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Jeep V-8 Power!

Posted in How To on October 24, 2003
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Say you have a CJ with a healthy Jeep V-8 for playing in the sand dunes or doing the rocks. Can there be any improvement to such a potent combination? Yes. Such was the case with Dave Zelinka's bright-yellow '79 CJ-7. The Jeep's mildly modified AMC 304 had reliably served the CJ, but Dave was ready for something with a bit more performance. It was time to revamp the powerplant and provide the Jeep with some Bow Tie power.

After the decision was made to go with a small-block Chevy transplant, the rest was easy. The engine would be stroked and modified as needed, and a multipoint fuel-injection system would ride atop the lifter valley. Chevy V-8 engines are relatively simple to work on, reliable, and provide numerous fuel-injection options.

The goals were to install an engine setup that would provide smooth operation from idle up to about 4,500 rpm. Low-end torque for slow-speed crawling was more important than all-out high-end horsepower. The mid-band power, however, had to remain plenty strong for sustained street and dune driving. Reliability and decent fuel mileage were also important.

The engine of choice was a Chevy 383, basically a small-block 350 using a Chevy 400 crankshaft to stroke the engine, increasing the overall displacement. The 383 provides the improved torque characteristics of a Chevy 400 without the cooling problems of the larger-bore, siamesed cylinders of the 400. While this article will mention some of the parts used for the engine build, it won't show all the details involved in building such an engine. The major purpose of this story is to illustrate many of the considerations toward swapping most any small-block Chevy engine into a Jeep CJ.

The engine for this application was built upon a '78 four-bolt main 350ci block and a GM 400ci cast-iron crank with the main bearing journals turned down to match the block. Rods are stock pieces, and the pistons are Keith Black hypereutectic 9.5:1 compression units. A Summit TPI Hydraulic flat-tappet cam opens and closes the valves using 1.5:1 rocker arms, and the aluminum cylinder heads are Edelbrock Performance items. A GM L98 tuned port injection is used along with a speed density GM 7730 ECM (computer). The factory GM system offers reliability, self-diagnostic features, good parts availability, and a limp-home feature in the event of sensor failure.

The stock Chevy fuel injectors are rated at 22 lb/hr. With the increase in displacement and added flow upgrades, the stock injectors were replaced with 24lb/hr units. In addition, the factory base manifold and plenum were ported for improved intake flow. A factory harmonic balancer and automatic transmission flexplate from a 400 ci Chevy were used, and the complete assembly was externally balanced.

There are quite a few different transmissions and transfers cases that can be used behind a small-block Chevy, and there are numerous aftermarket adapters available to make the job easier. For this swap, an Advanced Adapters steel adapter ring was bolted to the back of the Chevy engine block to mate the engine to the original AMC version T400 auto transmission. The adapter ring laterally rotates the transmission mounting location 10 degrees, so the transmission mount must be shimmed on the passenger side of its mount. An adapter piece is also pressed into the end of the Chevy crankshaft. This piece receives the snout of the torque converter and is necessary because the adapter thickness moves the crankshaft away from the tranny. Steel spacers are also used between the flexplate and the torque converter.

New weld-in motor mounts using polyurethane donuts were used. For '76-'79 CJs with the Quadra-Trac transfer case, the engine and tranny are actually offset to the driver side to provide front driveshaft clearance near the Turbo 400 transmission. With the new motor mounts bolted to the block, and the engine located at its final position, the frame perches were positioned on the frame and welded into place.

Tubular steel manifolds from an '88 Corvette were used to keep the exhaust routed inside the framerails. The factory headers were Jet-Hot ceramic-coated to retain a clean appearance and prevent metal corrosion. The rest of the exhaust had to be modified and uses dual mufflers and dual catalytic converters to be emission-compliant in all 50 states.

The tuned port injection requires a GM computer (ECM) for complete engine control. The ECM was mounted as high as possible under the dash on the passenger side for protection from rain and water. The heater box was temporarily removed from the interior to provide easy installation. Additionally, a TPI-style accelerator cable was required, and the opening in the firewall had to be modified to accept the new cable. A vehicle speed sensor (VSS) was added inline to the speedometer cable where it connects to the transfer case to provide speed information to the ECM.

To supply the needed 45-psi fuel pressure for the new motor, a Holley inline electric fuel pump was mounted on the framerail next to the fuel tank and connected through a steel pre-filter. The output of the pump was connected to the fuel-injection system using the existing hard fuel line plus some stainless-braided lines and AN fittings. A fuel return line was also needed for the system. Steel-braided hose was used to connect to the existing hardline on the Jeep that had previously been used as the connection between the tank vent and the evaporative canister.

