Mitsubishi’s 4G63 engine was released in 1980 as a 2.0L naturally aspirated inline-4. More popular today is the 4G63T, a turbocharged version of the original 4G63 that was released in 1988 in the Mitsubishi Galant VR4.
The 4G63T is most well known for powering the first nine generations of the Lancer Evo. Additionally, it powered the DSM Eclipse, Eagle Talon, and Plymouth Laser which are still heavily modified cars today.
The 4G63 engine is still in production today internationally but was phased out of the US around 2008. Throughout its history the engine went through numerous revisions. Most notably, a dual overhead cam version was added, the heads were changed from 6-bolt to 7-bolt in May 1992, and MIVEC variable valve timing was added for the Evo 9. The 4G63 was eventually replaced by the 4B11T in the Evo X.
The 4G63T has a cast iron block, aluminum heads, and a forged crankshaft and connecting rods. While the engine tends to be extremely reliable when stock, a number of problems arise when power is thrown at it.
4G63T Engine Problems
- Balance shaft belt & bearings
- Head gasket failure & lifting heads
The majority of these problems are going to be specific to the 4G63T engine. While the 4G63 does experience some of the same problems the majority of these problems occur on modified engines and not stock engines. So while they are still relevant they are simply not as common given the 4G63 engine doesn’t tend to be as heavily modified as the turbocharged versions.
1. 4G63 Balance Shaft Bearing & Belt Failure
The 4G63 uses a belt-driven balance shaft. The system uses two shafts with weights on it which spin in opposite directions at twice the speed of the engine. Without getting into the technical details, the force produced by the rotating balance shafts counteracts and reduces engine vibration.
Balance shafts use bearings to help with rotation and prevent friction. The balance shaft bearings on the 4G63 do fail commonly which results in improper rotation and added vibration. When the bearings fail they commonly take out the balance shaft belt with them.
The 4G63 balance shaft timing belt is driven off of the crankshaft and controls the rotation of the shafts. The stock belt is pretty weak leaving a lot of owners upgrading to stronger kevlar belts. However, the strength of the belt isn’t the problem. The problem is the excess vibration created from bad bearings causes the belts to snap. Kevlar belts will snap too from bad bearings, and since they are tighter and stronger they will snap with even more force.
When the balance shaft belt snaps it takes out the timing belt with it. This throws engine timing off and causes the valves to collide with the pistons. In a worst case scenario the valves collide and crack the pistons, which then score the cylinders, send metal shavings into the oil pan and crack the crankshaft. In this scenario a brand new engine is needed. Best case scenario the valves just bend but cause no other damage and only the valves need to be replaced.
Balance Shaft Bearing & Belt Failure Symptoms
- Increased engine vibration
- Ticking noise coming from rear of engine
- Rough idling
- Poor overall running
Unfortunately when the balance shaft timing belt fails it is usually pretty instantaneous and you can only hope for the best. The belt can snap from normal wear and tear even with good bearings so it’s a good idea to frequently check it for any wear.
If the balance shaft bearings are going bad you will likely have a few warning signs like increased vibration and noises coming from the engine. One of the best ways to prevent bearing failure is frequent oil changes. Bad oil causes improper lubrication of the bearings which is what causes them to wear and fail.
4G63 Balance Shaft Delete
Since the bearings fail frequently and leave the belts prone to snapping, deleting the balance shaft is a common form of preventative maintenance. With the balance shaft deleted the balance shaft timing belt can be deleted as well which will prevent it from breaking and taking out the timing belt too.
However, since deleting the balance shaft requires quite a bit of labor, most people only recommend deleting it if you are in the process of rebuilding your engine or if you are building your motor. While increased vibration isn’t good for performance the last thing you want is a bad belt to destroy your brand new built motor that has thousands of dollars of mods in it.
2. 4G63 Lifter Failure
Lifters get pushed upwards from the camshaft which then press against the rocker arms, controlling the opening and closing of the intake and exhaust valves. The 4G63 engines naturally received somewhat poor oiling. The oil pressure in the head runs low which causes the lifters to not receive proper lubrication.
When lifters don’t receive enough lubrication they can start to stick or cause the valve springs to collapse. The most common problem on the 4G63 is lifter tick. Lifter tick for the most part is just an annoying noise that the lifters make from poor oiling. While lifter tick can overtime develop into lifter failure, a lot of times it is just annoying but can be driven around on for awhile without any serious issues.
A common “fix” for the 4G63 is to run 3G lifters. However, since the issue is oiling related it is only a matter of time before the 3G lifters begin to tick as well. The only tried and true solution here is to port the oil galleys in the head to improve oil pressure and flow to the lifters. However, porting the oil galleys is a bit aggressive unless your engine is already opened up and being rebuilt. For the most part owners will just drive around with the annoying lifter tick until the lifters need to be replaced or the engine is being rebuilt.
