2g head on a 1g block

[TurboAnything]

The 2g head is a more modern design it has raised ports to direct the airflow down on the valve and speed up velocity. The 1g head is a crude way to get a lot of air to the valves but the velocity is reduced. Think about it i do not know of any modern engines that use intake ports as big as a 1g head. I would say if you had a choice go with a 2g head the raised port design is better for any car up to 600hp. You will get better atomization of the fuel with increased velocity and i do not think the smaller port would restrict airflow to the point of power loss. Raising a port is a common answer for freshening up an old head design. you just want to make the airflow come down on the valve instead of coming in from the side and making a 90 degree turn down to enter the combustion chamber.

 

[tqmx1]

A bad flowing port eather from the factory or some one thinking they know more than the factory is still going to be a bad flowing head no matter how much boost you put on top of it.

 

[yardie]

So for you people doing this swap, can/will the 1G Thermostat housing bolt up to the 2G head?

 

[empie1]

I currently run the setup of a 6bolt block and a 2g head, AND LOVE IT. You cannont tell the difference between the two, and if your that worried about it, the 2g head has more meat to be ported on it. The only thing to remember is, a 2g head needs the head bold holes reemed out by 1mm in order to fit 6 bolt head studs. This combo with ARPs forged internals and a stock 2g head has made me very happy. Alot of people on here are will disagree with me, but thats okay too! 2g Heads are where its at!

You only need to port the head bolt holes on 97-99 heads, the 95-96 heads fit over the 1g studs fine.

 

[dsm-onster]

You only need to port the head bolt holes on 97-99 heads, the 95-96 heads fit over the 1g studs fine.

Hmmm, Mitsubishi made the head bolt holes on the 1995-1996 heads one mm larger than neccesary for their stock head bolts?

the_jester had a 1995. We swapped in a 6-bolt and I personlly had to widen the headbolt holes.

 

[dsm-onster]

i dont see any point into arguing the 1g as a more dominant head design. it has already been proven (in my eyes) that the 2g has a more technical and proper design. it is almost the same as a late model EVO head. the only argument that i see from 1g head supporters is the, big ports=moer power and flow, which was already proven to be false.

i drew my conclusion a few years ago and the next motor i would build would be 6bolt bottom end with 2g head. rumor had it a while back that Shep used a 2g head and so did Sean Glazer. but that could be hear say.

i say if you want to factor in forced induction read some compressor maps for certain turbos and trim sizes, there has to be a math to figure it out.
cullen

Could you elaborate on this proof? Were can it be found? What is it?

 

[tqmx1]

Hmmm, Mitsubishi made the head bolt holes on the 1995-1996 heads one mm larger than neccesary for their stock head bolts?

the_jester had a 1995. We swapped in a 6-bolt and I personlly had to widen the headbolt holes.

Some of these I wonder if they thought they got a hold of a 7bolt head but in fact they have a 6bolt Hyundai head (big bolt holes/small ports)?

 

[ChunkyLover53]

This is kind of off topic/on topic. I searched and it didn't really turn up what I was looking for. My question is, if I put a 6 bolt Long block in my 2g, will I be able to retain all my smog components such as EGR? If I use the 2g head I know obviousely I will be using the 2g IM and that means I can keep everything, but I don't know about the 1G IM and keeping everything. California

 

[SBR Joe]

This is kind of off topic/on topic. I searched and it didn't really turn up what I was looking for. My question is, if I put a 6 bolt Long block in my 2g, will I be able to retain all my smog components such as EGR? If I use the 2g head I know obviousely I will be using the 2g IM and that means I can keep everything, but I don't know about the 1G IM and keeping everything. California

Youll be able to keep the egr and what not, only thing you will have to do is modify your 1g manifold to accept the MAP sensor otherwise it will throw the cel for it.


Joe

 

[ChunkyLover53]

Youll be able to keep the egr and what not, only thing you will have to do is modify your 1g manifold to accept the MAP sensor otherwise it will throw the cel for it.


