Chrysler - Dodge 3.5 Liter V-6 Engines

sections by Michael A. Cole

The 3.5 liter V6 has its roots in the 3.3 liter V6, launched in 1990, but was far more advanced. Chrysler’s top V6 engine for cars for most of its long life, it was always made in Trenton, Michigan.

marc rozman testing the 3.5 v6 engine

Engineering chief Francois Castaing wrote:

When we started the LH program in January, 1989, the only engine we knew we had for sure was the 3.3-liter V-6. But we felt if the car was to be a success, it needed a brand new, high power, high technology engine.

3.5 liter engine

The engine people on the team knew they had never designed a new engine that quickly (40 months). Also, the investment would be quite high. There also was the fear that when you commit a lot of money for the company, you want to commit it right and not make a mistake. Still, the team and engine people within the team realized the LH would not be a success unless the new engine was there at the same time we launched the car.

So instead of giving in to the negatives that it couldn't be done, that we couldn't get the technology, the slickness, the power, the low emissions, the fellows said, 'let's go for it.' They challenged themselves, they were convinced the 3.5 engine was an absolute cornerstone for the car.

3.5 engine power curves

In the 1993 LH cars, the 3.5 hit 214 horsepower at 5,800 rpm, with 221 foot pounds of torque at 2,800 rpm; and mechanical noise levels were the lowest of any engine ever measured by Chrysler. This was an exciting engine, compared to just about any competitor — yet it was highly reliable throughout its life.

The speed of development was quite fast when one considers that it only shared an oil pan with the 3.3; to reduce tooling costs, though, it had the same bore spacing and the same main journal and crankpin diameters as the existing 3.3 and 3.8 engines.

The main benchmark was the Acura Legend’s 3.2 liter V6. The executive engineer in charge, Gordon Rinschler, specified a deep-skirt cast iron block and forged steel crank to handle the power. The compact 60° V-engine had a cast iron block with over-square bore and stroke, and the highest compression ratio (10.4:1) of any recent Chrysler-built engine. It used bottom-feed fuel injectors, a first for high-volume passenger cars, to fit into the LH; they also improved hot restarts. Cross-bolts on the #2 and #3 main bearing caps added strength and cut noise; the forged crank was ready for power, and free-floating piston pins helpd performance.

“This truly is a premium engine and as ‘bullet proof’ as we could make it. At this stage, I’m more confident about the 3.5 than any engine I’ve ever been involved with,” said Howard B. Padgham, powertrain engineer — who had, at the time, 28 years in Chrysler engineering, including work on engines from the 2.2 Turbo to the 360 V-8 police package.

mopar 3.5 v6 testing

The LH cars’ Cab Forward design presented challenges: “It’s sloped like the hood to fit just like a hand in the underside of a glove. Notice the shape of the cylinder head, the design of the intake manifold. They reflect the space we had to work with.”

The 3.5 liter engine was first restricted to the Chrysler and Eagle cars, and was later used in the Dodge Intrepid R/T, down to 242 horsepower as it had been retuned for regular gas (normally, it needed midgrade, or US 89 octane, fuel). Power remained at 242 - 250 hp in the later Chrysler Pacifica, Dodge Charger, and Magnum, Chrysler 300C, and, with 232 hp due to the small engine bay, in the 2008 Dodge Avenger/2007 Chrysler Sebring.

3.5 liter engine

The 3.5 was a 24-valve design, with a 96 mm bore and 81 mm stroke; it started with distributorless ignition, shifting from coil packs to coil-on-plug in later years, and sequential multiple port fuel injection.

3.5 V6 development stories

John Hurst designed a single-cam-per-head setup with dual valve rocker arm shafts, cutting costs for the four-valve-per-cylinder setup. Spark plugs were centered in the combustion chambers, and the intake valves were 35 mm with 29 mm exhaust valves. The engine was free wheeling, to avoid damage if the timing belt (which also drove the water pump) broke. The aluminum intake manifold was built in two sections, with two throttle bodies. The intake branch length, 315 mm, was tuned to increase torque. (The 3.3, in contrast, was an interference engine with a timing chain.)

Two plenums were used in the first generation; a valve, normally closed, allowed them to connect quickly during wide open throttle in the 3,200 to 4,000 rpm range, for extra torque.

