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386 Posts
Discussion Starter · #1 ·
Legal Disclaimer -

This post does, in no way, reflect the beliefs, opinions or standards of DSMTalk or any of its affiliates. I accept no responsibility for any damages physical, medical, financial or otherwise resulting directly or indirectly from the use, mis-use, or misinterpretation of the content contained here-in - including but not limited to damages resulting in financial loss, personal injury and loss of life.

English -

You f*ck up, it's your own problem.

:) Now, onto the good stuff.

Part 1 - Prep

When to rebuild.

Many people will say that engines last only a certain number of miles before they need to be rebuilt. This is untrue. A properly maintained engine can last you well over 200,000 miles. So if your engine is still running, how do you know when is it time to rebuild?

* Oil Consumption - If the engine is using more than a quart of oil between changes (worn rings)

* Oil Pressure - If the engine's oil pressure is excessively low (excessive bearing clearance)

* Chronic or Recurring Oil Leaks - Notably on crank seals or camshaft seals (main bearings out of spec)

* Detonation & power loss - The tick that sounds like rocks hitting your floor pan won't go away without backing way off on your ignition timing, resulting in heavy power loss

If you're experiencing some or all of the above, things are starting to wear out. Your piston rings are allowing for blow-by, valve seal clearances are starting to open up, connecting rod bearings are probably starting to make a little noise, valves are ticking, and mopping up oil leaks is becoming a daily occurance.

If your motor is still pretty sound, and just exhibiting mild symptoms, it is by no means in need of immediate attention, as long as you've got a good stock of oil... Just keep it in the back of your mind that it's going to come due eventually.

If you plan to build a crazy turbo project car, or are looking to increase performance, you will want to do a rebuild. Doubling the power of a car with 180,000 miles on it, while fun, won't last long under the added stress.

Pick a time when you won't be under a lot of stress to get the car running again. Give yourself at leask 2 weeks so you can take your time and do it right. One bolt or nut torqueed under spec (or forgotten... are you the type that ends up with 10 or 12 extra bolts after you're done working on your car...) can lead to catastrophic failure.

For some cars, a rebuild is a losing financial proposition. For instance, if your car is a severely dented POS with ripped interior and a leaking roof, you may just want to look into getting another car (they're readily available) but if your car just needs some minor work, an engine rebuild can extend its life quite a bit.

When you do decide to do a rebuild.

Keep in mind that a rebuild, while it CAN be just a weekend job, is normally an all-week (sometimes all-month) job. Assuming your motor needs no machine work, removing the engine and taking it apart is still an all day affair. Internal engine parts are not exactly sitting on stock shelves at your local Napa, they need to be ordered, and this takes some time. You will be without wheels for a while, so you will need a way to get around (like an old beat up honda, or something) in case you need parts or tools - and you will need at least 1 assistant to do the job. Here's a list of the bare minimum of parts you'll need to change.

* Gaskets - Buy a full gasket set. You can get them for about $110, if you look hard enough. These cannot be re-used, once you take the torque off of them. If you don't change them all while the engine's out, you'll be sorry later when you have to change them with the engine installed. Use Silicone / RTV for additional sealing power.

* Piston Rings - These come in complete sets for all 4 pistons and normally run about $75

* Connecting Rod Bearings - These are the bearing inserts for the connecting rods, and are normally sold seperate from the main bearings. These take more abuse than the main bearings, so they are generally the first to fail. They look like crescent shaped pieces of tin, but they're actually coated teflon, and designed to pick up impurities in the oil so they don't get embedded in the crankshaft. There are 4 sets.

* Main Bearings - These are the bearing inserts for the crankshaft, much like the connecting rod bearings, only larger. There are 5 sets.

* RTV - silicone Gasket maker. You will need this to re-attatch your oil pan. Even if your gasket set comes with an oil pan gasket, I recommend using RTV instead, because of its sealing properties. Removing an oil pan while the engine is still in the car is a two hour job, so you want to do it right while the engine is out and not have any leaks. You can also use it to help seal the rest of the gaskets.

* Hydraulic Lash Adjusters - If you haven't changed them yet, now's the time.

* Clutch - The transmission is going to be out, and it's normally a 7 hour job.

Expensive things you MAY need to have done:

When you tear into an engine, you never know what you're going to find. Some of them are in great shape internally and just need new rings and seals. Others... well, others make you wonder how they were still running at all...

* Cylinder Re-bore - If the cylinders are badly worn, tapered, or out of round, they will need to be bored by a machine shop to clean them up. In this case, they'll normally bore the block out a few thousanths of an inch, and you will need to install 4 new oversized pistons.

* Resurfacing - If the deck of the block is warped, it will need to be milled down a few thousanths to seal properly with the cylinder head.

* Head Work - Valve lapping, reseating, milling - An experienced machine shop will be able to tell what is required. Normally, the head just needs milling, at most. If your engine has over 200,000 miles on it, you may want to look into reconditioning or replacing the valves and having the seats ground.

* Turning Down The Crank - If your engine has an extreme number of miles on it, has been run with low oil or low quality oil, overheated, or beaten to a pulp by an adolescent driver, it will probably be out of round and will need to be ground by a machine shop to the next size down to clean it up so it runs true again. You will also need oversized main and connecting rod bearings.

* Line Boring - In extreme cases, the main journal pockets and the bearing caps warp or become out of round. Normally this is not a problem, but if your motor won't rotate after you torque down your new main bearing caps, this may be the problem. Line boring involves boring the main journals out to make them round again. This process can theoretically be done to the cylinder head to get rid of imperfections in the camshaft bores, but there are no bearings in the head, so you would need to either find some, or buy a new head casting.

