4MG Rebuild

It does look like oil, but what I’m seeing is right by that spot the spray pattern from the nozzle looks a bit darker almost thicker. Might be optical illusion idk. If that is the case have that one pop tested. See if it’s leaking before the it pops.

I don’t really see any trace of oil on the chamber side of head. But take a light and shine in exhaust port and intake port. You looking for a valve stem that has more oil than the rest below the guide. That’s usually easy enough to spot. If so I’d say probably had a bridge slightly off

 

Ok, I misinterpreted that. It'll be just fine for you I believe!

 

The head looks great. I’m betting the rings didn’t seat good. Looks like there was a lot of carbon packing at the top of the cylinder wall.

 

Just load the 345 and take off to the hills. That’s plenty of load. I don’t think I would stress too much about it. Just build it and run it hard. I wouldn’t worry about a dyno for break in. Just keep idle low until you have put a few miles on it.

 

So far so good Ox .

 

That bowl is sorta close to the 160-1131. But not perfect. The 4MG and 7FB pistons have more meat at the top plus different bowls. So while compression ratio does matter that alone doesn’t mean that’s all that matters. There are 2 totally different 15.2 bowls and 14.5 bowls. The 3425 and 8785 were both designed to work with the 160-1131. The 3423 with the 4MG and 3421 with the 7FB.
You’ll have to play with the timing to get it to calm down on the smoke. The 3421 were a lot worse smoke wise than the 25’s. The 8785 I couldn’t really tell a difference on the pedal but never did compare them on dyno