I thought id make a thread re GNs.
Mines a 85 2.6 astron2 5 speed <130000 km, when I bought her i found the temp gauge stayed cold (~1/4).
Turned out someone 'jimmyed' the car to look like it was running cool, they fitted a short temp sender unit to the head (didnt hane the tip out in the coolant stream like the proper one has). So I changed it and found she ran just above the ends of the wavey lines at the center of the gauge....untill it got work, when it would heat up to 2/3 ~ 3/4.

I did some work to the carby and refilled the coolant (every filled with same amount I drained out + I purged the air out at the upper choke coolant connection), ran the eng up and started doing adjustments. I noticed the top rad hose was cold ! the bottom one was extreamly hot ! looked at the gauge !!!! hard over in the red.
Turned it off & removed the thermostat (it stuck shut) got hot water n refilled the cooling system before running the eng to cool, guess what? started getting milky oil :-( thought it might have just been the gasket, head was <0.002 thou out of flat.
So I did a valve job n put it back on, seemed ok but temp still behaved the same....then the milky started again (slight foaming in the coolant (air)).

Tryed using chemiweld, followed all recomendations. but after a month it got worce n started lossing coolant faster to the sump. removed the cam and rocker gear, wiped the head down and pressurized the cooling system (14 psi).
Beads of coolant apeared from the front of #3 cam bearing, it had a 3" crack traveling toward the rear of the head :-(.

Got a m6 casting to replace the m2 head, did the valves and installed the m2 cam n rocker gear etc (easy change over) :-) temp stays around 1/2 now what ever I do driving :460:


>>>Key points I found: 1 > heats up when eng is working (cooling sys in good cond)
2 > head was not adheared to head gasket (but the gasket did stick to the block)
3 > carfully moniter the temp of the hoses n gauge after anything involving coolant removal and replacement.

very surprised the bottom end still had the compression in the rings
after the cook out

next advice if it stats to smoke or burn oil add oil treatment/stop burn

ty dirtyhands, I want to make sure the rest of the cooling system (e.g. block) is good before I put a new ring & piston set (etc) near her ôô
Must be the scotish coming out in me, I do everything I can by my hand :-)

i started a sigma link on this forum

http://www.mitsubishiclubaustralia.com/forums/

feel free to add to it or start your own

its in how to do section
http://www.mitsubishiclubaustralia.com/for...opic.php?t=1650

well its 2 weeks since the m6 head went on, :grin: no trace of coolant mixing with eng oil & coolant level has been dead on the pen mark I made on the reservoir (every lunch time at work I checked it ).

I’ve upgraded the rear section of the exhaust system, it had 1 & 3/4" tube over the diff & through the rear muffler :( now its 2 & 1/4" with a glass pack.
Anyone know the jetting for the carb? its a mikuni 32-35 DIDTA I think ( id on the carb isn’t fully legible )black plastic main body.
I think the main circuit air jets have been mixed up at some point,
-Primary main jet 112.8, air jet 105
-Secondary main jet 195, air jet 80

the GH-GJ uses a 28-32 saturn and 30-32 for its astron

yours must be mikuni 32-35 DIDTA

no info about the jets

best solution is to have the car gas analaised to tune the carby properly