Special Tools you'll need

Torque wrench (duh)

* 8mm allen socket - this looks like a socket with part of an allen wrench sticking out. If you can't find one, use a hacksaw to cut off 2" of an allen wrench, apply some teflon tape to one end, and stick it into an 8mm socket. Make sure this socket fits the torque wrench, and is a minimum 3/8" drive. You'll be putting 55 ft/lbs on it.

* Ridge reamer - This is a tool that goes down in the cylinder head and grinds out the ridge created by cylinder wear at the top of the piston's stroke (we'll discuss this more later)

* Ball Hone - This is basically a tool to break the glaze on the cylinder surfaces. If you can't find one, a little 300 grit sandpaper will work - make sure you clean up the pieces. A little emery goes a long way. If you're getting the block bored, you won't need to break the glaze, the machine shop will do it for you.

* Engine Hoist - I use a chain hoist, but a cherry-picker style engine lift is better. If you use a chain hoist, you'll need a rolling floor jack as well to move the car out of the way after you lift the engine out. Have a plan on how you're going to get ahold of it and lift it out. I use a bracket to grab ahold of it, but most people just cradle it with a chain. Some people have a bunch of big muscular dudes pull it out with thier bare hands... But I wouldn't recommend that.

* Clutch Alignment Tool - A lot of clutch kits come with them, but make sure you have it, or you'll never get the transmission lined up with the bolt holes.

386 Posts
Discussion Starter · #2 ·
Part 2 - Engine Removal

Part 2 - Engine Removal

Get out a sharpie and some masking tape. Use it to mark every hose you disconnect. I obviously can't outline every wire and hose you need to disconnect, or this FAQ would go on for 50 pages. Mark everything with BIG BOLD letters in pairs. I use letters for electrical connectors, and numbers for vacuum hoses - it cuts down on the confusion. One piece of tape for the wire/hose and one piece of tape to what it was connected to. If you have a 91-94, the wires are all different, so it's harder to mix things up, but just the act of marking everything will set it in your mind that this... is connected to this... and when you reassemble it, you'll have an order to follow. A-A... B-B... C-C... It may seem stupid now, but when you come back after a week and try to put everything back together, you'll thank me. I also mark the connectors themselves, in the event that the tape comes off, or gets so covered in grease, it's unreadable. You also want to have some boxes or buckets to throw bolts and nuts into. You'll want to try to keep everything seperated in both a logical and chronological order. Wherever possible, if I take out both a nut and bolt, I screw them together with the parts they came out with.

Drain the coolant and discard it.

Unbolt the 4 bolts on the hood and remove it (get some assistance with this please).

Disconnect the battery and remove it.

Disconnect and remove the intake tube.

Disconnect the upper and lower radiator hoses, fan plugs and radiator temp sensor and remove the radiator.

Remove the hose that runs from the overflow bottle to the thermostat housing.

Disconnect the two sensors on the thermostat housing - LABEL EVERYTHING.

Disconnect the heater hoses from the engine.

Remove the two bolts holding the starter in (you don't need to disconnect it) and secure the starter on the firewall with bail wire or an old coat hanger.

Disconnect the downpipe from the exhaust manifold. If you can't get the bolts loose, spray some WD40 on them, proceed with other tasks and come back to them later. They need to come off.

Disconnect the O2 sensor.

Disconnect the ISC motor & TPS sensor (on the throttle body)

Disconnect the two connectors on the distributor.

Before you disconnect the 4 ignition wires, mark each with numbers corresponding to the cylinder numbers they go to (#1 is the closest to the driver's side) and mark the distributor. If you're looking at the distributor from the driver's seat, starting from the bottom, going clockwise, it should go 1-3-4-2. Now disconnect them and set them aside.

On the 4 fuel injectors, there are half-square type metal clips holding the connectors together. The clips slide out. Stick a screwdriver under one of them and pry it up and the half-square clip will slide right out. Do not break the connector on the injector, or you will be replacing the entire injector.

Remove the bolts holding the plastic injector wire harness to the intake plenum. You should now be able to maneuver it away from the engine and rest it near the firewall.

Remove the PCV hose, brake booster hose, and any other vacuum hoses plugged into the throttle body (this will vary according to year).

Remove the grounding strap on the rear of the intake manifold.

Remove the throttle cable and the cable support bracket. If you have a '90 equipped with cruise control, you will need to unbolt the cruise control box as well and secure it away from the engine so the cables don't get in the way. For 91-94 vehicles, the cruise control box is on the firewall, and you should be able to maneuver the engine around the cables. But if in doubt, remove the damn thing and get it out of the way.

On the MANUAL transmission - Unbolt the clutch slave cylinder, grounding strap, reverse switch, and unbolt the bracket for the clutch fliud line (do not disconnect the line). Also remove the cotter pins for the shifter linkage and remove the linkage bracket. Secure the cables off to the side.

On the Automatic transmission - Remove the elctrical connectors, selector linkage and the throttle cable.

Remove the speedometer cable.

Remove the accessory belts.

Remove the alternator, oil pressure sender, oil warning sender, and secure the harness away from the engine.

Unbolt the power steering pump (do not disconnect the lines) and secure it on the fender (put a towel down so it doesn't scratch, and if it leaks... well, if it leaks, you should be removing it and replacing it)

Remove the driver's side motor mount.

