cams cause 6g7* motors to blow up? (stock staggered setup)

[Sundance 6g72]

Is he a 3g owner talking out his --- or does this make sense?


Brent you ran an 11 with a stock cam and again with welding wire all over your headgaskets right? is this guy high?

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,

http://www.club3g.com/forum/2118672-post65.html

[Shadow24]

FYI most of that is specific to the 24v 2.5/3.0/3.5/3.8 motors. Ian Rezlo was one of the really knowledgeable people on the forum before he left the scene. His information is specifically regarding the pistons, ring gaps and cam setups on the 24v motors. the 12v motors seem a bit more resilient due to lower CR and different piston designs. the 24v, with its smaller ring lands, tight ring gaps and one cam biased for upper end power and one for low end power can have the issues he mentioned. ESPECIALLY if not tuned correctly. As a case in point, there was a member on club3g that was daily driving a 3.0 24v with 15psi on a stock motor with no ill effects.

If you do the research on the issue. one of the main issues is the intake temperature used in the common 24v boosted setups. Most are using the RIPP SDS system, non inter-cooled which can see intake temps in the mid 200s to over 300*. the people that actually spent the $$$ to do a proper turbo setup usually re-gapped the rings at a minimum and most went with better pistons. Those that had the extra $$$ also did cams. All three of which also tend to offset the common issues Ian describes.

Given the information I have researched starting with Ian's FAQ/FYI, is one of the MAIN reasons i will have such a honking big inter-cooler on my M90 setup. As long as you know how to tune and keep your intake temps down, a stock 24v 3.0 is quite boostable. Having an MS also puts me miles above most boosted 24v3.0 owners as most are using AEM's or the like in piggyback mode or trying to mess with the stock computer to work with boost. Only those that went with GOOD systems and tuners actually got anywhere decent on that motor/platform

[Vigo]

I remember when Rezlo didnt actually know anything.. then i came back many years later and he was the one everyone looked up to! hehe. Next i'll be stricken with arthritis and forget where i put my dentures and not be able to tell what color my hair is. heh

[Spycker]

nope hes a respected member, been a member of that site since 2007. then that " 6g72 24 blowing up etc etc etc " kept bothering me so i went with a better supported platform

[black86glhs]

Seriously, many engines have issues with high intake temps. That isn't really a "shocker", is it?

[Sundance 6g72]

Thats what im saying... Who is that dumb to run such a high intake temp and think it will be okay...

The week link is ring gaps until you get crazy power... I dont see how offet cams cause blowing up unless your tune is so far on the edge that the head that is offset gets slightly to lean for a second combined with your oem timing and million degree intake charge

[Spycker]

anyone on here want to tackle the 6g72 24v mitsubishi engine? like do a better run through and test?

[Ondonti]

Well he did get blown apart pretty well and maybe even banned for awhile from what I remember. IPS (3000gt and now a domestic builder) built a turbo 24v sohc and had a nice flat powerband which everyone thought was impossible. Rezlo and some others who I won't mention were bashing the car. They all got themselves owned as far as "knowledge goes" IPS owns the IRS corvette record of 7 something in the 1/4 so they know what they are doing. They built the first gt42R DOHC 6g72 and it ran 10's off the trailer with half boost, pig weight.


Both front and rear will blow up on a 12 valve. Rear does seem more apt to pop but they will both pop. Remember my first project I broke 3 ringlands on one pass when I turned the boost up too high (first time using a G valve, too scared to look at the readings, distributor set advanced 24 degrees, mix of front and rear broke) , changed the spark plugs, drove 1000 miles on a spun bearing, then popped another one, fixed the plug, popped another one (all these situations were on 50 degrees of timing, too much boost, etc, first project ever). The last piston standing was #4 front piston. I still have that piston and use it for ring gapping + it was used as a template for my forged pistons dish.

You can make a lot of power with staggered cams. They break pistons because they install incorrectly made forged pistons with small ring gaps or go with stock pistons and bad ring gaps and BAD tunes.

I don't remember where their engine is located but for us the rear cam is the hot cam and hot cams actually suffer more reversion so that will kill temperatures (near inert gas does not burn well, this is how EGR systems function to kill noX emissions etc).