Chrysler - Mopar 3.5 V6 vs Mercedes V6

3.5 v6 powerIn 1998, both Chrysler and Mercedes produced aluminum-block 3.5 liter V6 engines. Burke Brown said:

The only real difference is that ours was what we called semi-permanent mold, and we had cast in liners, casting in cast iron liners. So, at least by our view, we had the best of both worlds. We had a perfectly round iron bore, unlike a cast iron block, where the water jacket isn’t always the same thickness, so the water cooling for the cylinder isn’t as perfect as we could get it because everything was just the same.

... They had no liners. But they were doing a process where they would treat the aluminum and harden it. They were etching away the soft stuff until just the hard part of the aluminum cell structure was there. I forget all the fancy details, but it was working for them, but it was a more expensive process than our kind of brute force way.

But ours was bulletproof. To this day, I've never heard anybody talk about an aluminum engine that’s had a liner come loose or leak or anything like that. Never.

Chrysler 3.5 liter V6 engine

The second generation 3.5 liter V6 engine: 1999 to 2010

The 3.5 liter V6 engine was modified and switched to an aluminum block for its second generation; it produced 232 to 253 horsepower, but was most often rated at 250. Chrysler had benchmarked it, to the advantage of the 3.5, against numerous competitors, and wrote, “the new high output 3.5-liter engine is the best performing V6 available today in terms of total horsepower and torque — more than the BMW M3 [I6], Ford Taurus SHO [V8], Lexus GS300, or Mercedes E320 — with 250 horsepower at 6600 rpm, 250 pound-feet of torque and a compression ratio of 10.1:1  The high output 3.5-liter also is among the leaders in specific torque and the only one to optimally run using mid-grade fuel.”

3.5 liter V6

To get there was largely a matter of increasing airflow, from intake to exhaust; it had lower induction restriction, a larger throttle body, large intake valves, a large throat area, high flow intake ports, and smooth intake manifold runner surfaces (made of a composite, pioneered on the Neon 2.0).

The company looked at the size and shape of the exhaust valves and ports, manifold, and exhaust system, increasing the diameter of the exhaust pipes. A higher lift camshaft also increased air flow. A good deal of work was done in CATIA to optimize airflow.

The new engines increased gas mileage by around 10%, and met Tier 2 federal emissions standards; they were designed to meet the California Low Emission Vehicle standards in 2000.

plymouth prowler chassis

The company claimed that development time was cut by 26 weeks using CATIA software for modeling and prototyping; they claimed it was the industry's first “paperless” engine.

The high output 3.5 had a three-plenum intake manifold, with short runner valves and a manifold tuning valve which added up to being a variable intake system (building on Chrysler's work back in the 1950s and 60s). In short, varying the length of the intake manifold tubes created a supercharging effect at different engine speeds. Tuning the air tubes for a boost at one engine speed had, in the past, sacrificed power at another; the variable system provided benefits at multiple speeds.

3.5 liter V6 engine

In the first generation, each of the two banks of cylinders had their own intake manifold and throttle body. In the second, there was a single throttle body, with three plenums; valves controlled which runners would be used, short ones for extra power at high engine speeds and long ones for driveability at lower speeds.

 1990-971999
Compression10.44:19.9 or 10.1:1
HP @ rpm214 @ 5,800250 hp @ 6400
Lb-ft @ rpm221 @ 2,800250 lb-ft @ 3900
ValvesSOHC, 24SOHC, 24

To eliminate oil leaks and other reliability issues, the aluminum blocks were, as noted earlier, lined with cast iron, in what Chrysler called an industry-first process. The blocks were heat-treated. Crankshafts were still forged.

Oil drain passages were cast into the block for faster circulation under severe high-speed conditions, and ignition moved to “coil on plug” with 100,000 mile spark plugs.

The 3.5 liter V6 engine was created for the first generation LH series, debuting in 1993; it got a boost to 250 horsepower in 1999; and it finished production in 2010, still making 250 horsepower, as the standard powerplant in the Dodge Charger, Dodge Challenger, and Chrysler 300, maintaining a reputation as a solid motor the entire time. It was the basis of the 2.7, 3.2, and (finally) 4.0 V6 engines.

Maintenance and repairs

Jim Gathmann clarified that the first-generation cars had three coil packs, which would fire two plugs at once, one to ignite fuel and one unnecessarily (to save the cost of three more coil packs). Knock detectors were added in later, and allowed more aggressive timing with protection against bad gas.

Douglas Miske wrote that the change interval for the timing belt is 84 months or 105,000 miles / 170,000 km.

