enhancement for a V-8 in a Jeep. This AMC version is destined for Bryan Sterner’s 1980 CJ-7 that is running the stock 304. A proper-size 4-barrel carburetor and matching Edelbrock Performer camshaft completes the package.
Companies such as Edelbrock, Offenhauser, and Weiand make performance manifolds for the AMC V-8; most are made to work with 4-barrel carburetors and can be adapted to work with modern throttle body fuel-injection systems. The Edelbrock Performer series intake with its matching camshaft make an excellent combination to make some extra torque and horsepower from the engine that is nearly perfect for an on- and off-road Jeep. Most aftermarket manifolds can be purchased with or without emissions capabilities.
A small (470 to 670 cfm) 4-barrel carburetor or throttle-body fuel-injection system added to a V-8 running an aftermarket intake and cam provides better throttle response and starting. Two excellent carburetors for use in a Jeep are the Edelbrock Performer and the Holley Truck Avenger. When either is combined with the combination above, optimum performance on- and off-road can be achieved.
Holley carburetors have always been known for their exceptional performance, except when used off-road. The front and rear fuel bowl combined with the bowl venting location often caused fuel to dump into the throttle body when ascending or descending hills, resulting in flooding and stalling. Holley answered the call of off-roaders with a specially designed off-road carburetor called the Truck Avenger, featuring special metering blocks and off-road crossover vent tube.
The Edelbrock Performer Series carburetors are based on the Carter AFB and come in a variety of flow capacities. The integrated side-bowl design of the carburetor makes its off-road performance excellent compared to most other performance carburetors. The pre-tuned bolt-in design makes this a popular aftermarket carburetor.
The Edelbrock carburetor is based on the Carter 4-barrel but is specially tuned for the Performer Series products. The integrated main body side bowls and simple design make this very effective in a Jeep, especially off-road.
The Holley Truck Avenger is based upon the Holley 4160 with several modifications to make it perform in off-road conditions. Most notable is the crossover vent tube to prevent flooding on ascent and descent and spring-loaded needle and seat to control fuel flow. The Holley Truck Avenger is available in three CFM sizes. A 470-cfm suits the 304 and a 670-cfm suits the 360 and 401. Avoiding the tendency to over-carburete an engine; using the 770-cfm pays off in the form of performance and no tearing eyes from fumes.
Holley, Howell, and MSD produce electronic throttle body fuel-injection systems that replace the carburetor and can provide a high level of all-around performance, most notably in off-road conditions and starting in both cold and hot environments. These systems can operate with full, minimal, or no tuning; often through the use of the many sensors, the system tunes itself constantly while operating. A small drawback of these systems is the complexity of installation and the added potential points of failure.
Throttle body injection (TBI) systems offer a modern replacement to a traditional carburetor. The Holley Pro-Jection TBI was a popular system in the off-road community. Its simple design, easy starting, and steady engine performance at any angle were just a few of the positive features. This Holley Pro-Jection system has been running on this 350 Chevy-equipped 1985 CJ-7 for more than 20 years. Holley replaced the Pro-Jection system with the updated Holley Avenger electronic fuel injection (EFI) system.
In general these systems operate confidently, with most failures occurring with the fuel pumps. You can solve this by always carrying a spare on the trail. These systems can be expensive and the benefits may not outweigh their complexity and price.
V-8 Camshafts
A variety of camshafts are available for the AMC V-8. Many are made for strip or other racing applications, but a few exist that are perfect for the Jeep. As I mentioned before, the Edelbrock Performer Series components are nicely matched to each other. The Performer camshaft for the V-8 provides a nice power curve that increases low-end torque and mid-range horsepower. This mild build camshaft does not alter the low-end idle of the Jeep as a high-duration camshaft does, which is important when driving off-road slowly.
The small lobes and short duration on the stock camshaft in most engines made for smooth, fuel-efficient engines but at a cost to performance. Replacing a camshaft is an involved project that produces noticeable results compared to many other performance modifications. Choose a cam matched to the intake system for the best performance results. High-lift and long-duration cams sound nice but are difficult to drive off-road, as they sacrifice low-end torque for high-RPM horsepower.
Other camshafts in the 204/214 duration and 448/472 lift ranges provide added low-end torque. In addition to upgrading a camshaft, upgrading the engine’s timing chain to a dual roller completes the package.
V-8 Exhaust
The 1970–1991 AMC V-8 used a dogleg exhaust port that provided 20 percent better flow than prior-generation AMC heads. The factory V-8 used cast-iron exhaust manifolds that used a combining Y-pipe to exit the rear driver’s side of the Jeep. The factory exhaust manifolds flow well for the purpose of a street- and trail-used Jeep; they can be retained and when combined with an upgraded exhaust, increase flow and torque.
The dogleg port seen on this dirty AMC cylinder head is a unique feature of the AMC tall deck engines introduced in 1970. The extra port provided increased flow compared to the prior design.
Typically, a single exhaust is most common on trail-used Jeeps. The low-end torque on both the I-6 and especially the V-8 is better with a single exhaust system.
Although exhaust manifolds perform best on a street- and trail-used Jeep, a Jeep with headers, especially fenderwell headers, adds a cool factor that is hard to deny. Fenderwell headers exit the Jeep’s engine compartment just behind the front wheels. A small muffler or cherry bomb muffler is typically used to quiet the exhaust. Almost all fenderwell header Jeeps are loud, so you need to be able to tolerate the noise that comes with the classic look.
Headers improve exhaust flow slightly over the factory manifolds, and the use of matched tube-length headers provides balance to exhaust output. Fenderwell headers are troublesome when used off-road because they may become damaged on obstacles and interfere with the often-used side rocker protection rails. In-frame headers allow for the exhaust to be run within the frame rails, but space is tight on the passenger’s side due to the transfer case drop.
Fenderwell headers hold both a performance enhancement and a visual appeal. Many 1970s-era V-8 CJs can be seen running these type of headers with small mufflers or glass-packs. With these headers comes a fairly loud exhaust sound, which is sure to wake the neighbors.
Speaking anecdotally, many Jeep owners who have outfitted their Jeeps with headers of either kind have removed them to revert back to the factory manifolds. The reasons given for this are often constant exhaust leaks, excess underhood heat, and noise.
