The engine rebuild just got a little more complicated.

[labguy1970]

Hi All, I'm hoping you'll be able to help. I've done some searching on this, but have come up empty. I'm looking to replace my lower timing belt cover for my 88 L300(ie G64b engine), since mine is falling apart. It's got pieces broken out and missing, one piece fell in and stopped the engine, but that's a different story. I'm doing a rebuild on the engine now, and would like to find a cover that is at least whole. I'm not sure if I can use the cover off of a different year 4G64 engine or not, from the pictures I've seen it's a bit different. Does anyone have an suggestions.
Thanks much
Jason

[labguy1970]

I've found one at http://www.oemmitsubishiparts.com/ SouthWest Mitsubishi Parts.
Jason

[Yokohama]

The only difference between the G64B and 4G64 wide block, at least in 6-bolt crank configuration, is that the G64B version has a Jet-valve head. All RWD vans should be 6-bolt cranks.

Both the 4G64 and G64B came in wide and narrow blocks. It appears that all G64B's are 6-bolt cranks, and that the wideblock 4G64 came both 6 and 7-bolt depending on year and application.

[labguy1970]

Good to know, thanks for the info. I'm assuming if I need another head, I can go with one that doesn't have the jet valves. The site I posted above seems to have lots of parts for my 88, wish I'd found it a couple years ago.

[labguy1970]

Well I got the engine apart, and it looks like the #2 cylinder has some damage from a defective jet valve. It looks like the bottom part of the jet valve fell/broke off and was in the combustion camber for a while. There is damage to head and the piston. Looks like the broken jet valve piece got pinched between the two a good number of times before being spit out. Also looks like a crack between the intake and exhaust valves,not sure until I get it pressure checked. I was really hoping to avoid replacing the head and the pistons. Also found this piece under the valve cover just sitting in a corner of the head, anyone know what it is?
Jason

[Big-Bird]

That's the bottom of a threaded stud but I am not sure where on the head or valve cover that would have originated.

The piston might be salvagable provided the high points from the impact are levelled off. If there is any suspected cracks to the piston it might be better to get a new one.

The head is a different story and an engine machine shop should be consulted. They can do a dye penetrant test (because its aluminum) on the head which will show cracks very quickly. A pressure test won't tell you if there are small cracks in the space between the valves or anywhere else for that matter. The impact craters are also a potential source for cracks.

http://www.youtube.com/watch?v=109-Uzu2ihw

[labguy1970]

Thanks for the vid, didn't know that was how they checked aluminum cast pieces. I'm assuming the machine shop knows how to check it out. I've been talking to a friend about buying one of his, but it's in North Carolina and on an engine. I'm pretty sure the head is toasted; it looks like there is a small crack between the valves and the craters have really deformed that part of the head. I also took the valve rockers off, and it looks like the head wasn't built properly. there are lots of uneven wear were the cam sits. I've got new pistons coming to me, so those will be new, along with a good number of other parts. It's too bad on some levels, but I'll pretty much have a completely rebuilt engine.

Jason

[Big-Bird]

If you are doing pistons and a new/refurbished head you should also consider getting the crankshaft main bearings and connecting rod bearings. At the very least you should check the clearances with plastigauge. See video.

http://www.youtube.com/watch?v=rXp1vVtsp7s

[labguy1970]

Yep, got all the bearings ordered and on the way. Thanks for the link on the use of plastigauge, I've heard good things about using it. I'll have to try it out this time around. My friend in North Carolina has sent the head my way.
Cheers,
Jason