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Wildcard Customs
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Discussion Starter · #1 ·
My fiance' absolutely loves the 3.8 98 monte carlo i bought her. Now here's my issue...she wants it v8. I looked into a rwd conversion, and having her car tied up in my shop for about a year while a 427 ( her favorite V8 ) is fitted is unacceptable to her and cost prohibitive for my business. However...i looked at the 5.3l V8 that GM has in the 2006 and up w bodies. Definitely the better option and fairly low cost. But...has anyone ever messed around with this and how much effort is involved. I'm able to swap with no problem on fabrications. Where i'm a little leary is the electrical and body. Plus i don't really want a used engine. Where can i get a 5.3 FWD new and where do i need to work with the body?

Old(s) Fart
5,913 Posts
The FWD LS4 block comes with the 60 deg metric bellhousing, so it bolts to your current transaxle. I can't speak to transaxle strength, however. You're really going to want to transfer the complete wiring and ECU from a donor vehicle. Is emissions inspection a requirement where you live? If so, transfer all that from the donor and you should be legal.

1,454 Posts
Looks like you cant get new LS4's anymore, only as a reman.
The LS4 can be had for $3400 from crate engine depot as a reman.
$3466 2005-2006
5.3 Ltr - 323 C.I.D. - GM ENGINE 2005-2006 Reman 89018190

$3404 2007-2009
5.3 Ltr - 323 C.I.D. - LS4 GM ENGINE 2007-2009 Reman 19209697

2005-2006 LS4 $3344 (these 2 are also remans)
GM Goodwrench - 89018190 - Remanufactured GM 2005 - 2006 5.3L, 323 CID, 8 Cylinder Engine

$3599 2007-2009 LS4
GM Goodwrench - 19209697 - Remanufactured GM 2007 - 2009 5.3L, 323 CID, 8 Cylinder Engine

Here is an excerpt from GM about the LS4 V8
PONTIAC – General Motors’ new Gen IV 5.3L V-8 (LS4) engine debuts in the 2005 Pontiac Grand Prix GXP, making it the first V-8 offered in a Grand Prix since 1987. It also marks the first time since the small-block was introduced 50 years ago that it has been offered in a front-wheel-drive car.

Engineered specifically for front-drive layouts, the 5.3L V-8 is estimated to produce 303 horsepower and 323 lb.-ft. of torque. It incorporates Displacement On Demand technology (DOD), which helps the vehicle realize fuel economy gains of up to 12 percent per the EPA federal fuel economy test procedures. It does this by seamlessly alternating between eight- and four-cylinder operation.

When matched with the inherent smoothness and torque of the V-8 configuration, the 5.3L V-8 delivers strong performance – 90 percent of torque is available between 1500 rpm and 5200 rpm – and surprising economy. It’s a combination most competitors’ V-6 offerings can’t match.

“Over 50 years, the small-block V-8 has proven itself more adaptable than anyone could have imagined,” said Dave Muscaro, assistant chief engineer of small-block V-8 for passenger cars. “The small-block family has a tradition dating back to 1955 in which an excellent design makes possible the additions of new technology. The Displacement On Demand capable 5.3L V-8 is a fine example of that tradition”

Family ties
The all-aluminum 5.3L V-8 is the third displacement offering of the Gen IV small-block, which was introduced in the 2005 Chevrolet SSR, GTO and Corvette, as well as several 2005 GM SUVs. The 5.3L V-8 shares a common architecture with these other versions, including a deep-skirt block, six-bolt cross-bolted main bearing caps, and structural oil pan, but is modified to accommodate the “east-west” mounting position of the Grand Prix’s front-wheel-drive chassis.

To fit the “sideways” positioning in the Grand Prix, several changes were made to shorten the engine’s overall length. The crankshaft was shortened by 13 mm – 3 mm at the rear and 10 mm at the front – and the entire accessory drive system was designed to reduce space. The water pump and all other accessories, including the power steering pump, are driven on a single-belt drive system – the longest drive system in a GM vehicle.

Engineers devised an elongated water pump manifold, which features a remote-mounted pump that feeds the stock Gen IV coolant passages via the unique manifold. The design allowed the drive system to be mounted closer to the engine block. Because of the 5.3L V-8’s relatively low inertia, which can be up to 50 percent less at the crankshaft damper than a 6.0L V-8, a hydraulic belt tensioner was used instead of a conventional rotary tensioner.

Unique position
The sideways position of the 5.3L V-8 required revisions to the lubrication system. Engineers tested 5.3L V-8 equipped test vehicles on racetracks, subjecting them to high-load turns that guided the development of special oil pan baffles that ensure lubrication during cornering. In addition, because Gen IV engines don’t have a block-mounted oil filter – it’s located on the oil pan – the 5.3L V-8’s filter offers easy access.

The GM Oil Life System oil-change indicator system is standard, which can reduce the frequency of oil changes during the engine’s operating life. With the system, the engine control module (ECM) records cumulative data on a number of variables, including engine rpm, temperature, load or rpm variance and length of operation at any given load and temperature. Using this information, the system calculates oil degradation and recommends an oil change when the oil is near the end of its useful life – in other words, when an oil change is actually needed.

