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
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3226.jpg)
Combustion Chambers
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3228.jpg)
Inlet
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3227.jpg)
Exhaust
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3229.jpg)
Front
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3231.jpg)
Back
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3230.jpg)
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
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3203.jpg)
Combustion Chambers
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3205.jpg)
Inlet
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3206.jpg)
Exhaust
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3204.jpg)
Front
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3208.jpg)
Back
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3207.jpg)
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
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3209.jpg)
Combustion Chambers
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3212.jpg)
Inlet
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3214.jpg)
Exhaust
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3213.jpg)
Front
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3210.jpg)
Back
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3211.jpg)
M8 Specs.
Inlet Valve: 46mm
Inlet Port: 42mm
Exhaust Valve: 38mm
Exhaust Port: 40mm
M8 Pictures.
Top
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3221.jpg)
Combustion Chambers
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3223.jpg)
Inlet
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3222.jpg)
Exhaust
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3220.jpg)
Front
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3224.jpg)
Back
![Image](http://i58.photobucket.com/albums/g275/c_fernance/th_DSCF3225.jpg)