Hello... 1st time poster here.

I have an '89 MM... shortbed, few dings but exceptionally rugged truck. Motor & Carburetor (both stock) about shot. +/- 125k miles. Interior is almost mint (go figure).

I want to keep this truck, make it good 2 go for a good while... dependable, solid. Decided to do new motor.

I've looked around, most of the rebuilders shipping 4G52 motors only warranty 3-6 months. Having decidedly mixed luck w/rebuilds in the past, I'm hesitant to choose one. Here (Albuquerque) O'Reilly sells a "gold" rebuild w/3 year warranty. Unless someone steers me elsewhere, I'm inclined to drop in one of those (about $1750).

Also planning to do the Weber carburetor mentioned elsewhere here, mainly 'cause the stock Mikuni is only available in rebuilds and I don't trust rebuilt carbs.

Also (longshot), but... can anyone tell me detailed (or close to it, if even practical) of Fuel Injection conversion for this motor? Has it been done?

Appreciate any *experienced* comments/suggestion... eg: like collective wisdom from forum on good builders for this motor.

I'll also say... correctly or not, my impression is that these 4G52 motors were just "ok"... not bummers, but less then stellar for longevity. We have a U-Pull it yard here, littered w/Mighty Max's and D-50's. I've probably seen a dozen of 'em or so there w/this motor. Every single one looked fine and usable (eg: no wreck) and seemed out of charactar in this yard. Asking around (not any knowledgebale mechanic I can find on 4G52), the "word" seems to be as I said... motor is ok, runs well for +/- 125k, then that's about it.

Ok thanks.

Are you sure your 89 truck has a 4g52? or do you mean 4g54(g54b)? The g52b(4g52) wasn't used in these truck any later then 86, maybe 85.
To go from your carbed motor to the EFI 4g64, you would need the complete engine with all accessories and sensors, and also the engine wiring harness(one separate piece from the rest of the trucks wiring) to run the engine and sensors.

Thanks Josh...

Hmmm...

I don't recall why I had concluded I had a 2L motor, but there was a reason. This http://en.wikipedia.org/wiki/Mitsubishi_Astron_engine#4G52 Wiki page says the 4G52 was used on Ram 50's's through '89. I assumed that was the same for Mighty's, no?

Same page says the G54B was used for same years.

The metal stamp on fire wall in engine bay, however, says the engine is: G63B.

Hmmm...

According to this http://www.3si.org/wiki/index.php/Mitsubishi_Engine_codes,_Decoder,_6g73,_6g74,_4G63...site, that motor came in several configurations as well: 2 & 3 valve p/cylinder.

Hmmm....

What are motor options I can drop in this thing, then... and what were the best motors?

I'm willing to dig rear end and/or drive shaft & trans from U-Pull yard to match up w/a better motor, if there is one that will go in nicely. Thing is, though... I really like the mileage of this 2L, and want to put something in that keeps me in that range.

I had this truck about a year, use it around town a bit... but especially for our home remodeling projects and stuff. I bought if from elderly neighbors, the husband died. They had receipts for a rebuild, but no date or mileage on that, and she didn't know how long ago that was.

It ran very well when I bought it, and got +/- 30mpg overall. Not a screamer at all, but plenty of power when I needed it, even on freeway. With that mileage, I'm damn sure this thing is a 2L.

So, I guess I better nail this down then... no what the hell motor I've got before I get another.

Sure would be nice to know if you guys have consensus experience on good rebuilders for these things, however. Same with carbs. As I said, I'm leaning (no pun... 'r'r'r..) towards the Weber setup, but seems not everyone was happy w/that.

Ok, thanks for your help.

Ok, just thought I'd post what I've found.

My motor: G63B.

I should have been more precise in my 1st post. Specifically, there were 2 distinct issues w/this truck:

a) Carb fried
b) #4 plug was getting completely packed, between gap, w/grainy oil.

I orderd a Weber kit for problem a). I have good sources, now, which have done this swap with excellent results.

WRT b): I *had* little familiarity w/jet valve functioning, design etc. Only references here, and elsewhere, that they were problematic. Or, in summary, very general info w/out enough info to craft a solution.

I had assumed I had either bad rings or something broken in head assembly (eg: valve seat or ???). Thing is, I've never seen a plug pack up like that, because of a bad valve.

I had assumed, thus... decided, to replace the motor entirely, as I wanted something dependable. All these trucks in the U-Pull yard, dead (seemingly) w/+/- 125k miles w/no other visible reason to be there... just bothered me.

I kept digging, for specifics wrt these heads. I found this here: http://www.rebuiltautoengines.com/mitsubishi-articles.html


Ok, so followed that through, those seals are available.

Kept digging, and found these guys:
TopEnd Performance
[url]http://www.racetep.com/starhead.html
[/url]

They are machine shop, specializing in these old motors for some years.... only one I found who knew their stuff on these things.

In above link, they describe completely recast heads they sell, w/out jet valve machining. They have 2 of 'em: one is for NA motors, the other a more robust alloy for turbos.

Their guys spent a good hour on the phone w/me, answering all questions. I ordered my Weber from them. Also, after doing compression/Leak down test, I'm persuaded bottom end of mine is fine. They recommended (what they call) a Jet Valve elimination kit (essentially, plugs for machining where jet valves go): they say these are a more reliable fix then replacing the jet valve seals.

I had contacted about 1/2 dozen reputable rebuilders, across the country. Asked a lot about jet valve issues: none of those guys had anything to say, other then they redo stock heads, w/out mod, to spec.

If I were going (or, as it turns out, I need) to, I'd have a good bottom end build somewhere, then buy a head from TopEnd.

Kudos to those guys, glad to know there's a shop that knows their stuff wrt these Jet Valve heads.

Hope this is of use to someone out there.

Take care