Lifter Tick Symptoms
- Ticking noise from engine
- Rough idling
- Cylinder misfires
Again, on the 4G63 lifter failure itself isn’t quite as common as the annoying lifter tick. However, lifted tick is caused by poor lubrication and poor lubrication can eventually lead to complete lifter failure.
3. 4G63T Crankwalk
The 4G63 engine came in both a 6-bolt and 7-bolt versions. This represents the number of bolts that connect the flywheel to the crankshaft. The main bearings on the 7-bolt engines have narrower journals which makes them weaker than the 6-bolt versions and less desirable for performance builds.
Crankwalk only tends to occur on the 7-bolt engines. It happens when the thrust bearings on the crank wear down which allows the crankshaft to move, or “walk”. When this happens the crank wobbles around as it spins which throws the internals off. Additionally, the crank can move enough that it crushes the crank angle sensor which causes the engine to shut off and have difficulty starting.
- Difficulty shifting
- Sticky clutch on left hand turns
- Inconsistent clutch engagement
- RPM drops while clutch is pressed down
- Ticking noise from timing belt area
While crankwalk is more common on the 7-bolt engines it can also happen on the 6-bolts as well. It is suspected that about 5% of the 7-bolt engine will develop crankwalk. It is also worth mentioning that developing crankwalk is more common in high horsepower engines that are running upgraded clutches with with high pedal pressures.
4.4G63 Lifting Heads & Gasket Failure
Predominately affecting modded 4G63T engines is head lift and associated head gasket failure. The issue is the head bolts are very short, not even reaching half an inch down from the deck. Therefore, the head itself isn’t very tightly sealed to the block.
Head lift is caused by one of two things. First, the head bolts can stretch which leads to lifting. Secondly, which is argued to be the more accurate cause, is that the pressure put on the cylinder head pockets causes the head to lift and the washers to sink into the cylinder head.
In any instance a lifting head will also cause head gasket failure. Again, this problem occurs mostly on modified engines running higher levels of boost and a lot of torque. The solution here is to run ARP head studs and oversized washers by ARP. Oversized washers or shoulder dowels will require the head to be machined, so it is common for owners to just run the ARP studs for the time being.
Lifted Head Symptoms
- Oil leaks from the head
- White smoke out the exhaust
- Loss of cylinder compression
- Coolant loss and milky white substance in reservoir
- Poor performance, misfires, etc.
4G63T Power Limits
You will see everything on the internet. That the engine can only handle 400whp/400wtq before the block blows. You’ll also see people claiming 550whp is possible on the stock block, and some claiming that the stock block can handle 1000whp with minor improvements. It is generally agreed that if you want to surpass the 400whp mark you should start with a 6-bolt engine instead of a 7-bolt.
With forged rods and pistons, these are good until around the 500whp mark. The head bolts are very weak and will cause heads to lift around 325-350whp. With ARP studs the head and gasket are good until around the 500whp mark until the head needs to be further secured. The crankshaft is quite strong and usually doesn’t get maxed out, although cracked cranks is pretty common on the later model evo’s.
Lastly, the block. The 6-bolt block is very strong and is capable of handling 700+whp, however, this will require some improvements. The block is strong and the sleeves are good, but the mains and cast iron girdle are weak points. With respect to the block however, proper tuning is the key. Torque tends to be the killer of the lower end of the block, and not necessarily horsepower. Properly tuning your engine can go a long way in block (and internal) reliability when modded. Without modifications the 6-bolt can handle around 600awhp, but anything above 500 is considered to be pushing the limits. The 7-bolt is believed to be good for about 500-550whp.
Mitsubishi 4G63 Reliability
Completely stock, the 4G63 is a really strong engine and is capable of making it past the 250,000 mile mark. With forged internals and a strong block, the major engine components themselves are unlikely to ever show you any problems. Lifter problems and bearing shaft failure can still occur on stock engines, but crankwalk and lifting heads are almost exclusive to modified 4G63 engines.
However, stock reliability is a bit less meaningful on the 4G63T especially due to their popularity as a tuner engine. The 4G63 is considered to be reliable up to around the 450whp mark without any major reliability mods. However, once you start to break past these numbers you will need to start looking into upgrading various internal components and consider strengthening the block.
6-bolt engines are considered to be a bit more reliable and power capable than the later 7-bolt engines. Reliability of course tends to decrease as power increases. Cracked cranks, crankwalk, lifted heads, broken rods, low end block problems, etc. all become common problems once you take your 4G63 beyond the 500whp mark.
Overall, these engines are very stout and can produce crazy 1000whp+ levels when fully built. When completely stock and when fully built they are extremely reliable. In between they will require some upgrades and improvements when tuned. The 4G63 remains popular today due to it’s power limits and increased strength, especially compared to its 4B11T successor which tends to have block problems once torque gets close to 400wtq.
How has your experience been with reliability on modded 4G63 engines?