Pretty sure this can be done with internal components, but have some questions.
There's a GEMS P38 with 4.6 in my local yard. I'm thinking about yanking the crankshaft and pistons from it.

The pistons seem pretty easy to pull. Just drop the oil pan and unbolt the bearing caps. Pull the heads and pull the pistons?

1) How much of a pain is it to pull the crankshaft? Feasible to do it in a junkyard lot with minimal power tools?

2) What else would I need to make this work in my 3.9?

 

From what I've seen it might be doable but still a PITA. You'll need to pull the front cover, timing chain, unbolt the Torque converter and pull the journals. I think at that point you should be able to drop it down if you have enough room to clear everything.

 

Someone on here said the 4.6 won't clear the 3.9 block. Dunno if that's true or not. I think the 4.0 block has more beef and can be clearanced.

 

it wont fit. the bearing journals are bigger. why not take the whole thing and use that? you have to remove the transmission anyway to get the crankshaft out and thats by far the biggest pain in removing an engine

 

3.9 will not interchange with 4.0 and 4.6
Pull entire engine

Fyi you must pull pistons from top, the way block is cast won't come out bottom rover master tech showed me on a bare block

4.0 and 4.6 caps are bolted bottom and cross bolted

 

Your right about bearing journals but anyone converting over from the 14CUX over to GEMS might as well go the GM LS conversion instead because it's about the same difference PITA wise but with a far stronger end result. A 4.6 can be converted but the decisions give me a headache.

Fish, your stuck with the 4.2 crank/rods which aint so bad. Tough part is finding a donor motor cheap and still in decent shape. If you go the 4.6 in the 3.9 the block has to be nearly reborn at the milling machine and you'll come up against the cam problem. You'll need a bump stick to drive the dizzy and oil pump...... In my opinion it's just not worth the mods and cash to the 3.9 block to make it all work ya know?

 

I've got a friend that used the whole long block from a 97 Range Rover and bolted his 3.9 intake, front cover, flex plate and exhaust manifolds to it. And I already have a 4.2 14CUX ECU.
So I may just try to yank the whole engine out.
Anybody know how hard it is to pull a GEMS P38 engine?

 

People have been doing this since 1995. Its as trivial as changing a camshaft. You keep all the 14cux stuff, not the other way around. The only "custom" piece is a spacer for the front of the crankshaft, and these days you can buy one from the wedge shop. Back in the day you ground the teeth off a lower timing gear and used that.






I used a ground timing gear when I put a 4.0 in my 95, went with the TWS spacer when I installed the 4.6. There is nothing complicated about this that would compare it to throwing away the entire running gear of a vehicle and putting in another make engine.