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Been taking some pics and measurements of some different heads i have here. I've only linked thumbnail pics otherwise you'll wear your scroll button out. Click on the thumbnails for a larger pic.

Astron I

Easiest way to identify is the large half-circle cutaway for the PCV vent on the front of the head, and the lower inlet manifold bolts are directly below the inlet ports. Mechanically (screw) adjustable rockers.
These have a smaller combustion chamber designed to work with dished pistons or on the 2.0litre motors.

Inlet Valve: 43mm
Inlet Port: 36mm
Exhaust Valve: 35mm
Exhaust Port: 39.5mm

Pics are of a Turbo head, but there are only minor differences to a standard head. Most obvious of these are the clamp on the front for the fuel hose, and the section in front of #1 exhaust port being machined back for clearance to the carby.
Top

Combustion Chambers

Inlet

Exhaust

Front

Back


Astron II

Smaller cutaway at the front of the head, and lower inlet manifold bolts are either side of the inlet ports. Most feature hydraulic rockers.
RWD Astron II heads feature a narrow water passage towards the rear on the inlet side. Commonly found on Scorpions, Pajeros, Tritons, and 1985 onwards Sigmas.
FWD Astron II heads feature a large water passage towards the rear on the inlet side. These include some of the early 'M' series heads found on TM, TN and TP Magnas.
These heads have a larger combustion chamber designed to work with flat top pistons.

Inlet Valve: 46mm
Inlet Port: 40mm
Exhaust Valve: 38mm
Exhaust Port: 39.5mm

Top

Combustion Chambers

Inlet

Exhaust

Front

Back


TR Magna

The TR Magna head is said to be the pick of the bunch. They have have the largest ports and valves and therefore flow the best from the factory. They also have roller rockers. The later TS Magna heads feature the same valves, rockers, and so on but have a heart shaped combustion chamber rather than the typical 'hemi' shape of the earlier heads. These heads do not support a mechanical fuel pump as the lobe is missing from the roller rocker cam. The 'M7' head is most common, however I also have M6 and M8 heads that I have removed from TR's.
The 'M' number is located between #2 and #3 inlet ports, above #2 exhaust port, and in the tunnel under the cam.

M6 specs.
Inlet Valve: 47mm (possibly oversize? Head has been rebuilt at some stage)
Inlet Port: 42mm
Exhaust Valve: 38mm
Exhaust Port: 39.5mm

M6 Pictures.
Top

Combustion Chambers

Inlet

Exhaust

Front

Back


M8 Specs.
Inlet Valve: 46mm
Inlet Port: 42mm
Exhaust Valve: 38mm
Exhaust Port: 40mm

M8 Pictures.
Top

Combustion Chambers

Inlet

Exhaust

Front

Back

i like this, this is helpful
3 kudos to you

Should be a sticky

1st post updated with Astron I turbo head pics + specs, and M8 pics + specs.

Dont forget the m9 that has the kidney shaped combustion chambers.

You will also find that often certain model magnas dont have the proper cycling head they are supposed to because they have had reco's before. Just because its a TR dosnt mean it will have a m6.

Worth noting that magnas like to crack heads between the valves on cylinder 2 and 3 because the engine sits perfectly flat so air bubbles(when coolant gets low) go to the center of the head(the hottest place) unlike sigmas that have the motors on a slight tilt so air bubbles are sent to the back of the head.

I don't have any of the later kidney/heart shaped heads or any of the earlier M series heads. If anyone else want to take more pics and so on of any heads that I haven't included yet feel free. The more info the better.

I've also seen a few of the M series heads in the 20's. These are said to be replacement heads from Mitsubishi that correspond with the head the same as the last digit, eg. M24 is the same as M4.

Just to throw in some confusion

I have an M25 head. It came off a 92 Pajero. Being RWD it has the small rear water port.

I have a pic of a M29, and it is fitted with jet valves

Where do you find the heads

what car had what head ?

thats exactly what i was gonna ask..

Sigma's are easy

GE-GK Astron head
GN 2.0 Astron head
GN 2.6 Astron 2 head M1 (small rear water port)

The TN Magna also had a M1 (large port)

And what about M2-8?? What cars can these be found on?

yea myns a M4 any one no the speks of it?

MY GK 2.6 Astron 2 has an M2 head

what is the combustion chamber volumes between the different heads?

what is the Mitsubishi part number for the M9?

I have a M26 head here that came out of a late 87 sigma wagon. It seems to have the same specs as the Sigma Astron II and the engine No. corresponds to a 87 block so I guess that at the late stage of the sigma's they were using different heads all over the place. Or this might have been a replacement head.

yeah finally know!!!!

