I see a few people have fitted astron II's from TR/S to TM/N/P bodys. i was wondering if there is any difference in these motors, apart from the different EFI system and inlet manifold, I am also aware the heads on TS 4cyl have different combustion chambers,
What else was changed?
(i'm hoping this thread can become a resource for info on astron II's in magnas, so plz share what u know)

I think that the 2nd gen's astron II had a higher compression ratio than the 1st gen's :confused:

the EFI 2nd gen astrons had higher compression ratio, which was 9.0:1 instead of the 8.8:1 like all the carby 2nd gens and all of the 1st gens were.

the 2nd gen astrons also were fitted with a revised design of the timing and balance shaft chain assembly, in conjunction with an updated oil pump. This revision included a hydraulic tensioner unit for the balance shaft drive chain, and a ratchet mechanism incorporated to the oil pump/tensioner plunger.

and then theres the astrons out of the ford couriers and the mazda bravos (i think), that had the 2.6

they had basically the same 4cyl astron (bought from mitsubishi), but with a 12 valve head instead.. although i dont think anyone really knows atm whether or not the new 12valve head is interchangable in place of the old 8 valve :confused:

Boltwise, both Astrons are identical. (Investigated that path before dad towed the Elite)

I don't think the Mazda 2600 head and the Astron II head are interchangeable. But I'll accept correction if that's the case.

the motors in magnas are different to everything else as they were the only front wheel drive built using the astron II engine (that i know of). Magnas have an external waterpump and a waterpump port at the rear of the block, RWD's have a "normal" waterpump in the front of the block. The early jap built commercial engines (T2600 truck,bravo,triton,pajero) were 8 valve, the 12 valve head was fitted later (can anyone confirm this is on a 4g54) I think the jap commercials have a different gearbox bolt pattern or crank and different engine mount positions to sigmas. I know for certain that the carby is different to sigma/magna on the jap built commercial engines and they had different exhaust manifolds (the carby is the same for triton/pajero and bravo but local sigma/magna carbys are different and won't fit the commercials)

I have the answer to the question regarding the 12 valve head on the Mazda/Ford 2.6L motor. I had to replace the headgasket on one this week. The motor with the 12 valve head is called a Mazda G6. While i had the head off i compared the new headgasket against a magna head. The gallery ports for oil and water are in very different places so i have to say sorry guys it looks like the 12 valve head on an astron (4g54, 4G54B) doesn't exist.

iv got a 2.6ltr gh sigma scorpion, im look to put a holden 3.8ltr enging in, iv been told many times that i can be dont but im looking for a little more then hearsay, at the moment thought i need some help with tuning my carby if ny one has access to a service manual can you get in contact with me.

the EFI 2nd gen astrons had higher compression ratio, which was 9.0:1 instead of the 8.8:1 like all the carby 2nd gens and all of the 1st gens were.

the 2nd gen astrons also were fitted with a revised design of the timing and balance shaft chain assembly, in conjunction with an updated oil pump. This revision included a hydraulic tensioner unit for the balance shaft drive chain, and a ratchet mechanism incorporated to the oil pump/tensioner plunger.
yer i have been told the exact ive also been told there was yet a minor change from the TR to the TS as well

and the mazda 2600 my step dad owns one and they look fair similar i could measure up the head to see if theres any difference on the out side
altho even tho they have 12v over out 8v they have 1 less kw and hardly any more touque so theres not much difference

the 2nd gen astrons also were fitted with a revised design of the timing and balance shaft chain assembly, in conjunction with an updated oil pump. This revision included a hydraulic tensioner unit for the balance shaft drive chain, and a ratchet mechanism incorporated to the oil pump/tensioner plunger.

Actually late model TPs had this also. I had always found it to be useless - auto-adjusting balance shaft chains seem to rattle more than the ones you manually adjust.

Just another point of interest - I was looking through my ACL piston catalog yesterday and noticed that the TS has different pistons, the top of them is kidney shaped.

Just another point of interest - I was looking through my ACL piston catalog yesterday and noticed that the TS has different pistons, the top of them is kidney shaped.
yer thats right i knew there was another difference

Actually late model TPs had this also. I had always found it to be useless - auto-adjusting balance shaft chains seem to rattle more than the ones you manually adjust.

Just another point of interest - I was looking through my ACL piston catalog yesterday and noticed that the TS has different pistons, the top of them is kidney shaped.
Tell me about it!

I did a slight rollback, as I've found that the manually adjusting ones are more reliable.

I did a slight rollback, as I've found that the manually adjusting ones are more reliable.

It is bizarre really, but you get that :)

I had been toying with the idea of balance shaft removal, but the idea of doing that to a FWD is a little scary :redface:

Don't do it yet. I've nearly got a motor ready that's had to have a BSEK. I'll let you know how it runs. (My block that I'm utilising destroyed the BS when the chain broke) (Not related to the adjustment rollback. More necessitating...)

Actually late model TPs had this also. I had always found it to be useless - auto-adjusting balance shaft chains seem to rattle more than the ones you manually adjust.

Just another point of interest - I was looking through my ACL piston catalog yesterday and noticed that the TS has different pistons, the top of them is kidney shaped.

is that to say that the TS pistons have a kidney shaped recess in the top?

IN the ACL catalogue do the TR efi pistons have their own listing?

Don't do it yet. I've nearly got a motor ready that's had to have a BSEK. I'll let you know how it runs. (My block that I'm utilising destroyed the BS when the chain broke) (Not related to the adjustment rollback. More necessitating...)

I'll be interested to see how it goes :)

is that to say that the TS pistons have a kidney shaped recess in the top?

IN the ACL catalogue do the TR efi pistons have their own listing?

Page 151 of the catalog list TM,TN,TP,TR,TS with normal pistons and then 152 lists TS with kidney shaped topped pistons. I am assuming that the TS came out with the kidney shaped and that the mention of TS on page 151 is a typo.

If you want to look for yourself, the ACL catalogs are available from their website - www.acl.com.au

The TS pistons are also physically longer too, 20 thou difference.