Im busy writting and article about ACTUAL FACTS on why the 6G7* blow up and why.
This is not what ive heard or read this is from MANY MANY hours of working on them that I have learnt and realised why, ill update it every few days and add in more and more so people know what to look for and how to do it right.
6G7* info
Hope this helps some people
This is not what ive heard or read this is from MANY MANY hours of working on them that I have learnt and realised why, ill update it every few days and add in more and more so people know what to look for and how to do it right.
6G7* info
Hope this helps some people
6G72/3 SOHC 24v (95-05) truth's lies and misconceptions
Well there is so much confusion about the 95 -04 6G7* Sohc motors floating around I thought I would maybe shed some light on a few common lies and misconceptions mostly started by a article on Alpar about the intake manifolds being to blame then every other in the dark "builder/modifier" followed that and blamed it for the damage that occurs under high HP or boost
1st. The intake manifold on ANY 6G7* is not the cause for NO:4 or any piston on the front bank to go first
2nd. The 3L is not weaker than the 2.5L or more susceptible to blowing up under boost it just needs to be tuned better
3rd. The 3L heads are Identical to the 2.5L, they share the same valves, lifters rockers everything, the only difference is cams
4th. The only major difference in the 95-00 2.5 and the 2000-2004 3L are the pistons are 10mm larger and the cams are slightly more aggressive, other than that they share the same water pump, and the oil pump is the same but the 3L has a little tab that is different. This applies to both the variations
Ok why the front bank blows first...
There are numerous reasons, the MAIN reason is the cam shafts, from the factory mitsu runs a staggered cam setup, IE the front cam has a larger centerline than the rear (106 rear and 110 front), the only reason that they do that is to create an engine that has good amounts of top and bottom end (many other companies do that and Volvo was the first to pioneer and test it) Stock it works great but under boost it gets hotter and causes the problems,
What actually causes the pistons to crack around the ring land? Simple, the top piston ring is gapped tight from the factory for NA usage, under boost the ring expands and butt's causing extreme amounts of drag and then will crack the top of the ring land first because its so hot. The reason the 3L will crack faster is because it has even less ring gap than the 2.5L which is why some people that cant tune cars test on 2.5L's because they can take a little more abuse before it butt's
Another reason why the front gets hotter? the rod oil squirters all face the rear of the engine because of the rotation of the crank, this causes the front to get SLIGHTLY less oil which also makes the piston hotter and speeds up ring butting.
Now all you need to do on a stock motor is tune it correctly, I've had 2 or 3 3L's up over 15psi without a problem, you just have to make sure the AF and timing is where it should be to not let the pistons get to hot and butt, even better if you are installing a 3L re-gap the rings, the stock pistons will hold a lot more HP if they are gapped right.
General
When ever you plan to machine the block and heads (essential for high boost reliability) make sure you cater for needing to use ADJ cam gears, I would recommend Fidanza gears which you can get on eBay for $210 delivered, You need to dial your stock cams and record the info before you pull it all apart for reference and I can supply you with specs for where you should set the cams to and I can modify the distributor housing to allow you to set the timing back to where it was.
Dont use shitty oil filters, Mobil one, K&N and similar, they are worth the extra money, use Mobil-1 full synthetic or similar 5-30 summer and 0-20 or 0-25 if you car sits outside in the cold in winter.
Never use aftermarket parts like bearings, pumps, hydro tentioner, gaskets ectr, use genuine parts G/Y gattor back has a timing belt kit that is pretty damm good and includes both idlers and the belt far cheaper than the dealer
The 2.5 and 3L use identical crankshafts and the 3000gt is physically the same but can handle more HP
Bottom end
Stock top ring gaps are 10-15thou as ive measured on 6G7* engines under 50k, that is FAR to small for boost, in a mild boost applications I would recommend 18-20 thou and for higher boost or nitrous go with a 20-24 thou top ring gap on the 3L (2thou less on the 2.5) Always run the lower ring 2-4thou smaller than the top ring and set the oil control ring to stock for mild boost and 2 thou larger for high boost.
High boost applications I would recommend opening the oil squirters slightly, every rod ive measured has a different diameter, so go 1 to 2 thou larger for the rear rods and 3 thou larger on the fronts to help cool the front pistons down more.
