Chevy Engine Swap Compatibility Chart: SBC, BBC & LS Fit

Small-block, big-block and LS Chevy V8s share the same basic bellhousing bolt pattern, but an LS crankshaft is 0.400 in. shorter than earlier small-block and big-block cranks, per Summit Racing, so an older GM automatic needs a flexplate spacer. This guide is a sample of pairings documented by Chevrolet Performance, Holley, Hooker, Novak, Michigan Motorsports and Summit, plus the EPA and California rules for engine changes. It is not a universal chart.

Chevy Engine Swap Basics: What You Need to Know

An engine swap is a chain of matches, not one bolt pattern: engine and transmission, mounts, oil pan, controller and wiring, fuel system, and emissions status. Chevrolet Performance warns that retrofitting a crate engine into an earlier small-block application can need extra cooling, fuel, electrical or exhaust parts, and some fabrication.

Every row below names the engine, the vehicle and years where one applies, and the source. If a maker page does not document a pairing, it is not here. For which GM engine came in which platform, see our LS, LT and small-block fitment chart. Chevrolet Performance also says to support the vehicle on jack stands and to hand the work to a professional if you lack the training or tools.

Understanding Engine Families: Small Blocks vs. Big Blocks

Novak Conversions describes the Chevrolet bellhousing interface as virtually unchanged since 1955, and lists its Chevrolet pattern bellhousings for 1955-and-later Chevrolet V8 pattern engines: small-block, big-block, the 90-degree V6 such as the 4.3L, the inline-six, and LS Gen III and later. Its parts guide gives these ranges: small-block V8 Gen I-II 1955-1998+, big-block V8 1965-2007+ (409-454, 7.4L, 8.1L), and GM Gen III+ V8 1997-2010+.

Chevrolet Performance sells factory-matched engine and transmission packages. The list shows what the maker offers with each crate engine: supported pairings, not a limit on what builders have done. For two popular engines compared, see Chevy 5.3 vs 6.2.

Crate engine	Automatics offered	Manual offered
ZZ6, SP350/357, SP350/385	4L65-E	Super Magnum 6-speed
350 HO Turnkey	4L65-E	None listed
SP383	4L70-E	Super Magnum 6-speed
ZZ427/480	4L70-E	Super Magnum 6-speed
ZZ502/502, SP502/605, ZZ572/620	4L85-E	Super Magnum 6-speed
LS3 (430 hp)	4L65-E, 4L70-E, 6L80-E	Super Magnum 6-speed
LS3 376/525	4L70-E, 4L75-E, 6L80-E	Super Magnum 6-speed
LT1	4L70-E, 6L80-E, 8L90-E, 10L90-E	Super Magnum 6-speed
L8T	6L80-E, 10L90-E	None listed

Source: Chevrolet Performance Engine and Transmission Packages page.

Chevy Engine Bellhousing & Transmission Compatibility Chart

Most swap searches come down to two questions: does the bellhousing bolt up, and what changes at the crankshaft? This chart separates the bolt pattern from the crank flange. The older automatics are Powerglide, TH350, TH400, 200R4, 700R4 and 4L60.

Engine	Bellhousing pattern	Older GM automatic	Source
Small-block and big-block V8	Chevrolet V8 pattern	The baseline: the LS crank is 0.400 in. shorter than these	Novak, Summit
LS Gen III/IV	Standard GM pattern, dowels in the same spot, 5 of 6 bolt holes line up; LS bellhousings add a hole at 12 o’clock	Needs an adapter: flat flexplate with a spacer and longer bolts, or a cone-shaped flexplate with a pilot extension	Summit, Novak
LS4 (front-wheel drive)	Metric 60-degree Chevrolet V6 bellhousing	Different from other LS engines	Summit
Some early LQ4 and LR4	Longer crankshaft than other LS engines	Work with older transmissions without spacers	Summit
LSA and 1999-2000 long-crank LQ4	Not covered	The Michigan Motorsports spacer does not fit	Michigan Motorsports

Michigan Motorsports lists its spacer for Gen III/IV LS engines with TH350, TH400, 700R4, 4L60, 4L60E, 4L80, 4L80E and 4L85E transmissions. On a flat flexplate the spacer sits between the crankshaft and flexplate; on a dished flexplate it sits between the flexplate and converter. It needs longer flexplate bolts (the maker recommends ARP kit 244-2902) and is not required with an LS-specific converter on a dished flexplate.

Summit recommends a new flexplate at minimum and says to consider a new converter, since the LS power band differs. Match the flexplate to your converter’s bolt pattern and torque bolts to the maker’s instructions. For converter checks, see testing TH350 torque converter stator clearance.