Remove the water pump pulley.

Jack up the car and secure with jackstands.

Drain the engine oil and discard it.

Drain the transmission fluid and discard it.

Remove the driver's side tire.

Remove the 2 bolts securing the strut to the steering knuckle.

With the steering wheel turned to the extreme left, you should be able to push the driver's side axle out of the hub in steering knuckle. Crawl under the car, and with a large flat-tip screwdriver, gently pry the inside CV joint out of the drivers side of the transmission and remove the axle assembly. Do the same for the passenger side.

If equipped with AC, you will need to remove the AC tensioner, the 4 bolts securing the AC compressor to the block, and tie the compressor up to the firewall (out of the way) with an old coat hanger or a peice of bail wire (do not disconnect the lines).

Now at this point you have a choice. You can seperate the transmission (easier to pull, takes more time to do) or you can pull both the engine and transmission at the same time (harder to maneuver, easier to break stuff, weighs more, hurts when it falls on your foot...) okay, so it's a pretty simple choice.

Remove the lower coupling bolts (don't forget the one way in the back) and the flywheel's dust sheild and use a jack to support the transmission from the bottom if you're a wuss like me and you handle 300 lbs.

Do a cursory check to make sure you (or i) didn't forget any wires or supply lines.

Remove the transmission mount from the transmission and remove the center bolt holding the mount to the bay - Now remove the mount.

Remove the two upper coupling bolts, pull the transmission toward the passenger's side of the car, and we're out of there.

Attatch your engine hoist (or chain hoist) - removal of the valve cover may be necessary to mount a bracket to lift the engine out. Hopefully you worked that part out already.

Take the weight off the engine mounts (support the engine with a jack if necessary) and remove the center bolts from the front and rear mounts.

Lift the engine out of the car. Be careful with it. We don't want any DSMers getting killed by a falling engine.

If you're using a chain hoist, tied to the ceiling, you'll need to jack up the car with your rolling floor jack and gently push it backwards (even a 1 ton floor jack will support the wieght of the car without the engine) until you have room to set the engine down. Again, be very careful, there's a lot of potential energy hanging in your garage at this point.

Now to set your engine down. Lower it slowly, and don't let it fall over. If you drop it, it's ruined. Let it rest on the intake manifold, go inside and get some rest. Hell, I'm getting tired just typing this FAQ. I'll be back tomorrow with head removal, and more on doing your rebuild.

386 Posts
Discussion Starter · #3 ·
Part 3 - Head Removal / Disassembly

Part 3 - Head Removal / Disassembly

Head Removal

Remove the valve cover, if it's not already off.

Prop the engine up with some wood blocks (an apple crate works great for this, if you can get one).

Disconnect the throttle body heater hoses from the block and unbolt the intake manifold. there are 4 bolts on top, and 4 nuts on the bottom. Unbolt the intake manifold support bracket from the block and remove the intake manifold. If you wanted to block off the EGR valve, You can do this now, be removing the EGR valve from the manifold, and putting JBWeld into the hole.

Remove the exhaust manifold.

Remove the crank pulley and the upper and lower timing covers.

Crank the engine to top dead center, loosen the timing belt tensioner and remove the belt.

With a screwdriver, punch a match mark on both the head and the distributor - right where they meet. Remove the distributor and coil assembly.

Now we're going to remove the cylinder head. Using the allen driver in the torque wrench, remove the 10 cylinder head bolts in the following sequence:

| (4) (6) ( 9) (7) (1) [¯]
|______________________| |, <--- Cam Sprocket
|¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯| |'
| (2) (8) (10) (5) (3) [_]

It's important that you follow this sequence, or you can warp the cylinder head. Check each headbolt for stretching. The easiest way to do this is to roll the threads over a flat surface and look to see that they're all even. If they look hour-glass shaped, or any threads appear deformed, you will need to replace the bolt.

Remove the cylinder head from the block (you may need someone to help you carry it).

Cleaning and Inspection Points

* Clean off the old gasket, if there is still remnants of it on the head. You can use a screwdriver for this, or a gasket sracper or putty knife. Try not to gouge the head surface, or you will need to have it milled down.

* Check for warpage with a straight edge from corner to corner, end to end, and top to bottom over each cylinder. Use a feeler gauge if you have one, to feel for areas that have excessive clearance. But generally, you'll be able to actually see if there is any warpage.

* clean off the roof of the combustion chamber with a wire brush and some gasoline. Look for cracks in the wek points - Between the exhaust valve and spark plug, the intake valve and spark plug, and most importantly the bridge between the intake and exhaust valve. this is the most likely place for cracks to develop. It's difficult to see hairline cracks, and the easiest way to bring any to light is to take some chalk, mark over the areas I mentioned above, then pound elsewhere in the casting with a hammer - lightly, but hard enough to make a nice clink. If there are cracks below the chalk, the resonance will cause them to open up momentarily, and some oil will seep out and make them more obvious. If you don't see anything after a few wangs, you're good to go. If you do find any cracks, count on replacing the head.

Cam, Rockers and Lifters

Before you remove the cam, make sure it's set at TDC, and with white-out or nail polish, make a match mark on the cam and the arrow on the rocker tower (no, it doesn't matter which arrow, just pick one). This will assist you in timing later.