There really is not a whole bunch of reasons to change the stock crank, just have it re-balanced if you go with lighter pistons or rods, the stock rods should hold more than really needed on a FWD and I would say the $1000 for the set is a waist unless your a dyno queen, the stock rod bolts leave a lot to be desired and I would recommend upgrading them.
The reason the 2.5 can take more of a beating is that it has a far tighter quench area, less quench less lighly to detonate
Always remove the oil galley plugs when doing any machining on the block and make sure it gets hot tanked before assembly and correctly cleaned, make sure you chamfer the top of the barrel before attempting to install your pistons, if you have a 20 or larger thou upgraded piston I would make sure you take a sanding role and carefully round the bottom of the barrels to remove the sharp edges just make damm sure you don't nick the barrel, do all that then hot tank it. I would stay away from any break in lube on the pistons when installing them, use WD40 so the rings bed in fast and hard, don't pussy foot the new motor, let it heat up all the way and only when at operating temp give it the odd snap of the throttle a few times, then go drive it, don't pussy foot it, give it a few good hits, the rings need the combustion pressure to force them out and seal hard against the side of the barrel so they can use the rough honing to bed in or you'll land up with a motor that will have excessive blow by. Do not run anything else but regular penzoil 5-30 for the first 3000miles while it is breaking in and try not to let it get below 50 degrees during break in.
HEADS
Porting and Polishing - I've heard some people say it doesn't do anything on these heads and some even say it will hurt it, yes that is true, give a person with a dremel tool sitting at the kitchen table a head and ask him to port it the chances are you'll loose HP. These heads flow fairly well stock yet the lower manifold rarely matches up very well at all. I've seen some good castings and some terrible ones yet they are generally pretty decent. The only way to make real HP is to flow bench them. After doing 5-6 pairs you learn to know exactly where and how much needs to be removed. There is no way to guess how to port them but on the flow bench and before and after dyno testing. "THEY LOOSE EXTREME AMOUNTS OF HP IF YOU REMOVE TO MUCH EXHAUST AND INTAKE MATERIAL" They do tend to need quite a bit of bowl work to really pick up the top end power. All in all headwork does help out a lot with mild to wild applications. We have found the best results when we go in and do a 7 angle intake seal cut and radius exhaust cut right down the seat, we then blend them into the port and remove the right amount of material in the right locations then smooth them out enough to keep slight turbulence while keeping full flow, the bowls are machined and blended and dual back cut intake valves are used then it gets flow benched to ensure everything is identical across all 6 cylinders.
The 3L cams are a direct swap to the 2.5, they have slightly more lift and more duration.
Do not install any aftermarket head items without making 100% sure you have every stock aspect recorded should something not work right you don't have to start at square 1, I would not recommend using any aftermarket cam unless you are extremely familiar on how to dial them in right. Im working with RPW to design a set of more user friendly cams that we can all benefit from that will minimize or eliminate the centerline difference in higher HP and boost situations.
If you change anything in the cam make sure you depress the lifters so you get the valve to actually close properly when first assembling and starting.
When dialing the cams in make sure you use a piston stop to get correct TDC on Cyl 1 then use cyl 4 to dial the front bank in. Make sure you get them equal, it can take hours and hours to dial the cams right, it is extremely to mess up so double and triple check that they are right before finishing it up
Fuel
One main pain in the ass part of really getting HP out the 6G7*? fuel injectors, for some unknown reason we use high impedance versions of mitsu's normal 10.5mm inlet injector, now up to 275cc is cheap direct fit, after that you are in for a shock, I machined a set of ford motor sport 440cc injectors which worked brilliantly, but then I needed larger, I opted for a set of Siemens Deka 650cc's ($350 for all 6 brand new) which I could not machine to fit our PITA fuel rail so I went ahead and did what I should have done a while ago and made high flow fuel rails to take the larger 13mm inlet injector which will let me use near ANY Ford or GM high flow high impedance injector. I will sell these rails with 6an fittings for $320shipped should you require a pair.
