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Rebuilding the Chrysler V6 Engine Family
By Doug Anderson
Much of the information used to write this article was provided by Bruce Chapman, president, and the employees of Ontario Reman, Etobicoke, Ontario, Canada. Ontario Reman is an authorized Chrysler engine rebuilder selling remanufactured engines and small parts to Canadian Chrysler dealers. We thank them!
Chrysler introduced a whole new family of 60 degree V6 engines beginning with the 3.3L OHV in 1990. It was followed by the 3.8L OHV in 1991 and the 3.5L SOHC that came out in 1993. All three of these engines have performed well and provided good service, but the industry continues to change so quickly they were soon replaced in the cars by another family of SOHC and DOHC engines that were introduced in 1998!
The good news for rebuilders is that there are a lot of these engines installed in cars and vans that are worth fixing and they’re getting up there in miles, so there’s a growing market for the rebuilder who knows what to expect.
The 3.3L was originally designed to replace the 3.0L SOHC V6 Mitsubishi engine that Chrysler had been using since 1987 in its upscale cars and minivans. The 3.0L was a good engine, but it was a little low on torque in a heavy vehicle, so Chrysler designed a torquer to replace it, and did an incredible job of it in the process. In fact, the 3.3L is so good that it delivers 90% of its peak torque from 1200 rpm all the way on up to 4400 rpm!
Chrysler did it with a very modern, but conventional pushrod motor that has a 2.66" (93mm) bore and a 3.19" (81mm) stroke for a displacement of 201.5 cid. The aluminum heads have a heart-shaped chamber with two squish areas to provide optimum combustion, along with gorgeous exhaust ports that really help the flow of the exhaust gasses.
The over-square design allowed the engineers to install bigger valves to get more horsepower, so they used 1.80" (45.5mm) intake valves and 1.48" (37.5mm) exhausts. A nodular iron cam is used along with low friction, roller hydraulics.
Semi-conical, variable rate springs are used with light-weight retainers. The push rods are carefully spaced to avoid interfering with the free flowing, symmetrical intake ports. The engine has four mains nestled in a deep-skirted block that provides a rigid lower end and less noise. A flat pan rail ensures good gasket sealing. The nodular iron crank has rolled fillets and cross-drilled mains.
The connecting rods are forged steel that measure 6.18" (157mm) from center-to-center. There are small weight pads on both ends that are used for balancing. The ignition system and fuel injection are controlled by an ECM that gets information from both the crank and cam position sensors. The crank sensor is mounted on the bell housing where it gets a signal from the notches in the flex plate. The cam position sensor is mounted in the front cover so it can read the nine notches in the cam sprocket.
A knock sensor is used to detect detonation in the ’96 and ‘97 minivans. It’s interesting to note that the original engine managed to meet all the applicable emissions standards without an air pump, aspirator or EGR system, except in California where it needed an EGR valve to meet their tougher requirements.
All-in-all, the 3.3L was a very good pushrod motor and its 3.8L "big brother" was identical except for a bigger bore (3.78") and a longer stroke (3.43"). The 3.8L was rated at 162 hp, just like the later 3.3L engines, but it developed more torque at a lower rpm (213 at 3300 rpm vs. 194 at 3600 rpm), so it performed better in the bigger cars and vans.
THE 3.5L IS A DIFFERENT STORY
The 3.5L engine is a whole different story. Although it’s part of the same 60 degree family and shares some common specifications, it’s really a totally different engine because it has overhead cams instead of pushrods. It’s still an over-square design (3.78" x 3.19") so it breathes deeply and revs freely with its aluminum, four-valve, single overhead cam heads.
A forged steel crank and steel rods ensure durability. A distributorless ignition system is used along with electronic, sequential port injection. A split plenum with a special computer controlled "Manifold Tuning Valve" is used to regulate plenum volume according to the load. The end result is 214 hp at 5800 rpm with 90% of peak torque all the way from 2000 rpm on up to 5600 rpm. This is one stout motor with great low end torque that still makes almost one horsepower per cubic inch when it’s working hard.
Now that you have an overview of this entire engine family, let’s take a look at the pieces and parts that are used in each one to see what it’s made of and how it has evolved over the years. We’ll begin with the 3.3L and 3.8L since they are virtually identical, except for the components that were changed to accommodate the differences in bore and stroke.
3.3L: The original block that came out in ’90 (c/n 4448030) was used in transverse applications up through ’92. In ’93, when the 3.3L became the base engine in most of the new LH sedans, it was also installed longitudinally (front-to-back instead of transverse), so four additional threaded bosses were added to the block. Two were located just above the pan rail on the passenger side, and two were angled down just above the pan rail on the driver’s side. This block had a 4556430 casting number. See photo.