To gain access to the cam and lash adjusters, remove the 10 bolts holding the rocker assembly down. There's 2 small bolts closest to the cam sprocket that also need to come off, and two holding the rear timing cover to the head (behind the cam sprocket). Check the head for scoring. There isn't much you can do about it, but it's an obvious sign of oil starvation or oil contamination which may be what led to the engine's demise. With the rocker assembly off, you can now change the lash adjusters (lifters... tappits... whatever you want to call them). They'll probably just fall right out, but if any are stuck, just tap the top of the rocker softly with a hammer and they'll come out.

To install the new lifters, mitsubishi says you need a special tool to hold them in while you bolt the rocker assembly to the head (so they don't fall out). I say 8 rubber bands is cheaper than buying one tool from satan. :) Use the rubber bands to hold the lifters in the rocker arms when you re-install the rocker assembly.

Valves and Springs

Most times youre valves won't need any work. Check them for any signs of scorching (which means they're not sealing) or any deformitites in the seat area. Again, if you're getting the seats ground and having the valves refinished, this is best left for the machine shop. If you're just replacing the valves for whatever reason, or maybe you just want some cool paper weights you need to remove them from the head. To do this, you will need a valve spring compressor, or if you have access to a grinder, you can make one out of a socket and a large C-clamp. I have also seen people use a crowbar, and even a C-clamp with an open-end wrench! In any case, you'll need to compress the valve spring and remove the retainers from the end of the valve. Use your problem solving skills, or just buy the spring compressor. The retainer is two half-moon shaped pieces. After you take the pressure off the spring, the retainers will slide right out and the valve will drop out of the head.

Installation is just the opposite. This is where you can put in your fancy new titaium valve springs, your plastic valves and paper reatiners or whatever. Anyway, slide the valve up into the head, compress the spring, slide the retainers over the end notch and you're done. Again, if you're getting any head work done, pay the shop to do this.

The Often Overlooked

Most people don't know, but there's a freeze plug on the end of the head. If your area never gets cold enough to worry about freeze-over, JBWeld the edges shut. If you're in a cold climate area, change it. They're sold as "doorman plugs", "freeze plugs", "core plugs", "expansion plugs" and many other names. The plug is the same as the ones in the block, so if your parts store tells you they dont have a listing for the head plug, inform them. To remove the plug, drill a hole in it, stick a flat-tip screwdriver through it, and pry it out. When you install the new one, use RTV or some other type of silicone sealant on the edges.

You have the option of changing your manifold studs at this time. To remove the old ones, run a nut down about half way, then run another one down right after it and jam the two together. Then twist the whole works counterclockwise. The stud should start to back out. If the stud doesn't back out, you'll need to grip it with a set of vise grips, which will ultimately destroy the stud. So don't take them out unless you need to.

Most people don't know that when you install new ones, you should dab some loctite on the threads (I said dab some... not cover the thing). This will stop them from backing out later. I also put some RTV around the edges of the hole. There's water passages back there and this will alleviate the "ah crap, I just put my car together and I have to take it apart again because of ONE leaking exhaust stud" problem.

While you're in there, change the thermostat. Please change the thermostat. For goodness sakes, they're five bucks, and you have to go to the store to pick up more RTV anyway (you can never buy enough of that stuff the first time) -they're sitting right there on the shelf - please, just change the thermostat. Your car will thank you for it.

Some Other Reassembly Points

* Intake manifold gasket - The intake manifold gasket is reversible. But it's not reversible. It will go on either way. But if you put it in upside down, it won't seal the water passages and you'll have water leaking down that side of the block - and being sucked into the engine. Bad. Hydrolock breaks connecting rods. Make sure it's on the right way, and use RTV on both sides.

* Distributor Installation - With the cam aligned to TDC (you did make that timing mark, right?), take the distributor cap off and align the button to point down. On the shaft, near the gear, there is a punch mark and a timing mark. Line them up and slide the distributor shaft into the head. If you can't find the marks, point the button down as close to perpendicular you can get it and slide the distributor in and line it up with your match mark. It may be necessary for you to remove this and re-adjust it later. Re-attatch the cap. This should be set at just a few degrees before TDC. We can adjust it later.

* Thermostat housing - Too much torque on those 2 bolts will crack the housing. This is actually a very common mistake a lot of people make when rebuilding thier 4G37. Torque only until the RTV seeps out of the cracks enough to make a solid bead.

* Assembly Lube - I use Automatic Transmission Fluid. But they do make assembly lube. Just give all the moving parts and contact surfaces a shot of it to prevent stuff from breaking on the first start-up.

* RTV EVERYTHING - Any gasket or seal should be coated with a litte RTV. You can apply it now, or later, it's your choice. You should go through about 3 or 4 tubes by the time the engine is back together.

386 Posts
Discussion Starter · #5 ·
Part 4 - Engine Block Disassembly

Part 4 - Engine Block Disassembly

I had to split this into two parts, because there's so many steps and such a long wait between Disassembly, and Prep/Reassembly. So here's the first half of the journey into the 4G37 block.

Seperate your nuts and bolts and parts in a logical and orderly fashion so you know where everything goes when it comes time to reassemble. Don't email me with a photo of a nut or bolt asking me where it goes. I may have photographic memory, but it doesn't quite work that way ;)

Remove the pressure plate, clutch disk, and, if possible, the flywheel. If you can't get the bolts loose, leave it on, and proceed to the next step.

Reaming The Ridge

I've heard horror stories about people removing pistons and finding busted landings - when in fact the reason they were busted was because the pistons were not removed properly. You MUST ream the ridge before removing the pistons. Let me reiterate that. YOU MUST REAM THE RIDGE BEFORE REMOVING THE PISTONS. Removing the pistons before cutting the ridge will cause the piston rings go get hung up on the ridge and will break the piston lands.

