The only drawback to driving one of the most popular mini-trucks ever built is that they are obscenely underpowered. The Mazda B-Series, Chevy S-10, and GMC Sonoma, in four-cylinder form, are slow going and certainly not the most exciting machines to drive. There isn't a snowball's chance in hell of ever smoking another truck from stoplight to stoplight in one of these minis without performing some healthy modifications. Just how weak is the stock 2.2L four-cylinder engine in a GMC Sonoma? According to our tech center's Dynojet chassis dyno, our test truck made just 84 hp at the rear wheels! Of course you know where we are going with this story. Like you, we want more power from our four-bangers.
In the most basic of terms, your mini's engine is a large air pump. Its job is to suck in air and fuel, compress and burn it, and then push it out through the exhaust system. The quicker we can deliver air into the motor, efficiently burn it, and force it out, the more power the engine will make. The stock parts do a reasonably good job of performing these duties, but the aftermarket does offer something better. Our test mule was a body-dropped GMC Sonoma that had plenty of style, but not enough power to go along with it. We decided to perform the most basic bolt-on power additive by installing an aftermarket header. Our search for a smog-legal header for a 2.2L engine led us to Al's Headers and Fabrication for one of its ceramic-coated, tig-welded headers. Al's header bolts into the stock down tube and requires zero modifications to install. Once in place, the Sonoma came alive with more bottom-end grunt (good for burnouts) and extra top-end horsepower. In a nutshell, we spent 30 minutes installing the header and gained 12.6 hp and 22.4 lb-ft of torque at the wheels! These are mighty impressive numbers for a stock four-cylinder engine with no other modifications. For more information on this header, contact Al's Headers and Fabrication using the contact information listed in the source box.
1.The first step toward installing...
1.The first step toward installing the new header is to gain access to the stock exhaust manifold. The air intake is the first part to be removed.
2.Next, we loosened the air...
2.Next, we loosened the air conditioning compressor bolts, and after shifting the compressor, we pulled off the serpentine belt.
3.After removing the mounting...
3.After removing the mounting bolts for the compressor, we also unbolted the A/C condenser from its mount.
4.There is plenty of slack...
4.There is plenty of slack in the A/C lines to set both the compressor and the condenser on top of the radiator and out of the way.
5.The stock exhaust manifold...
5.The stock exhaust manifold and heat shield are unbolted next. Here is what the exhaust ports of the head look like.
6.Al's header is made from...
6.Al's header is made from 14-gauge tubing with an 1-7/8-inch-diameter that mates perfectly to the factory exhaust ports of the motor. There is no restriction or portwork necessary to make these headers flow.
7.The mounting flange is made...
7.The mounting flange is made from 3/8-inch-thick, laser-cut, cold-rolled steel. It won't bend or warp like most other headers.
8.This pre-production header...
8.This pre-production header is tig-welded to ensure perfect, leak-free welds. It also features a bung to retain the factory O2 sensor that will keep your local smog referee happy. Production headers will feature full mandrel-bent primary tubes and ceramic coating, which will aid in keeping the exhaust heat inside of the tubes and out of the engine compartment of your truck.
9.The main reason the stock...
9.The main reason the stock exhaust manifold is so restrictive is that the primary tubes meet at a very restrictive collector, which limits the tube length and necessitates smaller tubes.
10.Installation of Al's header...
10.Installation of Al's header is straightforward. The new header uses all of the factory hardware and fits with zero modifications.
11.The new header bolts right...
11.The new header bolts right up to the stock flex-fit downpipe.
12.After putting the Sonoma...
12.After putting the Sonoma back together, we headed over to the Primedia Tech Center, home to the Mustang Chassis Dyno.
14.We made three runs on the...
14.We made three runs on the dyno in Third gear to assess the performance gains of the new header. The engine made 96.6 hp and 117.4 lb-ft of torque at the rear wheels.
|Dyno Sheet |
Stock 2.2L Four-Cylinder Engine
|RPM ||POWER ||TORQUE |
|2,500 ||44.4 ||93.2 |
|3,000 ||51.3 ||89.8 |
|3,500 ||61.4 ||92.1 |
|4,000 ||71.8 ||94.3 |
|4,500 ||81.4 ||95.0 |
|5,000 ||84.0 ||88.2 |
|5,500 ||81.9 ||78.2 |
|2.2L Four-Cylinder Engine With |
|RPM ||POWER ||TORQUE |
|2,500 ||52.0 ||109.3 |
|3,000 ||67.0 ||117.4 |
|3,500 ||76.7 ||115.1 |
|4,000 ||84.8 ||111.4 |
|4,500 ||94.0 ||109.7 |
|5,000 ||96.6 ||101.5 |
|5,500 ||94.6 ||90.3 |