Your motor will probably pop on the cylinder with the least ring gap unless you have strange luck! With all big gaps, I bent a crankshaft instead of hurting pistons. Separated the girdle from the block! Thats why i upgraded with DSM headbolts BUT it was a tuning problem! Any failure I had was too much timing (n/a ecu).

For longevity, oem rings might not be the best when they see high heat over a long period of use but I would not worry about that.

[dodgeshadowchik]

BAD tunes.

This is usually the culprit in most cases. Might hurt the ego's a little bit.

[Sundance 6g72]

so are the sohc 24valve pistons truely weaker than ours or do the gaps just make them that way?

[Vigo]

Who is that dumb to run such a high intake temp and think it will be okay...

Because people think that if something is sold as a kit that means it is safe to use.

Ive never been a fan of centrifugal kits on motors that didnt make enough torque in the first place, and most of the dodge 24v's ever sold were 2.5s.

[Sundance 6g72]

my $70 intercooler keeps me at 50*f at 9.5psi when ambient is around 34ish

in the summer with no boost i was at 100ish F if that.. so with their mindset, i have 200*f to play with in the summer. thats horrible.

[Vigo]

Well, chances are good that an intercooler literally doubles the complexity of a centrifugal install, and probably also would make it not technically 'bolt on' since you usually have to modify the core support and some stuff in front of it to run an air/air intercooler.

[Sundance 6g72]

your right.. id much rather blow up my motor :P

[Ondonti]

so are the sohc 24valve pistons truely weaker than ours or do the gaps just make them that way?

Well if each version of the motor has slightly different tolerances, then ones with smaller tolerances would be more likely to have a very small gap that will "blow first"

I took apart that Diamante motor to regap and the smallest gap was .011" (below tolerance) and another was .019 (above tolerance). I definitly would have popped that small gapped piston, potentially without seeing any knock!

Something to note, I have not seen any 3.0's melt down from preignition. That is something that you can't avoid with ring gaps.

[Vigo]

Hehe... That's the problem with buying 'kits' that are catered to cheap cars. They're cost/difficulty conscious to the point of being FAR from ideal.

The sad fact is that MOST of the boosted cars are from kits. And the kit makers are in it to make money.

[Spycker]

Wait a minute. What you are saying is, that all the times Ive read that the " 6G72 24v blows up " is because of bad tunes and people just slapping on a kit?

[Ondonti]

Wait a minute. What you are saying is, that all the times Ive read that the " 6G72 24v blows up " is because of bad tunes and people just slapping on a kit?

The first to blame was Rippmods, who also sold centrifigal kits to 3000gt guys. Only 1 is known to be functional after all these years, after going completely aftermarket on all the junk that rippmods sold to make it run...fixed up by Ray Pampena and made good power.
The stuff they provided to TOON (not tune) the motor was a complete joke.

Thanks to the few who have decent cars, tons of people seem to want to invest in budget junk to save some money. If these people all ran a real tune, it would have been different. TJ blew up his not ghetto 24v sohc countless times and he had full control of his tune. His fault. He also bought garbage CP "turbo" pistons with n/a tolerances. Others have no control and blow up. Most give up. This means there are few good stories to tell. Me, I am yet to be impressed by a 24v sohc that ain't got MIVEC.

Also, there is a bit of a difference between people like us who know their car is unorthodox and 3g people who thought they were buying a sports car!

[Spycker]

Rippmods is still selling supercharger kits...hmmmm! I should turbo my V6 Stratus with the T03 Garrett!

[Ondonti]

Rippmods is still selling supercharger kits...hmmmm! I should turbo my V6 Stratus with the T03 Garrett!

Maybe they fixed their kits for those cars but there are 5 year going on more threads about their old kits that they never fully supported. Sold the junk and ran.
I don't pay attention to them because they have proven themselves to be super shady regardless of any improvements of late. Relying on hundreds of thousands of dollars worth of junk kits and screwed customers to eventually have something viable for new unknowing customers is very unethical.

I can't remember if the kit costed 3000 or 4000 or 5000, but people who got it running ended up spending over 10k fixing things (they provided parts often did not fit let alone the complete fairlure of the tuning device they provided to function properly) and then only one survived well.

I have no advice about turboing those vehicles as there is so much more to deal with then just the motor.