What's a ridge? Run your fingernail up the cylinder wall and you should feel a little spot where the depth changes and your fingernail catches. Take a look at how the engine works. The pistons move up and down in the cylinders, and they wear down the walls of the cylinders. But the piston doesn't come all the way to the top of the cylinder. So anywhere above where it stops is not going to have any wear. This leaves a cylinder ridge that MUST be removed. That's what the ridge reamer is for. Basically, a ridge reamer cuts the part of the cylinder walls that didn't get any wear from the pistons. This makes the walls flat again, so the piston can slide out evenly, without getting caught on anything.

The ridge reamer I use is spring loaded and rides down the cylinder like a hone, cutting away the excess material at the top of the cylinder wall. Mine automatically stops cutting when I finish cutting the ridge, but yours may be different. Follow the manufacturer's instructions. The ridge on our motors is nomally about 1/2" from the deck. So that's how far you need to run your reamer down.

Bottoms Up

Turn the block over, and remove the oil pan. There are a LOT of bolts. It may need some coaxing with a rubber hammer.

Remove the oil pickup tube and screen. Discard the gasket.

Use a wratchet, a length of pipe, or a thick piece of wood to jam the crankshaft so it doesn't move - if you're a paranoid wussburger like myself, wrap the wratchet or pipe in a rag first so it doesn't leave any impact scars on any of the parts. If you were previously unable to loosen the bolts on the flywheel, you will be able to this time. They're glued to the crankshaft with loctite, so they will take quite a bit of force to remove.

The flywheel is also glued to the crankshaft with loctite. So it may also take some coaxing with a rubber hammer to get off.

Remove the rear case assembly.

Front Case

Now remove the crankshaft sprocket. Easier said then done, huh. We maxed out a pneumatic wrench at over 150ft/lbs getting mine off the first time and ended up using an acetylene torch to heat the bolt and a breaker bar with a 2 foot extension to break it loose.

The Crank sprockets slide off one at a time.

Remove the oil pump sprocket and discard the seal.

Remove the tensioners and the front case assembly (there's a lot of bolts).

Water Pump

If you haven't replaced it yet, replace it now. If you already have a relatively new pump, change the gasket and replace the O-Ring for the front water pipe.

To remove the front water pipe, and gain access to the O-Ring, unbolt the bracket from the transmission-side of the block. The pipe is an L-shape. Pull toward the transmission-side (pull hard) and the pipe will eventually pop out of the water pump housing. There is a small rubber o-ring that goes around the edge of the pipe. Replace it. To remove the water pump, remove the pipe, then unbolt the water pump from the block.

When installing the new gasket, be sure to scrape off the old crud that's on there first, clean the surface and apply a little RTV to both sides of the new gasket. Do not overtorque the bolts or you will crack the water pump housing.

Balance Shafts

You CAN remove the balance shafts on manual transmission cars. On automatics, I've heard stories that you can't (I can't imagine why, the engines are identical). But for safety's sake, if you have an auto, consult a machine shop or leave them in.

Here's a FAQ for removing the shafts from the 2.0 - the procedure is pretty much the same for the 1.8 (though the pics are SLIGHTLY different), so I won't bother to re-type it.


I will outline a few points for those wanting to KEEP thier balance shafts, however.

The balance shafts will both come out with the front case assembly. You should change the bearings. I've never actually bought a set, so I wouldn't know where you'd get them - most people just remove them when they do an engine rebuild. I did call a few parts stores and they had no idea what I was talking about, so I assume you'd have to order a set from satan. err... the dealershit... err... dealership.

The front shaft has 2 bearings, the rear only has one. They should slide out rather easily with a few taps on a large socket or pipe. They're sleeve bearings, not the cut-in-half type on the crankshaft. Be sure to align the oil holes when pressing the new ones in or you'll be in for a hell of a nasty surprise.

Oil Pump

I am not going to outline all the inner workings of an oil pump. They RARELY fail, so you can normally just change the rubber seal. All you really need to do is check the shaft for play. If it's wobbling or making noise when you turn it, it's bad. If you suspect your oil pump IS bad, disassemble it and look for play in the shaft. There's two gears. That's about all it is. If you do disassemble your oil pump, just line up the marks on the gears when you reassemble it.

And of course, RTV everything.

Main and Rod Bearings

Before you unbolt them, mark them with white-out. Yes, they're punched at the factory, but you don't know that you'll be able to read them, you don't know that the original owner hasn't replaced them, and you don't want to take any chances. So mark them with white-out.

I Mark the mains with M1, M2, M3, M4 and M5, and mark thier DIRECTION. I normally mark a dot on the side that faces the front of the engine. Do the same for the connecting rods - I mark mine R1, R2, R3 and R4 They are NOT reversible.

Now remove the bearing caps and examine the bearing inserts.

These ought to give you an idea of thier condition.



Now examine your crankshaft. Look for scuffing, distortion, or drastic change in color on the contact surfaces. If you have a caliper or micrometer, use it to measure the crank journals at several different angles. If the measurement changes, even slightly, your crankshaft is out of round and will need to be ground. If you do not have a caliper or micrometer, have it inspected by a machine shop. If the engine was abused, or has an extremely high number of miles on it, normally the crankshaft will need to be turned down a few MM, and you will need to purchase oversized bearings. Make sure before you give it to them that you remove the woodruff key. If they lose it, (and they probably will) they're not likely to provide you with a replacement.

