Dynoed250 says the rods need to clear the top of the piston correctly. The 250 pistons have a 25 cc dish capacity capability. In English, that means the casting is thicker than the 200 casting, and I guess this is what needs to be clearanced.
I haven't done a stock 200 rod to stock 250 piston swap, I've only used the 305 Chev piston with a shorter stroke crank. My rods aren't even near the camin a 4.1 cross-flow block.
The base circle diameter of the cam is bigger on some camshafts. In English, that means it's thicker.
The cam bearings, lifters and rods need to be primo.
Being XF, it'd have no rope seal, so I'd look real close at the rod.
Boy, it must be heck of a thing to go through.
The cam profile, if its severe, will induce lots of load stress with stiff springs and lots of lifter pre-load. In English, that means the stock cam may be under a crap load of stress form the big heavy valves and moving bits.
I've seen a few cam failures lately, this isn't speeking well of the back-up from the after market.
Keep cool. I've got a windowed XF EFI block in my garage, which I thought was a rod bolt. Now, I'm thinking the cam must be under too much stress, 'cause the cam is snapped at cylinder 5.
Which cylinder was it that got windowed, number five?