Transmission Choices for Your Swap

Chevrolet Performance lists a torque limit for each SuperMatic automatic and its manual. Compare the limit with the engine you plan to run.

Transmission	Torque limit (lb-ft)
SuperMatic 4L65-E	430
SuperMatic 4L70-E	495
SuperMatic 4L75-E	650
SuperMatic 4L85-E	690
SuperMatic 6L80-E	650
SuperMatic 8L90-E (designed for LT engines)	715
SuperMatic 10L90-E (for Gen V engines)	650
Super Magnum 6-speed manual	700

For the manual, Chevrolet Performance’s Super Magnum instruction sheet (19329913) covers six kits. Bell housing kit 19329025 serves small-block and big-block engines, and 19329620 serves LS and LT engines.

Kit	Engine	Bell housing kit	Flywheel detail
19329900	Small-block	19329025	Flywheel for 1986 and later small-block
19329901	454 and 502	19329025	Externally balanced
19329902	427 and 572	19329025	Internally balanced
19329912	8-bolt LS/LT	19329620	Eight flywheel bolts
19331080	6-bolt LS	19329620	Six flywheel bolts
19331083	9-bolt LS	19329620	Nine flywheel bolts

Chevrolet’s LS3 guide lists pilot bearing 14061685 for a long input shaft and 12557583 for a short one, and warns to verify fit before installing the transmission. For mount choices, see transmission mounts.

Documented Engine-to-Vehicle Pairings: A Sample Chart

These rows come from maker instruction sheets and product pages. A pan or bracket kit is tied to a body style and year range, and the notes carry the limits.

Engine and part	Vehicle and years	What the maker documents	Source
LS Gen III/IV with Holley 302-1 oil pan	GM rear-wheel-drive cars originally built with a small-block or big-block Chevy; Holley names 1967-69 F-body and 1968-74 X-body	Max crank stroke 4.25 in.; not compatible with a G-body; engine position may need adjusting for crossmember or steering clearance	Holley 302-1 page, Holley Motor Life
LS Gen III/IV with Holley 302-2 oil pan	1967-69 Camaro/Firebird, 1968-74 Nova/Apollo/Ventura/Omega, 1982-92 F-body, 1978-87 G-body, 1964-72 A-body	Max stroke 3.62 in.; not for LS7 or strokers over 3.62 in.	Holley 302-2 page
LS with Hooker 12618HKR brackets	1967-69 F-body, 1968-74 X-body	With Hooker crossmembers, an LS with a Powerglide, TH350, TH400, 700R4, 2004R or 4L60/4L65/4L70 fits a 1967-69 F-body without cutting; X-body needs tunnel changes for a T56	Holley sheet 12618HKR
LS with Hooker 12512HKR and 12613HKR brackets	1970-74 and 1975-81 second-generation F-body	A 4L60/4L65/4L70 or Tremec LS F-body/GTO T56 fits without cutting except the shifter hole; cars without factory clamshell mounts need drilling	Holley sheet 199R10648
LS with Hooker 71221003HKR brackets	1982-92 F-body	Needs 1998-2002 Camaro/Firebird LS1 motor mounts and a Holley 302-2 or 302-3 pan	Holley sheet 199R10915
LS3 E-ROD kit 19435334 or 19435336	Vehicles with a GVWR of 5725 lb or less	Tires 26 to 30 in.; axle ratio 3.08 to 4.11; speed signal required; fuel tank, fill pipe and cap equivalent to 2006-or-later OEM	Chevrolet Performance 19435339
LS3 crate engine, showcase builds	1971 GMC C15, 1962 Chevrolet Deluxe Wagon, 1967 Camaro, 1972 C10, 1969 Corvette	Shown as LS3 builds; no fitment details published	Chevrolet Performance LS3 page

Hooker’s instructions say its geometry needs its own crossmembers and headers, and that other brands hurt installation ease, clearance and engine angle. For mount choices see engine mounts, and for big-blocks see our Chevy 454 swap guide.

Oil Pans and Motor Mounts: Where Clearance Runs Out

Holley’s LS oil pan article compares sump depth: the GM muscle car pan (19212593) measures 7.75 in. from rail to lowest point, the Holley 302-1 only 5.71 in. A deep sump can hang below the crossmember. The rear of the pan must sit flush with the rear of the block because the bellhousing bolts to the pan, so test fit the pan, mounts and bellhousing together.

Engine Controller, Wiring and Fuel System

Chevrolet Performance says LS3 crate engines require an engine control system and harness. Its LS control kit is designed for crate engines with 58x crankshaft reluctor wheels, 4x camshaft indexing and electronic throttle control, typically 2006 and newer. The LS3 page lists the LS3 with a 58x wheel but the Gen III LS364/450 with a 24x wheel, so confirm with Chevrolet Performance that a controller matches your exact engine.

