Some time earlier we introduced our modern Mouse collection that extended a totality slew of performance parts applied to a 5.3L LM7 truck engine. Given the popularity of the LS communication in contemporary machinery, muscle automobile swaps, and even trick trucks, modern-day Mouse seemed choose a natural. Toss in the ease of access and affordability and also you have the makings of the following go-to small-block. As famous as the 5.3L is, over there was another interesting offering that is equally available and affordable. To speak hello come the 4.8L LR4 (or Gen IV LY2). The 4.8L and also 5.3L share the exact same block and bore size, 3.78 inches. The distinction in displacement comes from a change in hit length. The 5.3L sporting activities the usual LS size of 3.622 inches however the smaller 4.8L spins a shorter stroke that 3.267 inches. Since the pistons space interchangeable between the 4.8L and the 5.3L (they re-publishing the exact same compression height), the difference in between the punch lengths is consisted of for by rise in the connecting rod length (6.098 vs. 6.275).
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Essentially, the 4.8L is a destroked 5.3L, lot like the initial 327 to be a destroked 350 and also the 302 to be a destroked 327. In terms of displacement, the 4.8L checks in a 293 cubic inches and while under on displacement to the larger 5.3L and also 6.0L, the short-stroke 4.8L is an amazing departure native the run-of-the-mill 5.3L. Provided the minimal displacement that the 4.8L, we couldn"t assist but speak to this task Mini Mouse. Like the contemporary Mouse collection on the 5.3L, the goal here is to show just exactly how well the 4.8L responds come a substantial array of performance upgrades. Naturally, there will be cam, head, and intake swaps, in addition to nitrous, forced-induction, and even displacement changes. Us don"t desire to duplicate the modern Mouse series, so us will try to cover different upgrades top top the 4.8L. There are plenty the 4.8L fans out there and also who knows, after this collection there may be many more. Understand that in ~ some suggest we arrangement on taking full benefit of the rpm ability offered by the short-stroke, yet that is jumping way ahead, therefore let"s crank increase the dyno and get down to business.
Obviously, we needed a beginning point and the best resource for a check mule is always the wrecking yard. We discovered a agency that specialization in cores so we picked up a 4.8L. Our initial intention to be to purchase a high-mileage unit, plop that on the dyno, and start making some severe power. The 4.8L looked OK indigenous the outside, but inside points were much from acceptable. Rust in the bores supposed a rebuild was in order. That gave us an possibility to begin fresh with Mini Mouse. The block to be cleaned and bored 0.010-over to get a set of SPR Professional-series pistons native JE. In addition to the strength, the forged slugs readily available generous valve reliefs for future cam upgrades and a slight (7.2cc) dome to rise the revolution compression. This would certainly really come in handy as soon as we perform a head swap, which nearly always increases the combustion chamber size. We also surfaced the block and also heads in addition to a quickie valve job. Once all to be said and also done we had actually a factory fresh 4.8L, albeit with a slight compression increase.
Our an initial order of company was to develop a baseline so us assembled the fresh machined engine and also headed to Westech performance in Mira Loma, California. Mini mouse was configured because that dyno use through an Accufab manual throttle body, Meziere electric water pump, and Holley HP EFI management system. Additionally present to be a collection of 36-lb/hr quick injectors, 1 3/4-inch long-tube headers, and also a Corvette damper. After a pair of break-in cycles, we adjusted the Lucas 5W-30 oil and were prepared to test. After ~ dialing in the air/fuel ratio and timing curves, Mini Mouse generated peak numbers of 336 hp in ~ 5,900 rpm and also 347 lb-ft that torque in ~ 4,900 rpm. The share heads and also intake had an ext power come give however the stock cam leveled off around 5,000 rpm climate took turn off on a bottom spiral after ~ 5,900 rpm. Us knew there was an ext power to be had actually from this mix so we decided the very first step to be to swap in a much better cam.
