In the Oct. '05 issue of Sport Truck, we started the task of powering up a GM Vortec big-block powerplant in a '96 Chevy Crew Cab dualie. The goal was to increase the amount of torque the fuel-injected big-block produced without negatively affecting fuel economy because this truck is a daily driver and frequent tow pig. We began by having Superior Automotive port the factory iron cylinder heads and upgrading the valves. The flow numbers the shop achieved with the undersized heads were very impressive. When the time came to reinstall the cylinder heads, we changed the plan at the shop and veered away from the combination the shop routinely installs in this motor for maximum power. Fuel prices had reached record levels in California, and with no end to the lunacy at the gas pumps in sight, we wimped out and had the shop keep the compression ratio low and the camshaft small. We still knew we'd gain torque, just not the amount we would have by bumping up the compression ratio and feeding the beast $3 a gallon for premium fuel every day.
When we went to install the heads and new valvetrain, we ran across a couple of problems that kept us from running the editorial last month, but we'll cover them in detail this round. As we stated in the last installment, we opened up the heads to flow better numbers, and we saw exceptional improvements, especially after replacing the intake and exhaust valves with larger Manley stainless swirls. The intake valve changed from 2.060 to 2.190 inches, and the exhaust changed from 1.720 to 1.800 inches, as well. This month, we are going to reinstall the cylinder heads and swap the stock GM valvetrain in favor of Comp Cams' off-the-shelf Gen V hydraulic roller cam, which is a plug-and-play setup. With this cam, you don't need to worry about degreeing the cam, because Comp Cams sets the centerline for you. This cam has 0.510 inch of lift, which we are going to increase with 1:8.1 rocker arms that will bring the lift closer to 0.550 inch. The conversion from a standard hydraulic flat tappet cam to a Comp Cams' full roller will also net a few more ponies by reducing friction in the valvetrain.
The first problem that came up during the installation was that 1996 was a cross-over year for the big-block in GM 1-ton trucks. This means that you could have one of a variety of different cylinder blocks between the framerails, depending upon when your truck was built. It would appear that both Gen V and Gen VI blocks were used, and we found out the hard way that there are a couple of differences between them. First off, the snout of the cam on the Gen V is stepped down and uses a completely different method of cam retention than the older-style block. This dramatically limits your off-the-shelf cam selection. Plus, there are no adjustable timing chains available for the newer-style cam, which means you are forced to either convert to the standard cam and timing cover, and work out the ignition pulse that is read by a sensor mounted in the timing chain cover, or pick from the narrower selection of Gen VI camshafts.
The second problem we encountered occurred when reinstalling the stock, low-profile valve covers, which hit the poly locks. If you decide to convert the Gen V to a roller system, make sure you ask for shorty poly locks for the rockers, because the long locks hit the valve cover. Forget about getting a taller cover, because the throttle body sits right atop the passenger-side valve cover. Should you decided to do these mods, it's essential you order the correct cam for your engine. Here is a list of descriptions that will help you identify your engine block.
Superior made sure the static compression ratio of our 454 stayed at 8.5:1, which ensured that we could pump 89 octane fuel into the tank under normal commuting conditions and switch to premium fuel, when the strains of towing a load demanded it. We were impressed with the power figures and the adjustability of this upgrade after all was said and done. We ran the combo on the dynamometer and found as much as 58 hp and 63 lb-ft of torque increase over the stock configuration, but that's not the impressive part. We liked that the powerband was spread out over 2,000 rpm. The truck retained its dismal 10-1/2-mpg fuel consumption but, with the additional torque on tap, was much easier to drive and tow with.
Dyno testing was conducted with an Innovative Motorsports band air/fuel ratio monitor plumbed into the exhaust system. Using this handy tuning tool, we noticed that the mid-throttle and open-throttle air/fuel ratios were in the 10s. This is way too rich, which would leave us to speculate that there is an additional 10 more ponies to be had with an air/fuel ratio closer to 13 or 14:1 on the top end. We also noticed a sizeable flat spot just off idle in the throttle response under light acceleration that we'll attend to in our next round of tuning.