Follow the detailed photos as we show some of the pertinent changes and mods that were required for the swap from the AMC V-8 to Chevy V-8.

0312or 01z+1979 Jeep CJ7+Front Drivers Side View Engine On Cherry Pick
<b>1.</b> The engine in this article was built up as a 383 ci stroker engine, but the tips and modifications described here are applicable to almost any small-block Chevy. 1. The engine in this article was built up as a 383 ci stroker engine, but the tips and modifications described here are applicable to almost any small-block Chevy.
<b>2.</b> The engine was assembled using Edelbrock aluminum heads with stamped steel roller rockers. A standard long-neck water pump was used, and standard V-belts were used for the accessories. The stock GM TPI forward-facing water neck was installed. 2. The engine was assembled using Edelbrock aluminum heads with stamped steel roller rockers. A standard long-neck water pump was used, and standard V-belts were used for the accessories. The stock GM TPI forward-facing water neck was installed.
<b>3.</b> To help get the engine cranking, a Summit Protorque small case, high-torque gear reduction starter was installed. The increase in power compared with a stock unit will ensure the stroker motor cranks reliably, and the smaller case size makes exhaust routing and heat considerations less of a problem. 3. To help get the engine cranking, a Summit Protorque small case, high-torque gear reduction starter was installed. The increase in power compared with a stock unit will ensure the stroker motor cranks reliably, and the smaller case size makes exhaust routing and heat considerations less of a problem.
<b>4.</b> An Advanced Adapters engine adapter plate was used to mate the Chevy engine block to the AMC Turbo 400 auto tranny. The original dowel pins were removed from the block and longer replacement pins were installed. 4. An Advanced Adapters engine adapter plate was used to mate the Chevy engine block to the AMC Turbo 400 auto tranny. The original dowel pins were removed from the block and longer replacement pins were installed.
<b>5.</b> To provide plenty of exhaust flow and keep the exhaust routed inside the framerails, '88 Corvette tubular steel manifolds were used. These manifolds have the emissions air-injection tubes to be used in conjunction with an air pump. 5. To provide plenty of exhaust flow and keep the exhaust routed inside the framerails, '88 Corvette tubular steel manifolds were used. These manifolds have the emissions air-injection tubes to be used in conjunction with an air pump.
<b>6. </b>  4WD Hardware Inc. weld-in engine mounts were welded to the framerails. These sturdy mounts allow the installer to fine-tune the engine placement according to transmission placement or other needs. A single polyurethane donut on each side provides vibration isolation at the ends of the two mounts. 6. 4WD Hardware Inc. weld-in engine mounts were welded to the framerails. These sturdy mounts allow the installer to fine-tune the engine placement according to transmission placement or other needs. A single polyurethane donut on each side provides vibration isolation at the ends of the two mounts.
<b>7. </b>  The engine half of the motor mount bolts solidly to the side of the block using three bolts. The knock sensor seen here on the side of the block is part of the GM tuned port EFI system. 7. The engine half of the motor mount bolts solidly to the side of the block using three bolts. The knock sensor seen here on the side of the block is part of the GM tuned port EFI system.
<b>8. </b>  The majority of the engine and its components were assembled on an engine stand. With much of the assembly complete, the V-8 was ready for a trial fit in the stripped-down engine bay. The grille support rods, fender support brackets, the front grille, and both front fenders had been removed to make the engine swap easier. 8. The majority of the engine and its components were assembled on an engine stand. With much of the assembly complete, the V-8 was ready for a trial fit in the stripped-down engine bay. The grille support rods, fender support brackets, the front grille, and both front fenders had been removed to make the engine swap easier.
<b>9. </b>  A simple support jig had been fabricated to support the transmission in the Jeep while the engine was removed. A short piece of angle iron was laid across the framerails. Two steel tabs welded to the angle bolt to the transmission mount holes and support the front of the transmission. 9. A simple support jig had been fabricated to support the transmission in the Jeep while the engine was removed. A short piece of angle iron was laid across the framerails. Two steel tabs welded to the angle bolt to the transmission mount holes and support the front of the transmission.
<b>10. </b>  This photo shows the installed engine and the mating of the upper and lower motor mount pieces. You can see that there is plenty of clearance between the engine and the framerails. 10. This photo shows the installed engine and the mating of the upper and lower motor mount pieces. You can see that there is plenty of clearance between the engine and the framerails.
