4,0 OHV cylinder heads

[Hetzer 88]

Hello, I have an '91 Explorer (with 90tm cylinder heads) and I'd like to chahge it for 93tm,95tm or 97tm for getting more power. Is it actually realy?

 

[Rhett]

Hello, I have an '91 Explorer (with 90tm cylinder heads) and I'd like to chahge it for 93tm,95tm or 97tm for getting more power. Is it actually realy?

It's been awhile but as I recall, if you run 95TM or later, you will want the later pistons also. Ford changed piston design if I recall correctly.

 

[Hetzer 88]

It's been awhile but as I recall, if you run 95TM or later, you will want the later pistons also. Ford changed piston design if I recall correctly.

New pistons are needed for correct compression ratio, is it right?

 

[Rhett]

New pistons are needed for correct compression ratio, is it right?

Correct. 95TM head has the heart-shaped "fast burn" combustion chamber. The dish on the 95TM's pistons should be 3.10" in diameter (vs. 2.40" on the 90TM/93TM pistons).

I am not sure about computer compatibility, which might be important. On some vehicles running an ECU set up for the 90TM head in a vehicle with a 95TM head resulted in poor running....but I am not an expert on that side of things by any means.

 

[jmdirk]

If I recall, if you swap to the newer heads without the compatible pistons, it bumps up the compression. You end up having to run premium fuel as a result