Unfortunately, there are two versions of this casting, one for the LH cars that has the two extra bosses on the passenger side sticking out prominently from the side of the block, and one for the transverse applications that has them machined off almost flush, so you have to see the block to know what it fits. See photo.
You can use the LH block in a minivan by machining down the two bosses on the right side, but that’s probably not a good idea since they’re in such short supply. You can’t use the minivan block with the shorter bosses in an LH car because the mounts won’t fit.
There’s another casting that came out in either ’94 or ’95 (c/n 4621763) that’s identical to the revised ’93 block, and one more new one that came out in ’96 (c/n 4621944) that’s used up through ’97. It has an additional threaded boss midway back on the driver’s side (that’s on the front when the engine is installed transversely), and about two inches up from the pan rail. It’s used for the knock sensor that’s required for the minivans. The LH cars didn’t have a knock sensor, so you can continue to use the 4556430 or 4621763 block without this extra boss in the ’96-’97 cars if you are short of the late ones.
3.8L: The 3.8L shares the same block with the 3.3L year-by-year. The only difference is the larger bore. The 3.8L never was used in the LH cars, though, so the two extra bosses on the right side (that’s on the back side when the engine is installed transversely) of the ’93 and later 3.8L castings are always machined down almost flush with the block, too.
There have been reports of significant core shift on all of these blocks, so it can be risky to bore the 3.8L blocks very far oversize. It’s better to bore a 3.3L block up to a 3.8L standard than to bore a 3.8L block oversize unless you check all the cylinders with an ultrasonic tester to make sure there aren’t any thin spots that will cause problems.
There are some main caps that have a wide groove for the bearing tang and others that have a narrow groove. If you use the bearings with the wide tang, you may have to file the cap to make sure they will fit from time-to-time. If you use the ones with the narrow tang, you will have to crowd the tang to the front in order to position the bearing correctly in the wide slot.
3.3L: The 3.3L has used only one crank since 1990, except for a few of the very early engines that had an unusual crank with smaller rod journals. The 3654 casting is found in 99.9% of the engines, but there are some rare ones that had the 8044 casting with the small rod journals (we’ve seen one). If you happen to end up with one of these cranks, just throw it away and replace it with a 3654 casting and a matching set of rods.
3.8L: The 3.8L crank is a 6433 casting. It has a 3.42" stroke instead of the 3.19" stroke that’s used on the 3.3L. It can easily be identified by the larger counterweights; the second one is noticeably bigger, along with some of the others. See photo.
3.3L: There have been several different rod castings used for the 3.3L including a 4448903, a 4654355 and a 4621694. They are all the same except for some minor differences in the size of the balance pads located on the caps. This creates a small difference in the weight of the rod, so it’s best to keep them in sets by both casting number and weight. See photo.
There are a few of the very early rods that were used with the odd-ball 8044 crank out there, too. They measure 2.0830" on the big end instead of 2.400" like all the rest of the rods. Throw them away if you end up with a set.
3.8L: The 3.8L rod is shorter than the 3.3L rod in order to compensate for the longer stroke with the same deck height. Look for a 4448904 or 4654356 casting. There have been reports of a few 3.8L rods literally breaking in half, so they should all be carefully inspected and probably even Magnafluxed.™ And, if there’s one broken rod in a motor, it would be wise to double check the rest of the set or throw them all away to play it safe.
The rod bolts used on both the 3.3L and 3.8L employ a torque-to-yield design that requires the use of a torque-turn technique during assembly. They can only be reused three times, so, theoretically, they could be at the end of their useful life by the time the rebuilder disassembles the engine, tightens the bolt to recondition the rod, loosens it to take it apart again, and then retightens it to assemble the engine. Some rebuilders are reusing the old ones quite successfully while others are using all new bolts. It’s your call.
3.3L: The 3.3L piston is a full-round design with a large, oblong dish in the middle of the crown. The pin is a press fit in the rod. The same piston has been used in this engine since 1990.
3.8L: The 3.8L piston looks similar to the 3.3L, but it has a deeper, oblong dish in the crown. Only one piston has been used since 1991.
CAMS AND TIMING
3.3L: There have been three cams used in the 3.3L during its lifetime. According to Chrysler, all the engines built from ’90 through ’93, prior to date code 626 and production number 4573132, should use the p/n 4448049 cam along with the early, "shrouded" head. All the engines built in ’93 after date code 627 and production number 4663497 should use a p/n 4761387 cam along with the new, "unshrouded" cylinder head.
