I have a big problem with my 01 Pajero RHD.

When i tried to start the car yesterday the starter would not rotate. So i checked the crankshaft and it was pretty stuck. I then took off the valve covers thinking a valve was blocking the piston and thus not rotating the crankshaft completely. To my suprise all valve were intact. I then went ahead and took the valve housings off to check teh cilinders and what do i see? 3 piston on the right bank everything fine. Now it comes.
When i took off the left valve house i only have 2 piston the other one is gone. Nothing left but a conrod. So far my 6g74 is guess. Big scratches on cilinder 3. At least 2 or 3 mm.

That got me thinking, i might buy 6 6g75 pistons and conrod(they should be the same) and bore my 3.5 up to a 3.8 using the gasket from the 3.8(6g75). Has anybody ever done this or know somebody who has or something like that.

And that was my first post on this forum

 

Ouch! Not a good find for you I think. I am using a 95 Montero 6g74 block - 93mm, bored out to accept stock bore 6g75 - 95mm, pistons. Of course the 6g75 also has a longer stroke, 90mm opposed to the 85.8mm stroke of the 6g74, so the pin height is different between the two engines. The rod lengths are identical although it has been my experience that the 74 rods are substantially stronger than the 75's.
Lincoln

 

Thanks for fast reply!
I'm pretty new to all this, i have never gone beyond the head gasket. Forced into it kind off.

Wall is damaged good. 93mm to 95mm pistons means 1 mm bore. I think that will not be enough. If it would be enough i could just use a 75 piston, no 6 75 pistons because off the headgasket. I can still use the 74 rods? I will need one new one cause mine is bent. Is there something else i need to check? Can the crankshaft be damaged. Where did the piston go? I'll try to post some picks.

 

Best picture i could make with my phone

 

Pic is good...well maybe not so good. The remainder of the piston is no doubt in the oil pan. Just by viewing the pic, I would assume the block is toast. Looks like the gouges are fairly deep and while it is possible to go 4mm over the stock 93mm bore, I would think it would need to be checked out by your machinist.
Don't know where you're located, but here locally 6g75 blocks are fairly reasonable. I can pick up a complete engine for $223 USD, and a bare block for $95 USD. Of course I must trek out to the wrecking yard myself, tools in hand for that price.
I would at a minimum replace that particular rod. It is possible to bend the crank, although your forged crank is pretty tough, still worth inspection to be sure it is true and straight. Remember, the pin height is different in the 74-vs-75 pistons because of stroke, as they use the same rod length. Imagine if you increased the stroke of your 74 by 4.2mm, the length of the 75 stroke. That 4.2mm of the piston would be protruding out the top of the bore at Top Dead Center. Therefor the 75 piston pin height is set higher up in the piston itself to accommodate the extra stroke.
Hope I have helped out at least a little.
Lincoln

 

Correction. The piston would actually sit 2.1mm higher in the bore at TDC as 1/2 of the increase stroke is below the center line of the crank. Sorry.
Lincoln

 

I am trying to understand what you are saying. First a block costs more then i paid for this ''find''. I live in South America by the way. I could contact some wrecking yards in the US and have a engine shipped this way by boat which is not a big deal but all engines i found were very expensive. So i'd like to try to get this one back running.

I did find 6 used pistons and rods from a 6g75. Can i get my block bored to 97 mm and keep my heads or would the new pistons touch them because it would sit higher? Cilinder 3 does need new valves i noticed. I have a Japanese RHD Pajero by the way. Should be almost the same as the American Montero 6g74.

One last question, what else could be damaged besides the crankshaft?
I am planning to get the engine out and opened later this week.

 

The stock 6g75 pistons will be 95mm. Although I am not able to directly view your cylinder bore, it appears to me that it will need to be bored the additional 2mm, to the over bore size of 97mm, to eliminate the damage...IF the offending pin didn't do any further damage: IE crack the cylinder wall whilst flailing about in there.. I THINK that this 97mm size is readily available in the aftermarket, but wouldn't be in any stock configuration. Again, which bore size you will be able to use will be determined by closer inspection/boring process.
The 6g75 pistons will need to stay with the 6g75 crankshaft due to stroke/piston pin location. I always use 6g74 rods-vs-6g75 rods as they are much stronger, albeit a bit heavier.
Also to consider is combustion chamber size and piston dome size. I believe the 6g75 had several different combustion chamber sizes. The 6g75 SOHC 24 valve heads I have seen are of the pent-roof design which require a slight dome on the piston to bring the compression ratio up. However, there are some 6g74 DOHC heads that have the smaller combustion chamber more like, or possibly the same as, the 6g72 heads. The 6g75 SOHC heads have larger valves than the SOHC 6g74 heads although they appear similar on the car. Whew! Now I probably have you totally confused I am sure, sorry. Just be sure that the pistons match the combustion chamber configuration.
If you check out the attached pic you will see on the right is the 6g74 piston with a slight dish to accommodate the small combustion chamber of the 6g74 DOHC heads. The center piston is the stock 6g75. Notice the slight dome. This accommodates the lager combustion chamber. The piston on the left is a 6g75 custom Ross design to lower the compression ratio to ~8.75 to 1 using the pent-roof 6g75 heads. (I plan on 25-30 psi of boost)
I hope I am helping you and not just confusing you. Please continue to ask if I am not explaining things well enough.
Lincoln

 

Again trying to understand. The pistons i have now are 93mm soi should need 97mm pistons and rings, heads and a crankshaft. My heads will not fit if i use 95 or 97mm pistons, is that what you are saying? My heads seem reusable. I might need to change some valves. 95mm pistons i can find used for a nice price. But 1mm bore will not suffice. Have i said that i want to spend as little as possible? 2 mm could be ok from i see and feel, not very certain though. The used heads i have found would bring me close to the price of a complete engine. Anyhow all those parts would cost way to much.

One other thing i don't know much about compression... yet. What would happen to the compression if i'd use 97mm pistons and 74 rods with my heads?

You say where you live engines are cheap. Got a link for a good salvage yard?

Thanks for your time and patience.

 

Sorry for the delay, been away on a short holiday.

If memory serves me, the compression ratio can change from a low of 7.5:1 to a high of 11.25:1 if pistons/heads are matched differently/improperly.

Just be sure the pistons you are going to use: 1) Match the stroke/crank (75 pistons and 75 crank or 74 pistons and 74 crank) and 2) piston dome size matches the combustion chamber.

A link to are local auto salvage yard price list:

url=http://u-pick-it-arizona.com/upaz/pricelist.php]U-Pick-It of Arizona Price List[/url

Think a complete engine is listed for $223 + $45 for the core. Of course those would be u-pick prices...no air tools aloud...HA! Looks like their inventory includes a couple of 2001 Montero's.