I have placed this in other parts of the land rover forum mostly because I didn't look to see if there was an engine specific thread first. but:
I have a cracked block on my 2003 Disco 2 with a 4.6. I purchased a 4.0 to replace it and am wondering... can I put the 4.6 crank in the 4.0 block without changing anything else. I am not rebuilding the 4.0 as it has few miles on it and has no issues, but as I have already got the 4.6 crank and new bearings, would it be OK to swap that out and increase the 4.0 to 4.6 or is there a difference in the connecting rods too?

 

"CAUTION: if crankshaft is to be replaced, ensure replacement is correct for engine being overhauled. Crankshafts are not interchangeable between 4.0 and 4.6 litre engines."

-- Land Rover 4.0 & 4.6 Litre V8 Engine Overhaul Manual (LRL0004ENG - 4th Ed), p.49.

 

Thanks so much, I understood it was the same block. Glad to have this forum just for this reason.

 

It's the same basic block, but I'm not familiar with the precise differences between the two capacity engines. The Overhaul Manual doesn't seem to specify.

 

Actually they are able to be swapped. Keep the 4.6 rods and use the 4.0 pistons. The only difference is the stroke between the 4.0 and 4.6, it's longer in the 4.6. The reason you want to keep the 4.0 pistons is they'll give you a fraction more compression than the 4.6's.

 

That's right. Abran was experimenting with 4.0 pistons in a 4.6 to increase the compression. But you would have to swap the connecting rods.