for choke and linkage changes along with it. When in doubt, match the carburetor to the pattern your manifold was cast for, and confirm year-specific details with a factory parts catalog or the manufacturer's documentation before ordering.