Hello! New to the mighty max world!

[notbernard]

Hello!

Recently I picked up a 89 mighty max with 256k on the clock, g63b and km132.

I’ve read issues on here how these have issues blowing head gaskets and cracking heads. Are the 2.0, 2.4 and 2.6 all interchangeable? Like cylinder head wise? I’ve seen online you can find the 2.4 and 2.6 heads opposite to the 2.0 heads. Not that I need one, but the more info the better lol.

I’ve also read how certain parts are difficult to find, from what I’ve seen is mainly radiators. I could be wrong but I haven’t dug that much.

I’m coming from the Ford IDI & Honda world, so these seem pretty simple.

Any info or advice is much appreciated, thanks!

[SubGothius]

Welcome!

For second-gen trucks ('87-94) the 2.0L would have been a G63B Sirius-family engine (indicated by the G6 in the engine code) related to the 2.4L 4G64 Sirius engine. There's recent thread here about swapping heads between those engines:

http://www.mightyram50.net/vbulletin/showthread.php/9660-Having-problems-finding-a-head-for-a-86-mighty-max-2-0

Some daring souls have also tackled swapping a DOHC head from later Sirius-equipped Mitsubishi models, covered in these threads among others:

http://www.mightyram50.net/vbulletin/showthread.php/2829-4G64-SOHC-to-DOHC-swap-info

http://www.mightyram50.net/vbulletin/showthread.php/4543-DSM-vs-Evo-for-RWD-Swaps-All-the-info-you-need-to-know

The 2.6L was 4G54/G54B Astron-family engine (G5 in the engine code), unrelated to the Sirius/G6 engine family, so that head won't swap to your block. Some first-gen trucks came with a 2.0L 4G52 Astron engine unrelated to your 2.0L.

AFAICT from specs in the Haynes manual, engine codes with the B-suffix and dropped leading 4 (e.g. 4G63 vs. G63B) indicate engine variants equipped with jet-valves in the head. Unless you have a specific reason to retain the jet-valve setup (e.g. emissions compliance in your area), most folks servicing or replacing a head tend to prefer eliminating the jet-valves for simplicity and reliability, either by swapping to a non-jet-valve head or by installing a jet-valve eliminator kit.

[notbernard]

So, a 2.4l head from a 4g64 would work if I kept it carbureted? SOHC 8v obviously, lol. But I would use the timing belt for a 2.0l block?

[SubGothius]

Haven't done it myself but seems like that should work in theory, yes.

[Grumpy]

So, a 2.4l head from a 4g64 would work if I kept it carbureted? SOHC 8v obviously, lol. But I would use the timing belt for a 2.0l block?
I think the 4g64 head would have a 68cc combustion chamber and the ‘63 head 47cc or 43cc
so it should make a difference to the compression ratio
if I remember correctly a ‘63 head on a ‘64 (both 8v sohc ) should be about 12.5 to 1

[SubGothius]

Interesting, I wonder if that chamber volume difference might be more a matter of chamber shape (which in turn might be a matter of jet- vs. non-jet-valve heads), not necessarily the cylinder displacement of the block? The other thread I ref'd above has pics of two different SOHC 8v Sirius heads, one with round chambers and the other with (likely smaller) oblong chambers:

http://www.mightyram50.net/vbulletin/showthread.php/9660-Having-problems-finding-a-head-for-a-86-mighty-max-2-0

I'd inferred the oblong-chamber head there was a 2.0L G63 head like OP's original head, but now I realize he didn't actually say that, so maybe that head could be from/for a different Sirius variant?