Power For Peanuts: Gen V Big Block Power

Is it possible to improve the power output of a lowly peanut-port 454 BBC?

By Richard Holdener/Photos by Author

We all love big-block Chevys, right? But does that love affair include the much –maligned, peanut-port motors?

For the uninitiated, peanut port refers to the small, oval-port heads used on the Gen-V 454 truck motors run prior to the introduction of the Gen VI in 1996. When Chevy introduced the Gen VI iteration, they replaced the small oval-port heads with conventional-sized oval ported that flowed considerably better than their smaller brethren.

In addition to the less-than-ideal, peanut-port heads, the Gen-V motors were also saddled with hydraulic flat-tappet cams.

Since head flow is one of the key components to power production, the peanut-port heads are often dismissed by big-block enthusiasts as little more than paper weights. While it is true that you can ultimately make more power with standard oval-port heads (like the much sought-after 049s), don’t rule out the plentiful peanut-ports for your daily driver, especially if you are looking for a cheap alternative that makes plenty of torque.

Though originally equipped with throttle-body fuel injection, we ran our junkyard, Gen –V 454 with a dual-plane intake from Speedmaster and 750-cfm, 4-barrel carb. The computer controller distributor was also replaced with a conventional distributor. Run on the dyno with long-tube headers, the peanut-port 454 produced 334 hp at 4,300 rpm and 448 lb-ft of torque at 3,500 rpm.

Besides, the junkyards are full of Gen-V motors just begging to be pulled and transformed. With torque production in mind for a heavy truck or towing application, we decided to see just what the peanut-ports had to offer.

To start our adventure, we took a trip over to our local wrecking yard to scoop up a Gen-V 454. While Gen-VI motors offer a number of desirable features, including a hydraulic-roller cam and larger oval-port heads, we wanted to start off with the peanut-ports heads.

We liked the fact that the Gen-V motors all came equipped with 4-bolt mains.

The Gen-V motors not only featured the smaller intake ports, but also hydraulic flat-tappet cams. These Gen-V motor will usually be topped by a simple throttle-body injection, which we removed prior to dyno testing. After grabbing a suitable candidate from a full-sized truck, we cleaned it (a little), installed it up on the dyno and began our dyno prep.

Because it now lacked an induction system, we installed a dual-plane intake from Speed Master. A dual-plane intake is the ideal choice for a low-rpm, torque application. The intake was teamed with a 750-cfm (4-barrel) carb, a conventional distributor and long-tube headers. Run in this configuration, the Gen V 454 produced 334 hp at 4,300 rpm and 448 lb-ft of torque at 3,500 rpm. While it was certainly no power house, we did have a running, usable big block, and that’s always a good thing!

While it’s possible to toss a cam and springs in this combo and call it good, we decided to rebuild the motor instead. Our thinking was that it was destined to serve long hours under grueling conditions, why not give it a new lease on life.

Besides, everything we did would only help power production with the peanut-port heads. After disassembly, the block was bored .030 over to receive forged (18-cc dome) pistons. The pistons were slung on the reconditioned, factory rods and a polished, stock crank. Obviously new rings were installed on the forged pistons.

The piston swap increased the static compression from pathetically low to a more reasonable 9.3:1. The peanut-port heads received a light surface and performance valve job, but were not ported in any way. Additional power would be possible with porting, as the stock head flow was certainly limiting power of our 461 (.030-over 454). After a fresh coat of paint, the 454 was almost ready to rock, all it needed was the major power producer.

This shot illustrates the port size difference between the factory peanut port and a typical rectangular port head. Fear not as the peanut port heads worked well on this mild application designed with torque production in mind.

Though Gen-V big-block enthusiasts are quick to point to the cylinder heads, the reality is that the limiting factor in terms of power production was actually the camshaft. Designed for towing, the factory truck cams were the mildest of the bunch.

Because a broad torque curve was the primary goal, we installed this dual-plane intake manifold from Speed Master. The intake design offered exceptional torque production though the entire rev range. It should be pointed out that the intake was designed for the larger oval-port heads and as such, offered a slight port mismatch with the smaller peanut-port heads.

To cure this problem, and maximize the power offered by the diminutive cylinder heads, we upgraded the factory camshaft. Cam selection is a function of usage, and while more power was certainly possible with a wilder profile, we chose the Xtreme Energy XE268H from Comp Cams. The XE268H offered an impressive combination of performance and drivability on our 461-inch motor.

The XE268H offered a .515/.520 lift split, a 224/230 duration split (measured at .050) and a 110-degree lobe separation angle. Small by big- blocks standards, the XE268H offered an impressive combination of idle quality and torque production.

The cam and lifters were installed with liberal doses of assembly lube. After the requisite break-in procedure, the Gen V eventually produced 446 hp at 4,900 rpm and an impressive 542 ft-lb of torque at 3,600 rpm. Torque production from the peanut ports exceeded 500 ft-lb from 2,800 rpm to 4,600 rpm. I guess there is power to be had from peanuts after all.