The camshaft was changed once more in ’94 (p/n 4621685) and used with the "unshrouded" head to add more low end torque and improve acceleration by 2% to 3%. This cam also "aids intake air flow for smoother high speed operation" and "reduces noise by five DBA at 5000 rpm." It was still used up through 1999.
Actually, all of these cams are very similar when you compare the specs; they are impossible to tell apart without a cam machine because they all have "645" stamped on the barrel behind the front bearing. Most rebuilders are using them interchangeably in spite of the subtle differences that are claimed. Let your conscience be your guide.
3.8L: Two of the cams used in the 3.3L have been used in the 3.8L engines. The 4448049 was used from ’91 through ’93. In ’94 it was replaced by the 4621685 cam that is still being used today. Most rebuilders are interchanging all of the V6 cams in these engines without any problems.
There have been a few reports of broken cams, especially in some of the earlier 3.3L engines. It appears that either the cam had too much initial clearance, or the middle bearings were too soft, so they wore quickly and allowed the cam to flex until it broke. It’s not a common problem, but it may show up occasionally.
The original timing chain was a soft-backed design that had to have a snubber bolted to the block to guide it. The later engines use a stiff-backed chain that doesn’t require the snubber, so some of the later blocks aren’t drilled for it; Chrysler says to throw it away when you install the newer chain. Both versions are available, so be sure to specify the one you prefer and use it with or without the snubber, as appropriate.
Both of the upper oil galley plugs in the front of the block, just behind the timing chain, have small bleed holes in them either to oil the timing chain or to allow any air that gets trapped in the oil galleys to escape. In either case, the replacement plugs should have the holes. You may have to drill them in the standard plugs because the drilled ones aren’t available in the aftermarket.
The cam gear and thrust plate were changed in ’94. The original plate was oval in shape and measured .217" thick. It goes with the thick gear that has the number 89707405 molded in the front of it. The later plate looks the same, but it’s .080" thicker (.297" total), and it’s used with a thinner cam gear that has the number 62207405 on it. The matching plate and gear must be used together or you will get to do it over again. A replacement kit with the thick plate and thin gear is available from Chrysler (p/n 4778707) as well as other aftermarket suppliers.
Both of these engines use roller hydraulic lifters. They originally came with the same unmetered lifter used in the early 318/360 roller motors. The pushrod socket in the rocker is blind and gets lubricated by oil coming up through the pushrod from the lifter. The oil dead-ends in the rocker socket so it doesn’t have to be metered, but you can use the metered lifters from the Magnum motors if you prefer because they will provide more than enough oil for the pushrod socket. The lifters are held in place with a six-fingered, steel retainer that is a dealer only item, but it’s cheap, so call the dealer if you need one.
3.3L and 3.8L: Both engines have used two different heads from 1990 through ’97. The original head was a 4448015 casting with a heart-shaped chamber that was shrouded around the backside of the intake valve (opposite the spark plug). It was replaced in mid-to-late ’93 by the 4621510 casting that had less shrouding around the intake valve.
According to the Chrysler parts book, the early, "shrouded" head should only be used with the early cam (p/n 4448049). The later, "unshrouded" head should only be used with one of the later cams (p/n 4761387 or p/n 4621685). However, since Chrysler is supplying only the late, "unshrouded" head in the box, no matter which one you order, it appears that either head can be used with either cam, although it’s probably best to use them in pairs. See photo.
All of these heads have proven to be quite durable, but they should be checked for two possible problems:
1) They occasionally crack by one of the inner head bolt holes on the lower edge; and
2) The rocker stand on the end sometimes breaks off almost flush with the top of the head surface.
We suspect that the bolt holding the rocker shaft down wasn’t torqued properly at the factory so it allowed the rocker shaft to flex until fatigue finally broke the rocker stand. You can fix it by welding it back on, and using a longer bolt.
Some of these heads have a hole drilled for a temperature sensor in one end of the head and others don’t. We don’t know which applications require a sensor, so it’s best to drill and tap all of them so they will work for any application.
Both the 3.3L and 3.8L use torque-to-yield head bolts. They are the same ones that are used for the 2.2L and 2.5L, so they are readily available. Chrysler says they can be reused up to three times. You can inspect them for stretch by comparing the threads on a used bolt to those on a new bolt. Or, better yet, you can play it safe and replace all the head bolts just to be sure the clamping force is uniform and correct.