I have the M8

the 85 to 87 2 and 2.6l astrons were the astron 2 engine the valves are bigger and thicker i will try and get photo of the information i have. it is out of the gregorys workshop manual sigma gk-gn 84 to87

Sorry to dig up an old thread here guys, but my 83 GJ has just a 6 above no.3 exhaust port, should it have an M infront of that? Or r they all just the number with no m?

Digging up an old thread but what models had what heads? M6 was T? Magna, M8 was T? Magna and so on?
I am looking for a M8 head and don't want to spend half the day walking around the wreckers looking for the right head.
Even if someone can define it roughly;
TN-P = M?
TR-S = M?
TE- = M?

The M6, M7, M8 and M9 heads are in the TR and TS Magna's.

Some M8 and M9 heads have the kidney shaped chamber but not all.

Not sure on the earlier Magna heads as I don't go looking for any others.

Cheers.

Cheers SS, the hunt is on
Can I still use my cam and rocker gear?

Yes, all the components are interchangeable.

You may need to do a bit of port matching with your Redline manifold as it is designed to fit both the Astron 1 and 2. This means the manifold ports will be 36mm, so it will still be compatible with the Astron 1.

The Redline manifold ports taper down towards the head, so the best bet is to get an inlet gasket, match it to the head first, then mark the manifold and start grinding.


Cheers.

M8 and M9 were found in the TS

M7 are on the TR

But that from my rounds of the wreckers yards. My magna got a M7 head and bedroom floor got an M9 sitting on the floor lol

I got a recon M28 which is off a TP, or so they told me. It has hydraulic lifters. Also my GN has a M16, are they just re issue from factory heads with the extra number in front?

Ive got an Astron 1 head small valves small ports and the small water port.
It has the kidney shaped chamber?? has anyone seen one of these.??? whats it of??
Its been ported and cleaned up.
Its running 500 holy on methanol for speedway.would an M8 head be better..??

I'm confused. The TR Magna head I have has M4 on it and has hemi chambers and roller rockers. The March 1987 GN Sigma sedan I bought yesterday has an Astron II reconditioned engine and M26 on it, but no roller rockers. Is this right?

BAD-SIG wrote:The TR Magna head I have has M4 on it and has hemi chambers and roller rockers.

Most likely it was replaced. M6 through M9 heads were standard on the TR-TS Magnas.

BAD-SIG wrote:The March 1987 GN Sigma sedan I bought yesterday has an Astron II reconditioned engine and M26 on it, but no roller rockers.

The roller followers actually, they only came out on the later magnas. Some earlier sigmas and scorps had hydraulic lifters but NONE came out with roller followers.


Cheers.

That's what can make it all so confusing, it's hard to know if the head has been replaced or not, it's not always obvious.

Superscan811 wrote:Yes, all the components are interchangeable.

You may need to do a bit of port matching with your Redline manifold as it is designed to fit both the Astron 1 and 2. This means the manifold ports will be 36mm, so it will still be compatible with the Astron 1.

The Redline manifold ports taper down towards the head, so the best bet is to get an inlet gasket, match it to the head first, then mark the manifold and start grinding.

Cheers.

You mentioned all components are interchangeable. Here is my situation: I currently have a Crow Cams mild street cam for an Astron 1 engine with adjustable rocker gear. I'm in the process of installing a freshened up and slightly worked Astron II engine out of a GN Sigma (new crank, new bore and slightly larger pistons, fully reconditioned, total of about 2595cc or so), which has the Astron II's hydraulic rocker gear. I really don't mind adjusting the valves myself, so my question is: am I better off leaving the stock Astron II hydraulic gear on and trying to find a mild Crow Cams camshaft to suit, or bolt on the Astron 1 rocker assembly and Astron 1 mild Crow Cams cam I already have? Would the Crow Cams Astron II mild camshaft provide better performance than the Astron 1 version? Can one assume it would because it should be made to take advantage of the Astron II's larger intake ports and valves?

This info is a bit old in my brain, but I think you shourld keep the rocker arm caps from the head, then use all the astron 1 cam with the solid adjustable lifters and drop that into the astron 2 head.
Hydraulic cams and solid cams must be used with their respective lifter.

If you a big girl and you want to run a hydraulic cam, look for some later model magna roller rockers.

Cam specs can only be measured against other cam specs... remember that astrons have big torque down low no matter how big the cam is....its a difficult motor to overcam when you have the astron 2 heads. Generally the solid cams are more aggresive than hydraulics and take more revs. Note that really big cams you will want to find new screw in adjusters (for solid lifters) sometimes called 'elephants feet', as big cams will shift the angle that the rocker acts on the top of the valve and the little screw in adjusters have a floating pad in the bottom so the rocker acts more directly on the valve.