Freeze Plugs

Same as in the head. If you live somewhere cold, change them. If not, JBWeld them shut. There are 7 of them on the block. To replace, drill a hole through the plug, pry it out with a screwdriver, Use RTV sealant around the edges and pound the replacement in with a hammer and socket.

Motor Mounts

If they're cracked, you can replace them, fill the cracks with silicone (I believe the product is called "the right stuff"), or leave them and hope for the best. In any case, if you unbolt the front or rear mount from the block, pay special attention when putting it
back together. You MUST use a thread sealer (loctite) on the bolts that go into the block or they will come loose and fall out.

Commonly Overlooked Areas

There are a number of commonly overlooked areas of block prep that can (and normally do) lead to leaks on your rebuilt motor further down the road. There are also a few simple tasks that should be done while the engine is out, rather than after it goes back in.

* Oil Filter Housing - 4 bolts, on the front of the block. Remove it and change the gasket.

* Oil Pump Seal - Change the round rubber seal behind the oil pump sprocket. High milage oil pumps especially. This is a real b*tch to change while the engine is still in the car.

* Oil Pickup Screen Gasket - This is one of the most important gaskets in the engine! If you neglect to change this seal, you are introducing air bubbles into the oiling system (or possibly just air and no oil... bad bad bad) so scrape both surfaces clean, and use RTV on both sides of the new gasket.

Hopefully by this stage, you have everything labeled and seperated into little plastic bags so you know where everything goes... I know I wouldn't... But it's a good idea none the less.

Now that everything's apart and you're waiting for your stuff to come back from the machine shop, take this time to clean up your garage, spray your engine with engine enamel, clean your engine bay, or go take a shower and watch some TV. For the next part, you'll need plastigauge (which probably came with your bearings if you bought them locally) and break out the torque wrench for reassembly. If you can't get plastigauge, I'll show you how to use newspaper as a crude clearance check. Get some rest. You'll need it.

- Kalani

386 Posts
Discussion Starter · #6 ·
Sorry this is taking so long to finish.

I got a show to prep for on the 7th.

386 Posts
Discussion Starter · #7 · (Edited)
Part 5 - Block Reassembly

Part 5 - Block Reassembly

I'm going to assume you took my advice and kept everything seperated and labeled. Now we're ready to replace your main bearings and your piston rings.

Prep Pistons

If you haven't done so already, push the pistons out of the block. Remove the rings, starting with the top ring. Be careful. The pistons are aluminum and you don't want to damage the cylinder surface. For extremly high milage motors, the rings may need some coaxing to get off. A screwdriver in the ring gap will break them loose so you can pull them off. Be careful. The rings are sharp and will dig into you like a dull knife - only more painful. The oil control ring (the big one on the bottom) is in three pieces - two small rings fited over one larger corrugated ring. Take the top and bottom rings off the oil control ring first, then seperate the corrugated ring. This, like the other two rings, will probably need some help to come off. In fact, if your engine is anything like mine was at 120K, the control ring will probably be frozen in the grooves. Take your time.

|____________________________| <--- 1st compression ring
|____________________________| <--- 2nd compression ring
|| | | | | | | | | | | | | | | <--- oil control ring (3 parts)
| . . . . . ./¯¯\. . . . . . |
| . . . . . ( () ) . . . . . |
| . . . . . .\__/. . . . . . |
| .________________________. |
| /         | | | |         \ |
|/          | | | |         \| <--- Piston Skirt
            | | | |
            | | | |
            | | | |
            | | | |
            | | | |
            | | | | <--- Connecting Rod
            | | | |
            | | | |
            | | | |

^--- Poor Drawing ---^

Once the rings are off the pistons, The ring lands need to be cleaned. You can do this with a ring cleaner tool, or a piece of a broken piston ring (the chances of you getting the old ones off without breaking one is pretty slim, but if you did, go ahead and bust one in half). I use gasoline to clean out the grooves once I'm done scraping out the carbon deposits. If you have access to a wire wheel, use it to brush the black crud off the tops of the pistons. Otherwise, a wire brush will work. A small putty knife works well for the really baked-on stuff.

Now you're ready to assemble the pistons again with new rings. Any respectable ring company will ship thier rings with directions, or at least label them 1st, 2nd and Oil Control. If yours don't have that, I'd suggest you take them back. Some rings are reversible, others are not. The instructions on the box of rings will tell you which side is up (if any). If you don't have instructions, look for a dot on the rings. The dotted side goes up.

Put the oil control ring on first. The corrugated ring goes on, then the two retainer rings. Stagger the gaps in the rings 180 degrees apart to prevent leakage and yeild a little more power. Now the #2 compression ring, and finally the top compression ring. Again, stagger the gaps 180 degrees apart, but make certain that they are not directly over the wrist pin, or directly perpendicular to the wrist pin. Make sense? I didn't think so. Just stagger the rings so they're not parallel with the connecting rods.

Main Bearings

The bearing inserts are made to close tolerances, so try not to scratch the surfaces. Insert the bearing halves into the block (they only go in one way). Oil the bearing surface with assembly lube (or ATF) and then lower the crankshaft into place. Now here's where we use the plastiguage. (if you don't have plastiguage, don't worry, we'll get to that).