3.3L: There are two front covers used on the 3.3L. Both of them house the oil pump and the water pump. The cover used on the transverse engines has one ear about even with the top of the water pump on the driver’s side (front) that’s reinforced and drilled for a bracket of some kind.
When the 3.3L was installed in the LH cars, a second ear with another bolt hole was added directly below the original one and about even with the bottom of the water pump. See photo.
3.8L: The 3.8L was only installed in transverse applications, so it always uses the front cover with only one ear on it.
That’s the story on the 3.3L and 3.8L engines. They are both pretty conventional OHV engines that are easy to rebuild. In fact, the only hard part is installing the cam bearings correctly because of the obstructed tunnel that is inherent in the design of the 60 degree block. Other than that, rebuilding one of these engines is about like doing any other small V6 with aluminum heads; there are no real surprises.
CHRYSLER 3.5L SOHC
The 3.5L SOHC motor, however, is a whole different story from start to finish. First, let’s take a look at all the different pieces and then we’ll look at how they go together. It’s a complicated little engine.
The 3.5L block shares its basic geometry with the 3.3L/3.8L engines. The bore spacing is still 4.45," the deck height is still 229mm, and the mains are the same size; but that’s where the similarity ends. It has four mains with the two middle ones cross-bolted for greater strength. The front of the block has been modified to accommodate a new oil pump and a different water pump along with a sprocket for the timing belt and the covers needed to shield it.
The drilled bosses on both sides of the block for the motor mounts and accessories are different, too. The deck surfaces were altered to provide oil feed and drain holes along with the crankcase vent holes. The water transfer holes were relocated. Two bosses were added in the valley for twin knock sensors.
There is only one version of the 3.5L block with two different casting numbers from ’94 through ’97. The casting numbers are 4556530 and 4663458.
The 3.5L uses a forged steel crank with "the most highly developed finish ever used at Chrysler." It has no identification number on it. The standard main journals are 64mm in diameter and the rods are 58mm. The counterweights are bigger than those on the 3.3L crank because of the increased reciprocating weight.
Chrysler specifies a 1177 gram bobweight on the #1 and #6 crank throws when balancing the engine. The nose of the crank was modified to accommodate the wide sprocket needed to drive the timing belt. The sprocket is interference fit on the straight snout and located with a pin that’s driven into the crank instead of being aligned with a keyway.
Chrysler uses a unique six-piece thrust bearing in this engine. The two thrust flanges are loosely held on each bearing with four small tabs so they can move around and align themselves to the crankshaft. They also incorporate the latest "ramp and flat" design that increases their load carrying capacity by a factor of three compared to that of a conventional, flat-faced, thrust bearing.
Rebuilders should be sure to use an equivalent bearing, because Chrysler’s FWD transmissions tend to load the thrust bearing pretty heavily. Be sure to notice that the upper main is grooved and the lower one isn’t; there’s a right way and a wrong way to install them.
The rods in the 3.5L are forged steel with a full floating pin. The bushing is available from Clevite Engine Parts under p/n B10011. These rods are unique because they don’t have any balance pads. Instead, Chrysler matches the rods with the pistons to equalize the weights. That’s something that needs to be considered when rebuilding this engine.
These rods can’t be bought separately from Chrysler. They are available only as an assembly that comes with a standard piston, so they are real expensive. There are two forging numbers on the rods; look for either 4573149 or 4663422.
The 3.5L pistons have a full-round, short-skirted design with four valve reliefs so they can "free-wheel" if the timing belt breaks. There’s a right and a left piston for both the early (’93-’94) and late (’95-’97) designs. The later piston has a wide chamfer on the edge of the crown along with a black anti-scuff coating on the major and minor thrust faces. See photo. It appears to be interchangeable with the earlier design from a rebuilder’s perspective.
The wrist pin is a full-floating design that is retained by two circlips in the piston. They are very difficult to install without a special tool because they don’t have a loop of any kind on either end. So, the guys at Ontario Reman made their own special tool to install the circlips. See photo. You will have to make something similar in order to install them correctly so they will stay in place when the engine gets some miles on it.
The cylinder head is an aluminum SOHC design with four valves per cylinder. The same head fits both sides, but there are two different versions. The original head (’93-’94) was a 4315807 casting. It had four indentations protruding into the chamber. The later head came out in ’95 and was used through ’97. It’s a 4663490 casting that has more of an oval chamber with only one indentation sticking into the chamber.
