Will a 305 flywheel fit a 350?
A 305 flywheel will generally fit a 350 small-block Chevy crank, but you must verify the proper pairing with your transmission and starter. In practice, compatibility hinges on the correct flywheel or flexplate, the ring-gear size, and the engine’s balance. If in doubt, confirm part numbers with the parts supplier or a qualified mechanic.
The question touches on a common automotive interchange: whether components from one small-block Chevy displacement can be used on another. While the 305 (5.0) and 350 (5.7) share many interface points, there are details that can trip a swap, particularly when changing transmissions or planning a balance-critical rebuild.
Compatibility basics
Understanding the key interfaces helps you decide whether a 305 flywheel will work with a 350. The main factors are the crank mounting pattern, the ring gear on the flywheel or flexplate, and the transmission type paired with the setup.
Common interfaces on SBC engines
The small-block Chevy family generally uses the same crank mounting pattern across many years and displacements for manual transmissions, and the flywheel or flexplate attaches to the crank with the same bolt circle. However, there are variations in ring-gear tooth count and diameter tied to specific transmissions and production years. The balance of the rotating assembly is also a consideration when mixing parts from different engines.
- Engine family: The 305 and 350 are both small-block Chevys and typically share the same basic crank-to-bellhousing interfaces.
- Transmission type: For a manual transmission, you’ll use a flywheel; for an automatic, you’ll use a flexplate. Make sure the part is specified for your exact transmission model and engine.
- Starter compatibility: The starter engages the ring gear on the flywheel or flexplate; mismatched tooth counts or diameters can prevent proper engagement.
Conclusion: A 305 flywheel will fit a 350 crank in most SBC builds, provided you pair it with the correct flexplate or flywheel for your transmission and confirm starter compatibility and balance. If you’re unsure, verify part numbers with a parts supplier or a mechanic before proceeding.
What to check before swapping
Before pulling parts, use this checklist to avoid misfits and downtime:
- Identify your transmission type (manual vs automatic) and confirm the compatible flywheel or flexplate part number.
- Check the ring-gear diameter and tooth count on the flywheel/flexplate and ensure your starter matches it.
- Verify flywheel weight and engine balance compatibility; mixing incompatible weights can cause vibrations or bearing wear.
- Measure the crankshaft rear flange/bolt pattern to ensure compatibility with the flywheel bolts and alignment dowels.
In practice, many builders reuse a 305 flywheel with a 350 engine for mild street applications, but if you’re automating the drivetrain, use a flexplate designed for your exact automatic transmission (for example, TH350 or 4L60E lineage) to ensure correct ring-gear engagement and balance.
Practical tips for swaps
To maximize the chances of a smooth swap, follow these recommendations:
- Use components that are matched to your intended configuration (manual-to-manual or auto-to-auto). Do not mix a manual flywheel with an automatic flexplate.
- When in doubt, replace the flywheel or flexplate with a new unit designed for your exact engine-transmission pairing to maintain proper balance and reliability.
Tip: If you’re converting from an automatic to a manual setup (or vice versa), you’ll likely need a different flywheel-to-flexplate assembly and possibly a different starter gear; coordinate with parts suppliers or a qualified shop.
Alternatives and caveats
There are a few caveats to consider if a direct fit isn’t readily available:
- Some early SBCs used different rear seal configurations that can affect flywheel or flexplate fitment. Verify the rear main seal type for your engine and the corresponding flywheel or flexplate.
- Balance considerations matter: both the 305 and 350 are commonly externally balanced; ensure the chosen flywheel/flexplate weight matches your engine’s balance specification.
- For performance builds or newer crate engines, follow the manufacturer’s guidance on flywheel/flexplate compatibility and weight class.
Bottom line: In most street-SBC applications, a 305 flywheel will fit a 350 crank, but you must pair it with the correct flexplate or flywheel for the transmission and confirm balance, ring-gear size, and starter compatibility.
Summary
Yes, a 305 flywheel can generally fit a 350 small-block Chevy crank, but exact compatibility depends on transmission type, ring-gear size, starter engagement, and engine balance. Always verify part numbers and specifications with a trusted parts supplier or mechanic before swapping, and consider replacing with a new, correctly matched unit to ensure reliability and safety.
What size are the flywheels on a Chevy?
You will find that transmission bellhousings will fit both the 153 tooth flywheels which is 12.835” in diameter, and the 168-tooth flywheel, which is 14.086” in diameter.
Will a 305 crank fit in a 350?
Yes and no. Same stroke, same size journals, same rod length. Even the same casting for the crank, however balance is different for bore size and piston weight, plus 305 rods are a bit lighter than 350 rods.
Can you put a 305 flexplate on a 350?
As long as you have the correct starter to match the flexplate yes. Basically all small blocks are internally balanced except the 400. The only time you'll have a problem is if you are with say a 305 to 350 is if one of them is one piece rear main seal.
Are the 305 and 350 the same?
And belts. So there's really only one difference well There's more than one but there's one basic difference between a 350 and a 305. And that is the bore. Size. So this is a 305 Chevy.
