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Jeep Engine Swaps - GM TBI V8

Posted in How To on October 1, 2008
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Contributors: John White

From 1987 to 1995, GM produced what was coded the "LO5" TBI 350. This engine combo was based on the solid 350ci V8 long-block with a throttle-body fuel-injection (TBI) system mounted directly on top of the intake manifold. This form of "wet intake" injection system didn't produce the higher horsepower figures later obtained with "dry intake" multiport fuel-injection (MPI) systems such as L98 or LT1 F-bodies (Vette and Camaro). However, the torque curve for the TBI engine was a perfect fit for 4x4s. Horsepower and torque values for the LO5 increased slightly over the production term ending in 1995 with 312 lb-ft of torque and a solid horsepower figure of 210. GM used the LO5 in several passenger cars such as the Caprice, but the most popular fit was the 1/2-ton pickup and Suburban line.

The GM Corvette and Camaro LT1 engine provided an excellent torque curve (high and flat). However, the Opti-Spark ignition mounted at the crankshaft height scared off a number of engine swappers. Early salvage-yard costs were high compared to a TBI engine.

After a few years of production, the LO5 started turning up in a variety of transplants from Jeeps to earlier fullsize trucks. For a number of years, the standard "swap" engine for Jeep builders was the TBI 350. The fuel-injection system on the LO5 is based on a dual-injector pod which is programmed to introduce a conical spray of fuel directly into the top of the intake manifold. This most basic EFI design proved to be perhaps the easiest to diagnose and tune of any to date. Quick ignition, smooth-running, and good fuel efficiency made the LO5 a great pick.

In an engine-swap application, the wiring required to support the TBI LO5 proved to be one of the most inexpensive and basic harnesses for the aftermarket to produce, and that still holds true today. Using the engine wiring harness from the donor vehicle wasn't a huge chore. However, the availability, simplicity, and price of a fresh aftermarket TBI harness, such as those available from Howell Engine Developments, remain hard to pass up.

In today's world of complex injection systems, composite intakes, and expensive wiring systems, the LO5 would seem to be the ideal engine for the salvage-yard searcher. Unfortunately, the chances of finding a low-mileage LO5 in decent condition is made worse by the fact that GM hasn't produced one in 13 years.

In 1995, the Vortec 350 emerged. However, like the LT1, early salvage costs were high. In addition, the central port injection system and composite intake manifold proved troublesome in the early years of production.

Scoggin-Dickey Parts Center (SDPC) in Lubbock, Texas, hasn't let the dwindling supply of original LO5s forfeit the benefits of the tried-and-true TBI 350. Not only does Scoggin-Dickey offer a replacement engine for the LO5, but the power output is bumped to 310 hp as opposed to the 1995 figure of 210 hp. The GM short-block (PN 12556121) is a new factory-built four-bolt main block filled with all-new engine components direct from the General. An added benefit of this SDPC engine is a warranty good for 12 months/12,000 miles.

The GM short-block was chosen by SDPC for this TBI package. This choice offers the correct lifter pads to allow an upgrade to the hydraulic roller cam and a modern one-piece rear oil seal. SDPC also selects a special-grind hydraulic roller cam from Crane Cams made specifically for the TBI application for added 4WD torque. COMP Cams 1.6 Roller Rocker Arms matched with COMP Cams pushrods are used to move the air through the Edelbrock aluminum Performer heads and intake manifold. The SDPC long-block is built with new parts and includes a new GM HEI distributor, MSD plug wires, new balancer, flexplate, Milodon oil pan, and is topped off with the Edelbrock Elite valve covers.

The Corvette and Camaro L98 Tuned Port Injection (TPI) 350 proved to be a hit with the street-rod market but never hit the mainstream for Jeeps and trucks. Stock horsepower for the L98 was better than the TBI but not by much.

If your Jeep project vehicle was equipped with a Buick V6, four-banger, or even the 4.0L inline-six, then a TBI 350 swap like this can be performed quite easily by almost anyone. The aftermarket-parts bin for this type of project has become so comprehensive that virtually every swap part is available for reasonable costs. Before going overboard with a new late-model Chevy Vortec 4.0 stroker kit or even a supercharger, give some serious thought to this $3,500, 100,000-mile option from Scoggin-Dickey Parts Center.

PhotosView Slideshow
PN SD350TBI-PK 350 Kit, Assembly Required
PN SD350TBI-PA 350 Assembled Long-Block
PN 3704 Edelbrock Performer TBI Intake Manifold
PN 4246 Edelbrock Elite Aluminum Valve Covers
PN 60859 Edelbrock Performer Centerbolt Cylinder Heads
  60cc chambers, 165cc intake ports
  Valve size (intake/exhaust): 2.02/1.60 in
PN CRA104211 SB {{{Chevrolet}}} PowerMax Hydraulic Roller Camshaft
Duration at 0.050 in (intake/exhaust) 194/204
Lift (intake/exhaust) with 1.6 ratio 0.434/0.458 in
Lobe Separation Angle 111


Scoggin-Dickey Parts Center
Lubbock, TX 79424
Turbo City
Orange, CA
JB Conversions Inc.
Sulphur, LA 70664

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