Rebuilding an EVO II motor

[EVOII]

Hey all,

I'm in the process of rebuilding my motor. I've basically just finished strippin the motor down today. i've got most of the parts, except for the pistons, bearings, stud kit which will all be ordered as soon as the motor gets into the machine shop.

It'll be a forged bottom end, but with a standard head rebuild.

I've actually got a fair few questions for those that have rebuilt evo motors. but these will do for now:

1. Wat are the pros and cons of removing the balance shafts from the motor? at the moment i'm just thinking of leaving them in there. but after reading some stuff about the 2G motor suffering from crankwalk problems, i need to know if removing balance shafts will eliminate this crankwalk problem or at least reduce it?

2. Wat clutch would u recommend using?? it had an organic heavy duty clutch in it b4 but it's completely goneski.

bigger ex gated turbo, haltech ecu and other stuffs are in part of the build process as well.

any input will be much appreciated.

Cheers,

Age

 

[EVO-00X]

1. Piss the balance shafts off. Too many times engines fail due to balance shaft bearing failure when you simply dont need them. When they go you can have bits of metal go through your system and cause even more harm to your bearings, turbo, valvetrain etc. If the balance shaft belt breaks it can also get caught within the timing belt and cause it to skip teeth or snap resulting in valve and piston collision and a lot of $$$ in repairs. The balance shafts are there to make the engine run 'smoother' with less vibrations. The benefits of removing them is you get slightly better oil pressure and no chance of balance shaft belt or bearing failure. The engine will also make a little more power due to the less rotating mass. When rebuilding an engine its best to get the whole bottom end rotating assembly fully balanced regardless. There will be people out there that say balancing the bottom end has nothing to do with harmonics but I still believe it does help emliminate vibrations rather than not. There are also people that will try and tell you that your engine will vibrate noticeably without the shafts but its a load of shit IMO. I've built and driven engines with the balance shafts removed and quite honestly when you have a modded car you wont even notice.

Look at it this way....

* Cost of a balance shaft eliminator kit = $45. It's good insurance against engine failure, bit more oil pressure, bit more power, and a tiny bit of vibration which you probably wont even notice.

* Cost of engine rebuild when the balance shaft bearing/belt fails = several hundred to several thousand and possibly even complete long motor and turbo replacement.

Which would you prefer?

As for crankwalk on the 2G dont get the American 2G engine confused with an EVO engine. Their engines had different oil squirters in them that robbed the oil from the bearing galleries which theoretically made them suffer from crankwalk far more than the Japanese EVO engines. In saying that however, the Japanese engines still DO INDEED suffer from crankwalk but it is not as common as their US counterparts. I've replaced EVO I-III cranks and an EVO V crank that have suffered from it. Removing the balance shafts will increase oil pressure a bit so it theoretically should assist in some way against crankwalk. Still, the reason why crankwalk occurs is yet to be 100% diagnosed.

2. Your new clutch would depend on how much power/torque you will be making and whether you want a slippable clutch for the street or not. There's horses for courses so to speak :lol: For example a couple of steps up from the heavy duty organic you used to have would be the Exedy heavy duty button, or heavy duty cushioned button clutch.

 

[ENGINR]

There's tonnes of posts about the balance shaft topic in this and other EVO forums. Do a search and you'll find that people are mixed on whether to leave them in or not. IMO I'd leave them in. I have in my engine and I can't say I'm feeling that my engine suffers from any sort of power loss at all. In regards to oil pressure, well if the factory Mitsu setup ran fine oil pressure with balance shafts, why wouldn't your rebuilt engine if you kept them in? Rob's quite right in that it's another component that COULD fail, but with proper installation, service and care why should it?

Rob's right - Crankwalk is one of those 'black hole mysteries' that almost everybody has a theory about but nobody is really sure why it happens - all I was told was that you should avoid sitting at the lights with your foot on the clutch. If your rebuilding your engine - you've got the opportunity to ensure that your crank, block and bearings are spot on before you bolt it all together, thus reducing the opp for crankwalk.

 

[Liberoz]

RSEII engine rebuilt with forged pistons and rods balance shafts left in and all rotating mass balanced to a high tolerance. Engine runs very smoothly and i don't seen to be having any issue's keeping up with later model evo's on the track with a ton of mods and $$$ thrown at them.

I left them in as i believe they were designed and engineered like that, why reinvent the wheel.

Crank walk is more due to heavy duty clutch and pressure plates being used, and riding the clutch puts all the weight of the heavy duty pressure plate on the crank, funny enough in the direction in which all that suffer with crank walk wear on the bearings and crank.

 

[EVO-00X]

^^^ and thats the other valid reason why they think crankwalk occurs and IMO I think thats the one that causes it Here's a pic I took of one of the cranks to show you the wear in the thrust journal side wall :roll: It looks like a very worn disc brake rotor.