<b>11. </b>  A GM power steering pump was used in place of the old AMC unit. The original Jeep high-pressure hose was used, and standard rubber power steering hose and clamps were used for the low-pressure line. 11. A GM power steering pump was used in place of the old AMC unit. The original Jeep high-pressure hose was used, and standard rubber power steering hose and clamps were used for the low-pressure line.
<b>12. </b>  The Jeep already had a high-quality three-row radiator. However, the hose outlets on the Chevy engine are on opposite sides of those on the AMC V-8. A local radiator shop relocated the inlet and outlet fittings as needed. Conversion radiators are also available with the proper fitting location. The original Jeep lower radiator hose was used, and a NAPA upper hose was installed. 12. The Jeep already had a high-quality three-row radiator. However, the hose outlets on the Chevy engine are on opposite sides of those on the AMC V-8. A local radiator shop relocated the inlet and outlet fittings as needed. Conversion radiators are also available with the proper fitting location. The original Jeep lower radiator hose was used, and a NAPA upper hose was installed.
<b>13. </b>  To allow for engine startup and break-in, a temporary exhaust system needed to be built. Later, the Jeep was taken to an exhaust shop so a full emission-legal dual-catalyst exhaust system could be installed. The exhaust also required the addition of an oxygen sensor fitting, since this is required for the GM tuned port injection system. 13. To allow for engine startup and break-in, a temporary exhaust system needed to be built. Later, the Jeep was taken to an exhaust shop so a full emission-legal dual-catalyst exhaust system could be installed. The exhaust also required the addition of an oxygen sensor fitting, since this is required for the GM tuned port injection system.
<b>14. </b>  Once you get fully involved in an extensive engine swap project, the wiring harness is likely to look similar to this. Wiring for the new engine falls into two areas, modifications to existing Jeep chassis wiring and installation of the stand-alone harness to run the EFI and ignition system. 14. Once you get fully involved in an extensive engine swap project, the wiring harness is likely to look similar to this. Wiring for the new engine falls into two areas, modifications to existing Jeep chassis wiring and installation of the stand-alone harness to run the EFI and ignition system.
<b>15. </b>   A harness from Howell Engine Development was used to mate the GM ECM to the fuel injectors and to the various sensor components in the system. The Howell harness wire colors all match the GM factory colors, so tracing wires using a factory manual is easier. 15. A harness from Howell Engine Development was used to mate the GM ECM to the fuel injectors and to the various sensor components in the system. The Howell harness wire colors all match the GM factory colors, so tracing wires using a factory manual is easier.
<b>16. </b>  A standard GM HEI distributor with integral coil was used. Since the stand-alone harness controls all fuel and ignition, the stock harness wires that went to the AMC distributor, ignition module, and ignition coil were removed. 16. A standard GM HEI distributor with integral coil was used. Since the stand-alone harness controls all fuel and ignition, the stock harness wires that went to the AMC distributor, ignition module, and ignition coil were removed.
<b>17. </b>  The wiring to the alternator was left intact and simply reconnected to the new GM alternator. The ignition power wire that went to the old ignition module was connected to the GM HEI distributor. Also, the tach output from the HEI was connected to the tach input wire, which previously went to the coil (negative) terminal. 17. The wiring to the alternator was left intact and simply reconnected to the new GM alternator. The ignition power wire that went to the old ignition module was connected to the GM HEI distributor. Also, the tach output from the HEI was connected to the tach input wire, which previously went to the coil (negative) terminal.
<b>18. </b>  With the addition of more power under the hood, a little extra braking power couldn't hurt. To improve the response of the brake system, the stock brake booster was replaced with a larger model from a Jeep Wagoneer. This swap required installation of the CJ pushrod into the Wagoneer diaphragm. 18. With the addition of more power under the hood, a little extra braking power couldn't hurt. To improve the response of the brake system, the stock brake booster was replaced with a larger model from a Jeep Wagoneer. This swap required installation of the CJ pushrod into the Wagoneer diaphragm.
<b>19. </b> Once the engine was installed, wiring completed, and cooling system plumbed, it was time to replace the front sheetmetal, hook up the battery, and fire it up. After a brief cam break-in, the Jeep was road-tested. Wow! What a difference in torque and overall power! 19. Once the engine was installed, wiring completed, and cooling system plumbed, it was time to replace the front sheetmetal, hook up the battery, and fire it up. After a brief cam break-in, the Jeep was road-tested. Wow! What a difference in torque and overall power!

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