Joe

Thank You for the reply, I have been searching for the answer to this for quite some time. Now I can finally start shopping for my head.

 

[D_Eclipse9916]

Please explain. I have a 1G 60mm TB and it lines up perfectly with my E3 IM plenum.

Good lord, dont listen to that man. Ive been running an evo 3 intake manifold with 1g throttle body on my 98 Eclipse GSX for a long time now, and there are many others that have too. No modifications necessary, I dont get where he is getting this bullshit.

 

[BOOSTIN21]

elaborate what? there are 3 paragraphs highlighted. all my cylinder head info came from Polk and DSMJim a few years ago. i never said it was proof, it is simply factual head design comparison.
The only way that this can be proved is to flow bench both heads with SMIM's and cams. until this is done we will just argue about this all day long.

Could you elaborate on this proof? Were can it be found? What is it?

 

[dsm-onster]

elaborate what? there are 3 paragraphs highlighted. all my cylinder head info came from Polk and DSMJim a few years ago. i never said it was proof, it is simply factual head design comparison.
The only way that this can be proved is to flow bench both heads with SMIM's and cams. until this is done we will just argue about this all day long.

Then there is no proof.

the only argument that i see from 1g head supporters is the, big ports=moer power and flow, which was already proven to be false.

 

[DSMunknown]

Yes, you got something there. The injectors on the evo 8 are mounted at the top of the intake manifold because the ports are higher. The 1G has injectors mounted in the head, so the gasket surface looks square.

You have to look beyond the gasket surface.

Here's a pic looking up in a 1G head. Just imagine if you sliced the gasket surface back by one inch. I bet the shape would look a lot like the evo head pic except for port height and size.

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I wonder why the newer designs of the Evo IMs place the injectors back farther away from the intake valves. Hasn't it been proven that injecting the fuel directly on the back of the valves (or, injecting the fuel as close to the valves/chamber) is superior to injecting fuel farther away?

 

[pneumo]

I wonder why the newer designs of the Evo IMs place the injectors back farther away from the intake valves. Hasn't it been proven that injecting the fuel directly on the back of the valves (or, injecting the fuel as close to the valves/chamber) is superior to injecting fuel farther away?

Yes, it seems that injecting fuel onto the backside of the intake valves is the prefered method. The evo injectors still squirt on the valves. The reason the evo injectors are mounted on the intake manifold is because the intake ports/mani are higher. They had to move the injectors slightly farther away to keep them pointed at the valves.

If you compare pics of the 1G, 2G and EVO intake ports you can see the heights of the ports by looking closely at how high the top of the port is located in relation to the bolt holes.

 

[pneumo]

Here's a few good pics comparing 1G to 2G intake mani and head. Intake differences between 1st and 2nd gense
You can see little notches on the 2G intake mani for injector clearance since the roof of the intake port was raised.

 

[Siral3x]

Please explain, because I am looking at an evo 3 intake manifold right now and the only thing different for a throttle body, is the size of the opening. The ears for the throttle cable are still on the back, not on the FRONT of the plenum. Also from the looks of pictures that I have found online, the throttle body closely resembles a n/t throttle body. Just because it doesn't use an elbow doesn't mean it wont work. Evo 3 manifolds have been used by dsmers for many years.

Yep, that was my bad, the bore should be 60mm, and indeed a 1g NT TB will work. Me and a bud tried to adapt a different TB and I mispoke myself. I ended up using an HKS since the 1G NT parts were hard to find in Europe.

 

[Siral3x]

And yes obviously a evo III intake manifold flows better....here are some pics of both TB and INTAKE MAN:

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The only diff between a 2g head and a evo I,II,III is the intake cam and exhaust cam. The evo exhaust cam is the same cam found in a 1G turbo MT....well it has the same part number anyways.\
To be on topic here, YES I would go with a 2G head because it's the LAST BEST improved cyl. head made by Mitsu in the pre 95' 4g63 era!