Properly maintained engines that are serviced with replacement parts including balance shaft bearings and belts should be fine. Its the risk of one letting go on a high powered $10,000+ engine that makes you think twice about putting them back in :lol:

 

[lozza]

heavy duty clutch plates are implicated in contributing to crankwalk, but this doesn't cause it. otherwise 1G's would suffer the same problem with a HD clutch. i can't see the thrust load differing any between the two, probably more of an oiling issue though as already stated. interesting pic EVO-OOX. :shock:

back to the topic, i am removing my balance shafts for peace of mind. remember that at 8k rpm your balance shafts are rotating at 16k rpm!!
the only downside i think is the potential high oil pressure, particularly if you are removing the oil squirters when doing a stroker build. i have heard of people blowing their front case from 100+psi, even with the ported bypass mod.

cheers
lorry

 

[ENGINR]

Why do you need to remove the oil squirters when building a stroker engine? I didn't have to on my 6-bolt one, neither did my mate who was building a 7-bolt one.

 

[DOUGMO]

mine clear on a 7 bolt too..its a bit tight but they fit fine

 

[shadow]

Personally, i've removed mine from my rebuilt motor. Yes if you think about keeping up maintenance etc why would they fail, however the engine wasn't designed to withstand the amount of power we're trying to get from it. Especially when we're talking about things such as a stroker.

The other thing that got me a little sus is the fact that mitsubishi maker an eliminator kit themselves.....

 

[EVOII]

cheers for the reply guys.

where can i get the balance shafts eliminator kit from?

 

[EVO-00X]

http://www.meek.com.au/ - I dont think its listed on the website but they should have them in.

 

[DOUGMO]

Personally, i've removed mine from my rebuilt motor. Yes if you think about keeping up maintenance etc why would they fail, however the engine wasn't designed to withstand the amount of power we're trying to get from it. Especially when we're talking about things such as a stroker.

The other thing that got me a little sus is the fact that mitsubishi maker an eliminator kit themselves.....

.mits dont actually make an eliminator kit as such. its just the parts
from a 4g61 twin cam as they do not have balance shafts
from the factory

 

[EVOII]

http://www.meek.com.au/ - I dont think its listed on the website but they should have them in.

alright, i'll give them a call since i need to order more parts for the motor.

wat sort of metal headgasket do u run on ur car?

 

[DOUGMO]

genuine part numbers (thanks to baz)

Balance Shaft Eliminator Parts

MD103722
Balance shaft
bearing, rear

MD040597
Balance shaft
bearing, front

MD092785
Balance shaft
cap (plug)

MD098626
Balance shaft
stub shaft

 

[Sloth]

Re CRANKWALK

Relates to 2G blocks & 7-bolt cranks.

The cause seems to be two-fold, one of which is the main problem, the other would just make the situation worse.

1 - Mitsubishi f#%@*d up on a couple of batches of crankshafts. One of the bearing journals (the one that takes the bearings with the thrust face) is the incorrect size. If you get the "usual correct" bearings, but have the crank from the crook batch, the tolerances on the thrust face are wrong. Add the extra force of a heavy-duty cluch to help shove the crank around...

2 - The oil squirters for the pistons are fed by the same gallery as the main bearings. Which would affect the oil flow to the journal....


Remember, that the oil is there to keep the metal from touching metal. If the gaps at the thrust face of the bearing are too large, the oil would "flow out" of the space quicker than it should. Lower oil pressure at the bearing faces - more likelihood for metal to metal contact....

The crankshafts are identified by number, and by a coloured mark. Once you have the block number & crank number & colour, you look up the correct bearing in the Mitsi manual. There are bearings with different thrust face thicknesses available - the dimensions are listed in the manual.


Hope this short explanation helps.


(copied from much earlier post....)

 

[revnit1]

I recently rebuild my evo2 engine and i got the phone call your crank is stuffed!!!!! didn't bother going 2nd hand i was basically put in a line up for em so i went brand new can still get them surprising enough but at a $$$$ , fitted Acl race bearings, eagle rods, Cp pistons fitted new bearings to balance shafts and balanced the bottom end and good as gold, removing shafts never came into it.

Some things have been mentioned already to slow the crank walk process down first don't run a extremely heavy clutch, also don't put foot on clutch at cold start or any time when starting and having clutch in at traffic lights not the best option either.

 

[CLuTZ]

You can get brand new topline 7-bolt cranks for $399 USD plus shipping


http://www.extremepsi.com/store/customer/home.php?cat=1365

 

[shadow]

Thats about the same price that I paid for my Eagle Crank rated upto 1500hp :twisted: :shock:

 

[EVOII]

ok cool, so the plan for my motor after speaking to a few ppl will be built as follows:

JE forged pistons (+20 thou)
Eagle Rods
ACL race series big end and main bearings
ARP head stud and main stud bolt kit
New Balance shaft bearings (keeping the balance shafts in there)
Reco'ed head
Tomei cam gears
All new tensioner pulley sets
Power enterprise timing belt
Gates balance shaft belt
New oil pump and water pump
Exedy Ceramic button clutch

motor will be fully balanced

 

[EVO-00X]

Good stuff ^^^ (except the balance shafts :lol: ) and a Cometic headgasket too I hope