Stock Injectors: 2.5L = 190cc , 3L = 210cc , 3.5L = 275cc (injector clips will need to be changed)
Hands down the best way to do a GOOD fuel system is a Walbro 255 in-tank pump, Paxton or similar LARGE 10 micron fuel filter, 6an up to the rail, then 6an out to a Vortec S-FMU, I ran 6an as a return but 4an will work as well. Fuel is the main thing that's going to keep your HP engine alive, don't go cheap or it will cost you alot like a blown motor and nightmare tuning. I ran my 3L blown at 10psi engine on a bone stock 2.5ecu with only fuel pressure controlling things, its not desired but it shows you how far a good fuel system will go to ensuring you a safe combination.
Intake and exhaust manifolds/headers
Again, the intake manifolds don't cause the engine to fail on 4 first then 2 and 6, yet there is a large amount of HP potential that can be extracted from a modified intake manifold. The main area that my custom manifolds help is top end HP which is were we suffer quite a bit. By shortening the runners and custom forming the plenum area you can control the power curve in any boost situation. It will also give far better air flow to all cylinders for those that boost higher than 12psi which is when it actually starts to make a difference in better air path for equal flow.
Headers, well thats pretty much a obvious, there are a few companies making headers for the 6G7*'s to be honest as long as they fit right and dont leak and you have a decent exhaust they will all perform well, is a $1200 better than a $600 pair? I highly highly doubt that it is worth a $100 difference let alone twice the price. For boost short VS long makes minimal differences, just make sure the primaries are all similar in length and have them coated, if not for under hood temps then do it for the fact you don't have to deal with ugly rusted headers 12 months down the line. For those that cant get access to headers (some turbo 3G's and a few 2.5's) there is another alternative, Port the stock manifolds and have them coated, I had done a few pairs of 3G and 2.5 units, You can get to near all areas to smooth it out substantially and clean up the castings for probably 2/3rd's the gains of short tube headers at a far better price and factory fitment, on a side note only extremely sharp carbide cutters will be able to port stock cast iron manifolds.
Boost - Turbo Vs. shaft driven hair dryer Vs. Roots/screw
Not this is a bitch topic, this is a 6G7* ONLY OUTLOOK, god im so sick of hearing the bitching so ill put it down as easy as I can from what I have seen, tuned and experienced. Maybe this will make you realize what I said is true and how Ripp's kit works so well and why.
Vortec chargers work well in the 6G72 for one reason and one reason only, IT DOES NOT GET THAT HOT so the rings dont bind up and crack the land even at higher boost!!! Pro's: predictable boost, ease of install Cons: Belt HP loss, no boost till higher in the RPM band, slow to come on and only makes max boost right up there, seen one to many of them have impeller failure resulting in engine failure
Turbo's will make more HP and top end and have less loss but they generate more heat so the front pistons want to go faster, that is the only reason!!! Pro's: amazing boost potential, faster boost than above, less HP draw Cons: like having a potato in your exhaust, extreme heat
Roots/screw (positive displacement) work extremely well because they are cooler and have more CFM per PSI than the above 2 (but I think there are only 2 of us running roots blowers on these motors. Pro's instant boost at any RPM, runs cooler than the above 2 Cons: HUGE, HP belt loss
Now run a 10psi intercooled turbo against a 10psi meth cooled Vortec (both stock engines) and the turbo will smoke the SC
I have ran 16psi daily threw my stock bottom end 3L with no problems, why? because my intake temps never get over 110F and most the time run 5-10 degrees more than ambient in summer and up to 20 degrees cooler in winter. Ive even ran 16psi once on the dyno with a bottle of nitrous opened onto the air filter for a Ecu compensation test and put almost 450whp down for 3 runs with ZERO problems, why? because it was getting super cold air from the after cooler and it was tuned right, thus not lifting the ring land.
The choice should be based on how far you want to go, the turbo will let you go further if you intercool it accordingly and use some creativity, if you just want a normal not very creative outlook go with a bolt on Vortech for reliability and the need not to use your brain to get it going well, for those that are a little mental like me try something different
Ive driven in all 3, I would go with a turbo any day of the week for all out perfomance, THIS IS MY OPINION YOURS MIGHT VARY I DONT CARE, THAT IS SIMPLY WHAT I HAVE SEEN AND KNOW FOR A FACT ON THESE MITSU V6's
sweet