For those who believe the 3.5 was a Mitsubishi engine, Kevin Cobabe sent us the following chart:

  Chrysler Mitsubishi
Power 250 hp
250 lb-ft
205 hp
231 lb-ft
Bore x Stroke 3.78 x 3.19 3.66 x 3.38
Compression 9.9:1 / 10.1:1 9.0:1

Transmission fluid leaks

Transmission fluid can leak from the hose between the cooler integrated into the radiator and the transmission. SAE mechanic “ImperialCrown” wrote, “Many times the hoses are okay, the clamps may just need re-tightening. The brace plate above the radiator unbolts and tips forward. Match up the washer paint marks when putting it back together for proper alignment. The lower clamps are harder to get at and you may need to jack the car up and have a jackstand in place.” (Bob Lincoln added that the hose must be rated for transmission oil; regular rubber hose can rupture fairly quickly when exposed to transmission fluid.)

Rough idling

Kestas: If the rough idle is accompanied by a drop in engine speed when the air conditioner goes on, it may be that the engine is not getting enough air. Clean the throttle body, then check to make sure the idle air controller is clean and has full travel to the open position. (Take off the idle air controller, check for free movement, and give it a good visual inspection to make sure it is clean. It may need a shot of carb cleaner on the moving surfaces.

Mark: The engine is prone to intake manifold gasket problems that can cause a rough idle.

"Mopar Man and Woman:" “Remove and clean both throttle bodies. Synchronize throttle bodies. Remove IAC (ASI) [idle air speed/automatic idle speed] motor, but do not spray or soak with cleaner. Wipe tip off with cleaner on shop towel. Spray cleaner into bore in manifold. Make sure that hose that goes to air cleaner duct to intake right behind IAC is not blocked, collapsed etc. This is the source for air flow to the IAC on the 3.5L.

“Perform minimum air flow test with DRB or other Scanner - should be 500-650rpm. If above, suspect vac leak, if low you have throttle body problems. At full operating temp, curb idle, what are desired IAC steps? Try cylinder balance test with scanner. If one or two cylinders are slightly different than rest, suspect intake manifold gasket failure. Also, after each repair, before starting, reset adaptive memory in PCM with scanner.”

There may also be a problem with the MAP sensor (instructions on diagnosing).

There may also be a problem with the EGR sensor (replacement guide)

Performance

Chrysler compared well to the competition in 1998, particularly when looking at cost.

VehicleEngineBHPRPMOctaneCost As Tested
Mercedes E420, 19974.2L2755500Premium$53,522
LHS/300M, 19983.5L2506600Regular$30,000
Ford SHO (V8), 19963.4L2356100Premium$28,250
Intrepid/Concorde, 19983.2L2206600Regular$24,000
LH series, '93-'973.5L2145850Mid-Grade$24,270
Mitsubishi Diamante, '973.5L2105000PremiumN/A
Intrepid/Concorde, 19982.7L2005800Regular$21,000
Ford Taurus, 19963.0L2005750Regular$24,205
Cadillac Catera, 19973.0L2006000Premium$34,750
Nissan Maxima, 19973.0L1905600Regular$24,675
Acura 25TL, 19972.5L1766300Premium$30,478

2.7, second-generation 3.5, and 4.0 compared

1998-2007
V6 Engines
2.7 Liter3.5 Liter (LX)3.5 Liter
(JS)
4.0 Liter
(2007+)
Bore x Stroke 3.39 x 3.09 3.78 x 3.19
3.78 x 3.58
Valve System 24 valves; Hydraulic end-pivot roller followers, hydraulic lifters
Construction Semi-permanent-mold aluminum block, cross-bolted main bearing caps
Compression 9.71:1*
9.9:110.0:110.3:1
Horsepower

200
@ 6000*

250 @6400235 @ 6,400 255 @ 5,800
Lb-ft torque

188 @ 4900*

250 @ 3900232 @ 4,000275 @ 4,000
Max. RPM 6464*6,8006,800 rpm5,800 rpm
Fuel 87 octane89 (midgrade) preferred, 87 (regular) OK
* Later retuned to 190 hp (142 kW) at 6,400 rpm and 190 lb-ft (258 Nm) at 4,000 rpm,
with a redline of 6,600 rpm and a compression ratio of 9.9:1.

Some creators of the 3.5 liter V6 engines: Willem WeertmanPete Hagenbuch • Marc Rozman

• all engines

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