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Chevy Small Block? Chevy V8 Specs & Options

Tech Q+A

Bloodlines
What is the difference between a standard 350 and a "Gen 2" LT1? Would it be possible to bolt a standard 350 into a '90s Caprice with the stock transmission? What about an LT1/TH350 combo? Are the engine mounts in the same location? Which engine parts are compatible, and which aren't?
Kipp Leland
Wood Ridge, NJ

Classic 350 complete assemblies physically bolt into the same space as Gen 2 engine complete assemblies (and vice versa). The following individual component parts interchange between Gen 2 (LT1/LT4) and "classic" 350ci small-blocks:

• Camshaft and lifters (with '87-and-later hydraulic roller cams and lifters when used with correct timing chain and gears; may need to change dowel pin)
• Cam, main, and rod bearings
• Classic 350 rear-mount distributor will fit Gen 2 (remove LT1/LT4 jackshaft, use GM Gen 2/LT1 carbureted intake manifold PN 24502592 and cover hole in front cover; front cover plug PN 12367600 works on '96 LT4 engines)
• Connecting rods
• Crankshaft (with '86-and-later one-piece- seal cranks only)
• Engine mounts
• Exhaust manifolds
• Flywheel or flexplate (with '86-and-later one-piece-seal cranks)
• Head bolts
• Main bearing cap bolts
• Oil filter (with correct adapter)
• Oil pan (with '86-and-later one-piece-seal pans)
• Oil pan windage tray (with correct trays designed for '86-and-later one-piece-seal oil pans)
• Pistons (compression ratio may be wrong)
• Rear block-face (bellhousing) bolt-pattern
• Rings (with late-model production pistons machined for metric ring grooves)
• Rocker covers (with '87-and-later center-bolt covers)
• Starter
• Valvetrain components (except LT4, which uses a net-lash valvetrain with 10mm rocker studs)

The following parts do not interchange:
• Cylinder block (different water jacket and front-end)
• Cylinder head (different water jacket)
• Gen-2 front-mount ignition system won't fit classic small-block
• Harmonic damper (Gen 2 balancer bolts onto hub that slips onto crank; no keyway or timing marks on balancer)
• Head gasket (different coolant passages)
• Intake manifold (different bolt angle and coolant passages)
• Thermostat
• Timing chain and gears (if retaining front-mount ignition system)
• Front timing cover (different shape and bolt-pattern)
• Water pump

As for bolting a standard 350 to a '90s Caprice trans, you did not address whether the engine would be computer-controlled. The 4L60-E transmissions, used '94-and-up, require a late-model computer or aftermarket stand-alone controller. The 4L60 and TH700-R4 can be made to work without a computer. Due to ignition system differences, an LT1 computer cannot be used to control a non-LT1 engine.

You can run an LT1 without a computer by defaulting to an old-style ignition and carburetor (see preceding list for parts compatibility). To remain fully emissions-compatible, a computerized LT1 requires a VSS (vehicle speed sensor), which installs in the tailshaft of late-model transmissions. Exact VSS configuration will vary according to the LT1's model year and original installation chassis, as well as the type of speedometer interface required for any nonstock installation.

The TH350 and similar vintage transmissions have no VSS provisions. Nonemissions LT1 applications may dispense with the VSS under certain circumstances provided the '96-and-later OBD-II computer is not used. For more information on VSS interface, including providing a VSS pulse-signal in applications where the trans has no provisions for a standard VSS pulse-generator, contact Howell Engine Developments or Street and Performance. Mike Knell's book, Chevrolet TPI and TBI Engine Swapping is a good guide to the intricacies of late-model EFI swaps, including solutions to the VSS problem (the book is available through Summit Racing).

Sources:
Howell Engine Developments
Dept. CC
6201 Industrial Way
Marine City, MI 48039-1326
810/765-5100
www.howell-efi.com

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