The P-38 uses the exact same engine as the Disco.
If it is the GEMS, same same.
Bosch, same same.
Just drop it in and go.

 

The Bosch breathes better and I personally think the GEMS was better build, not because it is a GEMS but because it was of a different year and quality control was better.

 

Man that is great!! Really, just drop it in and go??

 

Yes, any Bosch engine will work in any Bosch truck, and any GEMS engine will work in any GEMS truck, everything you need it already there, just bolt it up and go.
The truck will not know the difference.
HOWEVER, you will not notice the 4.6 power unless you also use the 4.6 ECU or have yours reprogrammed.
The RR ECU will NOT work in a Disco, the DII ECU can be reprogrammed by the stealer, I do not know about the GEMS ECU as the DI never came with the 4.6 but the DII did.
BUT you do NOT have to reprogram the ECU, you can drop it in and go, you just will not notice any more power.
So if you are just looking for a cheaper used engine and P-38's in rough shape are cheaper than a DII used engine...no reason not to buy it. And then scrap the rest.
I want the analog clock though if it works.

 

Mine already is a 4.6. It is an 04 so i guess i have a 4.6 ecu. Great news.
The clock is yours, Spike, with my thanks.
This place has helped me a ton.

 

Forgive me resurrecting an old thread, but I thought it better than starting my own. I'm having a top hat conversion done but I am not content to simply cover up the root problem with better liners and live with present or future cracks in the coolant ducts (even though the liners are "sealed"). Just got off the phone with JE Robinson and they recommended putting a 99-00 RR 4.6 in my 04 DII. This was his solution to the tooling issues which was not an issue with the previous 4.6L engines. He claims there are no fitment issues with the short block (I have secondary air, so the heads would be different). Can anyone else confirm this? I have no issues as long as it's plug/play.

 

Just seen your post today as I was searching for this thread. Mine also has SAI, not sure about the RR's.
I am sure Buzz or Spike or Mike would know, though.
Keep posting any new info on this topic as I may try this route.
Thanks

 

If you have secondary air just swap the heads, you were going to put new headgasket on the engine before you installed it correct

 

I would say so, yes.

 

There are P38's with SAI too.....