Hey guys, first off just want to thank you for all the info I have scavenged from here without posting myself.
My problem: 95 Montero 3.5L 180k miles - butterfly valve broke and fell into a cylinder. Pulled heads and damage to section of head and small scratch on cylinder wall, all others look great. Did compression test before removing heads and had 5 at 90 and the one at 0, but looks like head gasket was also blown. I will have the heads rebuilt.
Can I install new pistons/ rings without pulling engine? Could I get by for awile with just new heads? Thanks again, I'm sure I'll get the info I need.This is my wifes daily driver, dont need performance or good as new.

Now I can't guarantee this. but did coolent or Metal go to bottom of engine? If not the little scratch on cylinder may not do much of anything. Semi trucks can do partial engine rebuilds in truck. I doubt you could do it to this truck- 4x4 drive train and all will be in the way. Best guess is I'd replace the heads and put NEW lower intake on it. New Timing belt-tensioners seals and Water pump at least.

Oh man your post scares the crap out of me, i still need to deal with the butterfly issue...how many miles on ur monty when this happened?

Drained the oil and found no coolant, also no oil in the coolant. I had 180k on the engine when this happened and took me 2 weeks just to find a used lower plenum and even then the shaft the valves were attached to was sloppy.

When u said 'broke' do you mean the shaft broke? the butterfly broke into pieces and fell down, or did the little brass screws come out and drop down? OR, did the bushings fall apart and drop down, or some combination of the above?

I guess what I'm asking is how did the mechanism come apart? What pieces did you dig out of the cylinder?

Seer

I can't be sure but I believe what happens is that the bushing at one end wears down and the valve starts to hit the sides until it breaks (found pieces in the plenum as well as the cat converter). The valve that broke still had the screws in the shaft and the butterfly valve next to it was worn on the edges from hitting the sides. In the used plenum I bought the shaft was loose and I had to rig up a new bushing with a copper compression fitting. I'm still not at ease with the whole system and when I rebuild I may take the valves out completely, not worth the performance increase versus the chance of damage in a 16 year old engine.