Subscribe to the Free
Newsletter

Cam and Heads Add Over 100 hp to Small-Block - Mini Mouse, Part 2

Maximizing Mini

Richard Holdener Apr 22, 2015
View Full Gallery

Well, Super Chevy fans, we’re back with another installment of Mini Mouse. The smallest of the LS family, the 4.8L LR4 Mini Mouse was aptly named. But just because it is displacement-challenged, don’t count out the LR4. For the uninformed, the 4.8L shared the block and bore size with the larger 5.3L, but the 4.8L made due with a shorter 3.267-inch stroke (the 5.3L has a 3.622-inch stroke). Since the 4.8L and 5.3L share the same piston compression height, the difference in stroke was made up with the use of a longer connecting rod in the 4.8L (6.275 vs. 6.098). Enthusiasts are quick to point out the rpm potential of the short-stroke LS, a feature we plan on exploiting in the not-to-distant future. For now, we need to concentrate on getting more power out of the little 4.8L, and what better way than with a cam and head upgrade?

In part 1 of the Mini Mouse series, we treated the 4.8L to mild Crane cam followed by a pair of carbureted intake manifolds. For this round, we decided to stick with fuel injection, get more aggressive on the cam timing, and top things off with a head swap. A word of warning is in order here with regards to cam timing on the little 4.8L. The 4.8L does not need much cam timing to be a serious performer, so resist the temptation to go too big with a cam. Case in point, we added a relatively mild Crane cam with 224 degrees of intake duration and this pushed peak power production up to 6,800 rpm. Before making any changes, we first installed Mini Mouse back on the dyno and established a baseline with the stock cam, heads, and intake. In anticipation of the cam swaps, the stock 706 heads had been upgraded with beehive springs from Comp Cams (PN 26918). Run in stock trim, the 4.8L produced 336 hp at 5,500 rpm and 345 lb-ft of torque at 4,700 rpm.

With Mini Mouse primed and ready for a trip on Mr. Toad’s Wild Ride, the first order of business was to replace the factory camshaft. Out came the stock cam and in went a powerful profile from Crane Cams. The Crane cam offered 0.590-inch lift (intake and exhaust), a 224/232-degree duration split, and a wide 115-degree lobe separation angle. Installed in a 6.0L this would be considered a daily driver cam, but in the 4.8L this beast made peak power at nearly 7,000 rpm. Along with the cam we also installed a set of Crane hydraulic roller lifters and hardened pushrods. Since our JE forged SRP pistons featured generous valve reliefs, along with the previously installed valvespring upgrade, the cam profile presented no problems. After tuning the Holley 50-pound injectors with the Dominator ECU we were rewarded with peak numbers of 414 hp at 6,800 rpm and 363 lb-ft of torque at 5,400 rpm. The power gains came with no changes to the truck intake or factory cylinder heads. Measured peak to peak, the cam-only swap netted us an impressive 78 hp, but the gains exceeded 100 hp out near 6,600 rpm.

All it took to make Mini a 400hp Mouse was a simple cam swap, but we were far from finished. Next on the list was a cylinder head upgrade. The small bore and minimal displacement of the 4.8L required a dedicated cylinder head. After checking online, the ideal choice seemed to be the Gen X 205 heads from Trick Flow Specialties. Checking in with 205cc intake ports, the heads maximized flow while minimizing port volume. More than just CNC-porting, Trick Flow altered the valve angles from 15 to 13.5 degrees to improve flow. They then beefed up the rocker pedestals to improve valvetrain stability and relocated the spark plug holes to further enhance mid-lift flow. We also liked that the Gen X 205 heads featured 58cc combustion chambers, a 2.000/1.575 valve package, and dual valvesprings easily capable of swallowing our near 0.600-lift cam. Need some flow numbers? How does 284 cfm (enough to support over 550 hp) sound? To maximize sealing, we installed our heads using a set of Fel-Pro MLS head gaskets and ARP head studs. Although overkill for the naturally aspirated combo, these would later come into play when we installed the turbo, the blower, and nitrous.

Once the heads were torqued in place, we installed the Crane hardened pushrods and factory rockers. With everything hooked up, we punched a few keys on the ol’ keyboard and the TFS-headed Mini Mouse roared back to life. After some minor tuning, the head swap netted some excellent power gains. With the Gen X 205 heads, the peak numbers jumped to 442 hp at 6,900 rpm and 380 lb-ft of torque at 5,600 rpm. The head swap shifted peak torque by 200 rpm and peak power by 100 rpm. Every bit as impressive as the peak power gains was the fact that the heads improved power throughout the entire powerband, with gains increasing with engine speed. It should be pointed out that the limiting factor on this combination now was the factory truck intake, as it was never designed for 7,000-rpm power production. What this combo needed was a FAST LSXR or RT intake, but how do you complain about adding more than 100 hp? In the next installment look for some boost as we demonstrate not just what a turbo adds to the mix, but what the cam and heads are worth under boost.

No matter how often we witness a cam swap on an LS, the power gains are always amazing. Installation of the Crane 224 cam in this 4.8L was no exception, as Mini Mouse responded like any good LS with an additional 78 hp. With the stock cam, the 4.8L produced 336 hp at 5,500 rpm and 345 lb-ft of torque at 4,700 rpm. After installation of the Crane cam, these numbers jumped to 414 hp at 6,800 rpm and 363 lb-ft of torque at 5,400 rpm. The cam shifted the torque curve higher in the rev range, but note that there was no trade-off in power anywhere for the massive gains at the top of the rev range.