• Fuel pressure: the LS control kit needs a constant 400 kPa (60 psi), not vacuum referenced. The LS3 guide says roughly 58 to 60 psi in different places, so follow the instruction sheet with your controller.
• Fuel flow: at least 40 gph at 400 kPa for LS2, LS3 and LS376 engines, and 50 gph for the LSX454 and LS7.
• Airflow sensor: mount it in a straight run of at least 6 in. of 4 in. tube, at least 10 in. from the throttle body.
• Speed signal: the harness plugs into the 40-pulse output of the 4L60 and 4L80.
• Not included with the LS3: flexplate 12654640 or flywheel 12571611, starter 10465385, fuel pump, exhaust manifolds and the control system.

Fuel is under pressure, so read how to relieve fuel pressure safely before disconnecting any fuel line.

Emissions Rules for an Engine Swap: EPA and California

Not legal advice. Emissions rules decide whether a swap can be driven on the street, and agencies set them, not parts catalogs. Start with the EPA Tampering Policy and the California Bureau of Automotive Repair engine change page.

Federal. EPA’s November 2020 policy says the Clean Air Act prohibits tampering with emission controls for the life of a vehicle, and that the policy is nonbinding enforcement guidance. For engine switching, EPA typically finds a reasonable basis when the vehicle stays in the same product category, such as light-duty, and is identical in all emissions-related elements of design to a certified configuration of the same or newer model year as the chassis. Emissions testing is the alternative. EPA notes that cross-manufacturer swaps rarely conform and that it issues no pre-approvals.

California. The Bureau of Automotive Repair separates an engine replacement, meaning the same make, cylinder count and engine family with the original emission controls, from an engine change. An engine change must pass an initial Referee inspection and carry a Referee label in the engine compartment.

• The installed engine must be the same model year or newer than the vehicle, in the same GVWR-based class.
• Non-certified crate engines may not be installed in any emissions-controlled vehicle.
• An OBD II vehicle must keep the donor’s configuration, including transmission, evaporative system, exhaust and intake.

Chevrolet Performance’s guides say they apply to engines and vehicles used off public highways except where noted, and that parts with its Special Parts Notice should not go on a street vehicle. Whether a state accepts a given installation, even with its E-ROD kit, is for that state to say, so contact your state emissions agency or the California Referee program before buying the engine.

What This Guide Does Not Cover

• Pairings without a maker page, including most big-block and 632 swaps.
• Parts prices, which change often.
• Legal advice for your state; ask the state agency.

Keep reading

• Chevy 5.3 vs Ford 5.0: Which V8 Engine Wins?
• Your Essential Guide to a Flawless 454 Internals Swap
• Will a 1993 Chevy Gen 5 454 Fit a 1989 Mark IV 454

Frequently Asked Questions About Chevy Engine Swaps

Can I swap any Chevy V8 into any Chevy vehicle?

No. Maker pages document only specific pairings. Holley says its 302-1 LS swap oil pan is not compatible with a G-body, and Michigan Motorsports says its LS spacer does not fit LSA or 1999-2000 long-crank LQ4 engines.

Do small-block and big-block Chevy engines use the same bellhousing bolt pattern?

Yes. Novak Conversions lists its Chevrolet pattern bellhousings for 1955-and-later Chevrolet V8 pattern engines, including both, and Chevrolet Performance uses one Super Magnum bell housing kit, 19329025, for its small-block and big-block kits.

Does an LS engine fit a small-block bellhousing?

Summit says LS engines use the standard GM pattern, with dowels in the same spot and 5 of 6 bolt holes lining up. Novak says LS bellhousings add a hole at 12 o’clock, so use an LS bellhousing or confirm every hole.

Do I need a new transmission for a Chevy engine swap?

Not always. Summit says most GM transmissions will bolt to an LS, but you need at least a new flexplate and may want a different converter stall speed.

How difficult is wiring for an LS engine swap?

Chevrolet Performance says LS3 crate engines require an engine control system and harness, plus a constant 60 psi fuel supply, so plan wiring and fuel together.

Can I swap an engine from a newer Chevy into an older one?

California requires the installed engine to be the same model year or newer than the vehicle, and EPA looks for a certified configuration of the same or newer model year as the chassis. The engine must also match the vehicle’s category.

Conclusion

A Chevy swap is documented one pairing at a time. The bellhousing pattern is shared, the LS crank and flexplate are the exception, and mounts, oil pan, controller, fuel and emissions each carry their own limits. Confirm each part with its maker, and settle emissions with the state before buying.