* Plastigauge

Place a strip of plastiguage across the crankshaft journal, then insert the other half of the bearing into the main bearing cap and torque it down to 60 ft/lbs. Remove he bearing cap, and examine the palstiguage. It will have changed in width. Now read it with the paper gauge provided. Anything between .0008 and .004 is within spec. For new bearings, it should be very close to .0008. If the reading is too high or too low, you've got the wrong bearings, or your crankshaft is out of spec. If it's within spec, you're set. You should only need to do this reading with one main bearing, but if it makes you feel better, go ahead and do the rest.

* Newspaper

Tear off a strip of newspaper just big enough to go across the main journal on the crankshaft (1" by 1/2" should be plenty). Now insert this piece between the crankshaft and the main bearing and cap and torque the main bearing down to 60 ft/lbs. Newspaper is about 3 thousanths of an inch thick, so if your bearings and crank are within spec, this should cause the crankshaft to bind when you try and turn it. If the crankshaft turns freely, take the cap off and insert a 2nd strip of paper and torque the bearing cap down to 60 ft/lbs. This should definitely cause the crankshaft to bind. If the crank still spins freely, your bearings are the wrong size or your crankshaft is out of spec.

Now that we have tested to make sure our bearings are alright (and I hope they are), we can remove the plastigauge (or newspaper) and torque all 5 of the mains down to spec (58 ft/lbs). Use loctite. Please use loctite. For Goodness sakes, it's 2 bucks. Are you really willing to take a chance with something spinning at 6000 rpm after all this work...

Turn the engine a few turns. It should spin freely. If it doesn't, do a clearance check with plastiguage.

Front and Rear Case

Install the front and rear case assembly with new gaskets. If you can't find new gaskets, you CAN use RTV, but you have to be EXTREMELY careful to put it where it needs to go, and use ONLY a little bit, or it will bead off and clog oil passages (not good).

Install The Pistons

Now we're going to put the pistons back in the block. Turn the engine right side up. You'll need a piston ring compressor for this job. If you don't have one, I'll show you how to make one out of a few aluminum cans and a hose clamp.

Piston Ring Compressor

Cut the tops and bottoms off 2 cans.

- - - - - - - - <----------Cut here
|. . . . . . . .|
| D . U . F . F |
|. . . . . . . .|
| B . E . E . R |
|. . . . . . . .|
|. . . . . . . .|
|. . . . . . . .|
|. . . . . . . .|
|. . . . . . . .|
|. . . . . . . .|
|. . . . . . . .|
|. . . . . . . .|
- - - - - - - - <----------Cut here

Then cut lengthwise and unroll the cylinder.

|. . . . . . . .|
| D . U . F | F |
|. . . . . . . .|
| B . E . E | R |
|. . . . . . . .|
|. . . . . .|. .|
|. . . . . . . .|
|. . . . . .|. .|
|. . . . . . . .|
|. . . . . .|. .|
|. . . . . . . .|
|. . . . . .|. .|

Cut Here __^

Now oil the piston and put the two cans around the piston like sleeves, taking care to stagger the openings to surround the entire piston. Tighten a 2.5" hose clamp around the bottom. This will keep the rings compressed as the piston slides into the bore. If you can afford it, and you plan on doing any more serious engine work, a REAL ring compressor is well worth the investment. But in a pinch, this works just as well.

Breaking The Glaze

If you had the block bored by a machine shop, you can skip this step, since they already break the glaze at the shop when they cut the bore. If not, you need to break the glaze on the cylinder walls. If you have a ball type hone, you can put it in a drill and use that, or you can use some 300 grit sand paper. Scuff the cylinder walls just enough so they aren't shiny any more. This will give your rings a fresh surface to seat on. Wipe the insides of the cylinder wall with gasoline, then re-oil them.

Installing The Pistons

Cover the studs on the connecting rod with some 3/8" rubber hose so we don't damage the crankshaft. Install the connecting rod bearing halves onto the connecting rods (and install the other halves into the connecting rod bearing caps). Oil the cylinder walls. Put the piston in the ring compressor to the point where just the skirts of the piston are sticking out the bottom. Tighten it up and place it over the cylinder bore. Now tap (not pound) the top of the piston with the handle of a hammer (the handle only) until it slides into the bore. If you use too much force here, you can damage the piston and break the rings. Once the piston slides into the bore, the oil control ring will have wiped the oil out of the bore. Shoot more oil (or ATF) around the dome to keep oil above the piston.

Connecting Rod Bearings

Do the connecting rod bearings the same way you did the main bearings. Make sure you match the correct connecting rod to the correct bearing cap. Small differences in rod design and machining can lead to large differences in bearing clearance if you mix up the rods and caps (not good). Check your bearing clearances with either newspaper or plastiguage. The tolerance for rods is the same as that for main bearings. .0008 - .004 Now torque down the connecting rods to 45 ft/lbs. Use loctite. Please use loctite. I will not be responsible for crankshafts playing baseball with your rods or making stylish new holes in the sides of your block.

Turn the engine a few turns. It should spin freely. If it doesn't, do a clearance check with plastiguage until you find the offending rod, and replace the rod, bearing or have the crankshaft ground accordingly.

Oil Pan Installation

Do NOT make the mistake of taking this lightly. If your oil pan leaks, your car will spew oil EVERYWHERE. It's important to have a GOOD seal. To do this, use LOTS of RTV. If you can get a gasket, get a gasket and put RTV on both sides. If not, lay a thick bead around the pan (about 1/8") and tighten the pan up. Wait 1 hour, then remove the pan again, and add a second layer of RTV on top. Torque to 15 ft/lbs.

The bottom end of your motor should now be assembled. I am not going to detail all of the minor parts, as there's no special instructions, and the order they need to go back in is outlined in the removal a few posts up. I'll be back with more reassembly tips later. Call it a day and get some rest.

