340 rear main cap

Dan the man said

I have a simple solution to your problem, just simply replace the rear cap from a 318, as the 318's and the 340's have the same main bearing caps. I'm surprised that no one else thought of this. 318's are everywhere so locating one should be easily done. I can't believe that none of mopar specialists thought of this.

Click to expand...

Main caps are lined honed matched to each specific block as part of initial block machining after blocks are cast. You can not take ANY main cap off of ANY block and willy nilly slap it on another block without line honing the mains again. Otherwise the cap will be misaligned bind and eat the bearing. At which point the engine will need an entire rebuild. Super bad idea.

Now if this was an engine being rebuilt sure go find a 318 cap line hone it to the 340 block good to go. But the person asking is not rebuilding he is looking to get it running without rebuild.