 

[dsm-onster]

To be on topic here, YES I would go with a 2G head because it's the LAST BEST improved cyl. head made by Mitsu in the pre 95' 4g63 era!

Again. . . How has it been proven to be improved??? Where has it been proven the 2g head runner design gives a better power curve for say a td05h 14b?

A pertinent point: there is a whole lot more to generating velocity than intake runner diameter. You can gain velocity and lose flow very easily when shrinking a ports diameter. The stock runners may be smaller and may "promote velocity". But if you're not going to take it to a dyno, study the whole picture at least: runner shape, incoming intake manifold angle, ceiling radius to bowl, surface area shape (not smootheness), etc.

Also, the arguement that the 1g head has better cams and is the reason why they flow better is not sound. The converse can be stated about the 2g head and spool. It could be stated that the 2g head spools turbos quicker because of the MUCH larger stock cam overlap not the port shape; and so there is no increase in velocity and flow at low rpms becasue of smaller head ports. . .

But why would Mitsu set cam timing to increase the spool speed of a t25!?!? Clearly Mitsubishi designed the 2g head ports to match a lower powerband because the cam timing, turbo, and runner diameter all coincide with lower rpm performance. This goes along with the market at the time: lots of v6s and many american models w/ supercharging. Like the cam timing, the 2g ports match best the power band of a t25. . . Is that what you want for an evo3 16g? Again look at the fact that "yes high velocity at low volumes of air, probably moves more air, but there reaches a point in which flowing vastly larger amounts of air at even lower velocities yields more volume of air moved"-- Hakcenter.

The 1g comes stock with a MUCH bigger turbo and cams that match the turbo spool speed. Why wouldn't Mitsu adjust the port diamter to better match, but just the cams? The 1990 4g61 head ports are smaller. So the engineers/factories are capable of matching the ports to a smaller engine, but are lax on the 4g63 and just hog them out? The angle of attack on a 2g head may be better, but does the 2g head consequently flow more? Again there is no proof. It is just clearly apparent that Mitsu is matching port design to turbo (and consequently the market).

 

[DSMinn0vati0ns]

hey everyone im in the process of rippin out my motor and doing a 2.3 6bolt with 2g head from FFWD. However when switching to the 6 bolt i know i have to compensate the 2g head for the bigger head bolts. but i have some more questions.


1. i have dsm link currently for my 2g and was wondering if i would have to get a different version of the link to make it work.

2. would i have to get a difference CAS unit?

3. any fittment issues with the motor mounts or anything..

4. anything else im missing?

 

[SBR Joe]

hey everyone im in the process of rippin out my motor and doing a 2.3 6bolt with 2g head from FFWD. However when switching to the 6 bolt i know i have to compensate the 2g head for the bigger head bolts. but i have some more questions.


1. i have dsm link currently for my 2g and was wondering if i would have to get a different version of the link to make it work.

2. would i have to get a difference CAS unit?

3. any fittment issues with the motor mounts or anything..

4. anything else im missing?

No need to get new link, it is determined by the ECU, not by the engine. Youll need need the 1g CAS, no fitment issues with motormounts or anything.


Joe

 

[architechnik]

After viewing some of these comparisons, I have determined something that might be interesting to some: The head is not 1g or 2g! 1gb from past mid '93 has the '2g' head that you are talking about! More later - I have to go to class now.

 

[wishihadatalon]

Again. . . How has it been proven to be improved??? Where has it been proven the 2g head runner design gives a better power curve for say a td05h 14b?

A pertinent point: there is a whole lot more to generating velocity than intake runner diameter. You can gain velocity and lose flow very easily when shrinking a ports diameter. The stock runners may be smaller and may "promote velocity". But if you're not going to take it to a dyno, study the whole picture at least: runner shape, incoming intake manifold angle, ceiling radius to bowl, surface area shape (not smootheness), etc.