- K

469 Posts
The following quotes from this thread present incorrect specifications, and could result in engine damage:

ginsu417 said:
torque all 5 of the mains down to spec (58 ft/lbs).
The correct spec is 37-39 ft/lbs.

ginsu417 said:
Now torque down the connecting rods to 45 ft/lbs.
The factual rod torque specification for a 4g37 is 24-25 ft/lbs. If you try to torque the stock 4g37 rod caps to 45, you will end up breaking the bolt.

These specifications are correct. This document backs them up.

This is a minor issue but I have a problem with the following suggestion:

ginsu417 said:
You should go through about 3 or 4 tubes by the time the engine is back together.
I rebuilt the entire 4g37 engine using one tube of ultra black RTV. The person I bought it from owns a machine shop and said he rebuilds chevy small block v8's with 1 tube. If you use too much, it will squish out and block passageways. For example, on a gasket surface like the front and rear casing, or the oil pump housing, just squeeze out a small bead and then smooth and spread it with your finger. Cover the whole gasket surface in this manner. A little goes a long way. Just make sure you have sufficiently cleaned the mating surfaces of the old gasket material and you should be fine.

I have read other threads from the same poster that the head bolts are TTY (Torque To Yield) and should not be reused. This too is incorrect. The correct torque spec for the head bolts are 51-54 ft/lbs. I have the genuine Mitsu manual from 1992 and it doesn't suggest replacing the old head bolts with new.

469 Posts
The following info is also helpful for anyone attempting to rebuild the 4g37. It was originally posted on dsmlife.com, which is no longer up and running. It is still accessible using Google's cache feature though. I thought I should go ahead and repost it, since it helped me alot with my rebuild. I can vouch for the accuracy of the 4g37 specs, but I haven't substantiated the specs for 4g63.

--as originally posted by "The Hyena" on dsmlife.com:

I was bored so I thought I would go ahead and write this up. These are the torque specs required on different bolts/ in the engine bay (taken from my adventures through the haynes booklet). Unfortunately I was unable to find some torque specs such as O2 housing to turbo bolts/nut, manifold to turbocharger bolts and, more than likely, a few more. If you know the specs on any part that I missed or where I have made a mistake PM me with the correction or spec and I will add them and give credit where credit is due.

Note: If you do not find a spec in a specific engine grouping check the "All Engines" grouping.
All specs are in "ft-lbs" units unless otherwise noted.

Turbo 4g63 2.0L DOHC (also applicable to non-turbo unless marked with an "*"):

Balance Shaft sprocket nut - 31 to 35
Crankshaft Pulley bolts - 14 to 22
Camshaft bearing cap bolts - 14 to 15
Cylinder head bolts - 65 to 72
ARP Cylinder head stud nuts - 85
Downpipe to exhaust manifold bolts/nuts - 29
Exhaust Manifold nuts - 18 to 22
Exhaust manifold heat sheild bolts - 108 to 132 in-lbs
Front Case bolts - 14 to 16
Intake manifold nuts - 22 to 30
Intake manifold bolts - 132 to 168 in-lbs
*O2 to downpipe bolts/nuts - 43
Oil pump driven gear bolt - 25 to 29
Oil pump sprocket nut - 36 to 43
*Oil jet bolt - 22 to 25
Tiiming belt cover bolts - 84 to 108 in-lbs
Timing belt tensioner mounting bolts - 14 to 20
Timing belt tensioner pulley bolt/nut - 31 to 40
Valve cover to Cylinder head bolts - 36 in-lbs
Valve cover center bolts - 24 to 36 in-lbs
Connecting rod cap nuts

4G37 1.8L SOHC:
Balance Shaft sprocket nut - 31 to 35
Camshaft bearing cap bolts
-----Two front (small) bolts - 48 to 60 in-lbs
-----Ten large bolts 14 to 20
Crankshaft pulley bolts - 132 to 156 in-lbs
Cylinder head bolts - 51 to 54
Exhaust manifold nuts - 132 to 168 in-lbs
Front Case bolts - 132 to 156 in-lbs
Intake manifold to cylinder head bolts - 132 to 168 in-lbs
Intake manifold stay bolt - 13 to 18
Intake plenum-to-manifold bolts/nuts - 132 to 168 in-lbs
Oil pump driven gear bolt - 25 to 29
Oil pump sprocket nut - 26 to 29
Timing belt cover bolts - 108 in-lbs
Timing belt tensioner nut/bolt - 16 to 22
Valve cover bolts - 60 in-lbs

All Engines:
Balance shaft belt tensioner bolt - 132 to 192 in-lbs
Camshaft sprocket bolt - 58 to 72
Crankshaft sprocket bolt - 80 to 94
Flywheel or driveplate bolts - 94 to 101
Oil filter bracket bolts - 132 to 192 in-lbs
Oil pan bolts/nuts - 60 in-lbs
Oil pick up tube and screen mounting bolts - 15
Oil pressure switch - 72 to 108 in-lbs
Oil pump cover bolts - 132 to 156 in-lbs
Rear main oil sealretainer bolts - 84 to 144 in-lbs
Timing belt front cover bolts - 84 to 108 in-lbs
Water pump pulley bolts - 72 to 84​

386 Posts
Discussion Starter · #10 ·
You are correct! It would appear that my figures are incorrect and that I was reading off of the 4G63 torque spec chart. Thanks for the correction.
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