head

[sikmaturbo257]

what head for a 4g54 would be best for turbo?

cheers

[Paddles]

m6 or m7 seem to be the choice.

Paddles

[EVL076]

if your going carb turbo with the factory turbo set up, you will need a plate or mod the turbo inlet manifold to suit the magna head, as the bolt up pattern is slightly different from the sigma head

i run an M7 on my factory carb turbo set up, and that has a plate thats drilled to suit both manifold bolt patterns
it wouldnt be hard to make one up

[DragonCypher]

also the M6 onwards had a slightly downward pointing inlet face, right?

I'm fairly sure someone (I think Stealth, but my memory sucks) said they always use M4 heads with turbo and get equal if not better results than the later M7, but M7 is preferred for N/A setups.

I noticed a while back you can buy Pajero bare heads on ebay (fair few hundred though).. are they just factory recreations of demeaning quality or something useful? And what about complete 2nd hand NON-magna astron II heads?

[stealth]

theres a long and short way to anwser this
ill take the short way
if you are not going to do any port work M7
if your getting a head to go nuts on ,port work bigger valves and all that M4
the M4 is in MY OPINION is the best casting by far
as far as it goes all of the heads from M4 onwards in stock form would make
minimal difference to hp noticeable but minimal
cheers stealth

[cheaterparts]

if you are not going to do any port work M7
if your getting a head to go nuts on ,port work bigger valves and all that M4
the M4 is in MY OPINION is the best casting by far

why ? the M6/7 and M8/9 have a much better inner radis on the inlet side than the early
magna heads
and thats hard to get around even with port work the lower section needs to be built up in the early heads to fix this
or do you know something I havn't figured out

[stealth]

i agree that it is more work
but these castings are the thicker around the inlet and through the
top of the head so when you raise the inlet port .120" its not thin and
prone to leaking
also the deck is thicker and can be machined for clearance for up to .520"
lift at valve (major rework to achieve this)
and the main reason is to re-angle the valve guide so an astron can actually
flow some big numbers
that should get you thinking ! have fun cheater
cheers stealth

[cheaterparts]

i agree that it is more work
but these castings are the thicker around the inlet and through the
top of the head so when you raise the inlet port .120" its not thin and
prone to leaking

I think you will find that the m6/7 port is already higher in the head that would account for less material at the top of the port
just as the floor of the port is higher - needed to get the better inner rad
and of cause the m6 has a 2 mm bigger dia port than the 4m std
the port is not the main problem though its the size of the valve it realy needs to be 4 - 5 mm bigger than std

and the main reason is to re-angle the valve guide so an astron can actually
flow some big numbers
that should get you thinking ! have fun cheater
cheers stealth

dont worry this thought had crossed my mind before - its quite common in holden sixs to do this to fit bigger valves and to clear the bores

it would be nice to run some 50 mm inlets and 41 mm exhuasts - it would however be getting tight for room with a 92.5 mm bore

[panda]

what head for a 4g54 would be best for turbo?

cheers

Need more info to answer this.
Carb or EFI, if EFI, with or without intercooler ?
Which head, Sigma Astron I or Astron II or Magna ?

Lots of options. ;)

[sikmaturbo257]

efi intercooler astron 1 i think... out of a 84 gsr?

i hjave an m7 head i was just wasnt sure wether it was the best head to go with....

[panda]

84 GK uses an Astron I block, & the M7 head is an Astron II, but will bolt straight on. But... the GK uses dished pistons whereas the Astron II uses flat tops, you will lose compression unless you fit new pistons. If going EFI, then a modified Magna inlet manifold will bolt straight up the M7 head. Good luck.

[Sigmaproject]

I just bought a M25 head off a 92 Pajero. Looks identical to an M4. Looks like the Japanese engines never went to the Kidney shaped combustion chambers or roller rockers.

[panda]

I thought the M25 head was a cheap Asian Astron II after market head, not manufactured by Mitsubishi. (but I could be wrong !!)

[Sigmaproject]

It is the Jap Astron head , as opposed to the Australian Astron. The yanks are always refering to it on their Mitsu forums

They are M25 M27 M29. Could be others

[panda]

It is the Jap Astron head , as opposed to the Australian Astron. The yanks are always refering to it on their Mitsu forums

They are M25 M27 M29. Could be others

Thanks, thats answered another question that I wasn't sure about.

