3.9 converted to 4.?

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Author Message   jerry Posted on Monday, January 20, 2003 - 09:11 am:    I know this has been talked about before. I did a search and couldnt find the answer I was looking for. How hard is it to convert from the 3.9 to say a 4.6? I was looking in atlantic british catolog and the block is only about 300 dollars diffrent. what else would I need? Is it easier to just buy a low milage motor?   trevor griffiths (Trevorgriffiths) Posted on Tuesday, January 21, 2003 - 11:36 am:    A 3.9 (or a 4.2) are distributor engines, whereas the 4.0/4.6 are distributor less. The 4.2 crank, rods, and pistons will drop in and with the 4.2 chip in the ecu, give you at least 12hp. The 4.6 crank and pistons can be fitted to the 3.9 block, but the crankshaft has to be shortened on the nose where the pulleys mount, the main caps have to be bored to fit the larger crank journals, and the block has to be drilled to fit the side bolts for a 4-bolt main cap. I was trying to do this on my 94 Disco because I happened to have a 4.2 and 4.6 laying around, but most of it turned out to be unusable without herculean effort to fit them all together. In the end, I am trying to find a 4.6 short block, new , and go from there! Good luck!