Mercury 410 Overheating

[Porkchop]

I did not put sealant around the water ports, but I will do so whichever way I go. I hadn't done that with the stock manifolds on this engine or my 360 so I assumed wrong. I see now that it is a recommendation.

I set manifold back on with no gaskets and the driver's side of the manifold sits above the head by 0.013" and the passenger's side sits below the head by 0.073". The back is the same as the front. I'll post pictures.

Placing the same gaskets back in and resting the manifold in place, on the driver's side the manifold is 0.070" high. Manifold is about 0.030" higher on the passenger's side.

I am going to go along with feeler gauge and measure the gap.

[Porkchop]

Pics

[My427stang]

See if you can look at port alignment, could even be the casting that is making the edges high

However, if it's sitting level at the china wall and that crooked, I'd likely clean up the low side with a light cut to square it, and lean on the other.  Probably .050

Then it'd be square and you could use a thick gasket like the blue Felpro and get it all back in alignment

[Porkchop]

I will try to look at port alignment.

The China wall is relatively even. Maybe 0.002" smaller gap on passenger's side with no gaskets in place.

I used feeler gauges to check gap between head and manifold. On passenger's side, I could get a 0.015" gauge about halfway down all across the length of the manifold. On driver's side, I can get 0.003" toward the very front, and 0.0012" near the #8 port.

[Porkchop]

The factory S manifold valve cover gasket surface sits 0.040" lower than the heads on both sides in the front. And 0.027" lower in the back. So it is even left to right with some difference front to rear. And the gasket should lift it up to be flush.

Measuring the gap between the S manifold and the head, I can put a 0.017" gauge about halfway down all along the passenger's side. On the driver's side it is touching at the very front, 0.006" around #5 port, 0.009" around #6, and 0.014" around 7 and 8. So it is pretty similar to the aluminum intake.

China wall gaps also similar:
Cast iron 0.070"
Aluminum 0.070"
 

[Porkchop]

Pictures. Pictures make it look different side to side, but it's not.