If you room an LS owner (of any displacement) and are considering your first upgrade, know that you must be reasoning of nothing else however a camshaft. Every LS engines room blessed with adequate intake and also head flow yet where they are normally lacking is in electronic came timing. The factory video camer is designed no with top power in mind, so the engineers left many of power on the table. Despite a vast array okf camer profiles exist because that the LS engine family, we decided to begin with a mild cam, functioning our method up come wild in later on later installments. We wanted to pick a video camer that would work well as a performance upgrade for a daily driver. Come that end we selected a Crane file that available 0.551-inch lift, a 210/218-degree duration split, and also a 116-degree LSA. This electronic came offered nearly 19 inch of idle vacuum however it increased the power output of the 4.8L indigenous 336 hp and 347 lb-ft to 384 hp and 361 lb-ft of torque. Measured optimal to peak, the Crane cam swap added nearly 50 hp, however the difference was an impressive 80 hp out at 6,500 rpm (remember, the 4.8L loves to rev).
After the success of the cam swap, we decided to change gears and also tailor the next test to the carb contingent. Prefer the LM7 5.3L, the 4.8L is a famous swap candidate for muscle and also import vehicles. No everyone has the budget or technical skills to incorporate injection in the swap so there are a great many LS swaps running approximately with carburetion. For this critical test in component 1 that the Mini computer mouse series, we determined the age-old fight between single- and dual-plane join deserved a yet one more look. For the uninitiated, dual-plane manifolds offer better low-speed torque when the single-plane design is tuned for higher engine speeds. In her existing configuration, Mini mouse was admittedly mild however the test to be interesting even if just to display what not to run on a certain combination. How plenty of of us are tempted through the promise of large top-end power only to it is in reminded the our engine spends most of that is time well below the strength peak?
Anxious to uncover the "plane" truth, we eliminated the manufacturing facility truck manifold and also EFI components and also installed one Edelbrock dual-plane show RPM manifold, Holley 650 HP carb, and also MSD ignition controller. The demonstrate RPM seemed favor an ideal choice for the soft 4.8L, as displacement theatre a part in intake choice as well. The smaller sized the engine, the much better it will certainly most likely respond come a dual-plane. The MSD controller was a plug-and-play unit and allowed us to dial in the time curve of our choice. After jetting and timing sweeps, we were bonus with top numbers that 377 hp and 342 lb-ft the torque. The dual-plane intake readily available a level torque curve that surpassed 325 lb-ft all the means out to 5,700 rpm. ~ swapping on a Victor Jr. Single-plane we automatically recognized that the dual-plane to be the much better choice top top this gentle 4.8L. Back the Victor Jr. Readily available acceptable optimal numbers of 377 hp and also 336 lb-ft that torque, torque production was down considerably compared to the show RPM up to 5,700 rpm. If you have a mild combo, the performer RPM is a far better choice. But fear not, as we are just obtaining started with Mini Mouse, look because that even much more power next installment.
1. Is there power hiding what under the LR4 van manifold? project Mini Mouse has officially begun.
2. Our initial intention because that Mini mouse was to start with a high-mileage 4.8L appropriate from the wrecking yard. Unfortunately, our an option turned out to require some work before subjecting it to the dyno. After decking the block, we boring the cylinders 0.010-over and installed a collection of SRP expert forged pistons indigenous JE Pistons. The forged pistons (PN 315551) featured a 7.2cc dome (10.5:1), generous valve reliefs because that future electronic came upgrades, and were design to occupational with the 4.8L stock rod and also crank.
3. To establish our baseline, the 4.8L received the manufacturing facility LR4/LM7 camshaft. Mildest that the LS family, this cam was wimpy, even for a 4.8L.
4. The share 706 top were provided a surface and a valve job before the surroundings of a collection of valvesprings (PN 26918) from Comp Cams. Us knew electronic came swaps to be in the cards therefore we started off with valvesprings capable of sustaining these early video camer tests.
5. Mini mouse was run on the engine dyno v an Accufab hands-on throttle body, a Meziere electrical water pump, and also a collection of 1 3/4-inch long-tube headers. Tuning for the 36-lb/hr fast injectors came from a Holley HP EFI management system. Equipped through the share heads, cam, and also truck intake, the 4.8L created 336 hp at 5,900 rpm and 347 lb-ft of torque in ~ 4,900 rpm. Torque manufacturing exceeded 300 lb-ft from 3,200 rpm (the begin of the test) come 5,800 rpm. Owner of the initial 283 small-block will certainly envy this type of speak curve.
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6. It have to come together no surprise that a camer swap was very first on the perform for our small LS. For component 1, we made decision to begin small. Crane provided a little but powerful hydraulic roller file that readily available 0.551-inch lift, a 210/218-degree expression split, and 116-degree LSA.
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