Is big block Chevy and small-block Chevy water pump the same?
No. Big-block Chevy and small-block Chevy water pumps are not the same and are not directly interchangeable in most applications. This article explains the key differences, why a swap is usually not feasible, and how to verify compatibility when repairing or restoring an engine.
What sets them apart
Here are the main differences you should consider when evaluating SBC versus BBC water pumps. Each item highlights how a direct swap can fail without modification.
- Mounting pattern and timing cover interface: The pump bolts to the timing cover with different hole spacing and profiles between small-block and big-block designs, making a one-to-one bolt-on swap unreliable.
- Pump size, housing shape, and coolant outlets: The small-block pump is typically smaller with a different inlet/outlet orientation than the big-block pump, affecting hose routing and water neck compatibility.
- Impeller shaft size and drive geometry: The shaft diameter, bearing arrangement, and hub design differ, so reuse across block families is not generally feasible.
- Pulleys and belt alignment: The pump centerline and pulley spacing relative to the crank and other accessories vary, which can throw off belt tracking if swapped.
- Cooling system interface: The coolant passages in the timing cover and block are matched to each pump type; using the wrong pump can lead to leaks or overheating.
In summary, these differences affect mounting, routing, and operation, so a direct swap is not a reliable option in most cases.
Interchangeability in practice
Direct interchange is generally not recommended. If you need to reuse a pump across SBC and BBC architectures, you typically must address timing cover, water neck, and pulley compatibility, or opt for the correct pump designed for the specific engine family.
- Confirm engine family and year: Identify whether you’re dealing with SBC or BBC to ensure you’re selecting the correct part.
- Check bolt pattern and timing cover interface: Mismatched holes or spacing require modification or a different pump.
- Assess water neck and hose fittings: Outlet location and hose routing must align with the radiator and thermostat housing.
- Evaluate accessory drive alignment: Pulleys, belts, and fan mounting may need adjustments if a nonstandard pump is used.
Bottom line: While some pumps may appear to fit, reliable cooling performance and belt operation almost always require using the correct pump for your engine block and timing cover configuration.
What to check before buying a replacement
Before purchasing a new water pump, run through these compatibility checks to avoid misfits and cooling issues.
- Identify your engine family: Confirm whether you have a small-block or big-block Chevy using the block casting number or vehicle documentation.
- Match the mounting pattern: Ensure the number of bolts and their spacing align with the timing cover.
- Verify water neck and outlet orientation: Make sure the hose fittings and routing will line up with the radiator, thermostat housing, and hoses.
- Check pulley and drive compatibility: Ensure the pump’s pulley alignment matches the crank and other accessory drives.
- Consider timing cover changes: Some swaps require a different timing cover or thermostat housing to fit the pump properly.
If in doubt, consult the vehicle's service manual or a parts specialist to confirm the exact pump specification for your engine block and year.
Summary
The water pump is not universal between big-block and small-block Chevy engines. They differ in mounting, size, outlet orientation, and drive geometry, and a direct, one-to-one swap is usually not feasible. For restoration or repair, use the pump specified for your exact block and timing cover, or be prepared to change related components to maintain proper cooling and belt alignment. A careful check of mounting holes, water neck, and pulley alignment will help ensure reliable operation.
Are big block Chevy and small block Chevy motor mounts the same?
No, SBC (small-block Chevy) and BBC (big-block Chevy) motor mounts are not always the same; while the engine block mounting points are identical, the correct frame mounts and sometimes the mounts themselves can differ depending on the vehicle and year. Some early models use the same "short and wide" mounts, but later versions, or when swapping from SBC to BBC, often require "tall and narrow" or otherwise specific mounts to accommodate the larger engine's width and to maintain proper driveline alignment.
This video shows the difference between big block and small block engine mounts: 1mRoad Hard RoadhouseYouTube · Sep 30, 2020
Key differences
- Engine block: The bolt pattern on the engine block for the mounts is the same for both first-generation SBC and BBC engines.
- Frame mounts: The mounts that attach to the vehicle's frame are often different. This is because the big block engine is wider, and the frame mount needs to accommodate this difference.
- Mount type:
- Early style: Many early models (like some 1960s and 70s A-bodies) used a "short and wide" mount that works for both SBC and BBC.
- Later/Swapped: Aftermarket and later models often use "tall and narrow" mounts for big blocks to provide the correct width and header clearance, note this YouTube video.
- Engine positioning: Because of the width difference, the frame mounts and towers may need to be different to reposition the engine correctly in the chassis, which can affect the driveline and exhaust alignment.
- Other components: The transmission mount location may need to be adjusted, and the driveshaft might require modification due to the different length of some transmissions like the TH400 compared to a TH350.
What to do
- Check your vehicle's specific application: Always verify if your vehicle originally came with a big block or small block and the type of frame mounts used.
- Measure carefully: Measure the width of your existing frame mounts and the distance between the frame perch to ensure you order the correct mounts for a big block swap.
- Purchase a kit: For a complete swap, consider a kit designed for a big block swap to ensure compatibility.
This video explains the differences between big block and small block engines: 48sNate RiderYouTube · Jun 2, 2024
Does the big block Chevy have a short or long water pump?
All models of Chevy V8 engines from 1955 through 1968 came equipped standard with a short water pump. From 1969 and newer engines with v-belt drives into the 1980s had long water pumps. With so many engine swaps, it's possible your '68 and older car has a long water pump.
What's the difference between a long and short water pump on a small block Chevy?
The main difference is the length of the water pump shaft, which affects the distance between the engine and the radiator and the location of accessory brackets. A short pump has a shorter snout and is used when radiator clearance is tight, while a long pump has a longer snout and is often preferred for more accessory bracket options, especially on vehicles from 1969 onward.
This video explains the difference between long and short water pumps and how to identify which one you have: 16sSummit RacingYouTube · Oct 24, 2017
Short vs. Long Water Pump
| Feature | Short Water Pump | Long Water Pump |
|---|---|---|
| Length | Shorter snout | Longer snout |
| Clearance | Provides more room between the engine and radiator | Takes up more room between the engine and radiator |
| Accessory Brackets | Fewer bracket options available | More accessory bracket options available |
| Typical Application | Older vehicles (pre-1969) or specific builds needing more clearance | Newer vehicles (1969 and newer) |
| Identification | Narrow gap between pump and timing cover; measure ~5 5/8 inches from mounting flange to pulley hub | Larger gap between pump and timing cover; measure ~6 7/8 inches from mounting flange to pulley hub |
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Are small block and big block water pumps the same?
Small block “short” pumps measure 5-5/8-inch (5.625-inch). The Corvette used its own version of a short water pump from 1971-1982 due to engine compartment clearance issues with a special 5.795-inch height, so be aware of those as well. Big block “short” pumps measure in at 5-3/4-inch (5.750-inch).