Other 5.3L V-8 features include:
Electronic throttle control integrated with a new E40 engine controller
Lightweight, three-piece friction-welded composite intake manifold with throttle located at rear (driver’s side) of engine
Cylinder heads derived from the 6.0L V-8 LS2 engine
10.0:1 compression ratio
Unique camshaft designed to accommodate DOD technology
PCV valve replaced with maintenance-free fixed orifice

Because of the front-drive layout, the 5.3L V-8’s exhaust manifold routing includes two manifolds joined by a single crossover pipe, which connect to a single underbody catalytic converter. The crossover pipe allows the use of a single oxygen sensor, unlike north/south V-8 applications that have two oxygen sensors.

Displacement On Demand technology
GM’s Displacement on Demand technology debuted in 2005 GM extended midsize SUVs equipped with the Vortec 5.3L V-8 (LH6) engine. With the 5.3L V-8 (LS4), DOD technology enables fuel economy gains of up to 12 percent in certain driving conditions by reducing the number of cylinders engaged in the combustion process. A sophisticated, next-generation E40 engine controller determines when to deactivate cylinders, allowing the engine to maintain vehicle speed in lighter-load conditions such as highway cruising. When the cylinders are deactivated, the engine effectively operates as a V-4, with alternate cylinders on each cylinder bank disabled. The engine returns to V-8 mode the instant the controller determines the vehicle speed or load requires additional power. The process is seamless and virtually imperceptible.

“There’s nothing like the satisfying feel of a V-8 engine and the 5.3L V-8 provides a level of performance rarely available in competitors’ vehicles,” said Muscaro. “But when all eight cylinders aren’t required to maintain performance, DOD technology effectively turns the engine into a more efficient V-4.”

The key to DOD’s efficiency and virtually imperceptible operation is a set of special two-stage hydraulic valve lifters, which allows the lifters of deactivated cylinders to operate without actuating the valves. These lifters, used only on the cylinders which are deactivated, have inner and outer bodies which normally operate as a single unit. When the engine controller determines cylinder deactivation conditions are optimal, it activates solenoids in the engine lifter valley which direct high-pressure oil to the switching lifters. This oil pressure activates a release pin inside the lifter which allows the outer body of the lifter to move independently of the inner body. With the pin is released, the outer lifter body moves in conjunction with camshaft actuation, but the inner body does not move, thus holding the pushrod in place. This prevents the pushrod from actuating the valve, thereby halting the combustion process. Because the vibration and acoustic dynamics of the V-8 and V-4 modes are different, the exhaust system of DOD-equipped vehicles is tuned to compensate for the changes.

Engine stats:
2005-2009 LS4
303 [email protected] 5600 rpm
323 lb-ft @ 4400 rpm
Fuel Shutoff 6100rpm

3.8 V6-Supercharged(2005)
260 hp @ 5400 rpm (L32)
240 hp @ 5200 rpm (L67)
280 lb-ft @ 3600 rpm
Fuel Shuttoff: 6000rpm

Transmission is the 4T65E, unfortunatley they never offered the 4T80E like was used in the Pontiac Bonneville that was equipped with the 4.6 Northstar.

Transmission Stats:
Type: four-speed front-wheel-drive, electronically controlled, automatic overdrive transaxle with electronically controlled torque converter clutch.
Engine range: 2.5L - 5.3L
Maximum engine torque: 280 lb-ft (380 Nm)
Maximum gearbox torque: 400 lb-ft (542 Nm)
Gear ratios:
First: 2.92
Second: 1.56
Third: 1
Fourth: 0.7
Reverse: 2.38
Maximum shift speed: 1-2 7000 rpm
2-3 6500 rpm
3-4 6000 rpm

Type: four-speed front-wheel-drive, electronically controlled, automatic overdrive transaxle with viscous torque converter clutch. The viscous clutch will be replaced with an electronically controlled torque converter clutch as 2005 interim change.
Engine range: 4.6L
Maximum engine torque: 305 lb-ft (413 Nm)
Maximum gearbox torque: 461 lb-ft (625 Nm)
Gear ratios:
First: 2.96
Second: 1.63
Third: 1
Fourth: 0.68
Reverse: 2.13
Maximum shift speed: 1-2 6500 rpm
2-3 6500 rpm
3-4 6500 rpm
Maximum validated gross vehicle weight: 6800 lb (3084 kg)

It would be a good idea to get a donor car if possible. Then you will have a PCM, harness, mounts, exhaust manifolds etc etc.

A few simple mods to a Series III(3) 3800 supercharged engime would easily have you meet and exceed the LS4 output. The only thing that would be missing is the V8 sound, which is SO much better than the V6.


693 Posts
The 4t65hd trannies use 'torque management' to keep them from self destructing, which is one of the reasons that (in my experience) a stock LS4 car is only about a tenth quicker than a stock L67 car at the dragstrip even though the LS4 is rated at an additional 63 (peak) hp. I would also bet that the average power numbers of the 2 motors are a bit closer together than the peak numbers are.
It is possible to upgrade the trans and reduce/eliminate the torque management but it can get expensive in a hurry. Am also told that the axle shafts don't like hard launches much - if you're going to be doing that type of thing.
+1 on getting a donor car and you will also want some kind of tuning software, HP tuner or the like.

My (near stock) daily driver
2001 Buick Regal GS 1/4 mile trap speeds 0-60 -
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