I agreeà Should run but may still use oil. The piston top and the wall looks very clean like that cylinder is pumping a lot of oil. How do the other piston tops look in comparison?

Were the valve seals bad enough to account for the amount of oil you were using? In particular were you getting one plug that was fouling or had more deposits?

Basically, will putting on fresh heads get you an engine that is useable?

Kevin

I (and the shop) have not reassembled yet. So, it's just a prediction. After reading these comments here and hearing from friend's opinions, I started feeling that it should run, just like before the overhaul. The smoke issue might stay, though. Regarding overheat, I haven't had any but previous owener might have. (I bought this truck 3 years ago. That time, it had 70,000 mile. I changed the timing belt right after that. I changed transmission this year. Now it has 99,000.) A mechanic also asked the same question when he looked the scratches. I remember the transmission guy also asked about overheat. I should ask them to re-install and try if it starts or not. Unfortunately, I have to totally count on the shop now...

My friend. I have the same problem like you have and the same SUV with an 6G74 3500cc engine and same year; the only diference is that hace 230,000 miles. When I stop at a traffic light at idle speed and wait for about a minute its starts to smoke. My mecanic told me that I have to change the the piston-rings and the valve seales. There is something curios when the oil amount in the engine drops from 4.7 Liters to about 3 liters the smoke disapears, so that tells me the its more posible that the piston rings are the problems and not the valve seals.

When I save the image and look close at the honing pattern, the diagonal honing marks seem to continue thru the vertical scratches in almost all of the cases. That means some scotchbrite may well do the trick. I'd take a good close look at the honing pattern under strong light and evaluate it in person, then make your best call. If the honing pattern is mostly complete, you'll see slight oil burn. I'd look for piston rocking, too. Rotate the piston to about 3/4 of the way up the bore, and carefully measure the distance from piston top to block top on both the exhaust and intake sides. Now rotate the piston past tdc to about 1/4 the way down the bore, and repeat measurements. measuring tool must read to .0001, like a micrometer depth gauge. You're looking for piston rocking, and you may hear a slap as the piston cocks the other way as it passes tdc and bdc. Rotate more vigorously to get a more distinct sound. You should have been able to hear piston slap (like vavle ticking but louder) at and just off idle in the engine before if you have a collapsed/collapsing piston skirt.

Depth micrometer to .0001. I checked one out of the tool room once, it came with a case and a armed guard <img src="/forums/images/graemlins/lol.gif" alt="" />
He had orders to shoot me if I dropped it <img src="/forums/images/graemlins/cyclops.gif" alt="" />

They re-assembled and the result is... good so far. The smoke issue I had before the overhaul is gone. I did some Scotch Brite in a sideways motion, as suggested here. Did it work? Yeah, may-be. I will check if it still burns oil later.
Though it cost $900+, my Monty is back. It got a new water pump, thermostat, T-belt, belts, spark plugs, etc. Next stop would be shocks?
BTW, the ABS indicator doesn't go off. I remember this thing need to be reset. How can I do...
Photos - removing heads

Good deal, <img src="/forums/images/graemlins/kewl.gif" alt="" />

Good work! thank you for the pictures, I'll be getting into this soon enough! <img src="/forums/images/graemlins/kewl.gif" alt="" />