Cylinder heads: flush/recessed or protruding valve?

[Growlerbearnz]

Replacing your cylinder head? Be sure to buy the correct type.

Recognising the differences:
Early 4D56 engines (1987 to 1993-ish) have a protruding valve head: the valves stick out from the head surface when closed, like so:




Around 1993 the engine design changed slightly, and heads from then onwards have valves that are flush/recessed from the head surface:

The pistons under these valves also changed:

On the left: newer 1993-'99 (MD304847) pistons for flush valve heads, with a very slight cutout to help the fuel swirl.
On the right: older 1987-'93 (MD103308) pistons with larger cutouts to accommodate the protruding valves.

-You cannot put a protruding valve head over later flush-valve pistons, the pistons hit the valves.

-While it is physically possible to install a flush/recessed head over protruding valve pistons, the compression ratio will drop to about 18:1 (from 21:1) which will lose you torque and efficiency. See this thread here.

 

[sk66]

I found this online somewhere and figured it might be handy. I edited it because the first part number was off by 1 and the third lists as being for a 4D55... I haven't verified it's complete accuracy.

Above = Protruding.

 

[sk66]

Here's a question, does putting a recessed valve head over protruding valve pistons make it a non-interference engine? I rather doubt it, but that might be worth considering if it does.

 

[Growlerbearnz]

Here's a question, does putting a recessed valve head over protruding valve pistons make it a non-interference engine?

Nope. There's just not enough room to maintain high compression while making it non-interference.