Searching For Power: Truck Tech: Part 1--Dodge Dakota

We all know you people are buying trucks. Yeah, you've got a street machine or a project car, but you're probably getting to work in a pickup. So, we figured, "Why not do a series of engine, suspension, brake, and other tech stories that shows off what real hot rodders are doing to make their trucks more effective. No, this isn't crazy sport truck or monster mudder tech; it's stuff you can do to have more fun with a truck on which you're still making payments.

This month it's the Dodge Dakota, the only midsize truck that comes with a V-8 (Sorry, Ram fans, but the transition to the new platform means you'll have to wait). In November, it'll be Chevy's Silverado and such (with a little S-10 stuff thrown in), and in December we'll showcase Ford's F-150 and blown Lightning. Happy Hauling!

Regardless of what other magazines may state, as a whole, editors usually do not obtain any better results with their projects than readers do; we are just as prone to failure and disappointment as you. One would tend to think that the "magazine guys" would get special attention from the manufacturers. Sometimes this is the case, but more often than not we lay our money down on the promise of results that may or may not come to fruition. As you may have gathered by now, we are setting you up for the less than sterling results we obtained with our '00 Dakota R/T project. However, every engine has a story and this is ours.

Gene Werst is the owner of our subject Dakota, and he uses it to commute 100 miles round-trip per day in the grueling environment known to New Yorkers as the Long Island Expressway. PHR wanted to see how much power could be found in the popular R/T while not compromising the attributes of an everyday driver. We enlisted the services of Bob Ida's chassis dyno and tuning shop, testing each component and establishing a baseline. Gene's truck was not completely stock when we got to it; it had the Mopar Performance 1.6 roller rockers (better design with a stock ratio) and shorty-style Mopar Performance Parts headers. In this trim the truck produced a very impressive 224 hp at the rear wheels. We decided to go the bolt-on route to maintain emissions compliance and reliability. In essence, this meant anything other than a camshaft or a blower. Remember, this truck is driven every day on pump gas in all weather.

A systematic approach was taken and a Mopar Performance Parts cold-air kit, high-flow throttle body, and performance ECU were added in that order. Eliminating the factory airbox took no longer than 15 minutes and rewarded us with 9 hp at the rear wheels. The high-flow throttle body was a half-hour swap and yielded 6 hp, while the ECU installation took only 10 minutes and gave 5 hp. Our Dakota was now sitting pretty with 244 hp at the wheels, which equates to about 292 hp at the flywheel.

With 20 easy-to-find ponies, we wanted more--our goal now became 300 hp at the rears. Mopar told us that they had new Magnum ported heads with varying valve sizes, PN 4876257 with 1.97-inch intake/1.625-inch exhaust or PN 5007141 with 2.02/1.625 valves. The smaller valve version equaled the stock valve sizes, and we projected a 20hp gain as a direct bolt-on (with more port velocity and 39-cfm-more flow). They didn't tell us that the intake runner volume was 18 percent greater: 180 cc versus the stock 153 cc (but there it was, in the catalog...our mistake). This mistake would ultimately be our demise, with the large runner slowing down the charge and limiting volumetric efficiency.

With the cast-iron R/T cylinder heads on order we made plans for reworking the stock barrel-style intake manifold to support the new higher-flowing heads. Ace Porsche technician and Dakota enthusiast Thom Moehringer scribed the intake manifold to the gasket dimension so that it could be sent to Extrude-Hone for their abrasive flow media porting service. Then, it was off to Swain Tech Coatings for a thermal barrier coating on the bottom and a dispersant on the top to better control heat. Note: An EFI induction system passes only air and thus becomes excessively heated by thermal transfer from the engine. By limiting the heat transfer from the hot engine oil on the bottom and allowing the manifold to dissipate the heat through the top, the charge stays cooler, which equates to higher density. This will not only provide more power but also limit detonation and improve fuel efficiency.

With the engine back together it fired right up with just a twist of the key. The exhaust now had a snarl that was never there before, and with no load, the needle seemed to sweep the face of the tach quicker. We were all anxious to take it for a ride and experience the new power. However, our bubble was burst the first time the throttle was whacked to the floor. Below 4,000 rpm it felt no better than it did before we swapped the cylinder heads--opposite of what truck mods should present. Above that point it now pulled marginally stronger, holding power for a few-hundred rpm over stock. This was a paradox. The exhaust sounded strong, the idle quality was much better, and the truck pulled smoother but no faster. This just could not be, so we went back to Ida to dyno test.

When the rollers stopped turning on the Dyno-Jet, we could not believe our eyes. The run was a carbon copy of the last trip with only the bolt-on modifications in place. Exactly as our rump told us there was not one more pony to be had below 4,000 rpm. From that point on the power held in longer, but the peak was only 3hp more than our last session for a total of 247 hp. The interesting thing was the engine now pulled much more smoothly under load, and the trace detonation that was always heard around 3,000 rpm was gone, but the air/fuel ratio was the same, locked in at 10.9:1 at WOT. Knowing that we were giving away power with the rich mixture, Bob Ida suggested installing a Unichip system that works in concert with the factory ECU and enables him to take full control of the fuel curve. Bob is a dealer for this product, so we had him order the Unichip ECU and made an appointment to install and tune it. With the air/fuel ratio brought under control an additional 10 hp was discovered for a total of 257, a long cry from our goal of 300 hp.

In analysis, we think the problem is that the large runner in the R/T cylinder head was killing port velocity below 4,000 rpm. This was especially disturbing since the cylinder head was the keystone of our second phase of modifications and ultimately did not allow the Extrude-Hone and Swain Tech coating service, along with the tuneability of Ida's Unichip system, to show their potential. Without mincing words the Mopar cylinder head is a nice piece with a beautiful short turn and good flow numbers, but some may say it is not a good choice for a barrel intake manifold-equipped 360 with a short camshaft. Mopar's suggestion of a 20hp gain is realistic (actually, low) with their single-plane intake manifold conversion and a larger camshaft. However, that could kill the engine's low-end torque and smog-legal status.

Mathematically, the final power at the flywheel was 308 hp, and this is nothing to laugh about! Due to editorial deadlines we did not have the time or energy to take our own advice and port the small runner stock heads and swap them back-those are serious man-hours. We come away from this establishing for our readers what works on these trucks and learning, once more, a very important and expensive lesson: Success lies in the combination.

SOURCES:

Swain Tech Coatings Inc.
35 Main St., Dept. PHR
Scottsville, NY 14546
(716) 889-2786

IDA Automotive Inc.
600 Texas Rd., Dept. PHR
Morganville, NJ 07751
(732) 591-2630

Mopar Performance Parts
P.O. Box 559, Dept. PHR
Oxford, MI 48371
(248) 969-1690

Extrude Hone-Powerflow Inc.
1 Industry Blvd., Dept. PHR
Irwin, PA 15642-2794
(724) 863-5900