Also, the arguement that the 1g head has better cams and is the reason why they flow better is not sound. The converse can be stated about the 2g head and spool. It could be stated that the 2g head spools turbos quicker because of the MUCH larger stock cam overlap not the port shape; and so there is no increase in velocity and flow at low rpms becasue of smaller head ports. . .

But why would Mitsu set cam timing to increase the spool speed of a t25!?!? Clearly Mitsubishi designed the 2g head ports to match a lower powerband because the cam timing, turbo, and runner diameter all coincide with lower rpm performance. This goes along with the market at the time: lots of v6s and many american models w/ supercharging. Like the cam timing, the 2g ports match best the power band of a t25. . . Is that what you want for an evo3 16g? Again look at the fact that "yes high velocity at low volumes of air, probably moves more air, but there reaches a point in which flowing vastly larger amounts of air at even lower velocities yields more volume of air moved"-- Hakcenter.

The 1g comes stock with a MUCH bigger turbo and cams that match the turbo spool speed. Why wouldn't Mitsu adjust the port diamter to better match, but just the cams? The 1990 4g61 head ports are smaller. So the engineers/factories are capable of matching the ports to a smaller engine, but are lax on the 4g63 and just hog them out? The angle of attack on a 2g head may be better, but does the 2g head consequently flow more? Again there is no proof. It is just clearly apparent that Mitsu is matching port design to turbo (and consequently the market).

The 2g head has been shown to support over 600whp without choking. They are limited by rpm range. They can not flow enough at very high rpms, but that doesn't matter when you can only rev a stock DSM to 7000 or 7500. The whole arguement that the 2g head was designed to be used with the t25 is plain wrong. One thing that you fail to realize is that the 2g head was used on EVOs 1-3. Those didn't use a t25 or 2g cams and they made more than factory 1g DSMs. Look at that market, not a bunch of dumb Americans who only want some torque.

Also for what it is worth. Jon at TRE took a stock 4g61 with stock head (not sure on cams) to 119mph in the 1/4 mile on a 16g. He was reving it to around 9000rpms and obviously making great power.

 

[dsm-onster]

The 2g head has been shown to support over 600whp without choking. They are limited by rpm range. They can not flow enough at very high rpms, but that doesn't matter when you can only rev a stock DSM to 7000 or 7500. The whole arguement that the 2g head was designed to be used with the t25 is plain wrong. One thing that you fail to realize is that the 2g head was used on EVOs 1-3. Those didn't use a t25 or 2g cams and they made more than factory 1g DSMs. Look at that market, not a bunch of dumb Americans who only want some torque.

Also for what it is worth. Jon at TRE took a stock 4g61 with stock head (not sure on cams) to 119mph in the 1/4 mile on a 16g. He was reving it to around 9000rpms and obviously making great power.

What is it wrong with the thinking that Mitsu would design a head for more lowend torque then throw on a small quick spooling turbo and give the cams more overlap ??? I agree that the evo3 has similar port design, but more money is made in the american market than the japanese market. We'll never know all of how/why Mitsu made it's decisions.

Stating a 2g head does nothing to end the debate. There are 600whp 1g heads running around, too. 1g heads do the same as 2g heads. I've seen them ALL perform similarly with similar setups. No one has ever verified that a 2g head flows better than a 1g head. So the arguement that velocity is better than flow goes into a circle unless it's been proven. The best thing about the 1g head is the ability to use the better 1g intake manifold. No one has proven than the smaller ports cause the 2g head to outperform a 1g head due to higher velocity.

There is no proof of anything. . . Where are we going with this thread ?

 

[bane3d]

No need to get new link, it is determined by the ECU, not by the engine. Youll need need the 1g CAS, no fitment issues with motormounts or anything.


Joe

I don't think that is right Joe. I have a 2G CAS on mine and I'm running a 6 bolt with a 2G head. I chose it so I didn't have to switch around the sensors. I just reused them. I believe on the 2Gb version, it just bolts up. I verified and looked at my invoice and sure enough, 2G Crank Angle Sensor was used.

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