In truth, this head swap had everything going against it since the stock 706 heads flowed more than enough to support the power needs of the small-displacement 4.8L. The fact that the Gen X 205 heads offered any power is impressive enough, but that the peak power jumped from 414 hp and 363 lb-ft of torque to 442 hp and 380 lb-ft of torque is even more amazing. Put these TFS heads on an engine that can take full advantage of the flow potential and watch it exceed 550 hp. We are just getting started with the 4.8L, but with the TFS heads and the Crane 224 cam, what this engine needed most was something better than the stock truck intake manifold.

Small Block Engine Build Cam Swap Dyno Stand 2/20

1. Equipped with the stock cam and heads, Mini Mouse pumped out 336 hp at 5,500 rpm and 345 lb-ft of torque at 4,700 rpm.

Small Block Engine Build Comp Valvesprings 3/20

2. In anticipation of future cam swaps, the stock heads had been upgraded with a set of beehive valvesprings from Comp Cams (PN 26918).

Small Block Engine Build Crane Cam 4/20

3. The cam upgrade for the 4.8L included this hydraulic roller from Crane Cams. The performance grind featured 0.590-inch lift, a 224/232-degree duration split, and 115 LSA. Mild by most LS standards, it was an aggressive combo for the diminutive 4.8L.

Small Block Engine Build Stock Holley 50lb Injector 5/20

4. All testing was performed with the factory fuel rails feeding a set of Holley 50-pound injectors.

Small Block Engine Build Holley Dominator EFI 6/20

5. Tuning chores were handled by a Holley Dominator EFI system.

Small Block Engine Build Stock Cam Removal 7/20

6. Out came the stock cam to make way for the Crane upgrade. Care must be taken not to damage the cam bearings or drop a lifter during the swap.

Small Block Engine Build Crane Cam Install 8/20

7. With the stock cam removed, we installed the new Crane cam. We made sure to lubricate it before installation.

Small Block Engine Build Cam Swap Dyno Stand 9/20

8. The Crane cam transformed Mini Mouse. Gone was the mild-mannered, gentle performer, replaced by a high-rpm speed freak! The cam swap increased the power output from 336 hp and 345 lb-ft to 414 hp at 6,800 rpm and 363 lb-ft of torque at 5,400.

Small Block Engine Build Stock Head Removal 10/20

9. With our cam swap a success, it was time for some head work. Off came the stock 706 heads to make room for a new generation of LS heads.

Small Block Engine Build Trick Flow Specialties Gen X 205 Heads 11/20

10. Supplied by Trick Flow Specialties, these Gen X 205 heads were just what Mini Mouse needed.

Small Block Engine Build Gen X 205 Head Intake Port 12/20

11. The 205cc intake ports were not only sized properly for our displacement, they also offered exceptional flow. Sporting over 284 cfm, the smallest of the Gen X offerings had the flow potential to support over 550 hp.

Small Block Engine Build Gen X 205 Head Combustion Chamber 13/20

12. Every bit as important as the flow was the fact that the 58cc combustion chambers were sized for the 4.8L’s 3.78-inch bore. The Gen X 205 heads also featured a 2.000/1.575 valve combo.

Small Block Engine Build Gen X 205 Head Install 14/20

13. The Gen X 205 heads were installed using a set of Fel-Pro MLS head gaskets and ARP head studs. A good idea for this naturally aspirated combo, the studs and gasket would be put to a real test once we added a turbo in part 3.

Small Block Engine Build Rocker Stand Locaters 15/20

14. It was necessary to grind down the locaters on the factory rocker stands (as shown) to work with the Gen X 205 heads.

Small Block Engine Build Dyno Stand 16/20

15. Once installed, the Gen X 205 heads increased the power output of the 4.8L from 414 hp and 363 lb-ft of torque to 442 hp and 380 lb-ft of torque.

Small Block Engine Build Truck Intake 17/20

16. What this combo needed now was an intake tuned to make power higher in the rev range than the stock truck manifold.

Small Block Engine Build Turbocharger 18/20

17. Here is a sneak peek of Mini Mouse, part 3. We know what the cam and heads did naturally aspirated, but what are they worth once we add boost?

Small Block Engine Build Dyno Graph Stock Cam Crane 224 Cam 19/20

18. Mini Mouse Cam Test. Stock vs Crane 224.

Small Block Engine Build Dyno Graph Stock Heads Gen X 205 Heads 20/20

19. Mini Mouse Head Test. Stock vs TFS Gen X 205.


Check out Part 1 of the build HERE!

Sources

Trick Flow Specialties
Tallmadge, OH 44278
330-630-1555
www.trickflow.com
Crane Cams
Daytona Beach, FL 32117
866-388-5120
http://www.cranecams.com
Westech Performance
Mira Loma, CA 91752
951-685-4767
www.westechperformance.com
Lucas Oil
Corona, CA 92880
951-270-0154
www.lucasoil.com
Aeromotive
Lenexa, KS 66214
913-647-7300
http://www.aeromotiveinc.com
JE Pistons
Huntington Beach, CA 92649
714-898-9763
www.jepistons.com
Holley Performance Products
Bowling Green, KY 42101
866-464-6553
http://www.holley.com
ARP
800-826-3045
ARP-BOLTS.COM

MORE PHOTOS

VIEW FULL GALLERY
X

Connect With Us

Get Latest News and Articles. Newsletter Sign Up

sponsored links

subscribe to the magazine

get digital get print
CLOSE X
BUYER'S GUIDE
SEE THE ALL NEW
NEWS, REVIEWS & SPECS
TO TOP