Check in next month, when we use Innovative Motorsports tuning tools to dial in the tune.
|PRICES (Found at Summit Racing) |
|DESCRIPTION ||COST |
|Computer Tune ||$350 |
|Cam #: 01-445-8 ||$245 |
|Lifters #: 854-16 ||$425 |
|Pushrods (length to fit) ||$88 |
|Rockers #: 1128:16 ||$311.29 |
|Head Work by Superior ||$1,499 |
|Total ||$2,918.24 |
|CASTING # ||TYPE ||YEAR ||ENGINE |
|10069282 ||366T ||'90-'91 ||4-bolt, Mark IV, Tall deck |
|10069284 ||427T ||Various ||4-bolt, Mark IV, Tall deck |
|10069286 ||454 ||'90-'91 ||4-bolt, Mark IV, Short deck |
|10114182 ||454 ||'91-and-later ||4-bolt, Gen V |
|10114183 ||366T ||'91-and-later ||4-bolt, Gen V |
|10114184 ||427T ||'91-and-later ||4-bolt, Gen V |
|10134366 ||454T ||Various ||4-bolt, Bow Tie, Gen V, Tall deck |
|10185050 ||454 ||Various ||4-bolt, Bow Tie, Gen V, Short deck |
|10237297 ||454 ||'96-and-later ||4-bolt, Vortec 7400, "L-29" Gen VI |
|10237300 ||502 ||'96-and-later ||4-bolt, Gen VI, 4.466-inch bore |
|12550312 ||427T ||'96-and-later ||4-bolt, Gen VI, 4.250-inch bore, fuel pump and |
clutch linkage boss
|12550313 ||454 ||'91-and-later ||4-bolt, Gen V crate motor, Gen VI, |
4.250-inch bore, fuel pump boss
|12556110 ||496 ||'01-and-later ||4-bolt, Gen VII 8.1L, Vortec 8100, Truck |
|12561357 ||454 ||'96-and-later ||4-bolt, Gen VI |
|12561358 ||502 ||Various ||4-bolt, Gen VI |
|14015443 ||454 ||'87-'90 ||2- or 4-bolt, Mark IV, Truck, Motorhome |
|14015445 ||454 ||'78-'90 ||2- or 4-bolt |
|14044807 ||454T ||Various ||4-bolt, Bow Tie, Mark IV, Tall deck, |
4.25- or 4.495-inch bores
|14096859 ||502 ||Various ||4-bolt, Gen V, HO |
|24502504 ||454 ||Race ||4-bolt, Bow Tie, Gen V, 9.8 "Short" deck |
|24502506 ||454T ||Race ||4-bolt, Bow Tie, Gen V, 10.2 Tall deck height |
1.We converted our hydraulic tappet cam to a roller. This doesn't help noise but reduces w
2.The roller lifters are longer than the stock units. A new pushrod length will need to be
3.Due to the longer lifters, you will need two new lengths of pushrods. The exhaust (longe
4.The new rockers were made adjustable with poly locks. The poly locks needed a threaded s
5.As we discussed last month, a 1.8:1 roller rocker was used to increase the cam lift to 0
6.The old-school big-block design, with meaty 4-bolt main caps and thick rods, is an aweso
7.Superior's labor involves a complete port and polish, larger valves, a three-angle valve
8.Also included in Superior's head work is some new hardware: larger valves, anti-rotator
9.Here is a good indicator of which block you might have. The pushrod girdles are stamped
10.Here's our off-the-shelf cam's specs. It has a 0.510 lift, but that's based on a stock
11.The new big-blocks from GM use a cam retainer. This is how they keep the cam from drift
12.These new cams also have a different cam snout to accommodate the cam locator. This is