Although it’s too early to say for sure, these heads don’t seem to be prone to crack. However, we have seen some with damage to the cam bore due to a lack of lubrication. The head itself is really pretty simple, but the rocker setup gets a little bit busy with 12 roller rockers, each with its own miniature lash compensator, bolted to the head on top of one cam. One look at the pictures that are included with this article will tell the story better than a thousand words, so see for yourself.
The bad news is that the lifters are not available by themselves because they can’t be serviced separately. They are held tightly in the rockers with a wire clip that makes them almost impossible to remove without damaging either the lifter, the rocker, or both.
The lifters are available only as part of a rocker assembly that lists for close to $40. That means a set of lifters will probably cost a rebuilder more than $500 net until somebody figures out a way to remove and replace them without ruining the aluminum rockers, and the lifters themselves become available in the aftermarket.
There are four different rockers used. There are right and left versions of both the intakes and exhausts, so the rockers must be assembled accordingly. Each rocker assembly is bolted to the head with 10 bolts, but there’s a catch in ’93; the oil is metered to the rockers by the narrowed shank on the third bolt from the front on the top row.
There’s only one bolt with the narrowed shank used in 1993; it’s silver-plated instead of black like the rest of the bolts, so it can be easily identified and installed in the right place to provide oil to the rockers. Chrysler eliminated any possible confusion with these bolts in ’94 by installing the narrowed version in all 10 bolt holes.
The 3.5L uses two different head gaskets, too. They are clearly marked right and left, so that shouldn’t be a problem.
The spark plugs are located inside six long tubes that screw into the heads. They should be removed when rebuilding the heads, but they can be hard to get out. The service manual suggests the use of a vice grip to get them out and a couple of rocker cover nuts to put them back in, but that really doesn’t work. So, Ontario Reman adapted a small, expandable mandrel with a heavy knurl on the outside to remove and install them without damaging them in the process. It does work.
The 3.5L has right and left cams that are distinctly different. They can be identified by comparing the snouts on both of them. The cam for the left head is considerably longer and it has a wider front journal, too. See photo.
There are right and left timing sprockets, too, and they are both held on with a couple of long bolts that are also different on each side. The left sprocket is wider and has windows in it for the cam position sensor, and the left cam bolt is noticeably longer, too.
Chrysler uses three separate covers to house the oil pump and the water pump and enclose the back and sides of the timing belt. Take good care of them, because they are expensive if you have to replace them.
The timing belt also drives the water pump. It’s tensioned by a hydraulic tensioner on an idler pulley that’s located on the lower right corner, just above the oil pump. In ’95, Chrysler put a larger pulley on the water pump, changed the tensioner and switched to a longer belt. You can identify the later setup by the size of the pulley. See photo.
Timing the 3.5L is a little more involved because the cam sprockets are not keyed to the cams. They have a large "D" shaped hole that provides an approximate location for initial timing, but it requires several additional steps to get the cams timed right. First, the #1 piston must be up on TDC; it’s the right front cylinder on this engine.
The service manual explains how to find TDC after the heads are installed, but Ontario Reman says it’s easier to use a dial indicator on the #1 piston before installing the heads. After the heads are installed along with the three front covers, the cams are positioned and locked in place by using two of the Miller 6642 tools that are bolted on to the back of each head where the cam cover is normally bolted on.
Install the sprockets without tightening them while making sure that the dot on each one is located between the two dots on the adjacent housing. Slip the belt on correctly, hold it in place with some big paper clips and then tighten the sprockets down to 90 ft. lbs. (Yes, it takes a big metric wrench to hold the sprockets when you tighten the bolts).
You can verify the accuracy of the procedure on some engines by slipping a screwdriver through the hole in the upper housing; it will drop down into a hole in the cam if everything has been done right and the cam was drilled correctly in the first place. Remove the Miller tools from the back of the cams, release the tensioner and you’re ready to button it up once it’s been properly timed.
A word of caution: Be sure to use sealer on every bolt on the front of the engine. Some of them go into open holes that have oil or water behind them so they will seep and leak and cost you a lot of money when they need to be redone out in the field.
The 3.5L short block is simple to build and the heads themselves aren’t too bad either. You can even get at the valves without any problems. The real kicker is the rocker setup with the lifters that aren’t available separately. Timing the cams is a little time consuming, too, but practice makes perfect. All-in-all, it’s a pretty rebuildable engine and not nearly as bad as some other SOHC V6s.
So, that’s the story about "the little engines that could." All three of Chrysler’s 60 degree V6s have proven to be well-designed, durable workhorses in cars and vans. Although they are soon to be replaced by another whole new family of engines in the cars, the 3.3L and 3.8L will continue to be used in the minivans, so we will all be rebuilding them for many years to come.