So over a year later the car has just been parked so I finally decided to check it out more. I pulled the front head off and this is what I found.

Now I need to decide what the best route is here.

A) get a junkyard head for around $100 from a running engine, but unknown condition.
B) send the head to a machine shop to be rebuilt (haven't gotten price quote yet)
C) replace the broken valve myself and do valve steam seals (burning oil) and clean and lap all other valves on head

Any suggestions are welcome

 

Think I’d do C, but A is a close second. These 1MZ-FE V6’s aren’t known to commonly have head problems like that. So a junkyard head is likely to be OK.

 

This is the first major repair I've done myself on an engine. Time isn't an issue, so I know I could get it done but I have to learn on the way. I am willing to try and fix the issue myself, but I would need to buy any specialty tools and such as I don't have them on hand.

Another question I had was if I should do anything to the rear head while I have it taken apart. I ask because I'm not sure how to get the rear exhaust manifold off because of the clearance in the back and accessing the bolts. Aside from the valve steam seals possibly causing oil burning (something sure was but it could have only been the front head?), I have no concerns with the rear head. The rear spark plugs looked ok for having almost 80k on them.

 

If the valve stem seals are bad, you’ll see a puff or blast of blue smoke on cold starts. Was it doing that?

As for the oil consumption, does it have any significant leaks? It’s surprising how much a little dribble on the ground can be.

For the rear head, I’m kinda torn between leaving it alone, or pulling it to have a look. On the one hand, you’ve already done 90% of the work. On the other, there’s no reason to suspect something’s wrong. I’ve never pulled the rear head on the 1MZ, but on my 3VZ in my Camry, it was possible to remove the exhaust manifold in the engine bay.

 

Little update. I decided to pull the rear head and do all the same work to that one. To pull out the rear head I actually left the exhaust manifold attached to the head and removed it from the head once it was outside the car. So for both the front and rear heads I removed all valves and cleaned the carbon off of them, lapped all valves in, replaced valve steam seals, de-greased and pressure washed head assemblies, and now I'm going to be checking valve clearance and adjusting if out of spec.

Left valve is a new one to replace burnt one, middle is after cleaning carbon (but not lapped yet), and right is what they looked like when removed

Before lapping

After lapping

Top exhaust valve seat not lapped yet, bottom intake valve seat after being lapped

Both heads are finished and ready to go back on

 

Another update - I actually finished putting everything back together over a month ago and the car runs like new again, no codes, no smoke, or anything. (did notice a few oil drips, not sure where they are coming from. Car used to burn 1qt every 500 miles, I have put over 2000 miles on the car and the oil level hasn't moved!

Everything went back together nicely, but doing the valve lash adjustment was a pain in the ass. I ended up going to a junkyard and pulling the shims from the front head of 5 different 1mz motors that were there so I could get every size I might need. Ended up paying $10 for a bag I filled with around 40 shims (dealer price was $13 each).

Car actually runs quieter than it did before, so I must have had some loose valves. All I can say is I'm glad my other cars all have hydraulic lifters lol.

 

When I read the OP, I figured that this thread would be another "My car won't go - I have no clue" threads. I am happy to have learned that I misjudged the OP and I was wrong.

Good on 'ya for figuring it out, working through the issues AND especially good on you for posting updates with pictures!

I am guessing that you probably spent about $1K fixing the issues. That means that you have earned $6K for your effort - and that $6K is tax free!

 

Great work and a helluva of a nice finished job, especially with the lower oil consumption. It's good that you reused the heads you had and avoided used parts and potential problems from them. Not sure what you do for a living but I be you do it well. Thanks for the demonstration of perseverance.