[Cottees]

The head I have is off a Sigma GN with Astron II. The rear most coolant port on the intake side is too small for the Magna EFI intake. I am thinking about getting a bare Magna head and putting everything from the Sigma head onto the Magna head. Anyone know if that would work, or would getting a complete head be better? Where do I look for model number of the head? And does anyone have photos that show the difference between the different head models on the Astron II?

[Sigmaproject]

Is you water entry to the head at the front or the rear. If you have chenged the thermostat housing to the front , you dont need the big rear water port. Just Sigma size will do.

[Cottees]

Is you water entry to the head at the front or the rear. If you have chenged the thermostat housing to the front , you dont need the big rear water port. Just Sigma size will do.

At the moment my thermostat is at the rear of the engine.

[panda]

All Magna heads (Astron II) will have a 'M' number cast into the RHS between exhaust ports 2 & 3.
Common numbers were M2 for early Magna's, & M5, M6, M9 etc were used in the later models.
Major variations between these heads were some had hemispherical combustion chambers, while others had a 'heart shaped' chambers. Also some had roller rockers with hydraulic lifters, while others solid.
I use a M6 head with a TR inlet manifold which has both water exit ports matched. These ports are then plumbed together, & piped back to the radiator via the thermostat. Theres no difference that I can tell if you use a front or rear thermostat mounting.
Good luck.

[Sigmaproject]

I was talking to a Machanic with a lot of experience with Mitsubishi stuff and he said that if you are putting a Magna manifold on a Sigma with the thermostat on the rear (normal Magna position) that you have to use a Magna head.

Cottees has a Sigma Astron II, which has a very small rear water port. Magna Astron II has a large rear water port.

I have a Sigma M1 head on the wagon and a Magna M1 head in the shed. The rear water port is the only difference between the two.

[Redzone]

Hi guys, dragging up an old thread, but hey.. i have a 1988 GSR-VR starion with the G54B motor (ie 4G54 pretty much), has just cracked the original head (like a triton astron 2 head), i'm looking at putting on a magna head, cant find anything other than an M7 locally, do these have a compatible combustion chamber to suit the dished pistons i have? my car has the TBI manifold still, but this will be changed to a TR efi setup later in the year. i'll weld up the large rear water port in the head, the MPI intake will be converted to front thermo housing of course. i just dont have the time to do the full MPI swap right at this moment..

[Redzone]

anyone? or is there a thread somewhere with pics off the different heads and their chambers etc? i searched my ass off but the search engine wont take numbers such as M6 etc..

[Sigmaproject]

You will need a jap Astron head off a Triton or a Pajero.

[Superscan811]

cant find anything other than an M7 locally, do these have a compatible combustion chamber to suit the dished pistons i have?

The combustion chamber will be larger (ie:will lower your compression) compared to the standard. The M7 head is around 70cc and the standard dish piston is 17cc, so this will leave you with around a 7.4 Compression ratio.
Good if you want to run a lot of boost.

The standard M7 looks like this:











Cheers.

[Redzone]

anyone know what the RWD type aftermarket heads flow like and what the combustion chamber size is? i'm not 100% sure what cc the stock starion G54B head is, havnt pulled it off yet.. it is a jet valve head though. i'm pretty sure the stock starion G54B has fairly low compression anyways, although my car now has early generation ACL's in it... i noted the head had small cracks in it when i installed the pistons, but didnt have enough time to do anything about it as it was in pieces 2 days before gatton street sprints in march

my head guy is ordering up an aftermarket rwd head for me to look at, and compare to an M6 i have here of a customer's. are the M6 and M7 idenrtical?

[MrBishi]

red
Come down my place and inspect my collection of magna heads and starion. My opinion is M6 or M7 is best. Only need to take care of rear coolant port as you know. I'd recommend welding the port on the head (rather than manifold) to allow use of any RWD or FWD manifold. I did this on the M4 I'm running on the Starion now.

[Redzone]

Ah of course i should have known you'd have a stash anthony

i'm not sure when i'll be able to get there, i'll call you if i'm heading that way anyway..

i looked at one of those aftermarket M28 heads today and the ports are about 2mm smaller than the M6 head in my shop atm. also has NO short turn radius on the inlet ports!

[Sigmaproject]

The m28 is a factory Japanese head fitted to later Tritons and Pajero's and other Mitsu's sent to America . By this time they were more a truck engine, so no need for fancy heads.

Aftermarket are Marnel. Maybe some Chinese or Indian copies, but why would they bother.

[Redzone]

marnel are actually a USA distributor of chinese aftermarket heads

a lot of guys on G54B.com and starquestclub.com run those "marnel" heads, but yes they are definitely inferior flow-wise to a stock M6...