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Build Some Power With a '92-'96 Gen II LT1

Don't step over it in the mud. The forgotten small-block is supercheap to procure. Get to building.

Photography by Chad Golen, , Courtesy GM Media Archives, SAE International, Evans Cooling Systems
LT1 SPECS
Casting number: 10125327 (look for "327" cast on side near freeze plugs)
Block: Cast-iron two-bolt main bearing caps (middle three caps are four-bolt in Y-body)
Bore: 4.0 inches
Stroke: 3.48 inches
Crankshaft: Nodular iron
Connecting rods: Powdered-metal 5.7-inch
Pistons: Hypereutectic flat-top with valve reliefs
Cylinder heads: Aluminum
Cast-iron '94-'96 B/D-body
54cc combustion chambers
170cc intake port
212-cfm airflow
Valves: 1.94-inch intake, 1.50-inch exhaust
Rocker arms: Stamped steel 1.5:1
Camshaft: Roller lifter:
202/207 degrees of duration @ 0.050 inch
0.447/0.459-inch lift (varies slightly by year and application)
Horsepower: 300 @ 5,000 rpm
Torque: 340 @ 4,000 rpm

A Little History
Designing a new engine is a tough balancing act. Stringent fuel economy and emissions standards are always being imposed on the auto manufacturers, so any new engine being developed has to run cleaner and be more fuel-efficient. But at the same time, cars get heavier each model-year with the addition of new safety features, infotainment devices, creature comforts, and power everything. The new engine has to make enough power to handle the excess weight, plus not feel slow to the driver and burn less gas. In an attempt to improve upon the outgoing L98's 250 hp, GM's designers set a goal of 300 net horsepower for the LT1. To meet these goals they employed fairly standard techniques of increasing the compression ratio and improving the cylinder-head design. But they supported these changes with some interesting technology.

Though the LT1 and its offspring, the LT4 and L99 4.3L V-8 (the standard engine in '94-'96 Caprices), are called Gen II, they have more parts in common with the original SBC than not: The reciprocating assembly and valvetrain are interchangeable with the Gen I engine, for example. But the differences, though few, are substantial enough to warrant the new-generation designation. The engine block and cylinder heads are unique and cannot interchange with the previous design. Also specific to the Gen II are the ignition and cooling systems.

Reverse flow
Think LT1, and you likely think "reverse-flow cooling." This is understandable because the terms are used almost synonymously whenever mentioned in the magazines. But how well has the system ever been explained?

To be fair, reverse-flow cooling is not a new thing. Smokey Yunick developed a reverse-flow system for some of his Trans-Am race cars, and a few independent engineers and engine builders have developed systems of their own. But the LT1 was the first mass-produced engine with reverse-flow cooling. So how does it work?

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3 comments
bob_adams 4x4
bob_adams 4x4

hi all i have just converted my 96 lt1 from auto to manual troble is the starter gear is not reaching the ring gear it misses out by 11mm it lines up ok its like the flywheel needs to go back towards the engine 11mm for all to be good any advice please bob

plozier
plozier

Where do I find a pulley to replace the ac pump on an lt1 engine as mentioned in the articlePat

imgerry
imgerry

Since I just purchased a swapper out of a 1996 B car along with the 4L60E trans, brackets, wiring, ecm and periphials I was gratified to learn the answers from the questions I had about it before rereading the article online. I'm planting it in a '78 Z-28'ed frame under my 1958 Chevy Apache panel truck! By the way, the tech tip of the Y body accessory-drive system may keep me from having to dodge my frame rail...Thanks!!

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